root/kernel/workqueue.c

DEFINITIONS

1. work_debug_hint
2. work_is_static_object
3. work_fixup_init
4. work_fixup_free
5. debug_work_activate
6. debug_work_deactivate
7. __init_work
8. destroy_work_on_stack
9. destroy_delayed_work_on_stack
10. debug_work_activate
11. debug_work_deactivate
12. worker_pool_assign_id
13. unbound_pwq_by_node
14. work_color_to_flags
15. get_work_color
16. work_next_color
17. set_work_data
18. set_work_pwq
19. set_work_pool_and_keep_pending
20. set_work_pool_and_clear_pending
21. clear_work_data
22. get_work_pwq
23. get_work_pool
24. get_work_pool_id
25. mark_work_canceling
26. work_is_canceling
27. __need_more_worker
28. need_more_worker
29. may_start_working
30. keep_working
31. need_to_create_worker
32. too_many_workers
33. first_idle_worker
34. wake_up_worker
35. wq_worker_running
36. wq_worker_sleeping
37. wq_worker_last_func
38. worker_set_flags
39. worker_clr_flags
40. find_worker_executing_work
41. move_linked_works
42. get_pwq
43. put_pwq
44. put_pwq_unlocked
45. pwq_activate_delayed_work
46. pwq_activate_first_delayed
47. pwq_dec_nr_in_flight
48. try_to_grab_pending
49. insert_work
50. is_chained_work
51. wq_select_unbound_cpu
52. __queue_work
53. queue_work_on
54. workqueue_select_cpu_near
55. queue_work_node
56. delayed_work_timer_fn
57. __queue_delayed_work
58. queue_delayed_work_on
59. mod_delayed_work_on
60. rcu_work_rcufn
61. queue_rcu_work
62. worker_enter_idle
63. worker_leave_idle
64. alloc_worker
65. worker_attach_to_pool
66. worker_detach_from_pool
67. create_worker
68. destroy_worker
69. idle_worker_timeout
70. send_mayday
71. pool_mayday_timeout
72. maybe_create_worker
73. manage_workers
74. process_one_work
75. process_scheduled_works
76. set_pf_worker
77. worker_thread
78. rescuer_thread
79. check_flush_dependency
80. wq_barrier_func
81. insert_wq_barrier
82. flush_workqueue_prep_pwqs
83. flush_workqueue
84. drain_workqueue
85. start_flush_work
86. __flush_work
87. flush_work
88. cwt_wakefn
89. __cancel_work_timer
90. cancel_work_sync
91. flush_delayed_work
92. flush_rcu_work
93. __cancel_work
94. cancel_delayed_work
95. cancel_delayed_work_sync
96. schedule_on_each_cpu
97. execute_in_process_context
98. free_workqueue_attrs
99. alloc_workqueue_attrs
100. copy_workqueue_attrs
101. wqattrs_hash
102. wqattrs_equal
103. init_worker_pool
104. wq_init_lockdep
105. wq_unregister_lockdep
106. wq_free_lockdep
107. wq_init_lockdep
108. wq_unregister_lockdep
109. wq_free_lockdep
110. rcu_free_wq
111. rcu_free_pool
112. put_unbound_pool
113. get_unbound_pool
114. rcu_free_pwq
115. pwq_unbound_release_workfn
116. pwq_adjust_max_active
117. init_pwq
118. link_pwq
119. alloc_unbound_pwq
120. wq_calc_node_cpumask
121. numa_pwq_tbl_install
122. apply_wqattrs_cleanup
123. apply_wqattrs_prepare
124. apply_wqattrs_commit
125. apply_wqattrs_lock
126. apply_wqattrs_unlock
127. apply_workqueue_attrs_locked
128. apply_workqueue_attrs
129. wq_update_unbound_numa
130. alloc_and_link_pwqs
131. wq_clamp_max_active
132. init_rescuer
133. __printf
134. destroy_workqueue
135. workqueue_set_max_active
136. current_work
137. current_is_workqueue_rescuer
138. workqueue_congested
139. work_busy
140. set_worker_desc
141. print_worker_info
142. pr_cont_pool_info
143. pr_cont_work
144. show_pwq
145. show_workqueue_state
146. wq_worker_comm
147. unbind_workers
148. rebind_workers
149. restore_unbound_workers_cpumask
150. workqueue_prepare_cpu
151. workqueue_online_cpu
152. workqueue_offline_cpu
153. work_for_cpu_fn
154. work_on_cpu
155. work_on_cpu_safe
156. freeze_workqueues_begin
157. freeze_workqueues_busy
158. thaw_workqueues
159. workqueue_apply_unbound_cpumask
160. workqueue_set_unbound_cpumask
161. dev_to_wq
162. per_cpu_show
163. max_active_show
164. max_active_store
165. wq_pool_ids_show
166. wq_nice_show
167. wq_sysfs_prep_attrs
168. wq_nice_store
169. wq_cpumask_show
170. wq_cpumask_store
171. wq_numa_show
172. wq_numa_store
173. wq_unbound_cpumask_show
174. wq_unbound_cpumask_store
175. wq_sysfs_init
176. wq_device_release
177. workqueue_sysfs_register
178. workqueue_sysfs_unregister
179. workqueue_sysfs_unregister
180. wq_watchdog_reset_touched
181. wq_watchdog_timer_fn
182. wq_watchdog_touch
183. wq_watchdog_set_thresh
184. wq_watchdog_param_set_thresh
185. wq_watchdog_init
186. wq_watchdog_init
187. wq_numa_init
188. workqueue_init_early
189. workqueue_init

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * kernel/workqueue.c - generic async execution with shared worker pool
   4  *
   5  * Copyright (C) 2002           Ingo Molnar
   6  *
   7  *   Derived from the taskqueue/keventd code by:
   8  *     David Woodhouse <dwmw2@infradead.org>
   9  *     Andrew Morton
  10  *     Kai Petzke <wpp@marie.physik.tu-berlin.de>
  11  *     Theodore Ts'o <tytso@mit.edu>
  12  *
  13  * Made to use alloc_percpu by Christoph Lameter.
  14  *
  15  * Copyright (C) 2010           SUSE Linux Products GmbH
  16  * Copyright (C) 2010           Tejun Heo <tj@kernel.org>
  17  *
  18  * This is the generic async execution mechanism.  Work items as are
  19  * executed in process context.  The worker pool is shared and
  20  * automatically managed.  There are two worker pools for each CPU (one for
  21  * normal work items and the other for high priority ones) and some extra
  22  * pools for workqueues which are not bound to any specific CPU - the
  23  * number of these backing pools is dynamic.
  24  *
  25  * Please read Documentation/core-api/workqueue.rst for details.
  26  */
  27 
  28 #include <linux/export.h>
  29 #include <linux/kernel.h>
  30 #include <linux/sched.h>
  31 #include <linux/init.h>
  32 #include <linux/signal.h>
  33 #include <linux/completion.h>
  34 #include <linux/workqueue.h>
  35 #include <linux/slab.h>
  36 #include <linux/cpu.h>
  37 #include <linux/notifier.h>
  38 #include <linux/kthread.h>
  39 #include <linux/hardirq.h>
  40 #include <linux/mempolicy.h>
  41 #include <linux/freezer.h>
  42 #include <linux/debug_locks.h>
  43 #include <linux/lockdep.h>
  44 #include <linux/idr.h>
  45 #include <linux/jhash.h>
  46 #include <linux/hashtable.h>
  47 #include <linux/rculist.h>
  48 #include <linux/nodemask.h>
  49 #include <linux/moduleparam.h>
  50 #include <linux/uaccess.h>
  51 #include <linux/sched/isolation.h>
  52 #include <linux/nmi.h>
  53 
  54 #include "workqueue_internal.h"
  55 
  56 enum {
  57         /*
  58          * worker_pool flags
  59          *
  60          * A bound pool is either associated or disassociated with its CPU.
  61          * While associated (!DISASSOCIATED), all workers are bound to the
  62          * CPU and none has %WORKER_UNBOUND set and concurrency management
  63          * is in effect.
  64          *
  65          * While DISASSOCIATED, the cpu may be offline and all workers have
  66          * %WORKER_UNBOUND set and concurrency management disabled, and may
  67          * be executing on any CPU.  The pool behaves as an unbound one.
  68          *
  69          * Note that DISASSOCIATED should be flipped only while holding
  70          * wq_pool_attach_mutex to avoid changing binding state while
  71          * worker_attach_to_pool() is in progress.
  72          */
  73         POOL_MANAGER_ACTIVE     = 1 << 0,       /* being managed */
  74         POOL_DISASSOCIATED      = 1 << 2,       /* cpu can't serve workers */
  75 
  76         /* worker flags */
  77         WORKER_DIE              = 1 << 1,       /* die die die */
  78         WORKER_IDLE             = 1 << 2,       /* is idle */
  79         WORKER_PREP             = 1 << 3,       /* preparing to run works */
  80         WORKER_CPU_INTENSIVE    = 1 << 6,       /* cpu intensive */
  81         WORKER_UNBOUND          = 1 << 7,       /* worker is unbound */
  82         WORKER_REBOUND          = 1 << 8,       /* worker was rebound */
  83 
  84         WORKER_NOT_RUNNING      = WORKER_PREP | WORKER_CPU_INTENSIVE |
  85                                   WORKER_UNBOUND | WORKER_REBOUND,
  86 
  87         NR_STD_WORKER_POOLS     = 2,            /* # standard pools per cpu */
  88 
  89         UNBOUND_POOL_HASH_ORDER = 6,            /* hashed by pool->attrs */
  90         BUSY_WORKER_HASH_ORDER  = 6,            /* 64 pointers */
  91 
  92         MAX_IDLE_WORKERS_RATIO  = 4,            /* 1/4 of busy can be idle */
  93         IDLE_WORKER_TIMEOUT     = 300 * HZ,     /* keep idle ones for 5 mins */
  94 
  95         MAYDAY_INITIAL_TIMEOUT  = HZ / 100 >= 2 ? HZ / 100 : 2,
  96                                                 /* call for help after 10ms
  97                                                    (min two ticks) */
  98         MAYDAY_INTERVAL         = HZ / 10,      /* and then every 100ms */
  99         CREATE_COOLDOWN         = HZ,           /* time to breath after fail */
 100 
 101         /*
 102          * Rescue workers are used only on emergencies and shared by
 103          * all cpus.  Give MIN_NICE.
 104          */
 105         RESCUER_NICE_LEVEL      = MIN_NICE,
 106         HIGHPRI_NICE_LEVEL      = MIN_NICE,
 107 
 108         WQ_NAME_LEN             = 24,
 109 };
 110 
 111 /*
 112  * Structure fields follow one of the following exclusion rules.
 113  *
 114  * I: Modifiable by initialization/destruction paths and read-only for
 115  *    everyone else.
 116  *
 117  * P: Preemption protected.  Disabling preemption is enough and should
 118  *    only be modified and accessed from the local cpu.
 119  *
 120  * L: pool->lock protected.  Access with pool->lock held.
 121  *
 122  * X: During normal operation, modification requires pool->lock and should
 123  *    be done only from local cpu.  Either disabling preemption on local
 124  *    cpu or grabbing pool->lock is enough for read access.  If
 125  *    POOL_DISASSOCIATED is set, it's identical to L.
 126  *
 127  * A: wq_pool_attach_mutex protected.
 128  *
 129  * PL: wq_pool_mutex protected.
 130  *
 131  * PR: wq_pool_mutex protected for writes.  RCU protected for reads.
 132  *
 133  * PW: wq_pool_mutex and wq->mutex protected for writes.  Either for reads.
 134  *
 135  * PWR: wq_pool_mutex and wq->mutex protected for writes.  Either or
 136  *      RCU for reads.
 137  *
 138  * WQ: wq->mutex protected.
 139  *
 140  * WR: wq->mutex protected for writes.  RCU protected for reads.
 141  *
 142  * MD: wq_mayday_lock protected.
 143  */
 144 
 145 /* struct worker is defined in workqueue_internal.h */
 146 
 147 struct worker_pool {
 148         spinlock_t              lock;           /* the pool lock */
 149         int                     cpu;            /* I: the associated cpu */
 150         int                     node;           /* I: the associated node ID */
 151         int                     id;             /* I: pool ID */
 152         unsigned int            flags;          /* X: flags */
 153 
 154         unsigned long           watchdog_ts;    /* L: watchdog timestamp */
 155 
 156         struct list_head        worklist;       /* L: list of pending works */
 157 
 158         int                     nr_workers;     /* L: total number of workers */
 159         int                     nr_idle;        /* L: currently idle workers */
 160 
 161         struct list_head        idle_list;      /* X: list of idle workers */
 162         struct timer_list       idle_timer;     /* L: worker idle timeout */
 163         struct timer_list       mayday_timer;   /* L: SOS timer for workers */
 164 
 165         /* a workers is either on busy_hash or idle_list, or the manager */
 166         DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
 167                                                 /* L: hash of busy workers */
 168 
 169         struct worker           *manager;       /* L: purely informational */
 170         struct list_head        workers;        /* A: attached workers */
 171         struct completion       *detach_completion; /* all workers detached */
 172 
 173         struct ida              worker_ida;     /* worker IDs for task name */
 174 
 175         struct workqueue_attrs  *attrs;         /* I: worker attributes */
 176         struct hlist_node       hash_node;      /* PL: unbound_pool_hash node */
 177         int                     refcnt;         /* PL: refcnt for unbound pools */
 178 
 179         /*
 180          * The current concurrency level.  As it's likely to be accessed
 181          * from other CPUs during try_to_wake_up(), put it in a separate
 182          * cacheline.
 183          */
 184         atomic_t                nr_running ____cacheline_aligned_in_smp;
 185 
 186         /*
 187          * Destruction of pool is RCU protected to allow dereferences
 188          * from get_work_pool().
 189          */
 190         struct rcu_head         rcu;
 191 } ____cacheline_aligned_in_smp;
 192 
 193 /*
 194  * The per-pool workqueue.  While queued, the lower WORK_STRUCT_FLAG_BITS
 195  * of work_struct->data are used for flags and the remaining high bits
 196  * point to the pwq; thus, pwqs need to be aligned at two's power of the
 197  * number of flag bits.
 198  */
 199 struct pool_workqueue {
 200         struct worker_pool      *pool;          /* I: the associated pool */
 201         struct workqueue_struct *wq;            /* I: the owning workqueue */
 202         int                     work_color;     /* L: current color */
 203         int                     flush_color;    /* L: flushing color */
 204         int                     refcnt;         /* L: reference count */
 205         int                     nr_in_flight[WORK_NR_COLORS];
 206                                                 /* L: nr of in_flight works */
 207         int                     nr_active;      /* L: nr of active works */
 208         int                     max_active;     /* L: max active works */
 209         struct list_head        delayed_works;  /* L: delayed works */
 210         struct list_head        pwqs_node;      /* WR: node on wq->pwqs */
 211         struct list_head        mayday_node;    /* MD: node on wq->maydays */
 212 
 213         /*
 214          * Release of unbound pwq is punted to system_wq.  See put_pwq()
 215          * and pwq_unbound_release_workfn() for details.  pool_workqueue
 216          * itself is also RCU protected so that the first pwq can be
 217          * determined without grabbing wq->mutex.
 218          */
 219         struct work_struct      unbound_release_work;
 220         struct rcu_head         rcu;
 221 } __aligned(1 << WORK_STRUCT_FLAG_BITS);
 222 
 223 /*
 224  * Structure used to wait for workqueue flush.
 225  */
 226 struct wq_flusher {
 227         struct list_head        list;           /* WQ: list of flushers */
 228         int                     flush_color;    /* WQ: flush color waiting for */
 229         struct completion       done;           /* flush completion */
 230 };
 231 
 232 struct wq_device;
 233 
 234 /*
 235  * The externally visible workqueue.  It relays the issued work items to
 236  * the appropriate worker_pool through its pool_workqueues.
 237  */
 238 struct workqueue_struct {
 239         struct list_head        pwqs;           /* WR: all pwqs of this wq */
 240         struct list_head        list;           /* PR: list of all workqueues */
 241 
 242         struct mutex            mutex;          /* protects this wq */
 243         int                     work_color;     /* WQ: current work color */
 244         int                     flush_color;    /* WQ: current flush color */
 245         atomic_t                nr_pwqs_to_flush; /* flush in progress */
 246         struct wq_flusher       *first_flusher; /* WQ: first flusher */
 247         struct list_head        flusher_queue;  /* WQ: flush waiters */
 248         struct list_head        flusher_overflow; /* WQ: flush overflow list */
 249 
 250         struct list_head        maydays;        /* MD: pwqs requesting rescue */
 251         struct worker           *rescuer;       /* I: rescue worker */
 252 
 253         int                     nr_drainers;    /* WQ: drain in progress */
 254         int                     saved_max_active; /* WQ: saved pwq max_active */
 255 
 256         struct workqueue_attrs  *unbound_attrs; /* PW: only for unbound wqs */
 257         struct pool_workqueue   *dfl_pwq;       /* PW: only for unbound wqs */
 258 
 259 #ifdef CONFIG_SYSFS
 260         struct wq_device        *wq_dev;        /* I: for sysfs interface */
 261 #endif
 262 #ifdef CONFIG_LOCKDEP
 263         char                    *lock_name;
 264         struct lock_class_key   key;
 265         struct lockdep_map      lockdep_map;
 266 #endif
 267         char                    name[WQ_NAME_LEN]; /* I: workqueue name */
 268 
 269         /*
 270          * Destruction of workqueue_struct is RCU protected to allow walking
 271          * the workqueues list without grabbing wq_pool_mutex.
 272          * This is used to dump all workqueues from sysrq.
 273          */
 274         struct rcu_head         rcu;
 275 
 276         /* hot fields used during command issue, aligned to cacheline */
 277         unsigned int            flags ____cacheline_aligned; /* WQ: WQ_* flags */
 278         struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
 279         struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
 280 };
 281 
 282 static struct kmem_cache *pwq_cache;
 283 
 284 static cpumask_var_t *wq_numa_possible_cpumask;
 285                                         /* possible CPUs of each node */
 286 
 287 static bool wq_disable_numa;
 288 module_param_named(disable_numa, wq_disable_numa, bool, 0444);
 289 
 290 /* see the comment above the definition of WQ_POWER_EFFICIENT */
 291 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
 292 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
 293 
 294 static bool wq_online;                  /* can kworkers be created yet? */
 295 
 296 static bool wq_numa_enabled;            /* unbound NUMA affinity enabled */
 297 
 298 /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
 299 static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
 300 
 301 static DEFINE_MUTEX(wq_pool_mutex);     /* protects pools and workqueues list */
 302 static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
 303 static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
 304 static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait); /* wait for manager to go away */
 305 
 306 static LIST_HEAD(workqueues);           /* PR: list of all workqueues */
 307 static bool workqueue_freezing;         /* PL: have wqs started freezing? */
 308 
 309 /* PL: allowable cpus for unbound wqs and work items */
 310 static cpumask_var_t wq_unbound_cpumask;
 311 
 312 /* CPU where unbound work was last round robin scheduled from this CPU */
 313 static DEFINE_PER_CPU(int, wq_rr_cpu_last);
 314 
 315 /*
 316  * Local execution of unbound work items is no longer guaranteed.  The
 317  * following always forces round-robin CPU selection on unbound work items
 318  * to uncover usages which depend on it.
 319  */
 320 #ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
 321 static bool wq_debug_force_rr_cpu = true;
 322 #else
 323 static bool wq_debug_force_rr_cpu = false;
 324 #endif
 325 module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
 326 
 327 /* the per-cpu worker pools */
 328 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
 329 
 330 static DEFINE_IDR(worker_pool_idr);     /* PR: idr of all pools */
 331 
 332 /* PL: hash of all unbound pools keyed by pool->attrs */
 333 static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
 334 
 335 /* I: attributes used when instantiating standard unbound pools on demand */
 336 static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
 337 
 338 /* I: attributes used when instantiating ordered pools on demand */
 339 static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
 340 
 341 struct workqueue_struct *system_wq __read_mostly;
 342 EXPORT_SYMBOL(system_wq);
 343 struct workqueue_struct *system_highpri_wq __read_mostly;
 344 EXPORT_SYMBOL_GPL(system_highpri_wq);
 345 struct workqueue_struct *system_long_wq __read_mostly;
 346 EXPORT_SYMBOL_GPL(system_long_wq);
 347 struct workqueue_struct *system_unbound_wq __read_mostly;
 348 EXPORT_SYMBOL_GPL(system_unbound_wq);
 349 struct workqueue_struct *system_freezable_wq __read_mostly;
 350 EXPORT_SYMBOL_GPL(system_freezable_wq);
 351 struct workqueue_struct *system_power_efficient_wq __read_mostly;
 352 EXPORT_SYMBOL_GPL(system_power_efficient_wq);
 353 struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
 354 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
 355 
 356 static int worker_thread(void *__worker);
 357 static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
 358 
 359 #define CREATE_TRACE_POINTS
 360 #include <trace/events/workqueue.h>
 361 
 362 #define assert_rcu_or_pool_mutex()                                      \
 363         RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&                       \
 364                          !lockdep_is_held(&wq_pool_mutex),              \
 365                          "RCU or wq_pool_mutex should be held")
 366 
 367 #define assert_rcu_or_wq_mutex(wq)                                      \
 368         RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&                       \
 369                          !lockdep_is_held(&wq->mutex),                  \
 370                          "RCU or wq->mutex should be held")
 371 
 372 #define assert_rcu_or_wq_mutex_or_pool_mutex(wq)                        \
 373         RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&                       \
 374                          !lockdep_is_held(&wq->mutex) &&                \
 375                          !lockdep_is_held(&wq_pool_mutex),              \
 376                          "RCU, wq->mutex or wq_pool_mutex should be held")
 377 
 378 #define for_each_cpu_worker_pool(pool, cpu)                             \
 379         for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];               \
 380              (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
 381              (pool)++)
 382 
 383 /**
 384  * for_each_pool - iterate through all worker_pools in the system
 385  * @pool: iteration cursor
 386  * @pi: integer used for iteration
 387  *
 388  * This must be called either with wq_pool_mutex held or RCU read
 389  * locked.  If the pool needs to be used beyond the locking in effect, the
 390  * caller is responsible for guaranteeing that the pool stays online.
 391  *
 392  * The if/else clause exists only for the lockdep assertion and can be
 393  * ignored.
 394  */
 395 #define for_each_pool(pool, pi)                                         \
 396         idr_for_each_entry(&worker_pool_idr, pool, pi)                  \
 397                 if (({ assert_rcu_or_pool_mutex(); false; })) { }       \
 398                 else
 399 
 400 /**
 401  * for_each_pool_worker - iterate through all workers of a worker_pool
 402  * @worker: iteration cursor
 403  * @pool: worker_pool to iterate workers of
 404  *
 405  * This must be called with wq_pool_attach_mutex.
 406  *
 407  * The if/else clause exists only for the lockdep assertion and can be
 408  * ignored.
 409  */
 410 #define for_each_pool_worker(worker, pool)                              \
 411         list_for_each_entry((worker), &(pool)->workers, node)           \
 412                 if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
 413                 else
 414 
 415 /**
 416  * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
 417  * @pwq: iteration cursor
 418  * @wq: the target workqueue
 419  *
 420  * This must be called either with wq->mutex held or RCU read locked.
 421  * If the pwq needs to be used beyond the locking in effect, the caller is
 422  * responsible for guaranteeing that the pwq stays online.
 423  *
 424  * The if/else clause exists only for the lockdep assertion and can be
 425  * ignored.
 426  */
 427 #define for_each_pwq(pwq, wq)                                           \
 428         list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node,          \
 429                                 lockdep_is_held(&wq->mutex))            \
 430                 if (({ assert_rcu_or_wq_mutex(wq); false; })) { }       \
 431                 else
 432 
 433 #ifdef CONFIG_DEBUG_OBJECTS_WORK
 434 
 435 static struct debug_obj_descr work_debug_descr;
 436 
 437 static void *work_debug_hint(void *addr)
 438 {
 439         return ((struct work_struct *) addr)->func;
 440 }
 441 
 442 static bool work_is_static_object(void *addr)
 443 {
 444         struct work_struct *work = addr;
 445 
 446         return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
 447 }
 448 
 449 /*
 450  * fixup_init is called when:
 451  * - an active object is initialized
 452  */
 453 static bool work_fixup_init(void *addr, enum debug_obj_state state)
 454 {
 455         struct work_struct *work = addr;
 456 
 457         switch (state) {
 458         case ODEBUG_STATE_ACTIVE:
 459                 cancel_work_sync(work);
 460                 debug_object_init(work, &work_debug_descr);
 461                 return true;
 462         default:
 463                 return false;
 464         }
 465 }
 466 
 467 /*
 468  * fixup_free is called when:
 469  * - an active object is freed
 470  */
 471 static bool work_fixup_free(void *addr, enum debug_obj_state state)
 472 {
 473         struct work_struct *work = addr;
 474 
 475         switch (state) {
 476         case ODEBUG_STATE_ACTIVE:
 477                 cancel_work_sync(work);
 478                 debug_object_free(work, &work_debug_descr);
 479                 return true;
 480         default:
 481                 return false;
 482         }
 483 }
 484 
 485 static struct debug_obj_descr work_debug_descr = {
 486         .name           = "work_struct",
 487         .debug_hint     = work_debug_hint,
 488         .is_static_object = work_is_static_object,
 489         .fixup_init     = work_fixup_init,
 490         .fixup_free     = work_fixup_free,
 491 };
 492 
 493 static inline void debug_work_activate(struct work_struct *work)
 494 {
 495         debug_object_activate(work, &work_debug_descr);
 496 }
 497 
 498 static inline void debug_work_deactivate(struct work_struct *work)
 499 {
 500         debug_object_deactivate(work, &work_debug_descr);
 501 }
 502 
 503 void __init_work(struct work_struct *work, int onstack)
 504 {
 505         if (onstack)
 506                 debug_object_init_on_stack(work, &work_debug_descr);
 507         else
 508                 debug_object_init(work, &work_debug_descr);
 509 }
 510 EXPORT_SYMBOL_GPL(__init_work);
 511 
 512 void destroy_work_on_stack(struct work_struct *work)
 513 {
 514         debug_object_free(work, &work_debug_descr);
 515 }
 516 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
 517 
 518 void destroy_delayed_work_on_stack(struct delayed_work *work)
 519 {
 520         destroy_timer_on_stack(&work->timer);
 521         debug_object_free(&work->work, &work_debug_descr);
 522 }
 523 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
 524 
 525 #else
 526 static inline void debug_work_activate(struct work_struct *work) { }
 527 static inline void debug_work_deactivate(struct work_struct *work) { }
 528 #endif
 529 
 530 /**
 531  * worker_pool_assign_id - allocate ID and assing it to @pool
 532  * @pool: the pool pointer of interest
 533  *
 534  * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
 535  * successfully, -errno on failure.
