root/kernel/locking/lockdep.c

DEFINITIONS

1. graph_lock
2. graph_unlock
3. debug_locks_off_graph_unlock
4. hlock_class
5. lockstat_clock
6. lock_point
7. lock_time_inc
8. lock_time_add
9. lock_stats
10. clear_lock_stats
11. get_lock_stats
12. lock_release_holdtime
13. lock_release_holdtime
14. iterate_chain_key
15. lockdep_init_task
16. lockdep_off
17. lockdep_on
18. lockdep_set_selftest_task
19. class_filter
20. verbose
21. print_lockdep_off
22. traces_identical
23. save_trace
24. lockdep_stack_trace_count
25. lockdep_stack_hash_count
26. __get_key_name
27. lock_flag
28. get_usage_char
29. get_usage_chars
30. __print_lock_name
31. print_lock_name
32. print_lockdep_cache
33. print_lock
34. lockdep_print_held_locks
35. print_kernel_ident
36. very_verbose
37. static_obj
38. count_matching_names
39. look_up_lock_class
40. assign_lock_key
41. in_list
42. in_any_class_list
43. class_lock_list_valid
44. check_lock_chain_key
45. in_any_zapped_class_list
46. __check_data_structures
47. check_data_structures
48. check_data_structures
49. init_data_structures_once
50. keyhashentry
51. lockdep_register_key
52. is_dynamic_key
53. register_lock_class
54. alloc_list_entry
55. add_lock_to_list
56. __cq_init
57. __cq_empty
58. __cq_full
59. __cq_enqueue
60. __cq_dequeue
61. __cq_get_elem_count
62. mark_lock_accessed
63. lock_accessed
64. get_lock_parent
65. get_lock_depth
66. get_dep_list
67. __bfs
68. __bfs_forwards
69. __bfs_backwards
70. print_lock_trace
71. print_circular_bug_entry
72. print_circular_lock_scenario
73. print_circular_bug_header
74. class_equal
75. print_circular_bug
76. print_bfs_bug
77. noop_count
78. __lockdep_count_forward_deps
79. lockdep_count_forward_deps
80. __lockdep_count_backward_deps
81. lockdep_count_backward_deps
82. check_path
83. check_noncircular
84. check_redundant
85. usage_accumulate
86. usage_match
87. find_usage_forwards
88. find_usage_backwards
89. print_lock_class_header
90. print_shortest_lock_dependencies
91. print_irq_lock_scenario
92. print_bad_irq_dependency
93. state_name
94. exclusive_bit
95. invert_dir_mask
96. exclusive_mask
97. original_mask
98. find_exclusive_match
99. check_irq_usage
100. inc_chains
101. check_irq_usage
102. inc_chains
103. print_deadlock_scenario
104. print_deadlock_bug
105. check_deadlock
106. check_prev_add
107. check_prevs_add
108. lock_chain_get_class
109. get_first_held_lock
110. print_chain_key_iteration
111. print_chain_keys_held_locks
112. print_chain_keys_chain
113. print_collision
114. check_no_collision
115. lockdep_next_lockchain
116. lock_chain_count
117. alloc_lock_chain
118. add_chain_cache
119. lookup_chain_cache
120. lookup_chain_cache_add
121. validate_chain
122. validate_chain
123. check_chain_key
124. print_usage_bug_scenario
125. print_usage_bug
126. valid_state
127. print_irq_inversion_bug
128. check_usage_forwards
129. check_usage_backwards
130. print_irqtrace_events
131. HARDIRQ_verbose
132. SOFTIRQ_verbose
133. state_verbose
134. mark_lock_irq
135. mark_held_locks
136. __trace_hardirqs_on_caller
137. lockdep_hardirqs_on
138. lockdep_hardirqs_off
139. trace_softirqs_on
140. trace_softirqs_off
141. mark_usage
142. task_irq_context
143. separate_irq_context
144. mark_lock
145. mark_usage
146. task_irq_context
147. separate_irq_context
148. lockdep_init_map
149. print_lock_nested_lock_not_held
150. __lock_acquire
151. print_unlock_imbalance_bug
152. match_held_lock
153. find_held_lock
154. reacquire_held_locks
155. __lock_set_class
156. __lock_downgrade
157. __lock_release
158. __lock_is_held
159. __lock_pin_lock
160. __lock_repin_lock
161. __lock_unpin_lock
162. check_flags
163. lock_set_class
164. lock_downgrade
165. lock_acquire
166. lock_release
167. lock_is_held_type
168. lock_pin_lock
169. lock_repin_lock
170. lock_unpin_lock
171. print_lock_contention_bug
172. __lock_contended
173. __lock_acquired
174. lock_contended
175. lock_acquired
176. lockdep_reset
177. remove_class_from_lock_chain
178. remove_class_from_lock_chains
179. zap_class
180. reinit_class
181. within
182. inside_selftest
183. get_pending_free
184. call_rcu_zapped
185. __free_zapped_classes
186. free_zapped_rcu
187. __lockdep_free_key_range
188. lockdep_free_key_range_reg
189. lockdep_free_key_range_imm
190. lockdep_free_key_range
191. lock_class_cache_is_registered
192. __lockdep_reset_lock
193. lockdep_reset_lock_reg
194. lockdep_reset_lock_imm
195. lockdep_reset_lock
196. lockdep_unregister_key
197. lockdep_init
198. print_freed_lock_bug
199. not_in_range
200. debug_check_no_locks_freed
201. print_held_locks_bug
202. debug_check_no_locks_held
203. debug_show_all_locks
204. debug_show_held_locks
205. lockdep_sys_exit
206. lockdep_rcu_suspicious

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * kernel/lockdep.c
   4  *
   5  * Runtime locking correctness validator
   6  *
   7  * Started by Ingo Molnar:
   8  *
   9  *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  10  *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
  11  *
  12  * this code maps all the lock dependencies as they occur in a live kernel
  13  * and will warn about the following classes of locking bugs:
  14  *
  15  * - lock inversion scenarios
  16  * - circular lock dependencies
  17  * - hardirq/softirq safe/unsafe locking bugs
  18  *
  19  * Bugs are reported even if the current locking scenario does not cause
  20  * any deadlock at this point.
  21  *
  22  * I.e. if anytime in the past two locks were taken in a different order,
  23  * even if it happened for another task, even if those were different
  24  * locks (but of the same class as this lock), this code will detect it.
  25  *
  26  * Thanks to Arjan van de Ven for coming up with the initial idea of
  27  * mapping lock dependencies runtime.
  28  */
  29 #define DISABLE_BRANCH_PROFILING
  30 #include <linux/mutex.h>
  31 #include <linux/sched.h>
  32 #include <linux/sched/clock.h>
  33 #include <linux/sched/task.h>
  34 #include <linux/sched/mm.h>
  35 #include <linux/delay.h>
  36 #include <linux/module.h>
  37 #include <linux/proc_fs.h>
  38 #include <linux/seq_file.h>
  39 #include <linux/spinlock.h>
  40 #include <linux/kallsyms.h>
  41 #include <linux/interrupt.h>
  42 #include <linux/stacktrace.h>
  43 #include <linux/debug_locks.h>
  44 #include <linux/irqflags.h>
  45 #include <linux/utsname.h>
  46 #include <linux/hash.h>
  47 #include <linux/ftrace.h>
  48 #include <linux/stringify.h>
  49 #include <linux/bitmap.h>
  50 #include <linux/bitops.h>
  51 #include <linux/gfp.h>
  52 #include <linux/random.h>
  53 #include <linux/jhash.h>
  54 #include <linux/nmi.h>
  55 #include <linux/rcupdate.h>
  56 #include <linux/kprobes.h>
  57 
  58 #include <asm/sections.h>
  59 
  60 #include "lockdep_internals.h"
  61 
  62 #define CREATE_TRACE_POINTS
  63 #include <trace/events/lock.h>
  64 
  65 #ifdef CONFIG_PROVE_LOCKING
  66 int prove_locking = 1;
  67 module_param(prove_locking, int, 0644);
  68 #else
  69 #define prove_locking 0
  70 #endif
  71 
  72 #ifdef CONFIG_LOCK_STAT
  73 int lock_stat = 1;
  74 module_param(lock_stat, int, 0644);
  75 #else
  76 #define lock_stat 0
  77 #endif
  78 
  79 /*
  80  * lockdep_lock: protects the lockdep graph, the hashes and the
  81  *               class/list/hash allocators.