 536  */
 537 static int worker_pool_assign_id(struct worker_pool *pool)
 538 {
 539         int ret;
 540 
 541         lockdep_assert_held(&wq_pool_mutex);
 542 
 543         ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
 544                         GFP_KERNEL);
 545         if (ret >= 0) {
 546                 pool->id = ret;
 547                 return 0;
 548         }
 549         return ret;
 550 }
 551 
 552 /**
 553  * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
 554  * @wq: the target workqueue
 555  * @node: the node ID
 556  *
 557  * This must be called with any of wq_pool_mutex, wq->mutex or RCU
 558  * read locked.
 559  * If the pwq needs to be used beyond the locking in effect, the caller is
 560  * responsible for guaranteeing that the pwq stays online.
 561  *
 562  * Return: The unbound pool_workqueue for @node.
 563  */
 564 static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
 565                                                   int node)
 566 {
 567         assert_rcu_or_wq_mutex_or_pool_mutex(wq);
 568 
 569         /*
 570          * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
 571          * delayed item is pending.  The plan is to keep CPU -> NODE
 572          * mapping valid and stable across CPU on/offlines.  Once that
 573          * happens, this workaround can be removed.
 574          */
 575         if (unlikely(node == NUMA_NO_NODE))
 576                 return wq->dfl_pwq;
 577 
 578         return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
 579 }
 580 
 581 static unsigned int work_color_to_flags(int color)
 582 {
 583         return color << WORK_STRUCT_COLOR_SHIFT;
 584 }
 585 
 586 static int get_work_color(struct work_struct *work)
 587 {
 588         return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
 589                 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
 590 }
 591 
 592 static int work_next_color(int color)
 593 {
 594         return (color + 1) % WORK_NR_COLORS;
 595 }
 596 
 597 /*
 598  * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
 599  * contain the pointer to the queued pwq.  Once execution starts, the flag
 600  * is cleared and the high bits contain OFFQ flags and pool ID.
 601  *
 602  * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
 603  * and clear_work_data() can be used to set the pwq, pool or clear
 604  * work->data.  These functions should only be called while the work is
 605  * owned - ie. while the PENDING bit is set.
 606  *
 607  * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
 608  * corresponding to a work.  Pool is available once the work has been
 609  * queued anywhere after initialization until it is sync canceled.  pwq is
 610  * available only while the work item is queued.
 611  *
 612  * %WORK_OFFQ_CANCELING is used to mark a work item which is being
 613  * canceled.  While being canceled, a work item may have its PENDING set
 614  * but stay off timer and worklist for arbitrarily long and nobody should
 615  * try to steal the PENDING bit.
 616  */
 617 static inline void set_work_data(struct work_struct *work, unsigned long data,
 618                                  unsigned long flags)
 619 {
 620         WARN_ON_ONCE(!work_pending(work));
 621         atomic_long_set(&work->data, data | flags | work_static(work));
 622 }
 623 
 624 static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
 625                          unsigned long extra_flags)
 626 {
 627         set_work_data(work, (unsigned long)pwq,
 628                       WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
 629 }
 630 
 631 static void set_work_pool_and_keep_pending(struct work_struct *work,
 632                                            int pool_id)
 633 {
 634         set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
 635                       WORK_STRUCT_PENDING);
 636 }
 637 
 638 static void set_work_pool_and_clear_pending(struct work_struct *work,
 639                                             int pool_id)
 640 {
 641         /*
 642          * The following wmb is paired with the implied mb in
 643          * test_and_set_bit(PENDING) and ensures all updates to @work made
 644          * here are visible to and precede any updates by the next PENDING
 645          * owner.
 646          */
 647         smp_wmb();
 648         set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
 649         /*
 650          * The following mb guarantees that previous clear of a PENDING bit
 651          * will not be reordered with any speculative LOADS or STORES from
 652          * work->current_func, which is executed afterwards.  This possible
 653          * reordering can lead to a missed execution on attempt to queue
 654          * the same @work.  E.g. consider this case:
 655          *
 656          *   CPU#0                         CPU#1
 657          *   ----------------------------  --------------------------------
 658          *
 659          * 1  STORE event_indicated
 660          * 2  queue_work_on() {
 661          * 3    test_and_set_bit(PENDING)
 662          * 4 }                             set_..._and_clear_pending() {
 663          * 5                                 set_work_data() # clear bit
 664          * 6                                 smp_mb()
 665          * 7                               work->current_func() {
 666          * 8                                  LOAD event_indicated
 667          *                                 }
 668          *
 669          * Without an explicit full barrier speculative LOAD on line 8 can
 670          * be executed before CPU#0 does STORE on line 1.  If that happens,
 671          * CPU#0 observes the PENDING bit is still set and new execution of
 672          * a @work is not queued in a hope, that CPU#1 will eventually
 673          * finish the queued @work.  Meanwhile CPU#1 does not see
 674          * event_indicated is set, because speculative LOAD was executed
 675          * before actual STORE.
 676          */
 677         smp_mb();
 678 }
 679 
 680 static void clear_work_data(struct work_struct *work)
 681 {
 682         smp_wmb();      /* see set_work_pool_and_clear_pending() */
 683         set_work_data(work, WORK_STRUCT_NO_POOL, 0);
 684 }
 685 
 686 static struct pool_workqueue *get_work_pwq(struct work_struct *work)
 687 {
 688         unsigned long data = atomic_long_read(&work->data);
 689 
 690         if (data & WORK_STRUCT_PWQ)
 691                 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
 692         else
 693                 return NULL;
 694 }
 695 
 696 /**
 697  * get_work_pool - return the worker_pool a given work was associated with
 698  * @work: the work item of interest
 699  *
 700  * Pools are created and destroyed under wq_pool_mutex, and allows read
 701  * access under RCU read lock.  As such, this function should be
 702  * called under wq_pool_mutex or inside of a rcu_read_lock() region.
 703  *
 704  * All fields of the returned pool are accessible as long as the above
 705  * mentioned locking is in effect.  If the returned pool needs to be used
 706  * beyond the critical section, the caller is responsible for ensuring the
 707  * returned pool is and stays online.
 708  *
 709  * Return: The worker_pool @work was last associated with.  %NULL if none.
 710  */
 711 static struct worker_pool *get_work_pool(struct work_struct *work)
 712 {
 713         unsigned long data = atomic_long_read(&work->data);
 714         int pool_id;
 715 
 716         assert_rcu_or_pool_mutex();
 717 
 718         if (data & WORK_STRUCT_PWQ)
 719                 return ((struct pool_workqueue *)
 720                         (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
 721 
 722         pool_id = data >> WORK_OFFQ_POOL_SHIFT;
 723         if (pool_id == WORK_OFFQ_POOL_NONE)
 724                 return NULL;
 725 
 726         return idr_find(&worker_pool_idr, pool_id);
 727 }
 728 
 729 /**
 730  * get_work_pool_id - return the worker pool ID a given work is associated with
 731  * @work: the work item of interest
 732  *
 733  * Return: The worker_pool ID @work was last associated with.
 734  * %WORK_OFFQ_POOL_NONE if none.
 735  */
 736 static int get_work_pool_id(struct work_struct *work)
 737 {
 738         unsigned long data = atomic_long_read(&work->data);
 739 
 740         if (data & WORK_STRUCT_PWQ)
 741                 return ((struct pool_workqueue *)
 742                         (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
 743 
 744         return data >> WORK_OFFQ_POOL_SHIFT;
 745 }
 746 
 747 static void mark_work_canceling(struct work_struct *work)
 748 {
 749         unsigned long pool_id = get_work_pool_id(work);
 750 
 751         pool_id <<= WORK_OFFQ_POOL_SHIFT;
 752         set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
 753 }
 754 
 755 static bool work_is_canceling(struct work_struct *work)
 756 {
 757         unsigned long data = atomic_long_read(&work->data);
 758 
 759         return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
 760 }
 761 
 762 /*
 763  * Policy functions.  These define the policies on how the global worker
 764  * pools are managed.  Unless noted otherwise, these functions assume that
 765  * they're being called with pool->lock held.
 766  */
 767 
 768 static bool __need_more_worker(struct worker_pool *pool)
 769 {
 770         return !atomic_read(&pool->nr_running);
 771 }
 772 
 773 /*
 774  * Need to wake up a worker?  Called from anything but currently
 775  * running workers.
 776  *
 777  * Note that, because unbound workers never contribute to nr_running, this
 778  * function will always return %true for unbound pools as long as the
 779  * worklist isn't empty.
 780  */
 781 static bool need_more_worker(struct worker_pool *pool)
 782 {
 783         return !list_empty(&pool->worklist) && __need_more_worker(pool);
 784 }
 785 
 786 /* Can I start working?  Called from busy but !running workers. */
 787 static bool may_start_working(struct worker_pool *pool)
 788 {
 789         return pool->nr_idle;
 790 }
 791 
 792 /* Do I need to keep working?  Called from currently running workers. */
 793 static bool keep_working(struct worker_pool *pool)
 794 {
 795         return !list_empty(&pool->worklist) &&
 796                 atomic_read(&pool->nr_running) <= 1;
 797 }
 798 
 799 /* Do we need a new worker?  Called from manager. */
 800 static bool need_to_create_worker(struct worker_pool *pool)
 801 {
 802         return need_more_worker(pool) && !may_start_working(pool);
 803 }
 804 
 805 /* Do we have too many workers and should some go away? */
 806 static bool too_many_workers(struct worker_pool *pool)
 807 {
 808         bool managing = pool->flags & POOL_MANAGER_ACTIVE;
 809         int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
 810         int nr_busy = pool->nr_workers - nr_idle;
 811 
 812         return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
 813 }
 814 
 815 /*
 816  * Wake up functions.
 817  */
 818 
 819 /* Return the first idle worker.  Safe with preemption disabled */
 820 static struct worker *first_idle_worker(struct worker_pool *pool)
 821 {
 822         if (unlikely(list_empty(&pool->idle_list)))
 823                 return NULL;
 824 
 825         return list_first_entry(&pool->idle_list, struct worker, entry);
 826 }
 827 
 828 /**
 829  * wake_up_worker - wake up an idle worker
 830  * @pool: worker pool to wake worker from
 831  *
 832  * Wake up the first idle worker of @pool.
 833  *
 834  * CONTEXT:
 835  * spin_lock_irq(pool->lock).
 836  */
 837 static void wake_up_worker(struct worker_pool *pool)
 838 {
 839         struct worker *worker = first_idle_worker(pool);
 840 
 841         if (likely(worker))
 842                 wake_up_process(worker->task);
 843 }
 844 
 845 /**
 846  * wq_worker_running - a worker is running again
 847  * @task: task waking up
 848  *
 849  * This function is called when a worker returns from schedule()
 850  */
 851 void wq_worker_running(struct task_struct *task)
 852 {
 853         struct worker *worker = kthread_data(task);
 854 
 855         if (!worker->sleeping)
 856                 return;
 857         if (!(worker->flags & WORKER_NOT_RUNNING))
 858                 atomic_inc(&worker->pool->nr_running);
 859         worker->sleeping = 0;
 860 }
 861 
 862 /**
 863  * wq_worker_sleeping - a worker is going to sleep
 864  * @task: task going to sleep
 865  *
 866  * This function is called from schedule() when a busy worker is
 867  * going to sleep.
 868  */
 869 void wq_worker_sleeping(struct task_struct *task)
 870 {
 871         struct worker *next, *worker = kthread_data(task);
 872         struct worker_pool *pool;
 873 
 874         /*
 875          * Rescuers, which may not have all the fields set up like normal
 876          * workers, also reach here, let's not access anything before
 877          * checking NOT_RUNNING.
 878          */
 879         if (worker->flags & WORKER_NOT_RUNNING)
 880                 return;
 881 
 882         pool = worker->pool;
 883 
 884         if (WARN_ON_ONCE(worker->sleeping))
 885                 return;
 886 
 887         worker->sleeping = 1;
 888         spin_lock_irq(&pool->lock);
 889 
 890         /*
 891          * The counterpart of the following dec_and_test, implied mb,
 892          * worklist not empty test sequence is in insert_work().
 893          * Please read comment there.
 894          *
 895          * NOT_RUNNING is clear.  This means that we're bound to and
 896          * running on the local cpu w/ rq lock held and preemption
 897          * disabled, which in turn means that none else could be
 898          * manipulating idle_list, so dereferencing idle_list without pool
 899          * lock is safe.
 900          */
 901         if (atomic_dec_and_test(&pool->nr_running) &&
 902             !list_empty(&pool->worklist)) {
 903                 next = first_idle_worker(pool);
 904                 if (next)
 905                         wake_up_process(next->task);
 906         }
 907         spin_unlock_irq(&pool->lock);
 908 }
 909 
 910 /**
 911  * wq_worker_last_func - retrieve worker's last work function
 912  * @task: Task to retrieve last work function of.
 913  *
 914  * Determine the last function a worker executed. This is called from
 915  * the scheduler to get a worker's last known identity.
 916  *
 917  * CONTEXT:
 918  * spin_lock_irq(rq->lock)
 919  *
 920  * This function is called during schedule() when a kworker is going
 921  * to sleep. It's used by psi to identify aggregation workers during
 922  * dequeuing, to allow periodic aggregation to shut-off when that
 923  * worker is the last task in the system or cgroup to go to sleep.
 924  *
 925  * As this function doesn't involve any workqueue-related locking, it
 926  * only returns stable values when called from inside the scheduler's
 927  * queuing and dequeuing paths, when @task, which must be a kworker,
 928  * is guaranteed to not be processing any works.
 929  *
 930  * Return:
 931  * The last work function %current executed as a worker, NULL if it
 932  * hasn't executed any work yet.
 933  */
 934 work_func_t wq_worker_last_func(struct task_struct *task)
 935 {
 936         struct worker *worker = kthread_data(task);
 937 
 938         return worker->last_func;
 939 }
 940 
 941 /**
 942  * worker_set_flags - set worker flags and adjust nr_running accordingly
 943  * @worker: self
 944  * @flags: flags to set
 945  *
 946  * Set @flags in @worker->flags and adjust nr_running accordingly.
 947  *
 948  * CONTEXT:
 949  * spin_lock_irq(pool->lock)
 950  */
 951 static inline void worker_set_flags(struct worker *worker, unsigned int flags)
 952 {
 953         struct worker_pool *pool = worker->pool;
 954 
 955         WARN_ON_ONCE(worker->task != current);
 956 
 957         /* If transitioning into NOT_RUNNING, adjust nr_running. */
 958         if ((flags & WORKER_NOT_RUNNING) &&
 959             !(worker->flags & WORKER_NOT_RUNNING)) {
 960                 atomic_dec(&pool->nr_running);
 961         }
 962 
 963         worker->flags |= flags;
 964 }
 965 
 966 /**
 967  * worker_clr_flags - clear worker flags and adjust nr_running accordingly
 968  * @worker: self
 969  * @flags: flags to clear
 970  *
 971  * Clear @flags in @worker->flags and adjust nr_running accordingly.
 972  *
 973  * CONTEXT:
 974  * spin_lock_irq(pool->lock)
 975  */
 976 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
 977 {
 978         struct worker_pool *pool = worker->pool;
 979         unsigned int oflags = worker->flags;
 980 
 981         WARN_ON_ONCE(worker->task != current);
 982 
 983         worker->flags &= ~flags;
 984 
 985         /*
 986          * If transitioning out of NOT_RUNNING, increment nr_running.  Note
 987          * that the nested NOT_RUNNING is not a noop.  NOT_RUNNING is mask
 988          * of multiple flags, not a single flag.
 989          */
 990         if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
 991                 if (!(worker->flags & WORKER_NOT_RUNNING))
 992                         atomic_inc(&pool->nr_running);
 993 }
 994 
 995 /**
 996  * find_worker_executing_work - find worker which is executing a work
 997  * @pool: pool of interest
 998  * @work: work to find worker for
 999  *
1000  * Find a worker which is executing @work on @pool by searching
1001  * @pool->busy_hash which is keyed by the address of @work.  For a worker
1002  * to match, its current execution should match the address of @work and
1003  * its work function.  This is to avoid unwanted dependency between
1004  * unrelated work executions through a work item being recycled while still
1005  * being executed.
1006  *
1007  * This is a bit tricky.  A work item may be freed once its execution
1008  * starts and nothing prevents the freed area from being recycled for
1009  * another work item.  If the same work item address ends up being reused
1010  * before the original execution finishes, workqueue will identify the
1011  * recycled work item as currently executing and make it wait until the
1012  * current execution finishes, introducing an unwanted dependency.
1013  *
1014  * This function checks the work item address and work function to avoid
1015  * false positives.  Note that this isn't complete as one may construct a
1016  * work function which can introduce dependency onto itself through a
1017  * recycled work item.  Well, if somebody wants to shoot oneself in the
1018  * foot that badly, there's only so much we can do, and if such deadlock
1019  * actually occurs, it should be easy to locate the culprit work function.
1020  *
1021  * CONTEXT:
1022  * spin_lock_irq(pool->lock).
1023  *
1024  * Return:
1025  * Pointer to worker which is executing @work if found, %NULL
1026  * otherwise.
1027  */
1028 static struct worker *find_worker_executing_work(struct worker_pool *pool,
1029                                                  struct work_struct *work)
1030 {
1031         struct worker *worker;
1032 
1033         hash_for_each_possible(pool->busy_hash, worker, hentry,
1034                                (unsigned long)work)
1035                 if (worker->current_work == work &&
1036                     worker->current_func == work->func)
1037                         return worker;
1038 
1039         return NULL;
1040 }
1041 
1042 /**
1043  * move_linked_works - move linked works to a list
1044  * @work: start of series of works to be scheduled
1045  * @head: target list to append @work to
1046  * @nextp: out parameter for nested worklist walking
1047  *
1048  * Schedule linked works starting from @work to @head.  Work series to
1049  * be scheduled starts at @work and includes any consecutive work with
1050  * WORK_STRUCT_LINKED set in its predecessor.
1051  *
1052  * If @nextp is not NULL, it's updated to point to the next work of
1053  * the last scheduled work.  This allows move_linked_works() to be
1054  * nested inside outer list_for_each_entry_safe().
1055  *
1056  * CONTEXT:
1057  * spin_lock_irq(pool->lock).
1058  */
1059 static void move_linked_works(struct work_struct *work, struct list_head *head,
1060                               struct work_struct **nextp)
1061 {
1062         struct work_struct *n;
1063 
1064         /*
1065          * Linked worklist will always end before the end of the list,
1066          * use NULL for list head.
1067          */
1068         list_for_each_entry_safe_from(work, n, NULL, entry) {
1069                 list_move_tail(&work->entry, head);
1070                 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1071                         break;
1072         }
1073 
1074         /*
1075          * If we're already inside safe list traversal and have moved
1076          * multiple works to the scheduled queue, the next position
1077          * needs to be updated.
1078          */
1079         if (nextp)
1080                 *nextp = n;
1081 }
1082 
1083 /**
1084  * get_pwq - get an extra reference on the specified pool_workqueue
1085  * @pwq: pool_workqueue to get
1086  *
1087  * Obtain an extra reference on @pwq.  The caller should guarantee that
1088  * @pwq has positive refcnt and be holding the matching pool->lock.
1089  */
1090 static void get_pwq(struct pool_workqueue *pwq)
1091 {
1092         lockdep_assert_held(&pwq->pool->lock);
1093         WARN_ON_ONCE(pwq->refcnt <= 0);
1094         pwq->refcnt++;
1095 }
1096 
1097 /**
1098  * put_pwq - put a pool_workqueue reference
1099  * @pwq: pool_workqueue to put
1100  *
1101  * Drop a reference of @pwq.  If its refcnt reaches zero, schedule its
1102  * destruction.  The caller should be holding the matching pool->lock.
1103  */
1104 static void put_pwq(struct pool_workqueue *pwq)
1105 {
1106         lockdep_assert_held(&pwq->pool->lock);
1107         if (likely(--pwq->refcnt))
1108                 return;
1109         if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1110                 return;
1111         /*
1112          * @pwq can't be released under pool->lock, bounce to
1113          * pwq_unbound_release_workfn().  This never recurses on the same
1114          * pool->lock as this path is taken only for unbound workqueues and
1115          * the release work item is scheduled on a per-cpu workqueue.  To
1116          * avoid lockdep warning, unbound pool->locks are given lockdep
1117          * subclass of 1 in get_unbound_pool().
1118          */
1119         schedule_work(&pwq->unbound_release_work);
1120 }
1121 
1122 /**
1123  * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1124  * @pwq: pool_workqueue to put (can be %NULL)
1125  *
1126  * put_pwq() with locking.  This function also allows %NULL @pwq.
1127  */
1128 static void put_pwq_unlocked(struct pool_workqueue *pwq)
1129 {
1130         if (pwq) {
1131                 /*
1132                  * As both pwqs and pools are RCU protected, the
1133                  * following lock operations are safe.
1134                  */
1135                 spin_lock_irq(&pwq->pool->lock);
1136                 put_pwq(pwq);
1137                 spin_unlock_irq(&pwq->pool->lock);
1138         }
1139 }
1140 
1141 static void pwq_activate_delayed_work(struct work_struct *work)
1142 {
1143         struct pool_workqueue *pwq = get_work_pwq(work);
1144 
1145         trace_workqueue_activate_work(work);
1146         if (list_empty(&pwq->pool->worklist))
1147                 pwq->pool->watchdog_ts = jiffies;
1148         move_linked_works(work, &pwq->pool->worklist, NULL);
1149         __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1150         pwq->nr_active++;
1151 }
1152 
1153 static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1154 {
1155         struct work_struct *work = list_first_entry(&pwq->delayed_works,
1156                                                     struct work_struct, entry);
1157 
1158         pwq_activate_delayed_work(work);
1159 }
1160 
1161 /**
1162  * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1163  * @pwq: pwq of interest
1164  * @color: color of work which left the queue
1165  *
1166  * A work either has completed or is removed from pending queue,
1167  * decrement nr_in_flight of its pwq and handle workqueue flushing.
1168  *
1169  * CONTEXT:
1170  * spin_lock_irq(pool->lock).
1171  */
1172 static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1173 {
1174         /* uncolored work items don't participate in flushing or nr_active */
1175         if (color == WORK_NO_COLOR)
1176                 goto out_put;
1177 
1178         pwq->nr_in_flight[color]--;
1179 
1180         pwq->nr_active--;
1181         if (!list_empty(&pwq->delayed_works)) {
1182                 /* one down, submit a delayed one */
1183                 if (pwq->nr_active < pwq->max_active)
1184                         pwq_activate_first_delayed(pwq);
1185         }
1186 
1187         /* is flush in progress and are we at the flushing tip? */
1188         if (likely(pwq->flush_color != color))
1189                 goto out_put;
1190 
1191         /* are there still in-flight works? */
1192         if (pwq->nr_in_flight[color])
1193                 goto out_put;
1194 
1195         /* this pwq is done, clear flush_color */
1196         pwq->flush_color = -1;
1197 
1198         /*
1199          * If this was the last pwq, wake up the first flusher.  It
1200          * will handle the rest.
1201          */
1202         if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1203                 complete(&pwq->wq->first_flusher->done);
1204 out_put:
1205         put_pwq(pwq);
1206 }
1207 
1208 /**
1209  * try_to_grab_pending - steal work item from worklist and disable irq
1210  * @work: work item to steal
1211  * @is_dwork: @work is a delayed_work
1212  * @flags: place to store irq state
1213  *
1214  * Try to grab PENDING bit of @work.  This function can handle @work in any
1215  * stable state - idle, on timer or on worklist.
1216  *
1217  * Return:
1218  *  1           if @work was pending and we successfully stole PENDING
1219  *  0           if @work was idle and we claimed PENDING
1220  *  -EAGAIN     if PENDING couldn't be grabbed at the moment, safe to busy-retry
1221  *  -ENOENT     if someone else is canceling @work, this state may persist
1222  *              for arbitrarily long
1223  *
1224  * Note:
1225  * On >= 0 return, the caller owns @work's PENDING bit.  To avoid getting
1226  * interrupted while holding PENDING and @work off queue, irq must be
1227  * disabled on entry.  This, combined with delayed_work->timer being
1228  * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1229  *
1230  * On successful return, >= 0, irq is disabled and the caller is
1231  * responsible for releasing it using local_irq_restore(*@flags).
1232  *
1233  * This function is safe to call from any context including IRQ handler.
1234  */
1235 static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1236                                unsigned long *flags)
1237 {
1238         struct worker_pool *pool;
1239         struct pool_workqueue *pwq;
1240 
1241         local_irq_save(*flags);
1242 
1243         /* try to steal the timer if it exists */
1244         if (is_dwork) {
1245                 struct delayed_work *dwork = to_delayed_work(work);
1246 
1247                 /*
1248                  * dwork->timer is irqsafe.  If del_timer() fails, it's
1249                  * guaranteed that the timer is not queued anywhere and not
1250                  * running on the local CPU.
1251                  */
1252                 if (likely(del_timer(&dwork->timer)))
1253                         return 1;
1254         }
1255 
1256         /* try to claim PENDING the normal way */
1257         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1258                 return 0;
1259 
1260         rcu_read_lock();
1261         /*
1262          * The queueing is in progress, or it is already queued. Try to
1263          * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1264          */
1265         pool = get_work_pool(work);
1266         if (!pool)
1267                 goto fail;
1268 
1269         spin_lock(&pool->lock);
1270         /*
1271          * work->data is guaranteed to point to pwq only while the work
1272          * item is queued on pwq->wq, and both updating work->data to point
1273          * to pwq on queueing and to pool on dequeueing are done under
1274          * pwq->pool->lock.  This in turn guarantees that, if work->data
1275          * points to pwq which is associated with a locked pool, the work
1276          * item is currently queued on that pool.
1277          */
1278         pwq = get_work_pwq(work);
1279         if (pwq && pwq->pool == pool) {
1280                 debug_work_deactivate(work);
1281 
1282                 /*
1283                  * A delayed work item cannot be grabbed directly because
1284                  * it might have linked NO_COLOR work items which, if left
1285                  * on the delayed_list, will confuse pwq->nr_active
1286                  * management later on and cause stall.  Make sure the work
1287                  * item is activated before grabbing.
1288                  */
1289                 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1290                         pwq_activate_delayed_work(work);
1291 
1292                 list_del_init(&work->entry);
1293                 pwq_dec_nr_in_flight(pwq, get_work_color(work));
1294 
1295                 /* work->data points to pwq iff queued, point to pool */
1296                 set_work_pool_and_keep_pending(work, pool->id);
1297 
1298                 spin_unlock(&pool->lock);
1299                 rcu_read_unlock();
1300                 return 1;
1301         }
1302         spin_unlock(&pool->lock);
1303 fail:
1304         rcu_read_unlock();
1305         local_irq_restore(*flags);
1306         if (work_is_canceling(work))
1307                 return -ENOENT;
1308         cpu_relax();
1309         return -EAGAIN;
1310 }
1311 
1312 /**
1313  * insert_work - insert a work into a pool
1314  * @pwq: pwq @work belongs to
1315  * @work: work to insert
1316  * @head: insertion point
1317  * @extra_flags: extra WORK_STRUCT_* flags to set
1318  *
1319  * Insert @work which belongs to @pwq after @head.  @extra_flags is or'd to
1320  * work_struct flags.
1321  *
1322  * CONTEXT:
1323  * spin_lock_irq(pool->lock).
1324  */
1325 static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1326                         struct list_head *head, unsigned int extra_flags)
1327 {
1328         struct worker_pool *pool = pwq->pool;
1329 
1330         /* we own @work, set data and link */
1331         set_work_pwq(work, pwq, extra_flags);
1332         list_add_tail(&work->entry, head);
1333         get_pwq(pwq);
1334 
1335         /*
1336          * Ensure either wq_worker_sleeping() sees the above
1337          * list_add_tail() or we see zero nr_running to avoid workers lying
1338          * around lazily while there are works to be processed.
1339          */
1340         smp_mb();
1341 
1342         if (__need_more_worker(pool))
1343                 wake_up_worker(pool);
1344 }
1345 
1346 /*
1347  * Test whether @work is being queued from another work executing on the
1348  * same workqueue.
1349  */
1350 static bool is_chained_work(struct workqueue_struct *wq)
1351 {
1352         struct worker *worker;
1353 
1354         worker = current_wq_worker();
1355         /*
1356          * Return %true iff I'm a worker executing a work item on @wq.  If
1357          * I'm @worker, it's safe to dereference it without locking.
1358          */
1359         return worker && worker->current_pwq->wq == wq;
1360 }
1361 
1362 /*
1363  * When queueing an unbound work item to a wq, prefer local CPU if allowed
1364  * by wq_unbound_cpumask.  Otherwise, round robin among the allowed ones to
1365  * avoid perturbing sensitive tasks.
1366  */
1367 static int wq_select_unbound_cpu(int cpu)
1368 {
1369         static bool printed_dbg_warning;
1370         int new_cpu;
1371 
1372         if (likely(!wq_debug_force_rr_cpu)) {
1373                 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1374                         return cpu;
1375         } else if (!printed_dbg_warning) {
1376                 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1377                 printed_dbg_warning = true;
1378         }
1379 
1380         if (cpumask_empty(wq_unbound_cpumask))
1381                 return cpu;
1382 
1383         new_cpu = __this_cpu_read(wq_rr_cpu_last);
1384         new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1385         if (unlikely(new_cpu >= nr_cpu_ids)) {
1386                 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1387                 if (unlikely(new_cpu >= nr_cpu_ids))
1388                         return cpu;
1389         }
1390         __this_cpu_write(wq_rr_cpu_last, new_cpu);
1391 
1392         return new_cpu;
1393 }
1394 
1395 static void __queue_work(int cpu, struct workqueue_struct *wq,
1396                          struct work_struct *work)
1397 {
1398         struct pool_workqueue *pwq;
1399         struct worker_pool *last_pool;
1400         struct list_head *worklist;
1401         unsigned int work_flags;
1402         unsigned int req_cpu = cpu;
1403 
1404         /*
1405          * While a work item is PENDING && off queue, a task trying to
1406          * steal the PENDING will busy-loop waiting for it to either get
1407          * queued or lose PENDING.  Grabbing PENDING and queueing should
1408          * happen with IRQ disabled.
1409          */
1410         lockdep_assert_irqs_disabled();
1411 
1412         debug_work_activate(work);
1413 
1414         /* if draining, only works from the same workqueue are allowed */
1415         if (unlikely(wq->flags & __WQ_DRAINING) &&
1416             WARN_ON_ONCE(!is_chained_work(wq)))
1417                 return;
1418         rcu_read_lock();
1419 retry:
1420         /* pwq which will be used unless @work is executing elsewhere */
1421         if (wq->flags & WQ_UNBOUND) {
1422                 if (req_cpu == WORK_CPU_UNBOUND)
1423                         cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1424                 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1425         } else {
1426                 if (req_cpu == WORK_CPU_UNBOUND)
1427                         cpu = raw_smp_processor_id();
1428                 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1429         }
1430 
1431         /*
1432          * If @work was previously on a different pool, it might still be
1433          * running there, in which case the work needs to be queued on that
1434          * pool to guarantee non-reentrancy.
1435          */
1436         last_pool = get_work_pool(work);
1437         if (last_pool && last_pool != pwq->pool) {
1438                 struct worker *worker;
1439 
1440                 spin_lock(&last_pool->lock);
1441 
1442                 worker = find_worker_executing_work(last_pool, work);
1443 
1444                 if (worker && worker->current_pwq->wq == wq) {
1445                         pwq = worker->current_pwq;
1446                 } else {
1447                         /* meh... not running there, queue here */
1448                         spin_unlock(&last_pool->lock);
1449                         spin_lock(&pwq->pool->lock);
1450                 }
1451         } else {
1452                 spin_lock(&pwq->pool->lock);
1453         }
1454 
1455         /*
1456          * pwq is determined and locked.  For unbound pools, we could have
1457          * raced with pwq release and it could already be dead.  If its
1458          * refcnt is zero, repeat pwq selection.  Note that pwqs never die
1459          * without another pwq replacing it in the numa_pwq_tbl or while
1460          * work items are executing on it, so the retrying is guaranteed to
1461          * make forward-progress.
1462          */
1463         if (unlikely(!pwq->refcnt)) {
1464                 if (wq->flags & WQ_UNBOUND) {
1465                         spin_unlock(&pwq->pool->lock);
1466                         cpu_relax();
1467                         goto retry;
1468                 }
1469                 /* oops */
1470                 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1471                           wq->name, cpu);
1472         }
1473 
1474         /* pwq determined, queue */
1475         trace_workqueue_queue_work(req_cpu, pwq, work);
1476 
1477         if (WARN_ON(!list_empty(&work->entry)))
1478                 goto out;
1479 
1480         pwq->nr_in_flight[pwq->work_color]++;
1481         work_flags = work_color_to_flags(pwq->work_color);
1482 
1483         if (likely(pwq->nr_active < pwq->max_active)) {
1484                 trace_workqueue_activate_work(work);
1485                 pwq->nr_active++;
1486                 worklist = &pwq->pool->worklist;
1487                 if (list_empty(worklist))
1488                         pwq->pool->watchdog_ts = jiffies;
1489         } else {
1490                 work_flags |= WORK_STRUCT_DELAYED;
1491                 worklist = &pwq->delayed_works;
1492         }
1493 
1494         insert_work(pwq, work, worklist, work_flags);
1495 
1496 out:
1497         spin_unlock(&pwq->pool->lock);
1498         rcu_read_unlock();
1499 }
1500 
1501 /**
1502  * queue_work_on - queue work on specific cpu
1503  * @cpu: CPU number to execute work on
1504  * @wq: workqueue to use
1505  * @work: work to queue
1506  *
1507  * We queue the work to a specific CPU, the caller must ensure it
1508  * can't go away.
1509  *
1510  * Return: %false if @work was already on a queue, %true otherwise.
1511  */
1512 bool queue_work_on(int cpu, struct workqueue_struct *wq,
1513                    struct work_struct *work)
1514 {
1515         bool ret = false;
1516         unsigned long flags;
1517 
1518         local_irq_save(flags);
1519 
1520         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1521                 __queue_work(cpu, wq, work);
1522                 ret = true;
1523         }
1524 
1525         local_irq_restore(flags);
1526         return ret;
1527 }
1528 EXPORT_SYMBOL(queue_work_on);
1529 
1530 /**
1531  * workqueue_select_cpu_near - Select a CPU based on NUMA node
1532  * @node: NUMA node ID that we want to select a CPU from
1533  *
1534  * This function will attempt to find a "random" cpu available on a given
1535  * node. If there are no CPUs available on the given node it will return
1536  * WORK_CPU_UNBOUND indicating that we should just schedule to any
1537  * available CPU if we need to schedule this work.
1538  */
1539 static int workqueue_select_cpu_near(int node)
1540 {
1541         int cpu;
1542 
1543         /* No point in doing this if NUMA isn't enabled for workqueues */
1544         if (!wq_numa_enabled)
1545                 return WORK_CPU_UNBOUND;
1546 
1547         /* Delay binding to CPU if node is not valid or online */
1548         if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
1549                 return WORK_CPU_UNBOUND;
1550 
1551         /* Use local node/cpu if we are already there */
1552         cpu = raw_smp_processor_id();
1553         if (node == cpu_to_node(cpu))
1554                 return cpu;
1555 
1556         /* Use "random" otherwise know as "first" online CPU of node */
1557         cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
1558 
1559         /* If CPU is valid return that, otherwise just defer */
1560         return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
1561 }
1562 
1563 /**
1564  * queue_work_node - queue work on a "random" cpu for a given NUMA node
1565  * @node: NUMA node that we are targeting the work for
1566  * @wq: workqueue to use
1567  * @work: work to queue
1568  *
1569  * We queue the work to a "random" CPU within a given NUMA node. The basic
1570  * idea here is to provide a way to somehow associate work with a given
1571  * NUMA node.
1572  *
1573  * This function will only make a best effort attempt at getting this onto
1574  * the right NUMA node. If no node is requested or the requested node is
1575  * offline then we just fall back to standard queue_work behavior.
1576  *
1577  * Currently the "random" CPU ends up being the first available CPU in the
1578  * intersection of cpu_online_mask and the cpumask of the node, unless we
1579  * are running on the node. In that case we just use the current CPU.
1580  *
1581  * Return: %false if @work was already on a queue, %true otherwise.
1582  */
1583 bool queue_work_node(int node, struct workqueue_struct *wq,
1584                      struct work_struct *work)
1585 {
1586         unsigned long flags;
1587         bool ret = false;
1588 
1589         /*
1590          * This current implementation is specific to unbound workqueues.
1591          * Specifically we only return the first available CPU for a given
1592          * node instead of cycling through individual CPUs within the node.
1593          *
1594          * If this is used with a per-cpu workqueue then the logic in
1595          * workqueue_select_cpu_near would need to be updated to allow for
1596          * some round robin type logic.
1597          */
1598         WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
1599 
1600         local_irq_save(flags);
1601 
1602         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1603                 int cpu = workqueue_select_cpu_near(node);
1604 
1605                 __queue_work(cpu, wq, work);
1606                 ret = true;
1607         }
1608 
1609         local_irq_restore(flags);
1610         return ret;
1611 }
1612 EXPORT_SYMBOL_GPL(queue_work_node);
1613 
1614 void delayed_work_timer_fn(struct timer_list *t)
1615 {
1616         struct delayed_work *dwork = from_timer(dwork, t, timer);
1617 
1618         /* should have been called from irqsafe timer with irq already off */
1619         __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1620 }
1621 EXPORT_SYMBOL(delayed_work_timer_fn);
1622 
1623 static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1624                                 struct delayed_work *dwork, unsigned long delay)
1625 {
1626         struct timer_list *timer = &dwork->timer;
1627         struct work_struct *work = &dwork->work;
1628 
1629         WARN_ON_ONCE(!wq);
1630         WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
1631         WARN_ON_ONCE(timer_pending(timer));
1632         WARN_ON_ONCE(!list_empty(&work->entry));
1633 
1634         /*
1635          * If @delay is 0, queue @dwork->work immediately.  This is for
1636          * both optimization and correctness.  The earliest @timer can
1637          * expire is on the closest next tick and delayed_work users depend
1638          * on that there's no such delay when @delay is 0.
1639          */
1640         if (!delay) {
1641                 __queue_work(cpu, wq, &dwork->work);
1642                 return;
1643         }
1644 
1645         dwork->wq = wq;
1646         dwork->cpu = cpu;
1647         timer->expires = jiffies + delay;
1648 
1649         if (unlikely(cpu != WORK_CPU_UNBOUND))
1650                 add_timer_on(timer, cpu);
1651         else
1652                 add_timer(timer);
1653 }
1654 
1655 /**
1656  * queue_delayed_work_on - queue work on specific CPU after delay
1657  * @cpu: CPU number to execute work on
1658  * @wq: workqueue to use
1659  * @dwork: work to queue
1660  * @delay: number of jiffies to wait before queueing
1661  *
1662  * Return: %false if @work was already on a queue, %true otherwise.  If
1663  * @delay is zero and @dwork is idle, it will be scheduled for immediate
1664  * execution.
1665  */
1666 bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1667                            struct delayed_work *dwork, unsigned long delay)
1668 {
1669         struct work_struct *work = &dwork->work;
1670         bool ret = false;
1671         unsigned long flags;
1672 
1673         /* read the comment in __queue_work() */
1674         local_irq_save(flags);
1675 
1676         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1677                 __queue_delayed_work(cpu, wq, dwork, delay);
1678                 ret = true;
1679         }
1680 
1681         local_irq_restore(flags);
1682         return ret;
1683 }
1684 EXPORT_SYMBOL(queue_delayed_work_on);
1685 
1686 /**
1687  * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1688  * @cpu: CPU number to execute work on
1689  * @wq: workqueue to use
1690  * @dwork: work to queue
1691  * @delay: number of jiffies to wait before queueing
1692  *
1693  * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1694  * modify @dwork's timer so that it expires after @delay.  If @delay is
1695  * zero, @work is guaranteed to be scheduled immediately regardless of its
1696  * current state.
1697  *
1698  * Return: %false if @dwork was idle and queued, %true if @dwork was
1699  * pending and its timer was modified.
1700  *
1701  * This function is safe to call from any context including IRQ handler.
1702  * See try_to_grab_pending() for details.
1703  */
1704 bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1705                          struct delayed_work *dwork, unsigned long delay)
1706 {
1707         unsigned long flags;
1708         int ret;
1709 
1710         do {
1711                 ret = try_to_grab_pending(&dwork->work, true, &flags);
1712         } while (unlikely(ret == -EAGAIN));
1713 
1714         if (likely(ret >= 0)) {
1715                 __queue_delayed_work(cpu, wq, dwork, delay);
1716                 local_irq_restore(flags);
1717         }
1718 
1719         /* -ENOENT from try_to_grab_pending() becomes %true */
1720         return ret;
1721 }
1722 EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1723 
1724 static void rcu_work_rcufn(struct rcu_head *rcu)
1725 {
1726         struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
1727 
1728         /* read the comment in __queue_work() */
1729         local_irq_disable();
1730         __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
1731         local_irq_enable();
1732 }
1733 
1734 /**
1735  * queue_rcu_work - queue work after a RCU grace period
1736  * @wq: workqueue to use
1737  * @rwork: work to queue
1738  *
1739  * Return: %false if @rwork was already pending, %true otherwise.  Note
1740  * that a full RCU grace period is guaranteed only after a %true return.
1741  * While @rwork is guaranteed to be executed after a %false return, the
1742  * execution may happen before a full RCU grace period has passed.
1743  */
1744 bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
1745 {
1746         struct work_struct *work = &rwork->work;
1747 
1748         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1749                 rwork->wq = wq;
1750                 call_rcu(&rwork->rcu, rcu_work_rcufn);
1751                 return true;
1752         }
1753 
1754         return false;
1755 }
1756 EXPORT_SYMBOL(queue_rcu_work);
1757 
1758 /**
1759  * worker_enter_idle - enter idle state
1760  * @worker: worker which is entering idle state
1761  *
1762  * @worker is entering idle state.  Update stats and idle timer if
1763  * necessary.
1764  *
1765  * LOCKING:
1766  * spin_lock_irq(pool->lock).
1767  */
1768 static void worker_enter_idle(struct worker *worker)
1769 {
1770         struct worker_pool *pool = worker->pool;
1771 
1772         if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1773             WARN_ON_ONCE(!list_empty(&worker->entry) &&
1774                          (worker->hentry.next || worker->hentry.pprev)))
1775                 return;
1776 
1777         /* can't use worker_set_flags(), also called from create_worker() */
1778         worker->flags |= WORKER_IDLE;
1779         pool->nr_idle++;
1780         worker->last_active = jiffies;
1781 
1782         /* idle_list is LIFO */
1783         list_add(&worker->entry, &pool->idle_list);
1784 
1785         if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1786                 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1787 
1788         /*
1789          * Sanity check nr_running.  Because unbind_workers() releases
1790          * pool->lock between setting %WORKER_UNBOUND and zapping
1791          * nr_running, the warning may trigger spuriously.  Check iff
1792          * unbind is not in progress.
1793          */
1794         WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1795                      pool->nr_workers == pool->nr_idle &&
1796                      atomic_read(&pool->nr_running));
1797 }
1798 
1799 /**
1800  * worker_leave_idle - leave idle state
1801  * @worker: worker which is leaving idle state
1802  *
1803  * @worker is leaving idle state.  Update stats.
1804  *
1805  * LOCKING:
1806  * spin_lock_irq(pool->lock).
1807  */
1808 static void worker_leave_idle(struct worker *worker)
1809 {
1810         struct worker_pool *pool = worker->pool;
1811 
1812         if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1813                 return;
1814         worker_clr_flags(worker, WORKER_IDLE);
1815         pool->nr_idle--;
1816         list_del_init(&worker->entry);
1817 }
1818 
1819 static struct worker *alloc_worker(int node)
1820 {
1821         struct worker *worker;
1822 
1823         worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1824         if (worker) {
1825                 INIT_LIST_HEAD(&worker->entry);
1826                 INIT_LIST_HEAD(&worker->scheduled);
1827                 INIT_LIST_HEAD(&worker->node);
1828                 /* on creation a worker is in !idle && prep state */
1829                 worker->flags = WORKER_PREP;
1830         }
1831         return worker;
1832 }
1833 
1834 /**
1835  * worker_attach_to_pool() - attach a worker to a pool
1836  * @worker: worker to be attached
1837  * @pool: the target pool
1838  *
1839  * Attach @worker to @pool.  Once attached, the %WORKER_UNBOUND flag and
1840  * cpu-binding of @worker are kept coordinated with the pool across
1841  * cpu-[un]hotplugs.
1842  */
1843 static void worker_attach_to_pool(struct worker *worker,
1844                                    struct worker_pool *pool)
1845 {
1846         mutex_lock(&wq_pool_attach_mutex);
1847 
1848         /*
1849          * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1850          * online CPUs.  It'll be re-applied when any of the CPUs come up.
1851          */
1852         set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1853 
1854         /*
1855          * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
1856          * stable across this function.  See the comments above the flag
1857          * definition for details.
1858          */
1859         if (pool->flags & POOL_DISASSOCIATED)
1860                 worker->flags |= WORKER_UNBOUND;
1861 
1862         list_add_tail(&worker->node, &pool->workers);
1863         worker->pool = pool;
1864 
1865         mutex_unlock(&wq_pool_attach_mutex);
1866 }
1867 
1868 /**
1869  * worker_detach_from_pool() - detach a worker from its pool
1870  * @worker: worker which is attached to its pool
1871  *
1872  * Undo the attaching which had been done in worker_attach_to_pool().  The
1873  * caller worker shouldn't access to the pool after detached except it has
1874  * other reference to the pool.
1875  */
1876 static void worker_detach_from_pool(struct worker *worker)
1877 {
1878         struct worker_pool *pool = worker->pool;
1879         struct completion *detach_completion = NULL;
1880 
1881         mutex_lock(&wq_pool_attach_mutex);
1882 
1883         list_del(&worker->node);
1884         worker->pool = NULL;
1885 
1886         if (list_empty(&pool->workers))
1887                 detach_completion = pool->detach_completion;
1888         mutex_unlock(&wq_pool_attach_mutex);
1889 
1890         /* clear leftover flags without pool->lock after it is detached */
1891         worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1892 
1893         if (detach_completion)
1894                 complete(detach_completion);
1895 }
1896 
1897 /**
1898  * create_worker - create a new workqueue worker
1899  * @pool: pool the new worker will belong to
1900  *
1901  * Create and start a new worker which is attached to @pool.
1902  *
1903  * CONTEXT:
1904  * Might sleep.  Does GFP_KERNEL allocations.
1905  *
1906  * Return:
1907  * Pointer to the newly created worker.
1908  */
1909 static struct worker *create_worker(struct worker_pool *pool)
1910 {
1911         struct worker *worker = NULL;
1912         int id = -1;
1913         char id_buf[16];
1914 
1915         /* ID is needed to determine kthread name */
1916         id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
1917         if (id < 0)
1918                 goto fail;
1919 
1920         worker = alloc_worker(pool->node);
1921         if (!worker)
1922                 goto fail;
1923 
1924         worker->id = id;
1925 
1926         if (pool->cpu >= 0)
1927                 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1928                          pool->attrs->nice < 0  ? "H" : "");
1929         else
1930                 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1931 
1932         worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1933                                               "kworker/%s", id_buf);
1934         if (IS_ERR(worker->task))
1935                 goto fail;
1936 
1937         set_user_nice(worker->task, pool->attrs->nice);
1938         kthread_bind_mask(worker->task, pool->attrs->cpumask);
1939 
1940         /* successful, attach the worker to the pool */
1941         worker_attach_to_pool(worker, pool);
1942 
1943         /* start the newly created worker */
1944         spin_lock_irq(&pool->lock);
1945         worker->pool->nr_workers++;
1946         worker_enter_idle(worker);
1947         wake_up_process(worker->task);
1948         spin_unlock_irq(&pool->lock);
1949 
1950         return worker;
1951 
1952 fail:
1953         if (id >= 0)
1954                 ida_simple_remove(&pool->worker_ida, id);
1955         kfree(worker);
1956         return NULL;
1957 }
1958 
1959 /**
1960  * destroy_worker - destroy a workqueue worker
1961  * @worker: worker to be destroyed
1962  *
1963  * Destroy @worker and adjust @pool stats accordingly.  The worker should
1964  * be idle.
1965  *
1966  * CONTEXT:
1967  * spin_lock_irq(pool->lock).
1968  */
1969 static void destroy_worker(struct worker *worker)
1970 {
1971         struct worker_pool *pool = worker->pool;
1972 
1973         lockdep_assert_held(&pool->lock);
1974 
1975         /* sanity check frenzy */
1976         if (WARN_ON(worker->current_work) ||
1977             WARN_ON(!list_empty(&worker->scheduled)) ||
1978             WARN_ON(!(worker->flags & WORKER_IDLE)))
1979                 return;
1980 
1981         pool->nr_workers--;
1982         pool->nr_idle--;
1983 
1984         list_del_init(&worker->entry);
1985         worker->flags |= WORKER_DIE;
1986         wake_up_process(worker->task);
1987 }
1988 
1989 static void idle_worker_timeout(struct timer_list *t)
1990 {
1991         struct worker_pool *pool = from_timer(pool, t, idle_timer);
1992 
1993         spin_lock_irq(&pool->lock);
1994 
1995         while (too_many_workers(pool)) {
1996                 struct worker *worker;
1997                 unsigned long expires;
1998 
1999                 /* idle_list is kept in LIFO order, check the last one */
2000                 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2001                 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2002 
2003                 if (time_before(jiffies, expires)) {
2004                         mod_timer(&pool->idle_timer, expires);
2005                         break;
2006                 }
2007 
2008                 destroy_worker(worker);
2009         }
2010 
2011         spin_unlock_irq(&pool->lock);
2012 }
2013 
2014 static void send_mayday(struct work_struct *work)
2015 {
2016         struct pool_workqueue *pwq = get_work_pwq(work);
2017         struct workqueue_struct *wq = pwq->wq;
2018 
2019         lockdep_assert_held(&wq_mayday_lock);
2020 
2021         if (!wq->rescuer)
2022                 return;
2023 
2024         /* mayday mayday mayday */
2025         if (list_empty(&pwq->mayday_node)) {
2026                 /*
2027                  * If @pwq is for an unbound wq, its base ref may be put at
2028                  * any time due to an attribute change.  Pin @pwq until the
2029                  * rescuer is done with it.
2030                  */
2031                 get_pwq(pwq);
2032                 list_add_tail(&pwq->mayday_node, &wq->maydays);
2033                 wake_up_process(wq->rescuer->task);
2034         }
2035 }
2036 
2037 static void pool_mayday_timeout(struct timer_list *t)
2038 {
2039         struct worker_pool *pool = from_timer(pool, t, mayday_timer);
2040         struct work_struct *work;
2041 
2042         spin_lock_irq(&pool->lock);
2043         spin_lock(&wq_mayday_lock);             /* for wq->maydays */
2044 
2045         if (need_to_create_worker(pool)) {
2046                 /*
2047                  * We've been trying to create a new worker but
2048                  * haven't been successful.  We might be hitting an
2049                  * allocation deadlock.  Send distress signals to
2050                  * rescuers.
2051                  */
2052                 list_for_each_entry(work, &pool->worklist, entry)
2053                         send_mayday(work);
2054         }
2055 
2056         spin_unlock(&wq_mayday_lock);
2057         spin_unlock_irq(&pool->lock);
2058 
2059         mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
2060 }
2061 
2062 /**
2063  * maybe_create_worker - create a new worker if necessary
2064  * @pool: pool to create a new worker for
2065  *
2066  * Create a new worker for @pool if necessary.  @pool is guaranteed to
2067  * have at least one idle worker on return from this function.  If
2068  * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
2069  * sent to all rescuers with works scheduled on @pool to resolve
2070  * possible allocation deadlock.