  82  *
  83  * This is one of the rare exceptions where it's justified
  84  * to use a raw spinlock - we really dont want the spinlock
  85  * code to recurse back into the lockdep code...
  86  */
  87 static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
  88 static struct task_struct *lockdep_selftest_task_struct;
  89 
  90 static int graph_lock(void)
  91 {
  92         arch_spin_lock(&lockdep_lock);
  93         /*
  94          * Make sure that if another CPU detected a bug while
  95          * walking the graph we dont change it (while the other
  96          * CPU is busy printing out stuff with the graph lock
  97          * dropped already)
  98          */
  99         if (!debug_locks) {
 100                 arch_spin_unlock(&lockdep_lock);
 101                 return 0;
 102         }
 103         /* prevent any recursions within lockdep from causing deadlocks */
 104         current->lockdep_recursion++;
 105         return 1;
 106 }
 107 
 108 static inline int graph_unlock(void)
 109 {
 110         if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) {
 111                 /*
 112                  * The lockdep graph lock isn't locked while we expect it to
 113                  * be, we're confused now, bye!
 114                  */
 115                 return DEBUG_LOCKS_WARN_ON(1);
 116         }
 117 
 118         current->lockdep_recursion--;
 119         arch_spin_unlock(&lockdep_lock);
 120         return 0;
 121 }
 122 
 123 /*
 124  * Turn lock debugging off and return with 0 if it was off already,
 125  * and also release the graph lock:
 126  */
 127 static inline int debug_locks_off_graph_unlock(void)
 128 {
 129         int ret = debug_locks_off();
 130 
 131         arch_spin_unlock(&lockdep_lock);
 132 
 133         return ret;
 134 }
 135 
 136 unsigned long nr_list_entries;
 137 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
 138 static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
 139 
 140 /*
 141  * All data structures here are protected by the global debug_lock.
 142  *
 143  * nr_lock_classes is the number of elements of lock_classes[] that is
 144  * in use.
 145  */
 146 #define KEYHASH_BITS            (MAX_LOCKDEP_KEYS_BITS - 1)
 147 #define KEYHASH_SIZE            (1UL << KEYHASH_BITS)
 148 static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
 149 unsigned long nr_lock_classes;
 150 #ifndef CONFIG_DEBUG_LOCKDEP
 151 static
 152 #endif
 153 struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
 154 static DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
 155 
 156 static inline struct lock_class *hlock_class(struct held_lock *hlock)
 157 {
 158         unsigned int class_idx = hlock->class_idx;
 159 
 160         /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
 161         barrier();
 162 
 163         if (!test_bit(class_idx, lock_classes_in_use)) {
 164                 /*
 165                  * Someone passed in garbage, we give up.
 166                  */
 167                 DEBUG_LOCKS_WARN_ON(1);
 168                 return NULL;
 169         }
 170 
 171         /*
 172          * At this point, if the passed hlock->class_idx is still garbage,
 173          * we just have to live with it
 174          */
 175         return lock_classes + class_idx;
 176 }
 177 
 178 #ifdef CONFIG_LOCK_STAT
 179 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
 180 
 181 static inline u64 lockstat_clock(void)
 182 {
 183         return local_clock();
 184 }
 185 
 186 static int lock_point(unsigned long points[], unsigned long ip)
 187 {
 188         int i;
 189 
 190         for (i = 0; i < LOCKSTAT_POINTS; i++) {
 191                 if (points[i] == 0) {
 192                         points[i] = ip;
 193                         break;
 194                 }
 195                 if (points[i] == ip)
 196                         break;
 197         }
 198 
 199         return i;
 200 }
 201 
 202 static void lock_time_inc(struct lock_time *lt, u64 time)
 203 {
 204         if (time > lt->max)
 205                 lt->max = time;
 206 
 207         if (time < lt->min || !lt->nr)
 208                 lt->min = time;
 209 
 210         lt->total += time;
 211         lt->nr++;
 212 }
 213 
 214 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
 215 {
 216         if (!src->nr)
 217                 return;
 218 
 219         if (src->max > dst->max)
 220                 dst->max = src->max;
 221 
 222         if (src->min < dst->min || !dst->nr)
 223                 dst->min = src->min;
 224 
 225         dst->total += src->total;
 226         dst->nr += src->nr;
 227 }
 228 
 229 struct lock_class_stats lock_stats(struct lock_class *class)
 230 {
 231         struct lock_class_stats stats;
 232         int cpu, i;
 233 
 234         memset(&stats, 0, sizeof(struct lock_class_stats));
 235         for_each_possible_cpu(cpu) {
 236                 struct lock_class_stats *pcs =
 237                         &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
 238 
 239                 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
 240                         stats.contention_point[i] += pcs->contention_point[i];
 241 
 242                 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
 243                         stats.contending_point[i] += pcs->contending_point[i];
 244 
 245                 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
 246                 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
 247 
 248                 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
 249                 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
 250 
 251                 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
 252                         stats.bounces[i] += pcs->bounces[i];
 253         }
 254 
 255         return stats;
 256 }
 257 
 258 void clear_lock_stats(struct lock_class *class)
 259 {
 260         int cpu;
 261 
 262         for_each_possible_cpu(cpu) {
 263                 struct lock_class_stats *cpu_stats =
 264                         &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
 265 
 266                 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
 267         }
 268         memset(class->contention_point, 0, sizeof(class->contention_point));
 269         memset(class->contending_point, 0, sizeof(class->contending_point));
 270 }
 271 
 272 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
 273 {
 274         return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
 275 }
 276 
 277 static void lock_release_holdtime(struct held_lock *hlock)
 278 {
 279         struct lock_class_stats *stats;
 280         u64 holdtime;
 281 
 282         if (!lock_stat)
 283                 return;
 284 
 285         holdtime = lockstat_clock() - hlock->holdtime_stamp;
 286 
 287         stats = get_lock_stats(hlock_class(hlock));
 288         if (hlock->read)
 289                 lock_time_inc(&stats->read_holdtime, holdtime);
 290         else
 291                 lock_time_inc(&stats->write_holdtime, holdtime);
 292 }
 293 #else
 294 static inline void lock_release_holdtime(struct held_lock *hlock)
 295 {
 296 }
 297 #endif
 298 
 299 /*
 300  * We keep a global list of all lock classes. The list is only accessed with
 301  * the lockdep spinlock lock held. free_lock_classes is a list with free
 302  * elements. These elements are linked together by the lock_entry member in
 303  * struct lock_class.
 304  */
 305 LIST_HEAD(all_lock_classes);
 306 static LIST_HEAD(free_lock_classes);
 307 
 308 /**
 309  * struct pending_free - information about data structures about to be freed
 310  * @zapped: Head of a list with struct lock_class elements.
 311  * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
 312  *      are about to be freed.