2071  *
2072  * On return, need_to_create_worker() is guaranteed to be %false and
2073  * may_start_working() %true.
2074  *
2075  * LOCKING:
2076  * spin_lock_irq(pool->lock) which may be released and regrabbed
2077  * multiple times.  Does GFP_KERNEL allocations.  Called only from
2078  * manager.
2079  */
2080 static void maybe_create_worker(struct worker_pool *pool)
2081 __releases(&pool->lock)
2082 __acquires(&pool->lock)
2083 {
2084 restart:
2085         spin_unlock_irq(&pool->lock);
2086 
2087         /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
2088         mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
2089 
2090         while (true) {
2091                 if (create_worker(pool) || !need_to_create_worker(pool))
2092                         break;
2093 
2094                 schedule_timeout_interruptible(CREATE_COOLDOWN);
2095 
2096                 if (!need_to_create_worker(pool))
2097                         break;
2098         }
2099 
2100         del_timer_sync(&pool->mayday_timer);
2101         spin_lock_irq(&pool->lock);
2102         /*
2103          * This is necessary even after a new worker was just successfully
2104          * created as @pool->lock was dropped and the new worker might have
2105          * already become busy.
2106          */
2107         if (need_to_create_worker(pool))
2108                 goto restart;
2109 }
2110 
2111 /**
2112  * manage_workers - manage worker pool
2113  * @worker: self
2114  *
2115  * Assume the manager role and manage the worker pool @worker belongs
2116  * to.  At any given time, there can be only zero or one manager per
2117  * pool.  The exclusion is handled automatically by this function.
2118  *
2119  * The caller can safely start processing works on false return.  On
2120  * true return, it's guaranteed that need_to_create_worker() is false
2121  * and may_start_working() is true.
2122  *
2123  * CONTEXT:
2124  * spin_lock_irq(pool->lock) which may be released and regrabbed
2125  * multiple times.  Does GFP_KERNEL allocations.
2126  *
2127  * Return:
2128  * %false if the pool doesn't need management and the caller can safely
2129  * start processing works, %true if management function was performed and
2130  * the conditions that the caller verified before calling the function may
2131  * no longer be true.
2132  */
2133 static bool manage_workers(struct worker *worker)
2134 {
2135         struct worker_pool *pool = worker->pool;
2136 
2137         if (pool->flags & POOL_MANAGER_ACTIVE)
2138                 return false;
2139 
2140         pool->flags |= POOL_MANAGER_ACTIVE;
2141         pool->manager = worker;
2142 
2143         maybe_create_worker(pool);
2144 
2145         pool->manager = NULL;
2146         pool->flags &= ~POOL_MANAGER_ACTIVE;
2147         wake_up(&wq_manager_wait);
2148         return true;
2149 }
2150 
2151 /**
2152  * process_one_work - process single work
2153  * @worker: self
2154  * @work: work to process
2155  *
2156  * Process @work.  This function contains all the logics necessary to
2157  * process a single work including synchronization against and
2158  * interaction with other workers on the same cpu, queueing and
2159  * flushing.  As long as context requirement is met, any worker can
2160  * call this function to process a work.
2161  *
2162  * CONTEXT:
2163  * spin_lock_irq(pool->lock) which is released and regrabbed.
2164  */
2165 static void process_one_work(struct worker *worker, struct work_struct *work)
2166 __releases(&pool->lock)
2167 __acquires(&pool->lock)
2168 {
2169         struct pool_workqueue *pwq = get_work_pwq(work);
2170         struct worker_pool *pool = worker->pool;
2171         bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2172         int work_color;
2173         struct worker *collision;
2174 #ifdef CONFIG_LOCKDEP
2175         /*
2176          * It is permissible to free the struct work_struct from
2177          * inside the function that is called from it, this we need to
2178          * take into account for lockdep too.  To avoid bogus "held
2179          * lock freed" warnings as well as problems when looking into
2180          * work->lockdep_map, make a copy and use that here.
2181          */
2182         struct lockdep_map lockdep_map;
2183 
2184         lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2185 #endif
2186         /* ensure we're on the correct CPU */
2187         WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2188                      raw_smp_processor_id() != pool->cpu);
2189 
2190         /*
2191          * A single work shouldn't be executed concurrently by
2192          * multiple workers on a single cpu.  Check whether anyone is
2193          * already processing the work.  If so, defer the work to the
2194          * currently executing one.
2195          */
2196         collision = find_worker_executing_work(pool, work);
2197         if (unlikely(collision)) {
2198                 move_linked_works(work, &collision->scheduled, NULL);
2199                 return;
2200         }
2201 
2202         /* claim and dequeue */
2203         debug_work_deactivate(work);
2204         hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2205         worker->current_work = work;
2206         worker->current_func = work->func;
2207         worker->current_pwq = pwq;
2208         work_color = get_work_color(work);
2209 
2210         /*
2211          * Record wq name for cmdline and debug reporting, may get
2212          * overridden through set_worker_desc().
2213          */
2214         strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
2215 
2216         list_del_init(&work->entry);
2217 
2218         /*
2219          * CPU intensive works don't participate in concurrency management.
2220          * They're the scheduler's responsibility.  This takes @worker out
2221          * of concurrency management and the next code block will chain
2222          * execution of the pending work items.
2223          */
2224         if (unlikely(cpu_intensive))
2225                 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2226 
2227         /*
2228          * Wake up another worker if necessary.  The condition is always
2229          * false for normal per-cpu workers since nr_running would always
2230          * be >= 1 at this point.  This is used to chain execution of the
2231          * pending work items for WORKER_NOT_RUNNING workers such as the
2232          * UNBOUND and CPU_INTENSIVE ones.
2233          */
2234         if (need_more_worker(pool))
2235                 wake_up_worker(pool);
2236 
2237         /*
2238          * Record the last pool and clear PENDING which should be the last
2239          * update to @work.  Also, do this inside @pool->lock so that
2240          * PENDING and queued state changes happen together while IRQ is
2241          * disabled.
2242          */
2243         set_work_pool_and_clear_pending(work, pool->id);
2244 
2245         spin_unlock_irq(&pool->lock);
2246 
2247         lock_map_acquire(&pwq->wq->lockdep_map);
2248         lock_map_acquire(&lockdep_map);
2249         /*
2250          * Strictly speaking we should mark the invariant state without holding
2251          * any locks, that is, before these two lock_map_acquire()'s.
2252          *
2253          * However, that would result in:
2254          *
2255          *   A(W1)
2256          *   WFC(C)
2257          *              A(W1)
2258          *              C(C)
2259          *
2260          * Which would create W1->C->W1 dependencies, even though there is no
2261          * actual deadlock possible. There are two solutions, using a
2262          * read-recursive acquire on the work(queue) 'locks', but this will then
2263          * hit the lockdep limitation on recursive locks, or simply discard
2264          * these locks.
2265          *
2266          * AFAICT there is no possible deadlock scenario between the
2267          * flush_work() and complete() primitives (except for single-threaded
2268          * workqueues), so hiding them isn't a problem.
2269          */
2270         lockdep_invariant_state(true);
2271         trace_workqueue_execute_start(work);
2272         worker->current_func(work);
2273         /*
2274          * While we must be careful to not use "work" after this, the trace
2275          * point will only record its address.
2276          */
2277         trace_workqueue_execute_end(work);
2278         lock_map_release(&lockdep_map);
2279         lock_map_release(&pwq->wq->lockdep_map);
2280 
2281         if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2282                 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2283                        "     last function: %ps\n",
2284                        current->comm, preempt_count(), task_pid_nr(current),
2285                        worker->current_func);
2286                 debug_show_held_locks(current);
2287                 dump_stack();
2288         }
2289 
2290         /*
2291          * The following prevents a kworker from hogging CPU on !PREEMPT
2292          * kernels, where a requeueing work item waiting for something to
2293          * happen could deadlock with stop_machine as such work item could
2294          * indefinitely requeue itself while all other CPUs are trapped in
2295          * stop_machine. At the same time, report a quiescent RCU state so
2296          * the same condition doesn't freeze RCU.
2297          */
2298         cond_resched();
2299 
2300         spin_lock_irq(&pool->lock);
2301 
2302         /* clear cpu intensive status */
2303         if (unlikely(cpu_intensive))
2304                 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2305 
2306         /* tag the worker for identification in schedule() */
2307         worker->last_func = worker->current_func;
2308 
2309         /* we're done with it, release */
2310         hash_del(&worker->hentry);
2311         worker->current_work = NULL;
2312         worker->current_func = NULL;
2313         worker->current_pwq = NULL;
2314         pwq_dec_nr_in_flight(pwq, work_color);
2315 }
2316 
2317 /**
2318  * process_scheduled_works - process scheduled works
2319  * @worker: self
2320  *
2321  * Process all scheduled works.  Please note that the scheduled list
2322  * may change while processing a work, so this function repeatedly
2323  * fetches a work from the top and executes it.
2324  *
2325  * CONTEXT:
2326  * spin_lock_irq(pool->lock) which may be released and regrabbed
2327  * multiple times.
2328  */
2329 static void process_scheduled_works(struct worker *worker)
2330 {
2331         while (!list_empty(&worker->scheduled)) {
2332                 struct work_struct *work = list_first_entry(&worker->scheduled,
2333                                                 struct work_struct, entry);
2334                 process_one_work(worker, work);
2335         }
2336 }
2337 
2338 static void set_pf_worker(bool val)
2339 {
2340         mutex_lock(&wq_pool_attach_mutex);
2341         if (val)
2342                 current->flags |= PF_WQ_WORKER;
2343         else
2344                 current->flags &= ~PF_WQ_WORKER;
2345         mutex_unlock(&wq_pool_attach_mutex);
2346 }
2347 
2348 /**
2349  * worker_thread - the worker thread function
2350  * @__worker: self
2351  *
2352  * The worker thread function.  All workers belong to a worker_pool -
2353  * either a per-cpu one or dynamic unbound one.  These workers process all
2354  * work items regardless of their specific target workqueue.  The only
2355  * exception is work items which belong to workqueues with a rescuer which
2356  * will be explained in rescuer_thread().
2357  *
2358  * Return: 0
2359  */
2360 static int worker_thread(void *__worker)
2361 {
2362         struct worker *worker = __worker;
2363         struct worker_pool *pool = worker->pool;
2364 
2365         /* tell the scheduler that this is a workqueue worker */
2366         set_pf_worker(true);
2367 woke_up:
2368         spin_lock_irq(&pool->lock);
2369 
2370         /* am I supposed to die? */
2371         if (unlikely(worker->flags & WORKER_DIE)) {
2372                 spin_unlock_irq(&pool->lock);
2373                 WARN_ON_ONCE(!list_empty(&worker->entry));
2374                 set_pf_worker(false);
2375 
2376                 set_task_comm(worker->task, "kworker/dying");
2377                 ida_simple_remove(&pool->worker_ida, worker->id);
2378                 worker_detach_from_pool(worker);
2379                 kfree(worker);
2380                 return 0;
2381         }
2382 
2383         worker_leave_idle(worker);
2384 recheck:
2385         /* no more worker necessary? */
2386         if (!need_more_worker(pool))
2387                 goto sleep;
2388 
2389         /* do we need to manage? */
2390         if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2391                 goto recheck;
2392 
2393         /*
2394          * ->scheduled list can only be filled while a worker is
2395          * preparing to process a work or actually processing it.
2396          * Make sure nobody diddled with it while I was sleeping.
2397          */
2398         WARN_ON_ONCE(!list_empty(&worker->scheduled));
2399 
2400         /*
2401          * Finish PREP stage.  We're guaranteed to have at least one idle
2402          * worker or that someone else has already assumed the manager
2403          * role.  This is where @worker starts participating in concurrency
2404          * management if applicable and concurrency management is restored
2405          * after being rebound.  See rebind_workers() for details.
2406          */
2407         worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2408 
2409         do {
2410                 struct work_struct *work =
2411                         list_first_entry(&pool->worklist,
2412                                          struct work_struct, entry);
2413 
2414                 pool->watchdog_ts = jiffies;
2415 
2416                 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2417                         /* optimization path, not strictly necessary */
2418                         process_one_work(worker, work);
2419                         if (unlikely(!list_empty(&worker->scheduled)))
2420                                 process_scheduled_works(worker);
2421                 } else {
2422                         move_linked_works(work, &worker->scheduled, NULL);
2423                         process_scheduled_works(worker);
2424                 }
2425         } while (keep_working(pool));
2426 
2427         worker_set_flags(worker, WORKER_PREP);
2428 sleep:
2429         /*
2430          * pool->lock is held and there's no work to process and no need to
2431          * manage, sleep.  Workers are woken up only while holding
2432          * pool->lock or from local cpu, so setting the current state
2433          * before releasing pool->lock is enough to prevent losing any
2434          * event.
2435          */
2436         worker_enter_idle(worker);
2437         __set_current_state(TASK_IDLE);
2438         spin_unlock_irq(&pool->lock);
2439         schedule();
2440         goto woke_up;
2441 }
2442 
2443 /**
2444  * rescuer_thread - the rescuer thread function
2445  * @__rescuer: self
2446  *
2447  * Workqueue rescuer thread function.  There's one rescuer for each
2448  * workqueue which has WQ_MEM_RECLAIM set.
2449  *
2450  * Regular work processing on a pool may block trying to create a new
2451  * worker which uses GFP_KERNEL allocation which has slight chance of
2452  * developing into deadlock if some works currently on the same queue
2453  * need to be processed to satisfy the GFP_KERNEL allocation.  This is
2454  * the problem rescuer solves.
2455  *
2456  * When such condition is possible, the pool summons rescuers of all
2457  * workqueues which have works queued on the pool and let them process
2458  * those works so that forward progress can be guaranteed.
2459  *
2460  * This should happen rarely.
2461  *
2462  * Return: 0
2463  */
2464 static int rescuer_thread(void *__rescuer)
2465 {
2466         struct worker *rescuer = __rescuer;
2467         struct workqueue_struct *wq = rescuer->rescue_wq;
2468         struct list_head *scheduled = &rescuer->scheduled;
2469         bool should_stop;
2470 
2471         set_user_nice(current, RESCUER_NICE_LEVEL);
2472 
2473         /*
2474          * Mark rescuer as worker too.  As WORKER_PREP is never cleared, it
2475          * doesn't participate in concurrency management.
2476          */
2477         set_pf_worker(true);
2478 repeat:
2479         set_current_state(TASK_IDLE);
2480 
2481         /*
2482          * By the time the rescuer is requested to stop, the workqueue
2483          * shouldn't have any work pending, but @wq->maydays may still have
2484          * pwq(s) queued.  This can happen by non-rescuer workers consuming
2485          * all the work items before the rescuer got to them.  Go through
2486          * @wq->maydays processing before acting on should_stop so that the
2487          * list is always empty on exit.
2488          */
2489         should_stop = kthread_should_stop();
2490 
2491         /* see whether any pwq is asking for help */
2492         spin_lock_irq(&wq_mayday_lock);
2493 
2494         while (!list_empty(&wq->maydays)) {
2495                 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2496                                         struct pool_workqueue, mayday_node);
2497                 struct worker_pool *pool = pwq->pool;
2498                 struct work_struct *work, *n;
2499                 bool first = true;
2500 
2501                 __set_current_state(TASK_RUNNING);
2502                 list_del_init(&pwq->mayday_node);
2503 
2504                 spin_unlock_irq(&wq_mayday_lock);
2505 
2506                 worker_attach_to_pool(rescuer, pool);
2507 
2508                 spin_lock_irq(&pool->lock);
2509 
2510                 /*
2511                  * Slurp in all works issued via this workqueue and
2512                  * process'em.
2513                  */
2514                 WARN_ON_ONCE(!list_empty(scheduled));
2515                 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2516                         if (get_work_pwq(work) == pwq) {
2517                                 if (first)
2518                                         pool->watchdog_ts = jiffies;
2519                                 move_linked_works(work, scheduled, &n);
2520                         }
2521                         first = false;
2522                 }
2523 
2524                 if (!list_empty(scheduled)) {
2525                         process_scheduled_works(rescuer);
2526 
2527                         /*
2528                          * The above execution of rescued work items could
2529                          * have created more to rescue through
2530                          * pwq_activate_first_delayed() or chained
2531                          * queueing.  Let's put @pwq back on mayday list so
2532                          * that such back-to-back work items, which may be
2533                          * being used to relieve memory pressure, don't
2534                          * incur MAYDAY_INTERVAL delay inbetween.
2535                          */
2536                         if (need_to_create_worker(pool)) {
2537                                 spin_lock(&wq_mayday_lock);
2538                                 /*
2539                                  * Queue iff we aren't racing destruction
2540                                  * and somebody else hasn't queued it already.
2541                                  */
2542                                 if (wq->rescuer && list_empty(&pwq->mayday_node)) {
2543                                         get_pwq(pwq);
2544                                         list_add_tail(&pwq->mayday_node, &wq->maydays);
2545                                 }
2546                                 spin_unlock(&wq_mayday_lock);
2547                         }
2548                 }
2549 
2550                 /*
2551                  * Put the reference grabbed by send_mayday().  @pool won't
2552                  * go away while we're still attached to it.
2553                  */
2554                 put_pwq(pwq);
2555 
2556                 /*
2557                  * Leave this pool.  If need_more_worker() is %true, notify a
2558                  * regular worker; otherwise, we end up with 0 concurrency
2559                  * and stalling the execution.
2560                  */
2561                 if (need_more_worker(pool))
2562                         wake_up_worker(pool);
2563 
2564                 spin_unlock_irq(&pool->lock);
2565 
2566                 worker_detach_from_pool(rescuer);
2567 
2568                 spin_lock_irq(&wq_mayday_lock);
2569         }
2570 
2571         spin_unlock_irq(&wq_mayday_lock);
2572 
2573         if (should_stop) {
2574                 __set_current_state(TASK_RUNNING);
2575                 set_pf_worker(false);
2576                 return 0;
2577         }
2578 
2579         /* rescuers should never participate in concurrency management */
2580         WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2581         schedule();
2582         goto repeat;
2583 }
2584 
2585 /**
2586  * check_flush_dependency - check for flush dependency sanity
2587  * @target_wq: workqueue being flushed
2588  * @target_work: work item being flushed (NULL for workqueue flushes)
2589  *
2590  * %current is trying to flush the whole @target_wq or @target_work on it.
2591  * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2592  * reclaiming memory or running on a workqueue which doesn't have
2593  * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2594  * a deadlock.
2595  */
2596 static void check_flush_dependency(struct workqueue_struct *target_wq,
2597                                    struct work_struct *target_work)
2598 {
2599         work_func_t target_func = target_work ? target_work->func : NULL;
2600         struct worker *worker;
2601 
2602         if (target_wq->flags & WQ_MEM_RECLAIM)
2603                 return;
2604 
2605         worker = current_wq_worker();
2606 
2607         WARN_ONCE(current->flags & PF_MEMALLOC,
2608                   "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
2609                   current->pid, current->comm, target_wq->name, target_func);
2610         WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2611                               (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2612                   "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
2613                   worker->current_pwq->wq->name, worker->current_func,
2614                   target_wq->name, target_func);
2615 }
2616 
2617 struct wq_barrier {
2618         struct work_struct      work;
2619         struct completion       done;
2620         struct task_struct      *task;  /* purely informational */
2621 };
2622 
2623 static void wq_barrier_func(struct work_struct *work)
2624 {
2625         struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2626         complete(&barr->done);
2627 }
2628 
2629 /**
2630  * insert_wq_barrier - insert a barrier work
2631  * @pwq: pwq to insert barrier into
2632  * @barr: wq_barrier to insert
2633  * @target: target work to attach @barr to
2634  * @worker: worker currently executing @target, NULL if @target is not executing
2635  *
2636  * @barr is linked to @target such that @barr is completed only after
2637  * @target finishes execution.  Please note that the ordering
2638  * guarantee is observed only with respect to @target and on the local
2639  * cpu.
2640  *
2641  * Currently, a queued barrier can't be canceled.  This is because
2642  * try_to_grab_pending() can't determine whether the work to be
2643  * grabbed is at the head of the queue and thus can't clear LINKED
2644  * flag of the previous work while there must be a valid next work
2645  * after a work with LINKED flag set.
2646  *
2647  * Note that when @worker is non-NULL, @target may be modified
2648  * underneath us, so we can't reliably determine pwq from @target.
2649  *
2650  * CONTEXT:
2651  * spin_lock_irq(pool->lock).
2652  */
2653 static void insert_wq_barrier(struct pool_workqueue *pwq,
2654                               struct wq_barrier *barr,
2655                               struct work_struct *target, struct worker *worker)
2656 {
2657         struct list_head *head;
2658         unsigned int linked = 0;
2659 
2660         /*
2661          * debugobject calls are safe here even with pool->lock locked
2662          * as we know for sure that this will not trigger any of the
2663          * checks and call back into the fixup functions where we
2664          * might deadlock.
2665          */
2666         INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2667         __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2668 
2669         init_completion_map(&barr->done, &target->lockdep_map);
2670 
2671         barr->task = current;
2672 
2673         /*
2674          * If @target is currently being executed, schedule the
2675          * barrier to the worker; otherwise, put it after @target.
2676          */
2677         if (worker)
2678                 head = worker->scheduled.next;
2679         else {
2680                 unsigned long *bits = work_data_bits(target);
2681 
2682                 head = target->entry.next;
2683                 /* there can already be other linked works, inherit and set */
2684                 linked = *bits & WORK_STRUCT_LINKED;
2685                 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2686         }
2687 
2688         debug_work_activate(&barr->work);
2689         insert_work(pwq, &barr->work, head,
2690                     work_color_to_flags(WORK_NO_COLOR) | linked);
2691 }
2692 
2693 /**
2694  * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2695  * @wq: workqueue being flushed
2696  * @flush_color: new flush color, < 0 for no-op
2697  * @work_color: new work color, < 0 for no-op
2698  *
2699  * Prepare pwqs for workqueue flushing.
2700  *
2701  * If @flush_color is non-negative, flush_color on all pwqs should be
2702  * -1.  If no pwq has in-flight commands at the specified color, all
2703  * pwq->flush_color's stay at -1 and %false is returned.  If any pwq
2704  * has in flight commands, its pwq->flush_color is set to
2705  * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2706  * wakeup logic is armed and %true is returned.
2707  *
2708  * The caller should have initialized @wq->first_flusher prior to
2709  * calling this function with non-negative @flush_color.  If
2710  * @flush_color is negative, no flush color update is done and %false
2711  * is returned.
2712  *
2713  * If @work_color is non-negative, all pwqs should have the same
2714  * work_color which is previous to @work_color and all will be
2715  * advanced to @work_color.
2716  *
2717  * CONTEXT:
2718  * mutex_lock(wq->mutex).
2719  *
2720  * Return:
2721  * %true if @flush_color >= 0 and there's something to flush.  %false
2722  * otherwise.
2723  */
2724 static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2725                                       int flush_color, int work_color)
2726 {
2727         bool wait = false;
2728         struct pool_workqueue *pwq;
2729 
2730         if (flush_color >= 0) {
2731                 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2732                 atomic_set(&wq->nr_pwqs_to_flush, 1);
2733         }
2734 
2735         for_each_pwq(pwq, wq) {
2736                 struct worker_pool *pool = pwq->pool;
2737 
2738                 spin_lock_irq(&pool->lock);
2739 
2740                 if (flush_color >= 0) {
2741                         WARN_ON_ONCE(pwq->flush_color != -1);
2742 
2743                         if (pwq->nr_in_flight[flush_color]) {
2744                                 pwq->flush_color = flush_color;
2745                                 atomic_inc(&wq->nr_pwqs_to_flush);
2746                                 wait = true;
2747                         }
2748                 }
2749 
2750                 if (work_color >= 0) {
2751                         WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2752                         pwq->work_color = work_color;
2753                 }
2754 
2755                 spin_unlock_irq(&pool->lock);
2756         }
2757 
2758         if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2759                 complete(&wq->first_flusher->done);
2760 
2761         return wait;
2762 }
2763 
2764 /**
2765  * flush_workqueue - ensure that any scheduled work has run to completion.
2766  * @wq: workqueue to flush
2767  *
2768  * This function sleeps until all work items which were queued on entry
2769  * have finished execution, but it is not livelocked by new incoming ones.
2770  */
2771 void flush_workqueue(struct workqueue_struct *wq)
2772 {
2773         struct wq_flusher this_flusher = {
2774                 .list = LIST_HEAD_INIT(this_flusher.list),
2775                 .flush_color = -1,
2776                 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
2777         };
2778         int next_color;
2779 
2780         if (WARN_ON(!wq_online))
2781                 return;
2782 
2783         lock_map_acquire(&wq->lockdep_map);
2784         lock_map_release(&wq->lockdep_map);
2785 
2786         mutex_lock(&wq->mutex);
2787 
2788         /*
2789          * Start-to-wait phase
2790          */
2791         next_color = work_next_color(wq->work_color);
2792 
2793         if (next_color != wq->flush_color) {
2794                 /*
2795                  * Color space is not full.  The current work_color
2796                  * becomes our flush_color and work_color is advanced
2797                  * by one.
2798                  */
2799                 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2800                 this_flusher.flush_color = wq->work_color;
2801                 wq->work_color = next_color;
2802 
2803                 if (!wq->first_flusher) {
2804                         /* no flush in progress, become the first flusher */
2805                         WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2806 
2807                         wq->first_flusher = &this_flusher;
2808 
2809                         if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2810                                                        wq->work_color)) {
2811                                 /* nothing to flush, done */
2812                                 wq->flush_color = next_color;
2813                                 wq->first_flusher = NULL;
2814                                 goto out_unlock;
2815                         }
2816                 } else {
2817                         /* wait in queue */
2818                         WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2819                         list_add_tail(&this_flusher.list, &wq->flusher_queue);
2820                         flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2821                 }
2822         } else {
2823                 /*
2824                  * Oops, color space is full, wait on overflow queue.
2825                  * The next flush completion will assign us
2826                  * flush_color and transfer to flusher_queue.
2827                  */
2828                 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2829         }
2830 
2831         check_flush_dependency(wq, NULL);
2832 
2833         mutex_unlock(&wq->mutex);
2834 
2835         wait_for_completion(&this_flusher.done);
2836 
2837         /*
2838          * Wake-up-and-cascade phase
2839          *
2840          * First flushers are responsible for cascading flushes and
2841          * handling overflow.  Non-first flushers can simply return.
2842          */
2843         if (wq->first_flusher != &this_flusher)
2844                 return;
2845 
2846         mutex_lock(&wq->mutex);
2847 
2848         /* we might have raced, check again with mutex held */
2849         if (wq->first_flusher != &this_flusher)
2850                 goto out_unlock;
2851 
2852         wq->first_flusher = NULL;
2853 
2854         WARN_ON_ONCE(!list_empty(&this_flusher.list));
2855         WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2856 
2857         while (true) {
2858                 struct wq_flusher *next, *tmp;
2859 
2860                 /* complete all the flushers sharing the current flush color */
2861                 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2862                         if (next->flush_color != wq->flush_color)
2863                                 break;
2864                         list_del_init(&next->list);
2865                         complete(&next->done);
2866                 }
2867 
2868                 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2869                              wq->flush_color != work_next_color(wq->work_color));
2870 
2871                 /* this flush_color is finished, advance by one */
2872                 wq->flush_color = work_next_color(wq->flush_color);
2873 
2874                 /* one color has been freed, handle overflow queue */
2875                 if (!list_empty(&wq->flusher_overflow)) {
2876                         /*
2877                          * Assign the same color to all overflowed
2878                          * flushers, advance work_color and append to
2879                          * flusher_queue.  This is the start-to-wait
2880                          * phase for these overflowed flushers.
2881                          */
2882                         list_for_each_entry(tmp, &wq->flusher_overflow, list)
2883                                 tmp->flush_color = wq->work_color;
2884 
2885                         wq->work_color = work_next_color(wq->work_color);
2886 
2887                         list_splice_tail_init(&wq->flusher_overflow,
2888                                               &wq->flusher_queue);
2889                         flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2890                 }
2891 
2892                 if (list_empty(&wq->flusher_queue)) {
2893                         WARN_ON_ONCE(wq->flush_color != wq->work_color);
2894                         break;
2895                 }
2896 
2897                 /*
2898                  * Need to flush more colors.  Make the next flusher
2899                  * the new first flusher and arm pwqs.
2900                  */
2901                 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2902                 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2903 
2904                 list_del_init(&next->list);
2905                 wq->first_flusher = next;
2906 
2907                 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2908                         break;
2909 
2910                 /*
2911                  * Meh... this color is already done, clear first
2912                  * flusher and repeat cascading.
2913                  */
2914                 wq->first_flusher = NULL;
2915         }
2916 
2917 out_unlock:
2918         mutex_unlock(&wq->mutex);
2919 }
2920 EXPORT_SYMBOL(flush_workqueue);
2921 
2922 /**
2923  * drain_workqueue - drain a workqueue
2924  * @wq: workqueue to drain
2925  *
2926  * Wait until the workqueue becomes empty.  While draining is in progress,
2927  * only chain queueing is allowed.  IOW, only currently pending or running
2928  * work items on @wq can queue further work items on it.  @wq is flushed
2929  * repeatedly until it becomes empty.  The number of flushing is determined
2930  * by the depth of chaining and should be relatively short.  Whine if it
2931  * takes too long.
2932  */
2933 void drain_workqueue(struct workqueue_struct *wq)
2934 {
2935         unsigned int flush_cnt = 0;
2936         struct pool_workqueue *pwq;
2937 
2938         /*
2939          * __queue_work() needs to test whether there are drainers, is much
2940          * hotter than drain_workqueue() and already looks at @wq->flags.
2941          * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2942          */
2943         mutex_lock(&wq->mutex);
2944         if (!wq->nr_drainers++)
2945                 wq->flags |= __WQ_DRAINING;
2946         mutex_unlock(&wq->mutex);
2947 reflush:
2948         flush_workqueue(wq);
2949 
2950         mutex_lock(&wq->mutex);
2951 
2952         for_each_pwq(pwq, wq) {
2953                 bool drained;
2954 
2955                 spin_lock_irq(&pwq->pool->lock);
2956                 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2957                 spin_unlock_irq(&pwq->pool->lock);
2958 
2959                 if (drained)
2960                         continue;
2961 
2962                 if (++flush_cnt == 10 ||
2963                     (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2964                         pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2965                                 wq->name, flush_cnt);
2966 
2967                 mutex_unlock(&wq->mutex);
2968                 goto reflush;
2969         }
2970 
2971         if (!--wq->nr_drainers)
2972                 wq->flags &= ~__WQ_DRAINING;
2973         mutex_unlock(&wq->mutex);
2974 }
2975 EXPORT_SYMBOL_GPL(drain_workqueue);
2976 
2977 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2978                              bool from_cancel)
2979 {
2980         struct worker *worker = NULL;
2981         struct worker_pool *pool;
2982         struct pool_workqueue *pwq;
2983 
2984         might_sleep();
2985 
2986         rcu_read_lock();
2987         pool = get_work_pool(work);
2988         if (!pool) {
2989                 rcu_read_unlock();
2990                 return false;
2991         }
2992 
2993         spin_lock_irq(&pool->lock);
2994         /* see the comment in try_to_grab_pending() with the same code */
2995         pwq = get_work_pwq(work);
2996         if (pwq) {
2997                 if (unlikely(pwq->pool != pool))
2998                         goto already_gone;
2999         } else {
3000                 worker = find_worker_executing_work(pool, work);
3001                 if (!worker)
3002                         goto already_gone;
3003                 pwq = worker->current_pwq;
3004         }
3005 
3006         check_flush_dependency(pwq->wq, work);
3007 
3008         insert_wq_barrier(pwq, barr, work, worker);
3009         spin_unlock_irq(&pool->lock);
3010 
3011         /*
3012          * Force a lock recursion deadlock when using flush_work() inside a
3013          * single-threaded or rescuer equipped workqueue.
3014          *
3015          * For single threaded workqueues the deadlock happens when the work
3016          * is after the work issuing the flush_work(). For rescuer equipped
3017          * workqueues the deadlock happens when the rescuer stalls, blocking
3018          * forward progress.
3019          */
3020         if (!from_cancel &&
3021             (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
3022                 lock_map_acquire(&pwq->wq->lockdep_map);
3023                 lock_map_release(&pwq->wq->lockdep_map);
3024         }
3025         rcu_read_unlock();
3026         return true;
3027 already_gone:
3028         spin_unlock_irq(&pool->lock);
3029         rcu_read_unlock();
3030         return false;
3031 }
3032 
3033 static bool __flush_work(struct work_struct *work, bool from_cancel)
3034 {
3035         struct wq_barrier barr;
3036 
3037         if (WARN_ON(!wq_online))
3038                 return false;
3039 
3040         if (WARN_ON(!work->func))
3041                 return false;
3042 
3043         if (!from_cancel) {
3044                 lock_map_acquire(&work->lockdep_map);
3045                 lock_map_release(&work->lockdep_map);
3046         }
3047 
3048         if (start_flush_work(work, &barr, from_cancel)) {
3049                 wait_for_completion(&barr.done);
3050                 destroy_work_on_stack(&barr.work);
3051                 return true;
3052         } else {
3053                 return false;
3054         }
3055 }
3056 
3057 /**
3058  * flush_work - wait for a work to finish executing the last queueing instance
3059  * @work: the work to flush
3060  *
3061  * Wait until @work has finished execution.  @work is guaranteed to be idle
3062  * on return if it hasn't been requeued since flush started.
3063  *
3064  * Return:
3065  * %true if flush_work() waited for the work to finish execution,
3066  * %false if it was already idle.
3067  */
3068 bool flush_work(struct work_struct *work)
3069 {
3070         return __flush_work(work, false);
3071 }
3072 EXPORT_SYMBOL_GPL(flush_work);
3073 
3074 struct cwt_wait {
3075         wait_queue_entry_t              wait;
3076         struct work_struct      *work;
3077 };
3078 
3079 static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
3080 {
3081         struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
3082 
3083         if (cwait->work != key)
3084                 return 0;
3085         return autoremove_wake_function(wait, mode, sync, key);
3086 }
3087 
3088 static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
3089 {
3090         static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
3091         unsigned long flags;
3092         int ret;
3093 
3094         do {
3095                 ret = try_to_grab_pending(work, is_dwork, &flags);
3096                 /*
3097                  * If someone else is already canceling, wait for it to
3098                  * finish.  flush_work() doesn't work for PREEMPT_NONE
3099                  * because we may get scheduled between @work's completion
3100                  * and the other canceling task resuming and clearing
3101                  * CANCELING - flush_work() will return false immediately
3102                  * as @work is no longer busy, try_to_grab_pending() will
3103                  * return -ENOENT as @work is still being canceled and the
3104                  * other canceling task won't be able to clear CANCELING as
3105                  * we're hogging the CPU.
3106                  *
3107                  * Let's wait for completion using a waitqueue.  As this
3108                  * may lead to the thundering herd problem, use a custom
3109                  * wake function which matches @work along with exclusive
3110                  * wait and wakeup.
3111                  */
3112                 if (unlikely(ret == -ENOENT)) {
3113                         struct cwt_wait cwait;
3114 
3115                         init_wait(&cwait.wait);
3116                         cwait.wait.func = cwt_wakefn;
3117                         cwait.work = work;
3118 
3119                         prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
3120                                                   TASK_UNINTERRUPTIBLE);
3121                         if (work_is_canceling(work))
3122                                 schedule();
3123                         finish_wait(&cancel_waitq, &cwait.wait);
3124                 }
3125         } while (unlikely(ret < 0));
3126 
3127         /* tell other tasks trying to grab @work to back off */
3128         mark_work_canceling(work);
3129         local_irq_restore(flags);
3130 
3131         /*
3132          * This allows canceling during early boot.  We know that @work
3133          * isn't executing.
3134          */
3135         if (wq_online)
3136                 __flush_work(work, true);
3137 
3138         clear_work_data(work);
3139 
3140         /*
3141          * Paired with prepare_to_wait() above so that either
3142          * waitqueue_active() is visible here or !work_is_canceling() is
3143          * visible there.
3144          */
3145         smp_mb();
3146         if (waitqueue_active(&cancel_waitq))
3147                 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
3148 
3149         return ret;
3150 }
3151 
3152 /**
3153  * cancel_work_sync - cancel a work and wait for it to finish
3154  * @work: the work to cancel
3155  *
3156  * Cancel @work and wait for its execution to finish.  This function
3157  * can be used even if the work re-queues itself or migrates to
3158  * another workqueue.  On return from this function, @work is
3159  * guaranteed to be not pending or executing on any CPU.
3160  *
3161  * cancel_work_sync(&delayed_work->work) must not be used for
3162  * delayed_work's.  Use cancel_delayed_work_sync() instead.
3163  *
3164  * The caller must ensure that the workqueue on which @work was last
3165  * queued can't be destroyed before this function returns.
3166  *
3167  * Return:
3168  * %true if @work was pending, %false otherwise.
3169  */
3170 bool cancel_work_sync(struct work_struct *work)
3171 {
3172         return __cancel_work_timer(work, false);
3173 }
3174 EXPORT_SYMBOL_GPL(cancel_work_sync);
3175 
3176 /**
3177  * flush_delayed_work - wait for a dwork to finish executing the last queueing
3178  * @dwork: the delayed work to flush
3179  *
3180  * Delayed timer is cancelled and the pending work is queued for
3181  * immediate execution.  Like flush_work(), this function only
3182  * considers the last queueing instance of @dwork.
3183  *
3184  * Return:
3185  * %true if flush_work() waited for the work to finish execution,
3186  * %false if it was already idle.
3187  */
3188 bool flush_delayed_work(struct delayed_work *dwork)
3189 {
3190         local_irq_disable();
3191         if (del_timer_sync(&dwork->timer))
3192                 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
3193         local_irq_enable();
3194         return flush_work(&dwork->work);
3195 }
3196 EXPORT_SYMBOL(flush_delayed_work);
3197 
3198 /**
3199  * flush_rcu_work - wait for a rwork to finish executing the last queueing
3200  * @rwork: the rcu work to flush
3201  *
3202  * Return:
3203  * %true if flush_rcu_work() waited for the work to finish execution,
3204  * %false if it was already idle.
3205  */
3206 bool flush_rcu_work(struct rcu_work *rwork)
3207 {
3208         if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
3209                 rcu_barrier();
3210                 flush_work(&rwork->work);
3211                 return true;
3212         } else {
3213                 return flush_work(&rwork->work);
3214         }
3215 }
3216 EXPORT_SYMBOL(flush_rcu_work);
3217 
3218 static bool __cancel_work(struct work_struct *work, bool is_dwork)
3219 {
3220         unsigned long flags;
3221         int ret;
3222 
3223         do {
3224                 ret = try_to_grab_pending(work, is_dwork, &flags);
3225         } while (unlikely(ret == -EAGAIN));
3226 
3227         if (unlikely(ret < 0))
3228                 return false;
3229 
3230         set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3231         local_irq_restore(flags);
3232         return ret;
3233 }
3234 
3235 /**
3236  * cancel_delayed_work - cancel a delayed work
3237  * @dwork: delayed_work to cancel
3238  *
3239  * Kill off a pending delayed_work.
3240  *
3241  * Return: %true if @dwork was pending and canceled; %false if it wasn't
3242  * pending.
3243  *
3244  * Note:
3245  * The work callback function may still be running on return, unless
3246  * it returns %true and the work doesn't re-arm itself.  Explicitly flush or
3247  * use cancel_delayed_work_sync() to wait on it.
3248  *
3249  * This function is safe to call from any context including IRQ handler.
3250  */
3251 bool cancel_delayed_work(struct delayed_work *dwork)
3252 {
3253         return __cancel_work(&dwork->work, true);
3254 }
3255 EXPORT_SYMBOL(cancel_delayed_work);
3256 
3257 /**
3258  * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3259  * @dwork: the delayed work cancel
3260  *
3261  * This is cancel_work_sync() for delayed works.
3262  *
3263  * Return:
3264  * %true if @dwork was pending, %false otherwise.
3265  */
3266 bool cancel_delayed_work_sync(struct delayed_work *dwork)
3267 {
3268         return __cancel_work_timer(&dwork->work, true);
3269 }
3270 EXPORT_SYMBOL(cancel_delayed_work_sync);
3271 
3272 /**
3273  * schedule_on_each_cpu - execute a function synchronously on each online CPU
3274  * @func: the function to call
3275  *
3276  * schedule_on_each_cpu() executes @func on each online CPU using the
3277  * system workqueue and blocks until all CPUs have completed.
3278  * schedule_on_each_cpu() is very slow.
3279  *
3280  * Return:
3281  * 0 on success, -errno on failure.
3282  */
3283 int schedule_on_each_cpu(work_func_t func)
3284 {
3285         int cpu;
3286         struct work_struct __percpu *works;
3287 
3288         works = alloc_percpu(struct work_struct);
3289         if (!works)
3290                 return -ENOMEM;
3291 
3292         get_online_cpus();
3293 
3294         for_each_online_cpu(cpu) {
3295                 struct work_struct *work = per_cpu_ptr(works, cpu);
3296 
3297                 INIT_WORK(work, func);
3298                 schedule_work_on(cpu, work);
3299         }
3300 
3301         for_each_online_cpu(cpu)
3302                 flush_work(per_cpu_ptr(works, cpu));
3303 
3304         put_online_cpus();
3305         free_percpu(works);
3306         return 0;
3307 }
3308 
3309 /**
3310  * execute_in_process_context - reliably execute the routine with user context
3311  * @fn:         the function to execute
3312  * @ew:         guaranteed storage for the execute work structure (must
3313  *              be available when the work executes)
3314  *
3315  * Executes the function immediately if process context is available,
3316  * otherwise schedules the function for delayed execution.
3317  *
3318  * Return:      0 - function was executed
3319  *              1 - function was scheduled for execution
3320  */
3321 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3322 {
3323         if (!in_interrupt()) {
3324                 fn(&ew->work);
3325                 return 0;
3326         }
3327 
3328         INIT_WORK(&ew->work, fn);
3329         schedule_work(&ew->work);
3330 
3331         return 1;
3332 }
3333 EXPORT_SYMBOL_GPL(execute_in_process_context);
3334 
3335 /**
3336  * free_workqueue_attrs - free a workqueue_attrs
3337  * @attrs: workqueue_attrs to free
3338  *
3339  * Undo alloc_workqueue_attrs().
3340  */
3341 void free_workqueue_attrs(struct workqueue_attrs *attrs)
3342 {
3343         if (attrs) {
3344                 free_cpumask_var(attrs->cpumask);
3345                 kfree(attrs);
3346         }
3347 }
3348 
3349 /**
3350  * alloc_workqueue_attrs - allocate a workqueue_attrs
3351  *
3352  * Allocate a new workqueue_attrs, initialize with default settings and
3353  * return it.
3354  *
3355  * Return: The allocated new workqueue_attr on success. %NULL on failure.
3356  */
3357 struct workqueue_attrs *alloc_workqueue_attrs(void)
3358 {
3359         struct workqueue_attrs *attrs;
3360 
3361         attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
3362         if (!attrs)
3363                 goto fail;
3364         if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
3365                 goto fail;
3366 
3367         cpumask_copy(attrs->cpumask, cpu_possible_mask);
3368         return attrs;
3369 fail:
3370         free_workqueue_attrs(attrs);
3371         return NULL;
3372 }
3373 
3374 static void copy_workqueue_attrs(struct workqueue_attrs *to,
3375                                  const struct workqueue_attrs *from)
3376 {
3377         to->nice = from->nice;
3378         cpumask_copy(to->cpumask, from->cpumask);
3379         /*
3380          * Unlike hash and equality test, this function doesn't ignore
3381          * ->no_numa as it is used for both pool and wq attrs.  Instead,
3382          * get_unbound_pool() explicitly clears ->no_numa after copying.
3383          */
3384         to->no_numa = from->no_numa;
3385 }
3386 
3387 /* hash value of the content of @attr */
3388 static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3389 {
3390         u32 hash = 0;
3391 
3392         hash = jhash_1word(attrs->nice, hash);
3393         hash = jhash(cpumask_bits(attrs->cpumask),
3394                      BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3395         return hash;
3396 }
3397 
3398 /* content equality test */
3399 static bool wqattrs_equal(const struct workqueue_attrs *a,
3400                           const struct workqueue_attrs *b)
3401 {
3402         if (a->nice != b->nice)
3403                 return false;
3404         if (!cpumask_equal(a->cpumask, b->cpumask))
3405                 return false;
3406         return true;
3407 }
3408 
3409 /**
3410  * init_worker_pool - initialize a newly zalloc'd worker_pool
3411  * @pool: worker_pool to initialize
3412  *
3413  * Initialize a newly zalloc'd @pool.  It also allocates @pool->attrs.
3414  *
3415  * Return: 0 on success, -errno on failure.  Even on failure, all fields
3416  * inside @pool proper are initialized and put_unbound_pool() can be called
3417  * on @pool safely to release it.
3418  */
3419 static int init_worker_pool(struct worker_pool *pool)
3420 {
3421         spin_lock_init(&pool->lock);
3422         pool->id = -1;
3423         pool->cpu = -1;
3424         pool->node = NUMA_NO_NODE;
3425         pool->flags |= POOL_DISASSOCIATED;
3426         pool->watchdog_ts = jiffies;
3427         INIT_LIST_HEAD(&pool->worklist);
3428         INIT_LIST_HEAD(&pool->idle_list);
3429         hash_init(pool->busy_hash);
3430 
3431         timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3432 
3433         timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3434 
3435         INIT_LIST_HEAD(&pool->workers);
3436 
3437         ida_init(&pool->worker_ida);
3438         INIT_HLIST_NODE(&pool->hash_node);
3439         pool->refcnt = 1;
3440 
3441         /* shouldn't fail above this point */
3442         pool->attrs = alloc_workqueue_attrs();
3443         if (!pool->attrs)
3444                 return -ENOMEM;
3445         return 0;
3446 }
3447 
3448 #ifdef CONFIG_LOCKDEP
3449 static void wq_init_lockdep(struct workqueue_struct *wq)
3450 {
3451         char *lock_name;
3452 
3453         lockdep_register_key(&wq->key);
3454         lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
3455         if (!lock_name)
3456                 lock_name = wq->name;
3457 
3458         wq->lock_name = lock_name;
3459         lockdep_init_map(&wq->lockdep_map, lock_name, &wq->key, 0);
3460 }
3461 
3462 static void wq_unregister_lockdep(struct workqueue_struct *wq)
3463 {
3464         lockdep_unregister_key(&wq->key);
3465 }
3466 
3467 static void wq_free_lockdep(struct workqueue_struct *wq)
3468 {
3469         if (wq->lock_name != wq->name)
3470                 kfree(wq->lock_name);
3471 }
3472 #else
3473 static void wq_init_lockdep(struct workqueue_struct *wq)
3474 {
3475 }
3476 
3477 static void wq_unregister_lockdep(struct workqueue_struct *wq)
3478 {
3479 }
3480 
3481 static void wq_free_lockdep(struct workqueue_struct *wq)
3482 {
3483 }
3484 #endif
3485 
3486 static void rcu_free_wq(struct rcu_head *rcu)
3487 {
3488         struct workqueue_struct *wq =
3489                 container_of(rcu, struct workqueue_struct, rcu);
3490 
3491         wq_free_lockdep(wq);
3492 
3493         if (!(wq->flags & WQ_UNBOUND))
3494                 free_percpu(wq->cpu_pwqs);
3495         else
3496                 free_workqueue_attrs(wq->unbound_attrs);
3497 
3498         kfree(wq->rescuer);
3499         kfree(wq);
3500 }
3501 
3502 static void rcu_free_pool(struct rcu_head *rcu)
3503 {
3504         struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3505 
3506         ida_destroy(&pool->worker_ida);
3507         free_workqueue_attrs(pool->attrs);
3508         kfree(pool);
3509 }
3510 
3511 /**
3512  * put_unbound_pool - put a worker_pool
3513  * @pool: worker_pool to put
3514  *
3515  * Put @pool.  If its refcnt reaches zero, it gets destroyed in RCU
3516  * safe manner.  get_unbound_pool() calls this function on its failure path
3517  * and this function should be able to release pools which went through,
3518  * successfully or not, init_worker_pool().
3519  *
3520  * Should be called with wq_pool_mutex held.
3521  */
3522 static void put_unbound_pool(struct worker_pool *pool)
3523 {
3524         DECLARE_COMPLETION_ONSTACK(detach_completion);
3525         struct worker *worker;
3526 
3527         lockdep_assert_held(&wq_pool_mutex);
3528 
3529         if (--pool->refcnt)
3530                 return;
3531 
3532         /* sanity checks */
3533         if (WARN_ON(!(pool->cpu < 0)) ||
3534             WARN_ON(!list_empty(&pool->worklist)))
3535                 return;
3536 
3537         /* release id and unhash */
3538         if (pool->id >= 0)
3539                 idr_remove(&worker_pool_idr, pool->id);
3540         hash_del(&pool->hash_node);
3541 
3542         /*
3543          * Become the manager and destroy all workers.  This prevents
3544          * @pool's workers from blocking on attach_mutex.  We're the last
3545          * manager and @pool gets freed with the flag set.
3546          */
3547         spin_lock_irq(&pool->lock);
3548         wait_event_lock_irq(wq_manager_wait,
3549                             !(pool->flags & POOL_MANAGER_ACTIVE), pool->lock);
3550         pool->flags |= POOL_MANAGER_ACTIVE;
3551 
3552         while ((worker = first_idle_worker(pool)))
3553                 destroy_worker(worker);
3554         WARN_ON(pool->nr_workers || pool->nr_idle);
3555         spin_unlock_irq(&pool->lock);
3556 
3557         mutex_lock(&wq_pool_attach_mutex);
3558         if (!list_empty(&pool->workers))
3559                 pool->detach_completion = &detach_completion;
3560         mutex_unlock(&wq_pool_attach_mutex);
3561 
3562         if (pool->detach_completion)
3563                 wait_for_completion(pool->detach_completion);
3564 
3565         /* shut down the timers */
3566         del_timer_sync(&pool->idle_timer);
3567         del_timer_sync(&pool->mayday_timer);
3568 
3569         /* RCU protected to allow dereferences from get_work_pool() */
3570         call_rcu(&pool->rcu, rcu_free_pool);
3571 }
3572 
3573 /**
3574  * get_unbound_pool - get a worker_pool with the specified attributes
3575  * @attrs: the attributes of the worker_pool to get
3576  *
3577  * Obtain a worker_pool which has the same attributes as @attrs, bump the
3578  * reference count and return it.  If there already is a matching
3579  * worker_pool, it will be used; otherwise, this function attempts to
3580  * create a new one.
3581  *
3582  * Should be called with wq_pool_mutex held.
3583  *
3584  * Return: On success, a worker_pool with the same attributes as @attrs.
3585  * On failure, %NULL.
3586  */
3587 static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3588 {
3589         u32 hash = wqattrs_hash(attrs);
3590         struct worker_pool *pool;
3591         int node;
3592         int target_node = NUMA_NO_NODE;
3593 
3594         lockdep_assert_held(&wq_pool_mutex);
3595 
3596         /* do we already have a matching pool? */
3597         hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3598                 if (wqattrs_equal(pool->attrs, attrs)) {
3599                         pool->refcnt++;
3600                         return pool;
3601                 }
3602         }
3603 
3604         /* if cpumask is contained inside a NUMA node, we belong to that node */
3605         if (wq_numa_enabled) {
3606                 for_each_node(node) {
3607                         if (cpumask_subset(attrs->cpumask,
3608                                            wq_numa_possible_cpumask[node])) {
3609                                 target_node = node;
3610                                 break;
3611                         }
3612                 }
3613         }
3614 
3615         /* nope, create a new one */
3616         pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
3617         if (!pool || init_worker_pool(pool) < 0)
3618                 goto fail;
3619 
3620         lockdep_set_subclass(&pool->lock, 1);   /* see put_pwq() */
3621         copy_workqueue_attrs(pool->attrs, attrs);
3622         pool->node = target_node;
3623 
3624         /*
3625          * no_numa isn't a worker_pool attribute, always clear it.  See
3626          * 'struct workqueue_attrs' comments for detail.