 313  */
 314 struct pending_free {
 315         struct list_head zapped;
 316         DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
 317 };
 318 
 319 /**
 320  * struct delayed_free - data structures used for delayed freeing
 321  *
 322  * A data structure for delayed freeing of data structures that may be
 323  * accessed by RCU readers at the time these were freed.
 324  *
 325  * @rcu_head:  Used to schedule an RCU callback for freeing data structures.
 326  * @index:     Index of @pf to which freed data structures are added.
 327  * @scheduled: Whether or not an RCU callback has been scheduled.
 328  * @pf:        Array with information about data structures about to be freed.
 329  */
 330 static struct delayed_free {
 331         struct rcu_head         rcu_head;
 332         int                     index;
 333         int                     scheduled;
 334         struct pending_free     pf[2];
 335 } delayed_free;
 336 
 337 /*
 338  * The lockdep classes are in a hash-table as well, for fast lookup:
 339  */
 340 #define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
 341 #define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
 342 #define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
 343 #define classhashentry(key)     (classhash_table + __classhashfn((key)))
 344 
 345 static struct hlist_head classhash_table[CLASSHASH_SIZE];
 346 
 347 /*
 348  * We put the lock dependency chains into a hash-table as well, to cache
 349  * their existence:
 350  */
 351 #define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
 352 #define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
 353 #define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
 354 #define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
 355 
 356 static struct hlist_head chainhash_table[CHAINHASH_SIZE];
 357 
 358 /*
 359  * The hash key of the lock dependency chains is a hash itself too:
 360  * it's a hash of all locks taken up to that lock, including that lock.
 361  * It's a 64-bit hash, because it's important for the keys to be
 362  * unique.
 363  */
 364 static inline u64 iterate_chain_key(u64 key, u32 idx)
 365 {
 366         u32 k0 = key, k1 = key >> 32;
 367 
 368         __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
 369 
 370         return k0 | (u64)k1 << 32;
 371 }
 372 
 373 void lockdep_init_task(struct task_struct *task)
 374 {
 375         task->lockdep_depth = 0; /* no locks held yet */
 376         task->curr_chain_key = INITIAL_CHAIN_KEY;
 377         task->lockdep_recursion = 0;
 378 }
 379 
 380 void lockdep_off(void)
 381 {
 382         current->lockdep_recursion++;
 383 }
 384 EXPORT_SYMBOL(lockdep_off);
 385 
 386 void lockdep_on(void)
 387 {
 388         current->lockdep_recursion--;
 389 }
 390 EXPORT_SYMBOL(lockdep_on);
 391 
 392 void lockdep_set_selftest_task(struct task_struct *task)
 393 {
 394         lockdep_selftest_task_struct = task;
 395 }
 396 
 397 /*
 398  * Debugging switches:
 399  */
 400 
 401 #define VERBOSE                 0
 402 #define VERY_VERBOSE            0
 403 
 404 #if VERBOSE
 405 # define HARDIRQ_VERBOSE        1
 406 # define SOFTIRQ_VERBOSE        1
 407 #else
 408 # define HARDIRQ_VERBOSE        0
 409 # define SOFTIRQ_VERBOSE        0
 410 #endif
 411 
 412 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
 413 /*
 414  * Quick filtering for interesting events:
 415  */
 416 static int class_filter(struct lock_class *class)
 417 {
 418 #if 0
 419         /* Example */
 420         if (class->name_version == 1 &&
 421                         !strcmp(class->name, "lockname"))
 422                 return 1;
 423         if (class->name_version == 1 &&
 424                         !strcmp(class->name, "&struct->lockfield"))
 425                 return 1;
 426 #endif
 427         /* Filter everything else. 1 would be to allow everything else */
 428         return 0;
 429 }
 430 #endif
 431 
 432 static int verbose(struct lock_class *class)
 433 {
 434 #if VERBOSE
 435         return class_filter(class);
 436 #endif
 437         return 0;
 438 }
 439 
 440 static void print_lockdep_off(const char *bug_msg)
 441 {
 442         printk(KERN_DEBUG "%s\n", bug_msg);
 443         printk(KERN_DEBUG "turning off the locking correctness validator.\n");
 444 #ifdef CONFIG_LOCK_STAT
 445         printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
 446 #endif
 447 }
 448 
 449 unsigned long nr_stack_trace_entries;
 450 
 451 #ifdef CONFIG_PROVE_LOCKING
 452 /**
 453  * struct lock_trace - single stack backtrace
 454  * @hash_entry: Entry in a stack_trace_hash[] list.
 455  * @hash:       jhash() of @entries.
 456  * @nr_entries: Number of entries in @entries.
 457  * @entries:    Actual stack backtrace.
 458  */
 459 struct lock_trace {
 460         struct hlist_node       hash_entry;
 461         u32                     hash;
 462         u32                     nr_entries;
 463         unsigned long           entries[0] __aligned(sizeof(unsigned long));
 464 };
 465 #define LOCK_TRACE_SIZE_IN_LONGS                                \
 466         (sizeof(struct lock_trace) / sizeof(unsigned long))
 467 /*
 468  * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
 469  */
 470 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
 471 static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
 472 
 473 static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
 474 {
 475         return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
 476                 memcmp(t1->entries, t2->entries,
 477                        t1->nr_entries * sizeof(t1->entries[0])) == 0;
 478 }
 479 
 480 static struct lock_trace *save_trace(void)
 481 {
 482         struct lock_trace *trace, *t2;
 483         struct hlist_head *hash_head;
 484         u32 hash;
 485         int max_entries;
 486 
 487         BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
 488         BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
 489 
 490         trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
 491         max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
 492                 LOCK_TRACE_SIZE_IN_LONGS;
 493 
 494         if (max_entries <= 0) {
 495                 if (!debug_locks_off_graph_unlock())
 496                         return NULL;
 497 
 498                 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
 499                 dump_stack();
 500 
 501                 return NULL;
 502         }
 503         trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
 504 
 505         hash = jhash(trace->entries, trace->nr_entries *
 506                      sizeof(trace->entries[0]), 0);
 507         trace->hash = hash;
 508         hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
 509         hlist_for_each_entry(t2, hash_head, hash_entry) {
 510                 if (traces_identical(trace, t2))
 511                         return t2;
 512         }
 513         nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
 514         hlist_add_head(&trace->hash_entry, hash_head);
 515 
 516         return trace;
 517 }
 518 
 519 /* Return the number of stack traces in the stack_trace[] array. */
 520 u64 lockdep_stack_trace_count(void)
 521 {
 522         struct lock_trace *trace;
 523         u64 c = 0;
 524         int i;
 525 
 526         for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
 527                 hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
 528                         c++;
 529                 }
 530         }
 531 
 532         return c;
 533 }
 534 
 535 /* Return the number of stack hash chains that have at least one stack trace. */
 536 u64 lockdep_stack_hash_count(void)
 537 {
 538         u64 c = 0;
 539         int i;
 540 
 541         for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
 542                 if (!hlist_empty(&stack_trace_hash[i]))
 543                         c++;
 544 
 545         return c;
 546 }
 547 #endif
 548 
 549 unsigned int nr_hardirq_chains;
 550 unsigned int nr_softirq_chains;
 551 unsigned int nr_process_chains;
 552 unsigned int max_lockdep_depth;
 553 
 554 #ifdef CONFIG_DEBUG_LOCKDEP
 555 /*
 556  * Various lockdep statistics:
 557  */
 558 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
 559 #endif
 560 
 561 #ifdef CONFIG_PROVE_LOCKING
 562 /*
 563  * Locking printouts:
 564  */
 565 
 566 #define __USAGE(__STATE)                                                \
 567         [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W",       \
 568         [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W",         \
 569         [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
 570         [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
 571 
 572 static const char *usage_str[] =
 573 {
 574 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
 575 #include "lockdep_states.h"
 576 #undef LOCKDEP_STATE
 577         [LOCK_USED] = "INITIAL USE",
 578 };
 579 #endif
 580 
 581 const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
 582 {
 583         return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
 584 }
 585 
 586 static inline unsigned long lock_flag(enum lock_usage_bit bit)
 587 {
 588         return 1UL << bit;
 589 }
 590 
 591 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
 592 {
 593         /*
 594          * The usage character defaults to '.' (i.e., irqs disabled and not in
 595          * irq context), which is the safest usage category.