3627          */
3628         pool->attrs->no_numa = false;
3629 
3630         if (worker_pool_assign_id(pool) < 0)
3631                 goto fail;
3632 
3633         /* create and start the initial worker */
3634         if (wq_online && !create_worker(pool))
3635                 goto fail;
3636 
3637         /* install */
3638         hash_add(unbound_pool_hash, &pool->hash_node, hash);
3639 
3640         return pool;
3641 fail:
3642         if (pool)
3643                 put_unbound_pool(pool);
3644         return NULL;
3645 }
3646 
3647 static void rcu_free_pwq(struct rcu_head *rcu)
3648 {
3649         kmem_cache_free(pwq_cache,
3650                         container_of(rcu, struct pool_workqueue, rcu));
3651 }
3652 
3653 /*
3654  * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3655  * and needs to be destroyed.
3656  */
3657 static void pwq_unbound_release_workfn(struct work_struct *work)
3658 {
3659         struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3660                                                   unbound_release_work);
3661         struct workqueue_struct *wq = pwq->wq;
3662         struct worker_pool *pool = pwq->pool;
3663         bool is_last;
3664 
3665         if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3666                 return;
3667 
3668         mutex_lock(&wq->mutex);
3669         list_del_rcu(&pwq->pwqs_node);
3670         is_last = list_empty(&wq->pwqs);
3671         mutex_unlock(&wq->mutex);
3672 
3673         mutex_lock(&wq_pool_mutex);
3674         put_unbound_pool(pool);
3675         mutex_unlock(&wq_pool_mutex);
3676 
3677         call_rcu(&pwq->rcu, rcu_free_pwq);
3678 
3679         /*
3680          * If we're the last pwq going away, @wq is already dead and no one
3681          * is gonna access it anymore.  Schedule RCU free.
3682          */
3683         if (is_last) {
3684                 wq_unregister_lockdep(wq);
3685                 call_rcu(&wq->rcu, rcu_free_wq);
3686         }
3687 }
3688 
3689 /**
3690  * pwq_adjust_max_active - update a pwq's max_active to the current setting
3691  * @pwq: target pool_workqueue
3692  *
3693  * If @pwq isn't freezing, set @pwq->max_active to the associated
3694  * workqueue's saved_max_active and activate delayed work items
3695  * accordingly.  If @pwq is freezing, clear @pwq->max_active to zero.
3696  */
3697 static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3698 {
3699         struct workqueue_struct *wq = pwq->wq;
3700         bool freezable = wq->flags & WQ_FREEZABLE;
3701         unsigned long flags;
3702 
3703         /* for @wq->saved_max_active */
3704         lockdep_assert_held(&wq->mutex);
3705 
3706         /* fast exit for non-freezable wqs */
3707         if (!freezable && pwq->max_active == wq->saved_max_active)
3708                 return;
3709 
3710         /* this function can be called during early boot w/ irq disabled */
3711         spin_lock_irqsave(&pwq->pool->lock, flags);
3712 
3713         /*
3714          * During [un]freezing, the caller is responsible for ensuring that
3715          * this function is called at least once after @workqueue_freezing
3716          * is updated and visible.
3717          */
3718         if (!freezable || !workqueue_freezing) {
3719                 pwq->max_active = wq->saved_max_active;
3720 
3721                 while (!list_empty(&pwq->delayed_works) &&
3722                        pwq->nr_active < pwq->max_active)
3723                         pwq_activate_first_delayed(pwq);
3724 
3725                 /*
3726                  * Need to kick a worker after thawed or an unbound wq's
3727                  * max_active is bumped.  It's a slow path.  Do it always.
3728                  */
3729                 wake_up_worker(pwq->pool);
3730         } else {
3731                 pwq->max_active = 0;
3732         }
3733 
3734         spin_unlock_irqrestore(&pwq->pool->lock, flags);
3735 }
3736 
3737 /* initialize newly alloced @pwq which is associated with @wq and @pool */
3738 static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3739                      struct worker_pool *pool)
3740 {
3741         BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3742 
3743         memset(pwq, 0, sizeof(*pwq));
3744 
3745         pwq->pool = pool;
3746         pwq->wq = wq;
3747         pwq->flush_color = -1;
3748         pwq->refcnt = 1;
3749         INIT_LIST_HEAD(&pwq->delayed_works);
3750         INIT_LIST_HEAD(&pwq->pwqs_node);
3751         INIT_LIST_HEAD(&pwq->mayday_node);
3752         INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3753 }
3754 
3755 /* sync @pwq with the current state of its associated wq and link it */
3756 static void link_pwq(struct pool_workqueue *pwq)
3757 {
3758         struct workqueue_struct *wq = pwq->wq;
3759 
3760         lockdep_assert_held(&wq->mutex);
3761 
3762         /* may be called multiple times, ignore if already linked */
3763         if (!list_empty(&pwq->pwqs_node))
3764                 return;
3765 
3766         /* set the matching work_color */
3767         pwq->work_color = wq->work_color;
3768 
3769         /* sync max_active to the current setting */
3770         pwq_adjust_max_active(pwq);
3771 
3772         /* link in @pwq */
3773         list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3774 }
3775 
3776 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3777 static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3778                                         const struct workqueue_attrs *attrs)
3779 {
3780         struct worker_pool *pool;
3781         struct pool_workqueue *pwq;
3782 
3783         lockdep_assert_held(&wq_pool_mutex);
3784 
3785         pool = get_unbound_pool(attrs);
3786         if (!pool)
3787                 return NULL;
3788 
3789         pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3790         if (!pwq) {
3791                 put_unbound_pool(pool);
3792                 return NULL;
3793         }
3794 
3795         init_pwq(pwq, wq, pool);
3796         return pwq;
3797 }
3798 
3799 /**
3800  * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3801  * @attrs: the wq_attrs of the default pwq of the target workqueue
3802  * @node: the target NUMA node
3803  * @cpu_going_down: if >= 0, the CPU to consider as offline
3804  * @cpumask: outarg, the resulting cpumask
3805  *
3806  * Calculate the cpumask a workqueue with @attrs should use on @node.  If
3807  * @cpu_going_down is >= 0, that cpu is considered offline during
3808  * calculation.  The result is stored in @cpumask.
3809  *
3810  * If NUMA affinity is not enabled, @attrs->cpumask is always used.  If
3811  * enabled and @node has online CPUs requested by @attrs, the returned
3812  * cpumask is the intersection of the possible CPUs of @node and
3813  * @attrs->cpumask.
3814  *
3815  * The caller is responsible for ensuring that the cpumask of @node stays
3816  * stable.
3817  *
3818  * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3819  * %false if equal.
3820  */
3821 static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3822                                  int cpu_going_down, cpumask_t *cpumask)
3823 {
3824         if (!wq_numa_enabled || attrs->no_numa)
3825                 goto use_dfl;
3826 
3827         /* does @node have any online CPUs @attrs wants? */
3828         cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3829         if (cpu_going_down >= 0)
3830                 cpumask_clear_cpu(cpu_going_down, cpumask);
3831 
3832         if (cpumask_empty(cpumask))
3833                 goto use_dfl;
3834 
3835         /* yeap, return possible CPUs in @node that @attrs wants */
3836         cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3837 
3838         if (cpumask_empty(cpumask)) {
3839                 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
3840                                 "possible intersect\n");
3841                 return false;
3842         }
3843 
3844         return !cpumask_equal(cpumask, attrs->cpumask);
3845 
3846 use_dfl:
3847         cpumask_copy(cpumask, attrs->cpumask);
3848         return false;
3849 }
3850 
3851 /* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3852 static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3853                                                    int node,
3854                                                    struct pool_workqueue *pwq)
3855 {
3856         struct pool_workqueue *old_pwq;
3857 
3858         lockdep_assert_held(&wq_pool_mutex);
3859         lockdep_assert_held(&wq->mutex);
3860 
3861         /* link_pwq() can handle duplicate calls */
3862         link_pwq(pwq);
3863 
3864         old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3865         rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3866         return old_pwq;
3867 }
3868 
3869 /* context to store the prepared attrs & pwqs before applying */
3870 struct apply_wqattrs_ctx {
3871         struct workqueue_struct *wq;            /* target workqueue */
3872         struct workqueue_attrs  *attrs;         /* attrs to apply */
3873         struct list_head        list;           /* queued for batching commit */
3874         struct pool_workqueue   *dfl_pwq;
3875         struct pool_workqueue   *pwq_tbl[];
3876 };
3877 
3878 /* free the resources after success or abort */
3879 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3880 {
3881         if (ctx) {
3882                 int node;
3883 
3884                 for_each_node(node)
3885                         put_pwq_unlocked(ctx->pwq_tbl[node]);
3886                 put_pwq_unlocked(ctx->dfl_pwq);
3887 
3888                 free_workqueue_attrs(ctx->attrs);
3889 
3890                 kfree(ctx);
3891         }
3892 }
3893 
3894 /* allocate the attrs and pwqs for later installation */
3895 static struct apply_wqattrs_ctx *
3896 apply_wqattrs_prepare(struct workqueue_struct *wq,
3897                       const struct workqueue_attrs *attrs)
3898 {
3899         struct apply_wqattrs_ctx *ctx;
3900         struct workqueue_attrs *new_attrs, *tmp_attrs;
3901         int node;
3902 
3903         lockdep_assert_held(&wq_pool_mutex);
3904 
3905         ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_node_ids), GFP_KERNEL);
3906 
3907         new_attrs = alloc_workqueue_attrs();
3908         tmp_attrs = alloc_workqueue_attrs();
3909         if (!ctx || !new_attrs || !tmp_attrs)
3910                 goto out_free;
3911 
3912         /*
3913          * Calculate the attrs of the default pwq.
3914          * If the user configured cpumask doesn't overlap with the
3915          * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3916          */
3917         copy_workqueue_attrs(new_attrs, attrs);
3918         cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3919         if (unlikely(cpumask_empty(new_attrs->cpumask)))
3920                 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3921 
3922         /*
3923          * We may create multiple pwqs with differing cpumasks.  Make a
3924          * copy of @new_attrs which will be modified and used to obtain
3925          * pools.
3926          */
3927         copy_workqueue_attrs(tmp_attrs, new_attrs);
3928 
3929         /*
3930          * If something goes wrong during CPU up/down, we'll fall back to
3931          * the default pwq covering whole @attrs->cpumask.  Always create
3932          * it even if we don't use it immediately.
3933          */
3934         ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3935         if (!ctx->dfl_pwq)
3936                 goto out_free;
3937 
3938         for_each_node(node) {
3939                 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3940                         ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3941                         if (!ctx->pwq_tbl[node])
3942                                 goto out_free;
3943                 } else {
3944                         ctx->dfl_pwq->refcnt++;
3945                         ctx->pwq_tbl[node] = ctx->dfl_pwq;
3946                 }
3947         }
3948 
3949         /* save the user configured attrs and sanitize it. */
3950         copy_workqueue_attrs(new_attrs, attrs);
3951         cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3952         ctx->attrs = new_attrs;
3953 
3954         ctx->wq = wq;
3955         free_workqueue_attrs(tmp_attrs);
3956         return ctx;
3957 
3958 out_free:
3959         free_workqueue_attrs(tmp_attrs);
3960         free_workqueue_attrs(new_attrs);
3961         apply_wqattrs_cleanup(ctx);
3962         return NULL;
3963 }
3964 
3965 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3966 static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
3967 {
3968         int node;
3969 
3970         /* all pwqs have been created successfully, let's install'em */
3971         mutex_lock(&ctx->wq->mutex);
3972 
3973         copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
3974 
3975         /* save the previous pwq and install the new one */
3976         for_each_node(node)
3977                 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
3978                                                           ctx->pwq_tbl[node]);
3979 
3980         /* @dfl_pwq might not have been used, ensure it's linked */
3981         link_pwq(ctx->dfl_pwq);
3982         swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
3983 
3984         mutex_unlock(&ctx->wq->mutex);
3985 }
3986 
3987 static void apply_wqattrs_lock(void)
3988 {
3989         /* CPUs should stay stable across pwq creations and installations */
3990         get_online_cpus();
3991         mutex_lock(&wq_pool_mutex);
3992 }
3993 
3994 static void apply_wqattrs_unlock(void)
3995 {
3996         mutex_unlock(&wq_pool_mutex);
3997         put_online_cpus();
3998 }
3999 
4000 static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
4001                                         const struct workqueue_attrs *attrs)
4002 {
4003         struct apply_wqattrs_ctx *ctx;
4004 
4005         /* only unbound workqueues can change attributes */
4006         if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
4007                 return -EINVAL;
4008 
4009         /* creating multiple pwqs breaks ordering guarantee */
4010         if (!list_empty(&wq->pwqs)) {
4011                 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4012                         return -EINVAL;
4013 
4014                 wq->flags &= ~__WQ_ORDERED;
4015         }
4016 
4017         ctx = apply_wqattrs_prepare(wq, attrs);
4018         if (!ctx)
4019                 return -ENOMEM;
4020 
4021         /* the ctx has been prepared successfully, let's commit it */
4022         apply_wqattrs_commit(ctx);
4023         apply_wqattrs_cleanup(ctx);
4024 
4025         return 0;
4026 }
4027 
4028 /**
4029  * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
4030  * @wq: the target workqueue
4031  * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
4032  *
4033  * Apply @attrs to an unbound workqueue @wq.  Unless disabled, on NUMA
4034  * machines, this function maps a separate pwq to each NUMA node with
4035  * possibles CPUs in @attrs->cpumask so that work items are affine to the
4036  * NUMA node it was issued on.  Older pwqs are released as in-flight work
4037  * items finish.  Note that a work item which repeatedly requeues itself
4038  * back-to-back will stay on its current pwq.
4039  *
4040  * Performs GFP_KERNEL allocations.
4041  *
4042  * Assumes caller has CPU hotplug read exclusion, i.e. get_online_cpus().
4043  *
4044  * Return: 0 on success and -errno on failure.
4045  */
4046 int apply_workqueue_attrs(struct workqueue_struct *wq,
4047                           const struct workqueue_attrs *attrs)
4048 {
4049         int ret;
4050 
4051         lockdep_assert_cpus_held();
4052 
4053         mutex_lock(&wq_pool_mutex);
4054         ret = apply_workqueue_attrs_locked(wq, attrs);
4055         mutex_unlock(&wq_pool_mutex);
4056 
4057         return ret;
4058 }
4059 
4060 /**
4061  * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
4062  * @wq: the target workqueue
4063  * @cpu: the CPU coming up or going down
4064  * @online: whether @cpu is coming up or going down
4065  *
4066  * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4067  * %CPU_DOWN_FAILED.  @cpu is being hot[un]plugged, update NUMA affinity of
4068  * @wq accordingly.
4069  *
4070  * If NUMA affinity can't be adjusted due to memory allocation failure, it
4071  * falls back to @wq->dfl_pwq which may not be optimal but is always
4072  * correct.
4073  *
4074  * Note that when the last allowed CPU of a NUMA node goes offline for a
4075  * workqueue with a cpumask spanning multiple nodes, the workers which were
4076  * already executing the work items for the workqueue will lose their CPU
4077  * affinity and may execute on any CPU.  This is similar to how per-cpu
4078  * workqueues behave on CPU_DOWN.  If a workqueue user wants strict
4079  * affinity, it's the user's responsibility to flush the work item from
4080  * CPU_DOWN_PREPARE.
4081  */
4082 static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
4083                                    bool online)
4084 {
4085         int node = cpu_to_node(cpu);
4086         int cpu_off = online ? -1 : cpu;
4087         struct pool_workqueue *old_pwq = NULL, *pwq;
4088         struct workqueue_attrs *target_attrs;
4089         cpumask_t *cpumask;
4090 
4091         lockdep_assert_held(&wq_pool_mutex);
4092 
4093         if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
4094             wq->unbound_attrs->no_numa)
4095                 return;
4096 
4097         /*
4098          * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4099          * Let's use a preallocated one.  The following buf is protected by
4100          * CPU hotplug exclusion.
4101          */
4102         target_attrs = wq_update_unbound_numa_attrs_buf;
4103         cpumask = target_attrs->cpumask;
4104 
4105         copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
4106         pwq = unbound_pwq_by_node(wq, node);
4107 
4108         /*
4109          * Let's determine what needs to be done.  If the target cpumask is
4110          * different from the default pwq's, we need to compare it to @pwq's
4111          * and create a new one if they don't match.  If the target cpumask
4112          * equals the default pwq's, the default pwq should be used.
4113          */
4114         if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
4115                 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
4116                         return;
4117         } else {
4118                 goto use_dfl_pwq;
4119         }
4120 
4121         /* create a new pwq */
4122         pwq = alloc_unbound_pwq(wq, target_attrs);
4123         if (!pwq) {
4124                 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
4125                         wq->name);
4126                 goto use_dfl_pwq;
4127         }
4128 
4129         /* Install the new pwq. */
4130         mutex_lock(&wq->mutex);
4131         old_pwq = numa_pwq_tbl_install(wq, node, pwq);
4132         goto out_unlock;
4133 
4134 use_dfl_pwq:
4135         mutex_lock(&wq->mutex);
4136         spin_lock_irq(&wq->dfl_pwq->pool->lock);
4137         get_pwq(wq->dfl_pwq);
4138         spin_unlock_irq(&wq->dfl_pwq->pool->lock);
4139         old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
4140 out_unlock:
4141         mutex_unlock(&wq->mutex);
4142         put_pwq_unlocked(old_pwq);
4143 }
4144 
4145 static int alloc_and_link_pwqs(struct workqueue_struct *wq)
4146 {
4147         bool highpri = wq->flags & WQ_HIGHPRI;
4148         int cpu, ret;
4149 
4150         if (!(wq->flags & WQ_UNBOUND)) {
4151                 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
4152                 if (!wq->cpu_pwqs)
4153                         return -ENOMEM;
4154 
4155                 for_each_possible_cpu(cpu) {
4156                         struct pool_workqueue *pwq =
4157                                 per_cpu_ptr(wq->cpu_pwqs, cpu);
4158                         struct worker_pool *cpu_pools =
4159                                 per_cpu(cpu_worker_pools, cpu);
4160 
4161                         init_pwq(pwq, wq, &cpu_pools[highpri]);
4162 
4163                         mutex_lock(&wq->mutex);
4164                         link_pwq(pwq);
4165                         mutex_unlock(&wq->mutex);
4166                 }
4167                 return 0;
4168         }
4169 
4170         get_online_cpus();
4171         if (wq->flags & __WQ_ORDERED) {
4172                 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
4173                 /* there should only be single pwq for ordering guarantee */
4174                 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
4175                               wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
4176                      "ordering guarantee broken for workqueue %s\n", wq->name);
4177         } else {
4178                 ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
4179         }
4180         put_online_cpus();
4181 
4182         return ret;
4183 }
4184 
4185 static int wq_clamp_max_active(int max_active, unsigned int flags,
4186                                const char *name)
4187 {
4188         int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
4189 
4190         if (max_active < 1 || max_active > lim)
4191                 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4192                         max_active, name, 1, lim);
4193 
4194         return clamp_val(max_active, 1, lim);
4195 }
4196 
4197 /*
4198  * Workqueues which may be used during memory reclaim should have a rescuer
4199  * to guarantee forward progress.
4200  */
4201 static int init_rescuer(struct workqueue_struct *wq)
4202 {
4203         struct worker *rescuer;
4204         int ret;
4205 
4206         if (!(wq->flags & WQ_MEM_RECLAIM))
4207                 return 0;
4208 
4209         rescuer = alloc_worker(NUMA_NO_NODE);
4210         if (!rescuer)
4211                 return -ENOMEM;
4212 
4213         rescuer->rescue_wq = wq;
4214         rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->name);
4215         ret = PTR_ERR_OR_ZERO(rescuer->task);
4216         if (ret) {
4217                 kfree(rescuer);
4218                 return ret;
4219         }
4220 
4221         wq->rescuer = rescuer;
4222         kthread_bind_mask(rescuer->task, cpu_possible_mask);
4223         wake_up_process(rescuer->task);
4224 
4225         return 0;
4226 }
4227 
4228 __printf(1, 4)
4229 struct workqueue_struct *alloc_workqueue(const char *fmt,
4230                                          unsigned int flags,
4231                                          int max_active, ...)
4232 {
4233         size_t tbl_size = 0;
4234         va_list args;
4235         struct workqueue_struct *wq;
4236         struct pool_workqueue *pwq;
4237 
4238         /*
4239          * Unbound && max_active == 1 used to imply ordered, which is no
4240          * longer the case on NUMA machines due to per-node pools.  While
4241          * alloc_ordered_workqueue() is the right way to create an ordered
4242          * workqueue, keep the previous behavior to avoid subtle breakages
4243          * on NUMA.
4244          */
4245         if ((flags & WQ_UNBOUND) && max_active == 1)
4246                 flags |= __WQ_ORDERED;
4247 
4248         /* see the comment above the definition of WQ_POWER_EFFICIENT */
4249         if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4250                 flags |= WQ_UNBOUND;
4251 
4252         /* allocate wq and format name */
4253         if (flags & WQ_UNBOUND)
4254                 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
4255 
4256         wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
4257         if (!wq)
4258                 return NULL;
4259 
4260         if (flags & WQ_UNBOUND) {
4261                 wq->unbound_attrs = alloc_workqueue_attrs();
4262                 if (!wq->unbound_attrs)
4263                         goto err_free_wq;
4264         }
4265 
4266         va_start(args, max_active);
4267         vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4268         va_end(args);
4269 
4270         max_active = max_active ?: WQ_DFL_ACTIVE;
4271         max_active = wq_clamp_max_active(max_active, flags, wq->name);
4272 
4273         /* init wq */
4274         wq->flags = flags;
4275         wq->saved_max_active = max_active;
4276         mutex_init(&wq->mutex);
4277         atomic_set(&wq->nr_pwqs_to_flush, 0);
4278         INIT_LIST_HEAD(&wq->pwqs);
4279         INIT_LIST_HEAD(&wq->flusher_queue);
4280         INIT_LIST_HEAD(&wq->flusher_overflow);
4281         INIT_LIST_HEAD(&wq->maydays);
4282 
4283         wq_init_lockdep(wq);
4284         INIT_LIST_HEAD(&wq->list);
4285 
4286         if (alloc_and_link_pwqs(wq) < 0)
4287                 goto err_unreg_lockdep;
4288 
4289         if (wq_online && init_rescuer(wq) < 0)
4290                 goto err_destroy;
4291 
4292         if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4293                 goto err_destroy;
4294 
4295         /*
4296          * wq_pool_mutex protects global freeze state and workqueues list.
4297          * Grab it, adjust max_active and add the new @wq to workqueues
4298          * list.
4299          */
4300         mutex_lock(&wq_pool_mutex);
4301 
4302         mutex_lock(&wq->mutex);
4303         for_each_pwq(pwq, wq)
4304                 pwq_adjust_max_active(pwq);
4305         mutex_unlock(&wq->mutex);
4306 
4307         list_add_tail_rcu(&wq->list, &workqueues);
4308 
4309         mutex_unlock(&wq_pool_mutex);
4310 
4311         return wq;
4312 
4313 err_unreg_lockdep:
4314         wq_unregister_lockdep(wq);
4315         wq_free_lockdep(wq);
4316 err_free_wq:
4317         free_workqueue_attrs(wq->unbound_attrs);
4318         kfree(wq);
4319         return NULL;
4320 err_destroy:
4321         destroy_workqueue(wq);
4322         return NULL;
4323 }
4324 EXPORT_SYMBOL_GPL(alloc_workqueue);
4325 
4326 /**
4327  * destroy_workqueue - safely terminate a workqueue
4328  * @wq: target workqueue
4329  *
4330  * Safely destroy a workqueue. All work currently pending will be done first.
4331  */
4332 void destroy_workqueue(struct workqueue_struct *wq)
4333 {
4334         struct pool_workqueue *pwq;
4335         int node;
4336 
4337         /*
4338          * Remove it from sysfs first so that sanity check failure doesn't
4339          * lead to sysfs name conflicts.
4340          */
4341         workqueue_sysfs_unregister(wq);
4342 
4343         /* drain it before proceeding with destruction */
4344         drain_workqueue(wq);
4345 
4346         /* kill rescuer, if sanity checks fail, leave it w/o rescuer */
4347         if (wq->rescuer) {
4348                 struct worker *rescuer = wq->rescuer;
4349 
4350                 /* this prevents new queueing */
4351                 spin_lock_irq(&wq_mayday_lock);
4352                 wq->rescuer = NULL;
4353                 spin_unlock_irq(&wq_mayday_lock);
4354 
4355                 /* rescuer will empty maydays list before exiting */
4356                 kthread_stop(rescuer->task);
4357                 kfree(rescuer);
4358         }
4359 
4360         /* sanity checks */
4361         mutex_lock(&wq->mutex);
4362         for_each_pwq(pwq, wq) {
4363                 int i;
4364 
4365                 for (i = 0; i < WORK_NR_COLORS; i++) {
4366                         if (WARN_ON(pwq->nr_in_flight[i])) {
4367                                 mutex_unlock(&wq->mutex);
4368                                 show_workqueue_state();
4369                                 return;
4370                         }
4371                 }
4372 
4373                 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
4374                     WARN_ON(pwq->nr_active) ||
4375                     WARN_ON(!list_empty(&pwq->delayed_works))) {
4376                         mutex_unlock(&wq->mutex);
4377                         show_workqueue_state();
4378                         return;
4379                 }
4380         }
4381         mutex_unlock(&wq->mutex);
4382 
4383         /*
4384          * wq list is used to freeze wq, remove from list after
4385          * flushing is complete in case freeze races us.
4386          */
4387         mutex_lock(&wq_pool_mutex);
4388         list_del_rcu(&wq->list);
4389         mutex_unlock(&wq_pool_mutex);
4390 
4391         if (!(wq->flags & WQ_UNBOUND)) {
4392                 wq_unregister_lockdep(wq);
4393                 /*
4394                  * The base ref is never dropped on per-cpu pwqs.  Directly
4395                  * schedule RCU free.
4396                  */
4397                 call_rcu(&wq->rcu, rcu_free_wq);
4398         } else {
4399                 /*
4400                  * We're the sole accessor of @wq at this point.  Directly
4401                  * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4402                  * @wq will be freed when the last pwq is released.
4403                  */
4404                 for_each_node(node) {
4405                         pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4406                         RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4407                         put_pwq_unlocked(pwq);
4408                 }
4409 
4410                 /*
4411                  * Put dfl_pwq.  @wq may be freed any time after dfl_pwq is
4412                  * put.  Don't access it afterwards.
4413                  */
4414                 pwq = wq->dfl_pwq;
4415                 wq->dfl_pwq = NULL;
4416                 put_pwq_unlocked(pwq);
4417         }
4418 }
4419 EXPORT_SYMBOL_GPL(destroy_workqueue);
4420 
4421 /**
4422  * workqueue_set_max_active - adjust max_active of a workqueue
4423  * @wq: target workqueue
4424  * @max_active: new max_active value.
4425  *
4426  * Set max_active of @wq to @max_active.
4427  *
4428  * CONTEXT:
4429  * Don't call from IRQ context.
4430  */
4431 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4432 {
4433         struct pool_workqueue *pwq;
4434 
4435         /* disallow meddling with max_active for ordered workqueues */
4436         if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4437                 return;
4438 
4439         max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4440 
4441         mutex_lock(&wq->mutex);
4442 
4443         wq->flags &= ~__WQ_ORDERED;
4444         wq->saved_max_active = max_active;
4445 
4446         for_each_pwq(pwq, wq)
4447                 pwq_adjust_max_active(pwq);
4448 
4449         mutex_unlock(&wq->mutex);
4450 }
4451 EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4452 
4453 /**
4454  * current_work - retrieve %current task's work struct
4455  *
4456  * Determine if %current task is a workqueue worker and what it's working on.
4457  * Useful to find out the context that the %current task is running in.
4458  *
4459  * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4460  */
4461 struct work_struct *current_work(void)
4462 {
4463         struct worker *worker = current_wq_worker();
4464 
4465         return worker ? worker->current_work : NULL;
4466 }
4467 EXPORT_SYMBOL(current_work);
4468 
4469 /**
4470  * current_is_workqueue_rescuer - is %current workqueue rescuer?
4471  *
4472  * Determine whether %current is a workqueue rescuer.  Can be used from
4473  * work functions to determine whether it's being run off the rescuer task.
4474  *
4475  * Return: %true if %current is a workqueue rescuer. %false otherwise.
4476  */
4477 bool current_is_workqueue_rescuer(void)
4478 {
4479         struct worker *worker = current_wq_worker();
4480 
4481         return worker && worker->rescue_wq;
4482 }
4483 
4484 /**
4485  * workqueue_congested - test whether a workqueue is congested
4486  * @cpu: CPU in question
4487  * @wq: target workqueue
4488  *
4489  * Test whether @wq's cpu workqueue for @cpu is congested.  There is
4490  * no synchronization around this function and the test result is
4491  * unreliable and only useful as advisory hints or for debugging.
4492  *
4493  * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4494  * Note that both per-cpu and unbound workqueues may be associated with
4495  * multiple pool_workqueues which have separate congested states.  A
4496  * workqueue being congested on one CPU doesn't mean the workqueue is also
4497  * contested on other CPUs / NUMA nodes.
4498  *
4499  * Return:
4500  * %true if congested, %false otherwise.
4501  */
4502 bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4503 {
4504         struct pool_workqueue *pwq;
4505         bool ret;
4506 
4507         rcu_read_lock();
4508         preempt_disable();
4509 
4510         if (cpu == WORK_CPU_UNBOUND)
4511                 cpu = smp_processor_id();
4512 
4513         if (!(wq->flags & WQ_UNBOUND))
4514                 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4515         else
4516                 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4517 
4518         ret = !list_empty(&pwq->delayed_works);
4519         preempt_enable();
4520         rcu_read_unlock();
4521 
4522         return ret;
4523 }
4524 EXPORT_SYMBOL_GPL(workqueue_congested);
4525 
4526 /**
4527  * work_busy - test whether a work is currently pending or running
4528  * @work: the work to be tested
4529  *
4530  * Test whether @work is currently pending or running.  There is no
4531  * synchronization around this function and the test result is
4532  * unreliable and only useful as advisory hints or for debugging.
4533  *
4534  * Return:
4535  * OR'd bitmask of WORK_BUSY_* bits.
4536  */
4537 unsigned int work_busy(struct work_struct *work)
4538 {
4539         struct worker_pool *pool;
4540         unsigned long flags;
4541         unsigned int ret = 0;
4542 
4543         if (work_pending(work))
4544                 ret |= WORK_BUSY_PENDING;
4545 
4546         rcu_read_lock();
4547         pool = get_work_pool(work);
4548         if (pool) {
4549                 spin_lock_irqsave(&pool->lock, flags);
4550                 if (find_worker_executing_work(pool, work))
4551                         ret |= WORK_BUSY_RUNNING;
4552                 spin_unlock_irqrestore(&pool->lock, flags);
4553         }
4554         rcu_read_unlock();
4555 
4556         return ret;
4557 }
4558 EXPORT_SYMBOL_GPL(work_busy);
4559 
4560 /**
4561  * set_worker_desc - set description for the current work item
4562  * @fmt: printf-style format string
4563  * @...: arguments for the format string
4564  *
4565  * This function can be called by a running work function to describe what
4566  * the work item is about.  If the worker task gets dumped, this
4567  * information will be printed out together to help debugging.  The
4568  * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4569  */
4570 void set_worker_desc(const char *fmt, ...)
4571 {
4572         struct worker *worker = current_wq_worker();
4573         va_list args;
4574 
4575         if (worker) {
4576                 va_start(args, fmt);
4577                 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4578                 va_end(args);
4579         }
4580 }
4581 EXPORT_SYMBOL_GPL(set_worker_desc);
4582 
4583 /**
4584  * print_worker_info - print out worker information and description
4585  * @log_lvl: the log level to use when printing
4586  * @task: target task
4587  *
4588  * If @task is a worker and currently executing a work item, print out the
4589  * name of the workqueue being serviced and worker description set with
4590  * set_worker_desc() by the currently executing work item.
4591  *
4592  * This function can be safely called on any task as long as the
4593  * task_struct itself is accessible.  While safe, this function isn't
4594  * synchronized and may print out mixups or garbages of limited length.
4595  */
4596 void print_worker_info(const char *log_lvl, struct task_struct *task)
4597 {
4598         work_func_t *fn = NULL;
4599         char name[WQ_NAME_LEN] = { };
4600         char desc[WORKER_DESC_LEN] = { };
4601         struct pool_workqueue *pwq = NULL;
4602         struct workqueue_struct *wq = NULL;
4603         struct worker *worker;
4604 
4605         if (!(task->flags & PF_WQ_WORKER))
4606                 return;
4607 
4608         /*
4609          * This function is called without any synchronization and @task
4610          * could be in any state.  Be careful with dereferences.
4611          */
4612         worker = kthread_probe_data(task);
4613 
4614         /*
4615          * Carefully copy the associated workqueue's workfn, name and desc.
4616          * Keep the original last '\0' in case the original is garbage.
4617          */
4618         probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
4619         probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
4620         probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
4621         probe_kernel_read(name, wq->name, sizeof(name) - 1);
4622         probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
4623 
4624         if (fn || name[0] || desc[0]) {
4625                 printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
4626                 if (strcmp(name, desc))
4627                         pr_cont(" (%s)", desc);
4628                 pr_cont("\n");
4629         }
4630 }
4631 
4632 static void pr_cont_pool_info(struct worker_pool *pool)
4633 {
4634         pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4635         if (pool->node != NUMA_NO_NODE)
4636                 pr_cont(" node=%d", pool->node);
4637         pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4638 }
4639 
4640 static void pr_cont_work(bool comma, struct work_struct *work)
4641 {
4642         if (work->func == wq_barrier_func) {
4643                 struct wq_barrier *barr;
4644 
4645                 barr = container_of(work, struct wq_barrier, work);
4646 
4647                 pr_cont("%s BAR(%d)", comma ? "," : "",
4648                         task_pid_nr(barr->task));
4649         } else {
4650                 pr_cont("%s %ps", comma ? "," : "", work->func);
4651         }
4652 }
4653 
4654 static void show_pwq(struct pool_workqueue *pwq)
4655 {
4656         struct worker_pool *pool = pwq->pool;
4657         struct work_struct *work;
4658         struct worker *worker;
4659         bool has_in_flight = false, has_pending = false;
4660         int bkt;
4661 
4662         pr_info("  pwq %d:", pool->id);
4663         pr_cont_pool_info(pool);
4664 
4665         pr_cont(" active=%d/%d refcnt=%d%s\n",
4666                 pwq->nr_active, pwq->max_active, pwq->refcnt,
4667                 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4668 
4669         hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4670                 if (worker->current_pwq == pwq) {
4671                         has_in_flight = true;
4672                         break;
4673                 }
4674         }
4675         if (has_in_flight) {
4676                 bool comma = false;
4677 
4678                 pr_info("    in-flight:");
4679                 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4680                         if (worker->current_pwq != pwq)
4681                                 continue;
4682 
4683                         pr_cont("%s %d%s:%ps", comma ? "," : "",
4684                                 task_pid_nr(worker->task),
4685                                 worker == pwq->wq->rescuer ? "(RESCUER)" : "",
4686                                 worker->current_func);
4687                         list_for_each_entry(work, &worker->scheduled, entry)
4688                                 pr_cont_work(false, work);
4689                         comma = true;
4690                 }
4691                 pr_cont("\n");
4692         }
4693 
4694         list_for_each_entry(work, &pool->worklist, entry) {
4695                 if (get_work_pwq(work) == pwq) {
4696                         has_pending = true;
4697                         break;
4698                 }
4699         }
4700         if (has_pending) {
4701                 bool comma = false;
4702 
4703                 pr_info("    pending:");
4704                 list_for_each_entry(work, &pool->worklist, entry) {
4705                         if (get_work_pwq(work) != pwq)
4706                                 continue;
4707 
4708                         pr_cont_work(comma, work);
4709                         comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4710                 }
4711                 pr_cont("\n");
4712         }
4713 
4714         if (!list_empty(&pwq->delayed_works)) {
4715                 bool comma = false;
4716 
4717                 pr_info("    delayed:");
4718                 list_for_each_entry(work, &pwq->delayed_works, entry) {
4719                         pr_cont_work(comma, work);
4720                         comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4721                 }
4722                 pr_cont("\n");
4723         }
4724 }
4725 
4726 /**
4727  * show_workqueue_state - dump workqueue state
4728  *
4729  * Called from a sysrq handler or try_to_freeze_tasks() and prints out
4730  * all busy workqueues and pools.
4731  */
4732 void show_workqueue_state(void)
4733 {
4734         struct workqueue_struct *wq;
4735         struct worker_pool *pool;
4736         unsigned long flags;
4737         int pi;
4738 
4739         rcu_read_lock();
4740 
4741         pr_info("Showing busy workqueues and worker pools:\n");
4742 
4743         list_for_each_entry_rcu(wq, &workqueues, list) {
4744                 struct pool_workqueue *pwq;
4745                 bool idle = true;
4746 
4747                 for_each_pwq(pwq, wq) {
4748                         if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
4749                                 idle = false;
4750                                 break;
4751                         }
4752                 }
4753                 if (idle)
4754                         continue;
4755 
4756                 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4757 
4758                 for_each_pwq(pwq, wq) {
4759                         spin_lock_irqsave(&pwq->pool->lock, flags);
4760                         if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4761                                 show_pwq(pwq);
4762                         spin_unlock_irqrestore(&pwq->pool->lock, flags);
4763                         /*
4764                          * We could be printing a lot from atomic context, e.g.
4765                          * sysrq-t -> show_workqueue_state(). Avoid triggering
4766                          * hard lockup.
4767                          */
4768                         touch_nmi_watchdog();
4769                 }
4770         }
4771 
4772         for_each_pool(pool, pi) {
4773                 struct worker *worker;
4774                 bool first = true;
4775 
4776                 spin_lock_irqsave(&pool->lock, flags);
4777                 if (pool->nr_workers == pool->nr_idle)
4778                         goto next_pool;
4779 
4780                 pr_info("pool %d:", pool->id);
4781                 pr_cont_pool_info(pool);
4782                 pr_cont(" hung=%us workers=%d",
4783                         jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
4784                         pool->nr_workers);
4785                 if (pool->manager)
4786                         pr_cont(" manager: %d",
4787                                 task_pid_nr(pool->manager->task));
4788                 list_for_each_entry(worker, &pool->idle_list, entry) {
4789                         pr_cont(" %s%d", first ? "idle: " : "",
4790                                 task_pid_nr(worker->task));
4791                         first = false;
4792                 }
4793                 pr_cont("\n");
4794         next_pool:
4795                 spin_unlock_irqrestore(&pool->lock, flags);
4796                 /*
4797                  * We could be printing a lot from atomic context, e.g.
4798                  * sysrq-t -> show_workqueue_state(). Avoid triggering
4799                  * hard lockup.
4800                  */
4801                 touch_nmi_watchdog();
4802         }
4803 
4804         rcu_read_unlock();
4805 }
4806 
4807 /* used to show worker information through /proc/PID/{comm,stat,status} */
4808 void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
4809 {
4810         int off;
4811 
4812         /* always show the actual comm */
4813         off = strscpy(buf, task->comm, size);
4814         if (off < 0)
4815                 return;
4816 
4817         /* stabilize PF_WQ_WORKER and worker pool association */
4818         mutex_lock(&wq_pool_attach_mutex);
4819 
4820         if (task->flags & PF_WQ_WORKER) {
4821                 struct worker *worker = kthread_data(task);
4822                 struct worker_pool *pool = worker->pool;
4823 
4824                 if (pool) {
4825                         spin_lock_irq(&pool->lock);
4826                         /*
4827                          * ->desc tracks information (wq name or
4828                          * set_worker_desc()) for the latest execution.  If
4829                          * current, prepend '+', otherwise '-'.
4830                          */
4831                         if (worker->desc[0] != '\0') {
4832                                 if (worker->current_work)
4833                                         scnprintf(buf + off, size - off, "+%s",
4834                                                   worker->desc);
4835                                 else
4836                                         scnprintf(buf + off, size - off, "-%s",
4837                                                   worker->desc);
4838                         }
4839                         spin_unlock_irq(&pool->lock);
4840                 }
4841         }
4842 
4843         mutex_unlock(&wq_pool_attach_mutex);
4844 }
4845 
4846 #ifdef CONFIG_SMP
4847 
4848 /*
4849  * CPU hotplug.
4850  *
4851  * There are two challenges in supporting CPU hotplug.  Firstly, there
4852  * are a lot of assumptions on strong associations among work, pwq and
4853  * pool which make migrating pending and scheduled works very
4854  * difficult to implement without impacting hot paths.  Secondly,
4855  * worker pools serve mix of short, long and very long running works making
4856  * blocked draining impractical.
4857  *
4858  * This is solved by allowing the pools to be disassociated from the CPU
4859  * running as an unbound one and allowing it to be reattached later if the
4860  * cpu comes back online.
4861  */
4862 
4863 static void unbind_workers(int cpu)
4864 {
4865         struct worker_pool *pool;
4866         struct worker *worker;
4867 
4868         for_each_cpu_worker_pool(pool, cpu) {
4869                 mutex_lock(&wq_pool_attach_mutex);
4870                 spin_lock_irq(&pool->lock);
4871 
4872                 /*
4873                  * We've blocked all attach/detach operations. Make all workers
4874                  * unbound and set DISASSOCIATED.  Before this, all workers
4875                  * except for the ones which are still executing works from
4876                  * before the last CPU down must be on the cpu.  After
4877                  * this, they may become diasporas.
4878                  */
4879                 for_each_pool_worker(worker, pool)
4880                         worker->flags |= WORKER_UNBOUND;
4881 
4882                 pool->flags |= POOL_DISASSOCIATED;
4883 
4884                 spin_unlock_irq(&pool->lock);
4885                 mutex_unlock(&wq_pool_attach_mutex);
4886 
4887                 /*
4888                  * Call schedule() so that we cross rq->lock and thus can
4889                  * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4890                  * This is necessary as scheduler callbacks may be invoked
4891                  * from other cpus.
4892                  */
4893                 schedule();
4894 
4895                 /*
4896                  * Sched callbacks are disabled now.  Zap nr_running.
4897                  * After this, nr_running stays zero and need_more_worker()
4898                  * and keep_working() are always true as long as the
4899                  * worklist is not empty.  This pool now behaves as an
4900                  * unbound (in terms of concurrency management) pool which
4901                  * are served by workers tied to the pool.
4902                  */
4903                 atomic_set(&pool->nr_running, 0);
4904 
4905                 /*
4906                  * With concurrency management just turned off, a busy
4907                  * worker blocking could lead to lengthy stalls.  Kick off
4908                  * unbound chain execution of currently pending work items.
4909                  */
4910                 spin_lock_irq(&pool->lock);
4911                 wake_up_worker(pool);
4912                 spin_unlock_irq(&pool->lock);
4913         }
4914 }
4915 
4916 /**
4917  * rebind_workers - rebind all workers of a pool to the associated CPU
4918  * @pool: pool of interest
4919  *
4920  * @pool->cpu is coming online.  Rebind all workers to the CPU.
4921  */
4922 static void rebind_workers(struct worker_pool *pool)
4923 {
4924         struct worker *worker;
4925 
4926         lockdep_assert_held(&wq_pool_attach_mutex);
4927 
4928         /*
4929          * Restore CPU affinity of all workers.  As all idle workers should
4930          * be on the run-queue of the associated CPU before any local
4931          * wake-ups for concurrency management happen, restore CPU affinity
4932          * of all workers first and then clear UNBOUND.  As we're called
4933          * from CPU_ONLINE, the following shouldn't fail.
4934          */
4935         for_each_pool_worker(worker, pool)
4936                 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4937                                                   pool->attrs->cpumask) < 0);
4938 
4939         spin_lock_irq(&pool->lock);
4940 
4941         pool->flags &= ~POOL_DISASSOCIATED;
4942 
4943         for_each_pool_worker(worker, pool) {
4944                 unsigned int worker_flags = worker->flags;
4945 
4946                 /*
4947                  * A bound idle worker should actually be on the runqueue
4948                  * of the associated CPU for local wake-ups targeting it to
4949                  * work.  Kick all idle workers so that they migrate to the
4950                  * associated CPU.  Doing this in the same loop as
4951                  * replacing UNBOUND with REBOUND is safe as no worker will
4952                  * be bound before @pool->lock is released.
4953                  */
4954                 if (worker_flags & WORKER_IDLE)
4955                         wake_up_process(worker->task);
4956 
4957                 /*
4958                  * We want to clear UNBOUND but can't directly call
4959                  * worker_clr_flags() or adjust nr_running.  Atomically
4960                  * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4961                  * @worker will clear REBOUND using worker_clr_flags() when
4962                  * it initiates the next execution cycle thus restoring
4963                  * concurrency management.  Note that when or whether
4964                  * @worker clears REBOUND doesn't affect correctness.
4965                  *
4966                  * WRITE_ONCE() is necessary because @worker->flags may be
4967                  * tested without holding any lock in
4968                  * wq_worker_running().  Without it, NOT_RUNNING test may
4969                  * fail incorrectly leading to premature concurrency
4970                  * management operations.
4971                  */
4972                 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
4973                 worker_flags |= WORKER_REBOUND;
4974                 worker_flags &= ~WORKER_UNBOUND;
4975                 WRITE_ONCE(worker->flags, worker_flags);
4976         }
4977 
4978         spin_unlock_irq(&pool->lock);
4979 }
4980 
4981 /**
4982  * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4983  * @pool: unbound pool of interest
4984  * @cpu: the CPU which is coming up
4985  *
4986  * An unbound pool may end up with a cpumask which doesn't have any online
4987  * CPUs.  When a worker of such pool get scheduled, the scheduler resets
4988  * its cpus_allowed.  If @cpu is in @pool's cpumask which didn't have any
4989  * online CPU before, cpus_allowed of all its workers should be restored.
4990  */
4991 static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
4992 {
4993         static cpumask_t cpumask;
4994         struct worker *worker;
4995 
4996         lockdep_assert_held(&wq_pool_attach_mutex);
4997 
4998         /* is @cpu allowed for @pool? */
4999         if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
5000                 return;
5001 
5002         cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
5003 
5004         /* as we're called from CPU_ONLINE, the following shouldn't fail */
5005         for_each_pool_worker(worker, pool)
5006                 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
5007 }
5008 
5009 int workqueue_prepare_cpu(unsigned int cpu)
5010 {
5011         struct worker_pool *pool;
5012 
5013         for_each_cpu_worker_pool(pool, cpu) {
5014                 if (pool->nr_workers)
5015                         continue;
5016                 if (!create_worker(pool))
5017                         return -ENOMEM;
5018         }
5019         return 0;
5020 }
5021 
5022 int workqueue_online_cpu(unsigned int cpu)
5023 {
5024         struct worker_pool *pool;
5025         struct workqueue_struct *wq;
5026         int pi;
5027 
5028         mutex_lock(&wq_pool_mutex);
5029 
5030         for_each_pool(pool, pi) {
5031                 mutex_lock(&wq_pool_attach_mutex);
5032 
5033                 if (pool->cpu == cpu)
5034                         rebind_workers(pool);
5035                 else if (pool->cpu < 0)
5036                         restore_unbound_workers_cpumask(pool, cpu);
5037 
5038                 mutex_unlock(&wq_pool_attach_mutex);
5039         }
5040 
5041         /* update NUMA affinity of unbound workqueues */
5042         list_for_each_entry(wq, &workqueues, list)
5043                 wq_update_unbound_numa(wq, cpu, true);
5044 
5045         mutex_unlock(&wq_pool_mutex);
5046         return 0;
5047 }
5048 
5049 int workqueue_offline_cpu(unsigned int cpu)
5050 {
5051         struct workqueue_struct *wq;
5052 
5053         /* unbinding per-cpu workers should happen on the local CPU */
5054         if (WARN_ON(cpu != smp_processor_id()))
5055                 return -1;
5056 
5057         unbind_workers(cpu);
5058 
5059         /* update NUMA affinity of unbound workqueues */
5060         mutex_lock(&wq_pool_mutex);
5061         list_for_each_entry(wq, &workqueues, list)
5062                 wq_update_unbound_numa(wq, cpu, false);
5063         mutex_unlock(&wq_pool_mutex);
5064 
5065         return 0;
5066 }
5067 
5068 struct work_for_cpu {
5069         struct work_struct work;
5070         long (*fn)(void *);
5071         void *arg;
5072         long ret;
5073 };
5074 
5075 static void work_for_cpu_fn(struct work_struct *work)
5076 {
5077         struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
5078 
5079         wfc->ret = wfc->fn(wfc->arg);
5080 }
5081 
5082 /**
5083  * work_on_cpu - run a function in thread context on a particular cpu
5084  * @cpu: the cpu to run on
5085  * @fn: the function to run
5086  * @arg: the function arg
5087  *
5088  * It is up to the caller to ensure that the cpu doesn't go offline.
5089  * The caller must not hold any locks which would prevent @fn from completing.
5090  *
5091  * Return: The value @fn returns.
5092  */
5093 long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
5094 {
5095         struct work_for_cpu wfc = { .fn = fn, .arg = arg };
5096 
5097         INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
5098         schedule_work_on(cpu, &wfc.work);
5099         flush_work(&wfc.work);
5100         destroy_work_on_stack(&wfc.work);
5101         return wfc.ret;
5102 }
5103 EXPORT_SYMBOL_GPL(work_on_cpu);
5104 
5105 /**
5106  * work_on_cpu_safe - run a function in thread context on a particular cpu
5107  * @cpu: the cpu to run on
5108  * @fn:  the function to run
5109  * @arg: the function argument
5110  *
5111  * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
5112  * any locks which would prevent @fn from completing.
5113  *
5114  * Return: The value @fn returns.
5115  */
5116 long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
5117 {
5118         long ret = -ENODEV;
5119 
5120         get_online_cpus();
5121         if (cpu_online(cpu))
5122                 ret = work_on_cpu(cpu, fn, arg);
5123         put_online_cpus();
5124         return ret;
5125 }
5126 EXPORT_SYMBOL_GPL(work_on_cpu_safe);
5127 #endif /* CONFIG_SMP */
5128 
5129 #ifdef CONFIG_FREEZER
5130 
5131 /**
5132  * freeze_workqueues_begin - begin freezing workqueues
5133  *
5134  * Start freezing workqueues.  After this function returns, all freezable
5135  * workqueues will queue new works to their delayed_works list instead of
5136  * pool->worklist.
5137  *
5138  * CONTEXT:
5139  * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5140  */
5141 void freeze_workqueues_begin(void)
5142 {
5143         struct workqueue_struct *wq;
5144         struct pool_workqueue *pwq;
5145 
5146         mutex_lock(&wq_pool_mutex);
5147 
5148         WARN_ON_ONCE(workqueue_freezing);
5149         workqueue_freezing = true;
5150 
5151         list_for_each_entry(wq, &workqueues, list) {
5152                 mutex_lock(&wq->mutex);
5153                 for_each_pwq(pwq, wq)
5154                         pwq_adjust_max_active(pwq);
5155                 mutex_unlock(&wq->mutex);
5156         }
5157 
5158         mutex_unlock(&wq_pool_mutex);
5159 }
5160 
5161 /**
5162  * freeze_workqueues_busy - are freezable workqueues still busy?
5163  *
5164  * Check whether freezing is complete.  This function must be called
5165  * between freeze_workqueues_begin() and thaw_workqueues().
5166  *
5167  * CONTEXT:
5168  * Grabs and releases wq_pool_mutex.
5169  *
5170  * Return:
5171  * %true if some freezable workqueues are still busy.  %false if freezing
5172  * is complete.
5173  */
5174 bool freeze_workqueues_busy(void)
5175 {
5176         bool busy = false;
5177         struct workqueue_struct *wq;
5178         struct pool_workqueue *pwq;
5179 
5180         mutex_lock(&wq_pool_mutex);
5181 
5182         WARN_ON_ONCE(!workqueue_freezing);
5183 
5184         list_for_each_entry(wq, &workqueues, list) {
5185                 if (!(wq->flags & WQ_FREEZABLE))
5186                         continue;
5187                 /*
5188                  * nr_active is monotonically decreasing.  It's safe
5189                  * to peek without lock.
5190                  */
5191                 rcu_read_lock();
5192                 for_each_pwq(pwq, wq) {
5193                         WARN_ON_ONCE(pwq->nr_active < 0);
5194                         if (pwq->nr_active) {
5195                                 busy = true;
5196                                 rcu_read_unlock();
5197                                 goto out_unlock;
5198                         }
5199                 }
5200                 rcu_read_unlock();
5201         }
5202 out_unlock:
5203         mutex_unlock(&wq_pool_mutex);
5204         return busy;
5205 }
5206 
5207 /**
5208  * thaw_workqueues - thaw workqueues
5209  *
5210  * Thaw workqueues.  Normal queueing is restored and all collected
5211  * frozen works are transferred to their respective pool worklists.