 596          */
 597         char c = '.';
 598 
 599         /*
 600          * The order of the following usage checks matters, which will
 601          * result in the outcome character as follows:
 602          *
 603          * - '+': irq is enabled and not in irq context
 604          * - '-': in irq context and irq is disabled
 605          * - '?': in irq context and irq is enabled
 606          */
 607         if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
 608                 c = '+';
 609                 if (class->usage_mask & lock_flag(bit))
 610                         c = '?';
 611         } else if (class->usage_mask & lock_flag(bit))
 612                 c = '-';
 613 
 614         return c;
 615 }
 616 
 617 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
 618 {
 619         int i = 0;
 620 
 621 #define LOCKDEP_STATE(__STATE)                                          \
 622         usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE);     \
 623         usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
 624 #include "lockdep_states.h"
 625 #undef LOCKDEP_STATE
 626 
 627         usage[i] = '\0';
 628 }
 629 
 630 static void __print_lock_name(struct lock_class *class)
 631 {
 632         char str[KSYM_NAME_LEN];
 633         const char *name;
 634 
 635         name = class->name;
 636         if (!name) {
 637                 name = __get_key_name(class->key, str);
 638                 printk(KERN_CONT "%s", name);
 639         } else {
 640                 printk(KERN_CONT "%s", name);
 641                 if (class->name_version > 1)
 642                         printk(KERN_CONT "#%d", class->name_version);
 643                 if (class->subclass)
 644                         printk(KERN_CONT "/%d", class->subclass);
 645         }
 646 }
 647 
 648 static void print_lock_name(struct lock_class *class)
 649 {
 650         char usage[LOCK_USAGE_CHARS];
 651 
 652         get_usage_chars(class, usage);
 653 
 654         printk(KERN_CONT " (");
 655         __print_lock_name(class);
 656         printk(KERN_CONT "){%s}", usage);
 657 }
 658 
 659 static void print_lockdep_cache(struct lockdep_map *lock)
 660 {
 661         const char *name;
 662         char str[KSYM_NAME_LEN];
 663 
 664         name = lock->name;
 665         if (!name)
 666                 name = __get_key_name(lock->key->subkeys, str);
 667 
 668         printk(KERN_CONT "%s", name);
 669 }
 670 
 671 static void print_lock(struct held_lock *hlock)
 672 {
 673         /*
 674          * We can be called locklessly through debug_show_all_locks() so be
 675          * extra careful, the hlock might have been released and cleared.
 676          *
 677          * If this indeed happens, lets pretend it does not hurt to continue
 678          * to print the lock unless the hlock class_idx does not point to a
 679          * registered class. The rationale here is: since we don't attempt
 680          * to distinguish whether we are in this situation, if it just
 681          * happened we can't count on class_idx to tell either.
 682          */
 683         struct lock_class *lock = hlock_class(hlock);
 684 
 685         if (!lock) {
 686                 printk(KERN_CONT "<RELEASED>\n");
 687                 return;
 688         }
 689 
 690         printk(KERN_CONT "%px", hlock->instance);
 691         print_lock_name(lock);
 692         printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
 693 }
 694 
 695 static void lockdep_print_held_locks(struct task_struct *p)
 696 {
 697         int i, depth = READ_ONCE(p->lockdep_depth);
 698 
 699         if (!depth)
 700                 printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
 701         else
 702                 printk("%d lock%s held by %s/%d:\n", depth,
 703                        depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
 704         /*
 705          * It's not reliable to print a task's held locks if it's not sleeping
 706          * and it's not the current task.
 707          */
 708         if (p->state == TASK_RUNNING && p != current)
 709                 return;
 710         for (i = 0; i < depth; i++) {
 711                 printk(" #%d: ", i);
 712                 print_lock(p->held_locks + i);
 713         }
 714 }
 715 
 716 static void print_kernel_ident(void)
 717 {
 718         printk("%s %.*s %s\n", init_utsname()->release,
 719                 (int)strcspn(init_utsname()->version, " "),
 720                 init_utsname()->version,
 721                 print_tainted());
 722 }
 723 
 724 static int very_verbose(struct lock_class *class)
 725 {
 726 #if VERY_VERBOSE
 727         return class_filter(class);
 728 #endif
 729         return 0;
 730 }
 731 
 732 /*
 733  * Is this the address of a static object:
 734  */
 735 #ifdef __KERNEL__
 736 static int static_obj(const void *obj)
 737 {
 738         unsigned long start = (unsigned long) &_stext,
 739                       end   = (unsigned long) &_end,
 740                       addr  = (unsigned long) obj;
 741 
 742         if (arch_is_kernel_initmem_freed(addr))
 743                 return 0;
 744 
 745         /*
 746          * static variable?
 747          */
 748         if ((addr >= start) && (addr < end))
 749                 return 1;
 750 
 751         if (arch_is_kernel_data(addr))
 752                 return 1;
 753 
 754         /*
 755          * in-kernel percpu var?
 756          */
 757         if (is_kernel_percpu_address(addr))
 758                 return 1;
 759 
 760         /*
 761          * module static or percpu var?
 762          */
 763         return is_module_address(addr) || is_module_percpu_address(addr);
 764 }
 765 #endif
 766 
 767 /*
 768  * To make lock name printouts unique, we calculate a unique
 769  * class->name_version generation counter. The caller must hold the graph
 770  * lock.
 771  */
 772 static int count_matching_names(struct lock_class *new_class)
 773 {
 774         struct lock_class *class;
 775         int count = 0;
 776 
 777         if (!new_class->name)
 778                 return 0;
 779 
 780         list_for_each_entry(class, &all_lock_classes, lock_entry) {
 781                 if (new_class->key - new_class->subclass == class->key)
 782                         return class->name_version;
 783                 if (class->name && !strcmp(class->name, new_class->name))
 784                         count = max(count, class->name_version);
 785         }
 786 
 787         return count + 1;
 788 }
 789 
 790 static inline struct lock_class *
 791 look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
 792 {
 793         struct lockdep_subclass_key *key;
 794         struct hlist_head *hash_head;
 795         struct lock_class *class;
 796 
 797         if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
 798                 debug_locks_off();
 799                 printk(KERN_ERR
 800                         "BUG: looking up invalid subclass: %u\n", subclass);
 801                 printk(KERN_ERR
 802                         "turning off the locking correctness validator.\n");
 803                 dump_stack();
 804                 return NULL;
 805         }
 806 
 807         /*
 808          * If it is not initialised then it has never been locked,
 809          * so it won't be present in the hash table.
 810          */
 811         if (unlikely(!lock->key))
 812                 return NULL;
 813 
 814         /*
 815          * NOTE: the class-key must be unique. For dynamic locks, a static
 816          * lock_class_key variable is passed in through the mutex_init()
 817          * (or spin_lock_init()) call - which acts as the key. For static
 818          * locks we use the lock object itself as the key.
 819          */
 820         BUILD_BUG_ON(sizeof(struct lock_class_key) >
 821                         sizeof(struct lockdep_map));
 822 
 823         key = lock->key->subkeys + subclass;
 824 
 825         hash_head = classhashentry(key);
 826 
 827         /*
 828          * We do an RCU walk of the hash, see lockdep_free_key_range().
 829          */
 830         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
 831                 return NULL;
 832 
 833         hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
 834                 if (class->key == key) {
 835                         /*
 836                          * Huh! same key, different name? Did someone trample
 837                          * on some memory? We're most confused.
 838                          */
 839                         WARN_ON_ONCE(class->name != lock->name &&
 840                                      lock->key != &__lockdep_no_validate__);
 841                         return class;
 842                 }
 843         }
 844 
 845         return NULL;
 846 }
 847 
 848 /*
 849  * Static locks do not have their class-keys yet - for them the key is
 850  * the lock object itself. If the lock is in the per cpu area, the
 851  * canonical address of the lock (per cpu offset removed) is used.
 852  */
 853 static bool assign_lock_key(struct lockdep_map *lock)
 854 {
 855         unsigned long can_addr, addr = (unsigned long)lock;
 856 
 857 #ifdef __KERNEL__
 858         /*
 859          * lockdep_free_key_range() assumes that struct lock_class_key
 860          * objects do not overlap. Since we use the address of lock
 861          * objects as class key for static objects, check whether the
 862          * size of lock_class_key objects does not exceed the size of
 863          * the smallest lock object.
 864          */
 865         BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
 866 #endif
 867 
 868         if (__is_kernel_percpu_address(addr, &can_addr))
 869                 lock->key = (void *)can_addr;
 870         else if (__is_module_percpu_address(addr, &can_addr))
 871                 lock->key = (void *)can_addr;
 872         else if (static_obj(lock))
 873                 lock->key = (void *)lock;
 874         else {
 875                 /* Debug-check: all keys must be persistent! */
 876                 debug_locks_off();
 877                 pr_err("INFO: trying to register non-static key.\n");
 878                 pr_err("the code is fine but needs lockdep annotation.\n");
 879                 pr_err("turning off the locking correctness validator.\n");
 880                 dump_stack();
 881                 return false;
 882         }
 883 
 884         return true;
 885 }
 886 
 887 #ifdef CONFIG_DEBUG_LOCKDEP
 888 
 889 /* Check whether element @e occurs in list @h */
 890 static bool in_list(struct list_head *e, struct list_head *h)
 891 {
 892         struct list_head *f;
 893 
 894         list_for_each(f, h) {
 895                 if (e == f)
 896                         return true;
 897         }
 898 
 899         return false;
 900 }
 901 
 902 /*
 903  * Check whether entry @e occurs in any of the locks_after or locks_before
 904  * lists.
 905  */
 906 static bool in_any_class_list(struct list_head *e)
 907 {
 908         struct lock_class *class;
 909         int i;
 910 
 911         for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
 912                 class = &lock_classes[i];
 913                 if (in_list(e, &class->locks_after) ||
 914                     in_list(e, &class->locks_before))
 915                         return true;
 916         }
 917         return false;
 918 }
 919 
 920 static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
 921 {
 922         struct lock_list *e;
 923 
 924         list_for_each_entry(e, h, entry) {
 925                 if (e->links_to != c) {
 926                         printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
 927                                c->name ? : "(?)",
 928                                (unsigned long)(e - list_entries),
 929                                e->links_to && e->links_to->name ?
 930                                e->links_to->name : "(?)",
 931                                e->class && e->class->name ? e->class->name :
 932                                "(?)");
 933                         return false;
 934                 }
 935         }
 936         return true;
 937 }
 938 
 939 #ifdef CONFIG_PROVE_LOCKING
 940 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
 941 #endif
 942 
 943 static bool check_lock_chain_key(struct lock_chain *chain)
 944 {
 945 #ifdef CONFIG_PROVE_LOCKING
 946         u64 chain_key = INITIAL_CHAIN_KEY;
 947         int i;
 948 
 949         for (i = chain->base; i < chain->base + chain->depth; i++)
 950                 chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
 951         /*
 952          * The 'unsigned long long' casts avoid that a compiler warning
 953          * is reported when building tools/lib/lockdep.
 954          */
 955         if (chain->chain_key != chain_key) {
 956                 printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
 957                        (unsigned long long)(chain - lock_chains),
 958                        (unsigned long long)chain->chain_key,
 959                        (unsigned long long)chain_key);
 960                 return false;
 961         }
 962 #endif
 963         return true;
 964 }
 965 
 966 static bool in_any_zapped_class_list(struct lock_class *class)
 967 {
 968         struct pending_free *pf;
 969         int i;
 970 
 971         for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
 972                 if (in_list(&class->lock_entry, &pf->zapped))
 973                         return true;
 974         }
 975 
 976         return false;
 977 }
 978 
 979 static bool __check_data_structures(void)
 980 {
 981         struct lock_class *class;
 982         struct lock_chain *chain;
 983         struct hlist_head *head;
 984         struct lock_list *e;
 985         int i;
 986 
 987         /* Check whether all classes occur in a lock list. */
 988         for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
 989                 class = &lock_classes[i];
 990                 if (!in_list(&class->lock_entry, &all_lock_classes) &&
 991                     !in_list(&class->lock_entry, &free_lock_classes) &&
 992                     !in_any_zapped_class_list(class)) {
 993                         printk(KERN_INFO "class %px/%s is not in any class list\n",
 994                                class, class->name ? : "(?)");
 995                         return false;
 996                 }
 997         }
 998 
 999         /* Check whether all classes have valid lock lists. */
1000         for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1001                 class = &lock_classes[i];
1002                 if (!class_lock_list_valid(class, &class->locks_before))
1003                         return false;
1004                 if (!class_lock_list_valid(class, &class->locks_after))
1005                         return false;
1006         }
1007 
1008         /* Check the chain_key of all lock chains. */
1009         for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
1010                 head = chainhash_table + i;
1011                 hlist_for_each_entry_rcu(chain, head, entry) {
1012                         if (!check_lock_chain_key(chain))
1013                                 return false;
1014                 }
1015         }
1016 
1017         /*
1018          * Check whether all list entries that are in use occur in a class
1019          * lock list.
1020          */
1021         for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1022                 e = list_entries + i;
1023                 if (!in_any_class_list(&e->entry)) {
1024                         printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
1025                                (unsigned int)(e - list_entries),
1026                                e->class->name ? : "(?)",
1027                                e->links_to->name ? : "(?)");
1028                         return false;
1029                 }
1030         }
1031 
1032         /*
1033          * Check whether all list entries that are not in use do not occur in
1034          * a class lock list.
1035          */
1036         for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1037                 e = list_entries + i;
1038                 if (in_any_class_list(&e->entry)) {
1039                         printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
1040                                (unsigned int)(e - list_entries),
1041                                e->class && e->class->name ? e->class->name :
1042                                "(?)",
1043                                e->links_to && e->links_to->name ?
1044                                e->links_to->name : "(?)");
1045                         return false;
1046                 }
1047         }
1048 
1049         return true;
1050 }
1051 
1052 int check_consistency = 0;
1053 module_param(check_consistency, int, 0644);
1054 
1055 static void check_data_structures(void)
1056 {
1057         static bool once = false;
1058 
1059         if (check_consistency && !once) {
1060                 if (!__check_data_structures()) {
1061                         once = true;
1062                         WARN_ON(once);
1063                 }
1064         }
1065 }
1066 
1067 #else /* CONFIG_DEBUG_LOCKDEP */
1068 
1069 static inline void check_data_structures(void) { }
1070 
1071 #endif /* CONFIG_DEBUG_LOCKDEP */
1072 
1073 /*
1074  * Initialize the lock_classes[] array elements, the free_lock_classes list
1075  * and also the delayed_free structure.