5212  *
5213  * CONTEXT:
5214  * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5215  */
5216 void thaw_workqueues(void)
5217 {
5218         struct workqueue_struct *wq;
5219         struct pool_workqueue *pwq;
5220 
5221         mutex_lock(&wq_pool_mutex);
5222 
5223         if (!workqueue_freezing)
5224                 goto out_unlock;
5225 
5226         workqueue_freezing = false;
5227 
5228         /* restore max_active and repopulate worklist */
5229         list_for_each_entry(wq, &workqueues, list) {
5230                 mutex_lock(&wq->mutex);
5231                 for_each_pwq(pwq, wq)
5232                         pwq_adjust_max_active(pwq);
5233                 mutex_unlock(&wq->mutex);
5234         }
5235 
5236 out_unlock:
5237         mutex_unlock(&wq_pool_mutex);
5238 }
5239 #endif /* CONFIG_FREEZER */
5240 
5241 static int workqueue_apply_unbound_cpumask(void)
5242 {
5243         LIST_HEAD(ctxs);
5244         int ret = 0;
5245         struct workqueue_struct *wq;
5246         struct apply_wqattrs_ctx *ctx, *n;
5247 
5248         lockdep_assert_held(&wq_pool_mutex);
5249 
5250         list_for_each_entry(wq, &workqueues, list) {
5251                 if (!(wq->flags & WQ_UNBOUND))
5252                         continue;
5253                 /* creating multiple pwqs breaks ordering guarantee */
5254                 if (wq->flags & __WQ_ORDERED)
5255                         continue;
5256 
5257                 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
5258                 if (!ctx) {
5259                         ret = -ENOMEM;
5260                         break;
5261                 }
5262 
5263                 list_add_tail(&ctx->list, &ctxs);
5264         }
5265 
5266         list_for_each_entry_safe(ctx, n, &ctxs, list) {
5267                 if (!ret)
5268                         apply_wqattrs_commit(ctx);
5269                 apply_wqattrs_cleanup(ctx);
5270         }
5271 
5272         return ret;
5273 }
5274 
5275 /**
5276  *  workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
5277  *  @cpumask: the cpumask to set
5278  *
5279  *  The low-level workqueues cpumask is a global cpumask that limits
5280  *  the affinity of all unbound workqueues.  This function check the @cpumask
5281  *  and apply it to all unbound workqueues and updates all pwqs of them.
5282  *
5283  *  Retun:      0       - Success
5284  *              -EINVAL - Invalid @cpumask
5285  *              -ENOMEM - Failed to allocate memory for attrs or pwqs.
5286  */
5287 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
5288 {
5289         int ret = -EINVAL;
5290         cpumask_var_t saved_cpumask;
5291 
5292         if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
5293                 return -ENOMEM;
5294 
5295         /*
5296          * Not excluding isolated cpus on purpose.
5297          * If the user wishes to include them, we allow that.
5298          */
5299         cpumask_and(cpumask, cpumask, cpu_possible_mask);
5300         if (!cpumask_empty(cpumask)) {
5301                 apply_wqattrs_lock();
5302 
5303                 /* save the old wq_unbound_cpumask. */
5304                 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
5305 
5306                 /* update wq_unbound_cpumask at first and apply it to wqs. */
5307                 cpumask_copy(wq_unbound_cpumask, cpumask);
5308                 ret = workqueue_apply_unbound_cpumask();
5309 
5310                 /* restore the wq_unbound_cpumask when failed. */
5311                 if (ret < 0)
5312                         cpumask_copy(wq_unbound_cpumask, saved_cpumask);
5313 
5314                 apply_wqattrs_unlock();
5315         }
5316 
5317         free_cpumask_var(saved_cpumask);
5318         return ret;
5319 }
5320 
5321 #ifdef CONFIG_SYSFS
5322 /*
5323  * Workqueues with WQ_SYSFS flag set is visible to userland via
5324  * /sys/bus/workqueue/devices/WQ_NAME.  All visible workqueues have the
5325  * following attributes.
5326  *
5327  *  per_cpu     RO bool : whether the workqueue is per-cpu or unbound
5328  *  max_active  RW int  : maximum number of in-flight work items
5329  *
5330  * Unbound workqueues have the following extra attributes.
5331  *
5332  *  pool_ids    RO int  : the associated pool IDs for each node
5333  *  nice        RW int  : nice value of the workers
5334  *  cpumask     RW mask : bitmask of allowed CPUs for the workers
5335  *  numa        RW bool : whether enable NUMA affinity
5336  */
5337 struct wq_device {
5338         struct workqueue_struct         *wq;
5339         struct device                   dev;
5340 };
5341 
5342 static struct workqueue_struct *dev_to_wq(struct device *dev)
5343 {
5344         struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5345 
5346         return wq_dev->wq;
5347 }
5348 
5349 static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5350                             char *buf)
5351 {
5352         struct workqueue_struct *wq = dev_to_wq(dev);
5353 
5354         return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5355 }
5356 static DEVICE_ATTR_RO(per_cpu);
5357 
5358 static ssize_t max_active_show(struct device *dev,
5359                                struct device_attribute *attr, char *buf)
5360 {
5361         struct workqueue_struct *wq = dev_to_wq(dev);
5362 
5363         return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5364 }
5365 
5366 static ssize_t max_active_store(struct device *dev,
5367                                 struct device_attribute *attr, const char *buf,
5368                                 size_t count)
5369 {
5370         struct workqueue_struct *wq = dev_to_wq(dev);
5371         int val;
5372 
5373         if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5374                 return -EINVAL;
5375 
5376         workqueue_set_max_active(wq, val);
5377         return count;
5378 }
5379 static DEVICE_ATTR_RW(max_active);
5380 
5381 static struct attribute *wq_sysfs_attrs[] = {
5382         &dev_attr_per_cpu.attr,
5383         &dev_attr_max_active.attr,
5384         NULL,
5385 };
5386 ATTRIBUTE_GROUPS(wq_sysfs);
5387 
5388 static ssize_t wq_pool_ids_show(struct device *dev,
5389                                 struct device_attribute *attr, char *buf)
5390 {
5391         struct workqueue_struct *wq = dev_to_wq(dev);
5392         const char *delim = "";
5393         int node, written = 0;
5394 
5395         get_online_cpus();
5396         rcu_read_lock();
5397         for_each_node(node) {
5398                 written += scnprintf(buf + written, PAGE_SIZE - written,
5399                                      "%s%d:%d", delim, node,
5400                                      unbound_pwq_by_node(wq, node)->pool->id);
5401                 delim = " ";
5402         }
5403         written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
5404         rcu_read_unlock();
5405         put_online_cpus();
5406 
5407         return written;
5408 }
5409 
5410 static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5411                             char *buf)
5412 {
5413         struct workqueue_struct *wq = dev_to_wq(dev);
5414         int written;
5415 
5416         mutex_lock(&wq->mutex);
5417         written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5418         mutex_unlock(&wq->mutex);
5419 
5420         return written;
5421 }
5422 
5423 /* prepare workqueue_attrs for sysfs store operations */
5424 static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5425 {
5426         struct workqueue_attrs *attrs;
5427 
5428         lockdep_assert_held(&wq_pool_mutex);
5429 
5430         attrs = alloc_workqueue_attrs();
5431         if (!attrs)
5432                 return NULL;
5433 
5434         copy_workqueue_attrs(attrs, wq->unbound_attrs);
5435         return attrs;
5436 }
5437 
5438 static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
5439                              const char *buf, size_t count)
5440 {
5441         struct workqueue_struct *wq = dev_to_wq(dev);
5442         struct workqueue_attrs *attrs;
5443         int ret = -ENOMEM;
5444 
5445         apply_wqattrs_lock();
5446 
5447         attrs = wq_sysfs_prep_attrs(wq);
5448         if (!attrs)
5449                 goto out_unlock;
5450 
5451         if (sscanf(buf, "%d", &attrs->nice) == 1 &&
5452             attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
5453                 ret = apply_workqueue_attrs_locked(wq, attrs);
5454         else
5455                 ret = -EINVAL;
5456 
5457 out_unlock:
5458         apply_wqattrs_unlock();
5459         free_workqueue_attrs(attrs);
5460         return ret ?: count;
5461 }
5462 
5463 static ssize_t wq_cpumask_show(struct device *dev,
5464                                struct device_attribute *attr, char *buf)
5465 {
5466         struct workqueue_struct *wq = dev_to_wq(dev);
5467         int written;
5468 
5469         mutex_lock(&wq->mutex);
5470         written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5471                             cpumask_pr_args(wq->unbound_attrs->cpumask));
5472         mutex_unlock(&wq->mutex);
5473         return written;
5474 }
5475 
5476 static ssize_t wq_cpumask_store(struct device *dev,
5477                                 struct device_attribute *attr,
5478                                 const char *buf, size_t count)
5479 {
5480         struct workqueue_struct *wq = dev_to_wq(dev);
5481         struct workqueue_attrs *attrs;
5482         int ret = -ENOMEM;
5483 
5484         apply_wqattrs_lock();
5485 
5486         attrs = wq_sysfs_prep_attrs(wq);
5487         if (!attrs)
5488                 goto out_unlock;
5489 
5490         ret = cpumask_parse(buf, attrs->cpumask);
5491         if (!ret)
5492                 ret = apply_workqueue_attrs_locked(wq, attrs);
5493 
5494 out_unlock:
5495         apply_wqattrs_unlock();
5496         free_workqueue_attrs(attrs);
5497         return ret ?: count;
5498 }
5499 
5500 static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
5501                             char *buf)
5502 {
5503         struct workqueue_struct *wq = dev_to_wq(dev);
5504         int written;
5505 
5506         mutex_lock(&wq->mutex);
5507         written = scnprintf(buf, PAGE_SIZE, "%d\n",
5508                             !wq->unbound_attrs->no_numa);
5509         mutex_unlock(&wq->mutex);
5510 
5511         return written;
5512 }
5513 
5514 static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
5515                              const char *buf, size_t count)
5516 {
5517         struct workqueue_struct *wq = dev_to_wq(dev);
5518         struct workqueue_attrs *attrs;
5519         int v, ret = -ENOMEM;
5520 
5521         apply_wqattrs_lock();
5522 
5523         attrs = wq_sysfs_prep_attrs(wq);
5524         if (!attrs)
5525                 goto out_unlock;
5526 
5527         ret = -EINVAL;
5528         if (sscanf(buf, "%d", &v) == 1) {
5529                 attrs->no_numa = !v;
5530                 ret = apply_workqueue_attrs_locked(wq, attrs);
5531         }
5532 
5533 out_unlock:
5534         apply_wqattrs_unlock();
5535         free_workqueue_attrs(attrs);
5536         return ret ?: count;
5537 }
5538 
5539 static struct device_attribute wq_sysfs_unbound_attrs[] = {
5540         __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5541         __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5542         __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5543         __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5544         __ATTR_NULL,
5545 };
5546 
5547 static struct bus_type wq_subsys = {
5548         .name                           = "workqueue",
5549         .dev_groups                     = wq_sysfs_groups,
5550 };
5551 
5552 static ssize_t wq_unbound_cpumask_show(struct device *dev,
5553                 struct device_attribute *attr, char *buf)
5554 {
5555         int written;
5556 
5557         mutex_lock(&wq_pool_mutex);
5558         written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5559                             cpumask_pr_args(wq_unbound_cpumask));
5560         mutex_unlock(&wq_pool_mutex);
5561 
5562         return written;
5563 }
5564 
5565 static ssize_t wq_unbound_cpumask_store(struct device *dev,
5566                 struct device_attribute *attr, const char *buf, size_t count)
5567 {
5568         cpumask_var_t cpumask;
5569         int ret;
5570 
5571         if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5572                 return -ENOMEM;
5573 
5574         ret = cpumask_parse(buf, cpumask);
5575         if (!ret)
5576                 ret = workqueue_set_unbound_cpumask(cpumask);
5577 
5578         free_cpumask_var(cpumask);
5579         return ret ? ret : count;
5580 }
5581 
5582 static struct device_attribute wq_sysfs_cpumask_attr =
5583         __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5584                wq_unbound_cpumask_store);
5585 
5586 static int __init wq_sysfs_init(void)
5587 {
5588         int err;
5589 
5590         err = subsys_virtual_register(&wq_subsys, NULL);
5591         if (err)
5592                 return err;
5593 
5594         return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5595 }
5596 core_initcall(wq_sysfs_init);
5597 
5598 static void wq_device_release(struct device *dev)
5599 {
5600         struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5601 
5602         kfree(wq_dev);
5603 }
5604 
5605 /**
5606  * workqueue_sysfs_register - make a workqueue visible in sysfs
5607  * @wq: the workqueue to register
5608  *
5609  * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5610  * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5611  * which is the preferred method.
5612  *
5613  * Workqueue user should use this function directly iff it wants to apply
5614  * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5615  * apply_workqueue_attrs() may race against userland updating the
5616  * attributes.
5617  *
5618  * Return: 0 on success, -errno on failure.
5619  */
5620 int workqueue_sysfs_register(struct workqueue_struct *wq)
5621 {
5622         struct wq_device *wq_dev;
5623         int ret;
5624 
5625         /*
5626          * Adjusting max_active or creating new pwqs by applying
5627          * attributes breaks ordering guarantee.  Disallow exposing ordered
5628          * workqueues.
5629          */
5630         if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
5631                 return -EINVAL;
5632 
5633         wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5634         if (!wq_dev)
5635                 return -ENOMEM;
5636 
5637         wq_dev->wq = wq;
5638         wq_dev->dev.bus = &wq_subsys;
5639         wq_dev->dev.release = wq_device_release;
5640         dev_set_name(&wq_dev->dev, "%s", wq->name);
5641 
5642         /*
5643          * unbound_attrs are created separately.  Suppress uevent until
5644          * everything is ready.
5645          */
5646         dev_set_uevent_suppress(&wq_dev->dev, true);
5647 
5648         ret = device_register(&wq_dev->dev);
5649         if (ret) {
5650                 put_device(&wq_dev->dev);
5651                 wq->wq_dev = NULL;
5652                 return ret;
5653         }
5654 
5655         if (wq->flags & WQ_UNBOUND) {
5656                 struct device_attribute *attr;
5657 
5658                 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5659                         ret = device_create_file(&wq_dev->dev, attr);
5660                         if (ret) {
5661                                 device_unregister(&wq_dev->dev);
5662                                 wq->wq_dev = NULL;
5663                                 return ret;
5664                         }
5665                 }
5666         }
5667 
5668         dev_set_uevent_suppress(&wq_dev->dev, false);
5669         kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5670         return 0;
5671 }
5672 
5673 /**
5674  * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5675  * @wq: the workqueue to unregister
5676  *
5677  * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5678  */
5679 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5680 {
5681         struct wq_device *wq_dev = wq->wq_dev;
5682 
5683         if (!wq->wq_dev)
5684                 return;
5685 
5686         wq->wq_dev = NULL;
5687         device_unregister(&wq_dev->dev);
5688 }
5689 #else   /* CONFIG_SYSFS */
5690 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)     { }
5691 #endif  /* CONFIG_SYSFS */
5692 
5693 /*
5694  * Workqueue watchdog.
5695  *
5696  * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5697  * flush dependency, a concurrency managed work item which stays RUNNING
5698  * indefinitely.  Workqueue stalls can be very difficult to debug as the
5699  * usual warning mechanisms don't trigger and internal workqueue state is
5700  * largely opaque.
5701  *
5702  * Workqueue watchdog monitors all worker pools periodically and dumps
5703  * state if some pools failed to make forward progress for a while where
5704  * forward progress is defined as the first item on ->worklist changing.
5705  *
5706  * This mechanism is controlled through the kernel parameter
5707  * "workqueue.watchdog_thresh" which can be updated at runtime through the
5708  * corresponding sysfs parameter file.
5709  */
5710 #ifdef CONFIG_WQ_WATCHDOG
5711 
5712 static unsigned long wq_watchdog_thresh = 30;
5713 static struct timer_list wq_watchdog_timer;
5714 
5715 static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
5716 static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
5717 
5718 static void wq_watchdog_reset_touched(void)
5719 {
5720         int cpu;
5721 
5722         wq_watchdog_touched = jiffies;
5723         for_each_possible_cpu(cpu)
5724                 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5725 }
5726 
5727 static void wq_watchdog_timer_fn(struct timer_list *unused)
5728 {
5729         unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
5730         bool lockup_detected = false;
5731         struct worker_pool *pool;
5732         int pi;
5733 
5734         if (!thresh)
5735                 return;
5736 
5737         rcu_read_lock();
5738 
5739         for_each_pool(pool, pi) {
5740                 unsigned long pool_ts, touched, ts;
5741 
5742                 if (list_empty(&pool->worklist))
5743                         continue;
5744 
5745                 /* get the latest of pool and touched timestamps */
5746                 pool_ts = READ_ONCE(pool->watchdog_ts);
5747                 touched = READ_ONCE(wq_watchdog_touched);
5748 
5749                 if (time_after(pool_ts, touched))
5750                         ts = pool_ts;
5751                 else
5752                         ts = touched;
5753 
5754                 if (pool->cpu >= 0) {
5755                         unsigned long cpu_touched =
5756                                 READ_ONCE(per_cpu(wq_watchdog_touched_cpu,
5757                                                   pool->cpu));
5758                         if (time_after(cpu_touched, ts))
5759                                 ts = cpu_touched;
5760                 }
5761 
5762                 /* did we stall? */
5763                 if (time_after(jiffies, ts + thresh)) {
5764                         lockup_detected = true;
5765                         pr_emerg("BUG: workqueue lockup - pool");
5766                         pr_cont_pool_info(pool);
5767                         pr_cont(" stuck for %us!\n",
5768                                 jiffies_to_msecs(jiffies - pool_ts) / 1000);
5769                 }
5770         }
5771 
5772         rcu_read_unlock();
5773 
5774         if (lockup_detected)
5775                 show_workqueue_state();
5776 
5777         wq_watchdog_reset_touched();
5778         mod_timer(&wq_watchdog_timer, jiffies + thresh);
5779 }
5780 
5781 notrace void wq_watchdog_touch(int cpu)
5782 {
5783         if (cpu >= 0)
5784                 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5785         else
5786                 wq_watchdog_touched = jiffies;
5787 }
5788 
5789 static void wq_watchdog_set_thresh(unsigned long thresh)
5790 {
5791         wq_watchdog_thresh = 0;
5792         del_timer_sync(&wq_watchdog_timer);
5793 
5794         if (thresh) {
5795                 wq_watchdog_thresh = thresh;
5796                 wq_watchdog_reset_touched();
5797                 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
5798         }
5799 }
5800 
5801 static int wq_watchdog_param_set_thresh(const char *val,
5802                                         const struct kernel_param *kp)
5803 {
5804         unsigned long thresh;
5805         int ret;
5806 
5807         ret = kstrtoul(val, 0, &thresh);
5808         if (ret)
5809                 return ret;
5810 
5811         if (system_wq)
5812                 wq_watchdog_set_thresh(thresh);
5813         else
5814                 wq_watchdog_thresh = thresh;
5815 
5816         return 0;
5817 }
5818 
5819 static const struct kernel_param_ops wq_watchdog_thresh_ops = {
5820         .set    = wq_watchdog_param_set_thresh,
5821         .get    = param_get_ulong,
5822 };
5823 
5824 module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
5825                 0644);
5826 
5827 static void wq_watchdog_init(void)
5828 {
5829         timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
5830         wq_watchdog_set_thresh(wq_watchdog_thresh);
5831 }
5832 
5833 #else   /* CONFIG_WQ_WATCHDOG */
5834 
5835 static inline void wq_watchdog_init(void) { }
5836 
5837 #endif  /* CONFIG_WQ_WATCHDOG */
5838 
5839 static void __init wq_numa_init(void)
5840 {
5841         cpumask_var_t *tbl;
5842         int node, cpu;
5843 
5844         if (num_possible_nodes() <= 1)
5845                 return;
5846 
5847         if (wq_disable_numa) {
5848                 pr_info("workqueue: NUMA affinity support disabled\n");
5849                 return;
5850         }
5851 
5852         wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs();
5853         BUG_ON(!wq_update_unbound_numa_attrs_buf);
5854 
5855         /*
5856          * We want masks of possible CPUs of each node which isn't readily
5857          * available.  Build one from cpu_to_node() which should have been
5858          * fully initialized by now.
5859          */
5860         tbl = kcalloc(nr_node_ids, sizeof(tbl[0]), GFP_KERNEL);
5861         BUG_ON(!tbl);
5862 
5863         for_each_node(node)
5864                 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5865                                 node_online(node) ? node : NUMA_NO_NODE));
5866 
5867         for_each_possible_cpu(cpu) {
5868                 node = cpu_to_node(cpu);
5869                 if (WARN_ON(node == NUMA_NO_NODE)) {
5870                         pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5871                         /* happens iff arch is bonkers, let's just proceed */
5872                         return;
5873                 }
5874                 cpumask_set_cpu(cpu, tbl[node]);
5875         }
5876 
5877         wq_numa_possible_cpumask = tbl;
5878         wq_numa_enabled = true;
5879 }
5880 
5881 /**
5882  * workqueue_init_early - early init for workqueue subsystem
5883  *
5884  * This is the first half of two-staged workqueue subsystem initialization
5885  * and invoked as soon as the bare basics - memory allocation, cpumasks and
5886  * idr are up.  It sets up all the data structures and system workqueues
5887  * and allows early boot code to create workqueues and queue/cancel work
5888  * items.  Actual work item execution starts only after kthreads can be
5889  * created and scheduled right before early initcalls.
5890  */
5891 int __init workqueue_init_early(void)
5892 {
5893         int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5894         int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
5895         int i, cpu;
5896 
5897         WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5898 
5899         BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
5900         cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(hk_flags));
5901 
5902         pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5903 
5904         /* initialize CPU pools */
5905         for_each_possible_cpu(cpu) {
5906                 struct worker_pool *pool;
5907 
5908                 i = 0;
5909                 for_each_cpu_worker_pool(pool, cpu) {
5910                         BUG_ON(init_worker_pool(pool));
5911                         pool->cpu = cpu;
5912                         cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5913                         pool->attrs->nice = std_nice[i++];
5914                         pool->node = cpu_to_node(cpu);
5915 
5916                         /* alloc pool ID */
5917                         mutex_lock(&wq_pool_mutex);
5918                         BUG_ON(worker_pool_assign_id(pool));
5919                         mutex_unlock(&wq_pool_mutex);
5920                 }
5921         }
5922 
5923         /* create default unbound and ordered wq attrs */
5924         for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5925                 struct workqueue_attrs *attrs;
5926 
5927                 BUG_ON(!(attrs = alloc_workqueue_attrs()));
5928                 attrs->nice = std_nice[i];
5929                 unbound_std_wq_attrs[i] = attrs;
5930 
5931                 /*
5932                  * An ordered wq should have only one pwq as ordering is
5933                  * guaranteed by max_active which is enforced by pwqs.
5934                  * Turn off NUMA so that dfl_pwq is used for all nodes.
5935                  */
5936                 BUG_ON(!(attrs = alloc_workqueue_attrs()));
5937                 attrs->nice = std_nice[i];
5938                 attrs->no_numa = true;
5939                 ordered_wq_attrs[i] = attrs;
5940         }
5941 
5942         system_wq = alloc_workqueue("events", 0, 0);
5943         system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5944         system_long_wq = alloc_workqueue("events_long", 0, 0);
5945         system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
5946                                             WQ_UNBOUND_MAX_ACTIVE);
5947         system_freezable_wq = alloc_workqueue("events_freezable",
5948                                               WQ_FREEZABLE, 0);
5949         system_power_efficient_wq = alloc_workqueue("events_power_efficient",
5950                                               WQ_POWER_EFFICIENT, 0);
5951         system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
5952                                               WQ_FREEZABLE | WQ_POWER_EFFICIENT,
5953                                               0);
5954         BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
5955                !system_unbound_wq || !system_freezable_wq ||
5956                !system_power_efficient_wq ||
5957                !system_freezable_power_efficient_wq);
5958 
5959         return 0;
5960 }
5961 
5962 /**
5963  * workqueue_init - bring workqueue subsystem fully online
5964  *
5965  * This is the latter half of two-staged workqueue subsystem initialization
5966  * and invoked as soon as kthreads can be created and scheduled.
5967  * Workqueues have been created and work items queued on them, but there
5968  * are no kworkers executing the work items yet.  Populate the worker pools
5969  * with the initial workers and enable future kworker creations.
5970  */
5971 int __init workqueue_init(void)
5972 {
5973         struct workqueue_struct *wq;
5974         struct worker_pool *pool;
5975         int cpu, bkt;
5976 
5977         /*
5978          * It'd be simpler to initialize NUMA in workqueue_init_early() but
5979          * CPU to node mapping may not be available that early on some
5980          * archs such as power and arm64.  As per-cpu pools created
5981          * previously could be missing node hint and unbound pools NUMA
5982          * affinity, fix them up.
5983          *
5984          * Also, while iterating workqueues, create rescuers if requested.
5985          */
5986         wq_numa_init();
5987 
5988         mutex_lock(&wq_pool_mutex);
5989 
5990         for_each_possible_cpu(cpu) {
5991                 for_each_cpu_worker_pool(pool, cpu) {
5992                         pool->node = cpu_to_node(cpu);
5993                 }
5994         }
5995 
5996         list_for_each_entry(wq, &workqueues, list) {
5997                 wq_update_unbound_numa(wq, smp_processor_id(), true);
5998                 WARN(init_rescuer(wq),
5999                      "workqueue: failed to create early rescuer for %s",
6000                      wq->name);
6001         }
6002 
6003         mutex_unlock(&wq_pool_mutex);
6004 
6005         /* create the initial workers */
6006         for_each_online_cpu(cpu) {
6007                 for_each_cpu_worker_pool(pool, cpu) {
6008                         pool->flags &= ~POOL_DISASSOCIATED;
6009                         BUG_ON(!create_worker(pool));
6010                 }
6011         }
6012 
6013         hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
6014                 BUG_ON(!create_worker(pool));
6015 
6016         wq_online = true;
6017         wq_watchdog_init();
6018 
6019         return 0;
6020 }