1076  */
1077 static void init_data_structures_once(void)
1078 {
1079         static bool ds_initialized, rcu_head_initialized;
1080         int i;
1081 
1082         if (likely(rcu_head_initialized))
1083                 return;
1084 
1085         if (system_state >= SYSTEM_SCHEDULING) {
1086                 init_rcu_head(&delayed_free.rcu_head);
1087                 rcu_head_initialized = true;
1088         }
1089 
1090         if (ds_initialized)
1091                 return;
1092 
1093         ds_initialized = true;
1094 
1095         INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
1096         INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
1097 
1098         for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1099                 list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
1100                 INIT_LIST_HEAD(&lock_classes[i].locks_after);
1101                 INIT_LIST_HEAD(&lock_classes[i].locks_before);
1102         }
1103 }
1104 
1105 static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
1106 {
1107         unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
1108 
1109         return lock_keys_hash + hash;
1110 }
1111 
1112 /* Register a dynamically allocated key. */
1113 void lockdep_register_key(struct lock_class_key *key)
1114 {
1115         struct hlist_head *hash_head;
1116         struct lock_class_key *k;
1117         unsigned long flags;
1118 
1119         if (WARN_ON_ONCE(static_obj(key)))
1120                 return;
1121         hash_head = keyhashentry(key);
1122 
1123         raw_local_irq_save(flags);
1124         if (!graph_lock())
1125                 goto restore_irqs;
1126         hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1127                 if (WARN_ON_ONCE(k == key))
1128                         goto out_unlock;
1129         }
1130         hlist_add_head_rcu(&key->hash_entry, hash_head);
1131 out_unlock:
1132         graph_unlock();
1133 restore_irqs:
1134         raw_local_irq_restore(flags);
1135 }
1136 EXPORT_SYMBOL_GPL(lockdep_register_key);
1137 
1138 /* Check whether a key has been registered as a dynamic key. */
1139 static bool is_dynamic_key(const struct lock_class_key *key)
1140 {
1141         struct hlist_head *hash_head;
1142         struct lock_class_key *k;
1143         bool found = false;
1144 
1145         if (WARN_ON_ONCE(static_obj(key)))
1146                 return false;
1147 
1148         /*
1149          * If lock debugging is disabled lock_keys_hash[] may contain
1150          * pointers to memory that has already been freed. Avoid triggering
1151          * a use-after-free in that case by returning early.
1152          */
1153         if (!debug_locks)
1154                 return true;
1155 
1156         hash_head = keyhashentry(key);
1157 
1158         rcu_read_lock();
1159         hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1160                 if (k == key) {
1161                         found = true;
1162                         break;
1163                 }
1164         }
1165         rcu_read_unlock();
1166 
1167         return found;
1168 }
1169 
1170 /*
1171  * Register a lock's class in the hash-table, if the class is not present
1172  * yet. Otherwise we look it up. We cache the result in the lock object
1173  * itself, so actual lookup of the hash should be once per lock object.
1174  */
1175 static struct lock_class *
1176 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
1177 {
1178         struct lockdep_subclass_key *key;
1179         struct hlist_head *hash_head;
1180         struct lock_class *class;
1181 
1182         DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1183 
1184         class = look_up_lock_class(lock, subclass);
1185         if (likely(class))
1186                 goto out_set_class_cache;
1187 
1188         if (!lock->key) {
1189                 if (!assign_lock_key(lock))
1190                         return NULL;
1191         } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
1192                 return NULL;
1193         }
1194 
1195         key = lock->key->subkeys + subclass;
1196         hash_head = classhashentry(key);
1197 
1198         if (!graph_lock()) {
1199                 return NULL;
1200         }
1201         /*
1202          * We have to do the hash-walk again, to avoid races
1203          * with another CPU:
1204          */
1205         hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
1206                 if (class->key == key)
1207                         goto out_unlock_set;
1208         }
1209 
1210         init_data_structures_once();
1211 
1212         /* Allocate a new lock class and add it to the hash. */
1213         class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
1214                                          lock_entry);
1215         if (!class) {
1216                 if (!debug_locks_off_graph_unlock()) {
1217                         return NULL;
1218                 }
1219 
1220                 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
1221                 dump_stack();
1222                 return NULL;
1223         }
1224         nr_lock_classes++;
1225         __set_bit(class - lock_classes, lock_classes_in_use);
1226         debug_atomic_inc(nr_unused_locks);
1227         class->key = key;
1228         class->name = lock->name;
1229         class->subclass = subclass;
1230         WARN_ON_ONCE(!list_empty(&class->locks_before));
1231         WARN_ON_ONCE(!list_empty(&class->locks_after));
1232         class->name_version = count_matching_names(class);
1233         /*
1234          * We use RCU's safe list-add method to make
1235          * parallel walking of the hash-list safe:
1236          */
1237         hlist_add_head_rcu(&class->hash_entry, hash_head);
1238         /*
1239          * Remove the class from the free list and add it to the global list
1240          * of classes.
1241          */
1242         list_move_tail(&class->lock_entry, &all_lock_classes);
1243 
1244         if (verbose(class)) {
1245                 graph_unlock();
1246 
1247                 printk("\nnew class %px: %s", class->key, class->name);
1248                 if (class->name_version > 1)
1249                         printk(KERN_CONT "#%d", class->name_version);
1250                 printk(KERN_CONT "\n");
1251                 dump_stack();
1252 
1253                 if (!graph_lock()) {
1254                         return NULL;
1255                 }
1256         }
1257 out_unlock_set:
1258         graph_unlock();
1259 
1260 out_set_class_cache:
1261         if (!subclass || force)
1262                 lock->class_cache[0] = class;
1263         else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
1264                 lock->class_cache[subclass] = class;
1265 
1266         /*
1267          * Hash collision, did we smoke some? We found a class with a matching
1268          * hash but the subclass -- which is hashed in -- didn't match.
1269          */
1270         if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1271                 return NULL;
1272 
1273         return class;
1274 }
1275 
1276 #ifdef CONFIG_PROVE_LOCKING
1277 /*
1278  * Allocate a lockdep entry. (assumes the graph_lock held, returns
1279  * with NULL on failure)
1280  */
1281 static struct lock_list *alloc_list_entry(void)
1282 {
1283         int idx = find_first_zero_bit(list_entries_in_use,
1284                                       ARRAY_SIZE(list_entries));
1285 
1286         if (idx >= ARRAY_SIZE(list_entries)) {
1287                 if (!debug_locks_off_graph_unlock())
1288                         return NULL;
1289 
1290                 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
1291                 dump_stack();
1292                 return NULL;
1293         }
1294         nr_list_entries++;
1295         __set_bit(idx, list_entries_in_use);
1296         return list_entries + idx;
1297 }
1298 
1299 /*
1300  * Add a new dependency to the head of the list:
1301  */
1302 static int add_lock_to_list(struct lock_class *this,
1303                             struct lock_class *links_to, struct list_head *head,
1304                             unsigned long ip, int distance,
1305                             const struct lock_trace *trace)
1306 {
1307         struct lock_list *entry;
1308         /*
1309          * Lock not present yet - get a new dependency struct and
1310          * add it to the list:
1311          */
1312         entry = alloc_list_entry();
1313         if (!entry)
1314                 return 0;
1315 
1316         entry->class = this;
1317         entry->links_to = links_to;
1318         entry->distance = distance;
1319         entry->trace = trace;
1320         /*
1321          * Both allocation and removal are done under the graph lock; but
1322          * iteration is under RCU-sched; see look_up_lock_class() and
1323          * lockdep_free_key_range().
1324          */
1325         list_add_tail_rcu(&entry->entry, head);
1326 
1327         return 1;
1328 }
1329 
1330 /*
1331  * For good efficiency of modular, we use power of 2
1332  */
1333 #define MAX_CIRCULAR_QUEUE_SIZE         4096UL
1334 #define CQ_MASK                         (MAX_CIRCULAR_QUEUE_SIZE-1)
1335 
1336 /*
1337  * The circular_queue and helpers are used to implement graph
1338  * breadth-first search (BFS) algorithm, by which we can determine
1339  * whether there is a path from a lock to another. In deadlock checks,
1340  * a path from the next lock to be acquired to a previous held lock
1341  * indicates that adding the <prev> -> <next> lock dependency will
1342  * produce a circle in the graph. Breadth-first search instead of
1343  * depth-first search is used in order to find the shortest (circular)
1344  * path.
1345  */
1346 struct circular_queue {
1347         struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
1348         unsigned int  front, rear;
1349 };
1350 
1351 static struct circular_queue lock_cq;
1352 
1353 unsigned int max_bfs_queue_depth;
1354 
1355 static unsigned int lockdep_dependency_gen_id;
1356 
1357 static inline void __cq_init(struct circular_queue *cq)
1358 {
1359         cq->front = cq->rear = 0;
1360         lockdep_dependency_gen_id++;
1361 }
1362 
1363 static inline int __cq_empty(struct circular_queue *cq)
1364 {
1365         return (cq->front == cq->rear);
1366 }
1367 
1368 static inline int __cq_full(struct circular_queue *cq)
1369 {
1370         return ((cq->rear + 1) & CQ_MASK) == cq->front;
1371 }
1372 
1373 static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
1374 {
1375         if (__cq_full(cq))
1376                 return -1;
1377 
1378         cq->element[cq->rear] = elem;
1379         cq->rear = (cq->rear + 1) & CQ_MASK;
1380         return 0;
1381 }
1382 
1383 /*
1384  * Dequeue an element from the circular_queue, return a lock_list if
1385  * the queue is not empty, or NULL if otherwise.
1386  */
1387 static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
1388 {
1389         struct lock_list * lock;
1390 
1391         if (__cq_empty(cq))
1392                 return NULL;
1393 
1394         lock = cq->element[cq->front];
1395         cq->front = (cq->front + 1) & CQ_MASK;
1396 
1397         return lock;
1398 }
1399 
1400 static inline unsigned int  __cq_get_elem_count(struct circular_queue *cq)
1401 {
1402         return (cq->rear - cq->front) & CQ_MASK;
1403 }
1404 
1405 static inline void mark_lock_accessed(struct lock_list *lock,
1406                                         struct lock_list *parent)
1407 {
1408         unsigned long nr;
1409 
1410         nr = lock - list_entries;
1411         WARN_ON(nr >= ARRAY_SIZE(list_entries)); /* Out-of-bounds, input fail */
1412         lock->parent = parent;
1413         lock->class->dep_gen_id = lockdep_dependency_gen_id;
1414 }
1415 
1416 static inline unsigned long lock_accessed(struct lock_list *lock)
1417 {
1418         unsigned long nr;
1419 
1420         nr = lock - list_entries;
1421         WARN_ON(nr >= ARRAY_SIZE(list_entries)); /* Out-of-bounds, input fail */
1422         return lock->class->dep_gen_id == lockdep_dependency_gen_id;
1423 }
1424 
1425 static inline struct lock_list *get_lock_parent(struct lock_list *child)
1426 {
1427         return child->parent;
1428 }
1429 
1430 static inline int get_lock_depth(struct lock_list *child)
1431 {
1432         int depth = 0;
1433         struct lock_list *parent;
1434 
1435         while ((parent = get_lock_parent(child))) {
1436                 child = parent;
1437                 depth++;
1438         }
1439         return depth;
1440 }
1441 
1442 /*
1443  * Return the forward or backward dependency list.
1444  *
1445  * @lock:   the lock_list to get its class's dependency list
1446  * @offset: the offset to struct lock_class to determine whether it is
1447  *          locks_after or locks_before
1448  */
1449 static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
1450 {
1451         void *lock_class = lock->class;
1452 
1453         return lock_class + offset;
1454 }
1455 
1456 /*
1457  * Forward- or backward-dependency search, used for both circular dependency
1458  * checking and hardirq-unsafe/softirq-unsafe checking.
1459  */
1460 static int __bfs(struct lock_list *source_entry,
1461                  void *data,
1462                  int (*match)(struct lock_list *entry, void *data),
1463                  struct lock_list **target_entry,
1464                  int offset)
1465 {
1466         struct lock_list *entry;
1467         struct lock_list *lock;
1468         struct list_head *head;
1469         struct circular_queue *cq = &lock_cq;
1470         int ret = 1;
1471 
1472         if (match(source_entry, data)) {
1473                 *target_entry = source_entry;
1474                 ret = 0;
1475                 goto exit;
1476         }
1477 
1478         head = get_dep_list(source_entry, offset);
1479         if (list_empty(head))
1480                 goto exit;
1481 
1482         __cq_init(cq);
1483         __cq_enqueue(cq, source_entry);
1484 
1485         while ((lock = __cq_dequeue(cq))) {
1486 
1487                 if (!lock->class) {
1488                         ret = -2;
1489                         goto exit;
1490                 }
1491 
1492                 head = get_dep_list(lock, offset);
1493 
1494                 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1495 
1496                 list_for_each_entry_rcu(entry, head, entry) {
1497                         if (!lock_accessed(entry)) {
1498                                 unsigned int cq_depth;
1499                                 mark_lock_accessed(entry, lock);
1500                                 if (match(entry, data)) {
1501                                         *target_entry = entry;
1502                                         ret = 0;
1503                                         goto exit;
1504                                 }
1505 
1506                                 if (__cq_enqueue(cq, entry)) {
1507                                         ret = -1;
1508                                         goto exit;
1509                                 }
1510                                 cq_depth = __cq_get_elem_count(cq);
1511                                 if (max_bfs_queue_depth < cq_depth)
1512                                         max_bfs_queue_depth = cq_depth;
1513                         }
1514                 }
1515         }
1516 exit:
1517         return ret;
1518 }
1519 
1520 static inline int __bfs_forwards(struct lock_list *src_entry,
1521                         void *data,
1522                         int (*match)(struct lock_list *entry, void *data),
1523                         struct lock_list **target_entry)
1524 {
1525         return __bfs(src_entry, data, match, target_entry,
1526                      offsetof(struct lock_class, locks_after));
1527 
1528 }
1529 
1530 static inline int __bfs_backwards(struct lock_list *src_entry,
1531                         void *data,
1532                         int (*match)(struct lock_list *entry, void *data),
1533                         struct lock_list **target_entry)
1534 {
1535         return __bfs(src_entry, data, match, target_entry,
1536                      offsetof(struct lock_class, locks_before));
1537 
1538 }
1539 
1540 static void print_lock_trace(const struct lock_trace *trace,
1541                              unsigned int spaces)
1542 {
1543         stack_trace_print(trace->entries, trace->nr_entries, spaces);
1544 }
1545 
1546 /*
1547  * Print a dependency chain entry (this is only done when a deadlock
1548  * has been detected):
1549  */
1550 static noinline void
1551 print_circular_bug_entry(struct lock_list *target, int depth)
1552 {
1553         if (debug_locks_silent)
1554                 return;
1555         printk("\n-> #%u", depth);
1556         print_lock_name(target->class);
1557         printk(KERN_CONT ":\n");
1558         print_lock_trace(target->trace, 6);
1559 }
1560 
1561 static void
1562 print_circular_lock_scenario(struct held_lock *src,
1563                              struct held_lock *tgt,
1564                              struct lock_list *prt)
1565 {
1566         struct lock_class *source = hlock_class(src);
1567         struct lock_class *target = hlock_class(tgt);
1568         struct lock_class *parent = prt->class;
1569 
1570         /*
1571          * A direct locking problem where unsafe_class lock is taken
1572          * directly by safe_class lock, then all we need to show
1573          * is the deadlock scenario, as it is obvious that the
1574          * unsafe lock is taken under the safe lock.
1575          *
1576          * But if there is a chain instead, where the safe lock takes
1577          * an intermediate lock (middle_class) where this lock is
1578          * not the same as the safe lock, then the lock chain is
1579          * used to describe the problem. Otherwise we would need
1580          * to show a different CPU case for each link in the chain
1581          * from the safe_class lock to the unsafe_class lock.
1582          */
1583         if (parent != source) {
1584                 printk("Chain exists of:\n  ");
1585                 __print_lock_name(source);
1586                 printk(KERN_CONT " --> ");
1587                 __print_lock_name(parent);
1588                 printk(KERN_CONT " --> ");
1589                 __print_lock_name(target);
1590                 printk(KERN_CONT "\n\n");
1591         }
1592 
1593         printk(" Possible unsafe locking scenario:\n\n");
1594         printk("       CPU0                    CPU1\n");
1595         printk("       ----                    ----\n");
1596         printk("  lock(");
1597         __print_lock_name(target);
1598         printk(KERN_CONT ");\n");
1599         printk("                               lock(");
1600         __print_lock_name(parent);
1601         printk(KERN_CONT ");\n");
1602         printk("                               lock(");
1603         __print_lock_name(target);
1604         printk(KERN_CONT ");\n");
1605         printk("  lock(");
1606         __print_lock_name(source);
1607         printk(KERN_CONT ");\n");
1608         printk("\n *** DEADLOCK ***\n\n");
1609 }
1610 
1611 /*
1612  * When a circular dependency is detected, print the
1613  * header first:
1614  */
1615 static noinline void
1616 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1617                         struct held_lock *check_src,
1618                         struct held_lock *check_tgt)
1619 {
1620         struct task_struct *curr = current;
1621 
1622         if (debug_locks_silent)
1623                 return;
1624 
1625         pr_warn("\n");
1626         pr_warn("======================================================\n");
1627         pr_warn("WARNING: possible circular locking dependency detected\n");
1628         print_kernel_ident();
1629         pr_warn("------------------------------------------------------\n");
1630         pr_warn("%s/%d is trying to acquire lock:\n",
1631                 curr->comm, task_pid_nr(curr));
1632         print_lock(check_src);
1633 
1634         pr_warn("\nbut task is already holding lock:\n");
1635 
1636         print_lock(check_tgt);
1637         pr_warn("\nwhich lock already depends on the new lock.\n\n");
1638         pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
1639 
1640         print_circular_bug_entry(entry, depth);
1641 }
1642 
1643 static inline int class_equal(struct lock_list *entry, void *data)
1644 {
1645         return entry->class == data;
1646 }
1647 
1648 static noinline void print_circular_bug(struct lock_list *this,
1649                                         struct lock_list *target,
1650                                         struct held_lock *check_src,
1651                                         struct held_lock *check_tgt)
1652 {
1653         struct task_struct *curr = current;
1654         struct lock_list *parent;
1655         struct lock_list *first_parent;
1656         int depth;
1657 
1658         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1659                 return;
1660 
1661         this->trace = save_trace();
1662         if (!this->trace)
1663                 return;
1664 
1665         depth = get_lock_depth(target);
1666 
1667         print_circular_bug_header(target, depth, check_src, check_tgt);
1668 
1669         parent = get_lock_parent(target);
1670         first_parent = parent;
1671 
1672         while (parent) {
1673                 print_circular_bug_entry(parent, --depth);
1674                 parent = get_lock_parent(parent);
1675         }
1676 
1677         printk("\nother info that might help us debug this:\n\n");
1678         print_circular_lock_scenario(check_src, check_tgt,
1679                                      first_parent);
1680 
1681         lockdep_print_held_locks(curr);
1682 
1683         printk("\nstack backtrace:\n");
1684         dump_stack();
1685 }
1686 
1687 static noinline void print_bfs_bug(int ret)
1688 {
1689         if (!debug_locks_off_graph_unlock())
1690                 return;
1691 
1692         /*
1693          * Breadth-first-search failed, graph got corrupted?
1694          */
1695         WARN(1, "lockdep bfs error:%d\n", ret);
1696 }
1697 
1698 static int noop_count(struct lock_list *entry, void *data)
1699 {
1700         (*(unsigned long *)data)++;
1701         return 0;
1702 }
1703 
1704 static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1705 {
1706         unsigned long  count = 0;
1707         struct lock_list *uninitialized_var(target_entry);
1708 
1709         __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1710 
1711         return count;
1712 }
1713 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1714 {
1715         unsigned long ret, flags;
1716         struct lock_list this;
1717 
1718         this.parent = NULL;
1719         this.class = class;
1720 
1721         raw_local_irq_save(flags);
1722         current->lockdep_recursion = 1;
1723         arch_spin_lock(&lockdep_lock);
1724         ret = __lockdep_count_forward_deps(&this);
1725         arch_spin_unlock(&lockdep_lock);
1726         current->lockdep_recursion = 0;
1727         raw_local_irq_restore(flags);
1728 
1729         return ret;
1730 }
1731 
1732 static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1733 {
1734         unsigned long  count = 0;
1735         struct lock_list *uninitialized_var(target_entry);
1736 
1737         __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1738 
1739         return count;
1740 }
1741 
1742 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1743 {
1744         unsigned long ret, flags;
1745         struct lock_list this;
1746 
1747         this.parent = NULL;
1748         this.class = class;
1749 
1750         raw_local_irq_save(flags);
1751         current->lockdep_recursion = 1;
1752         arch_spin_lock(&lockdep_lock);
1753         ret = __lockdep_count_backward_deps(&this);
1754         arch_spin_unlock(&lockdep_lock);
1755         current->lockdep_recursion = 0;
1756         raw_local_irq_restore(flags);
1757 
1758         return ret;
1759 }
1760 
1761 /*
1762  * Check that the dependency graph starting at <src> can lead to
1763  * <target> or not. Print an error and return 0 if it does.
1764  */
1765 static noinline int
1766 check_path(struct lock_class *target, struct lock_list *src_entry,
1767            struct lock_list **target_entry)
1768 {
1769         int ret;
1770 
1771         ret = __bfs_forwards(src_entry, (void *)target, class_equal,
1772                              target_entry);
1773 
1774         if (unlikely(ret < 0))
1775                 print_bfs_bug(ret);
1776 
1777         return ret;
1778 }
1779 
1780 /*
1781  * Prove that the dependency graph starting at <src> can not
1782  * lead to <target>. If it can, there is a circle when adding
1783  * <target> -> <src> dependency.
1784  *
1785  * Print an error and return 0 if it does.
1786  */
1787 static noinline int
1788 check_noncircular(struct held_lock *src, struct held_lock *target,
1789                   struct lock_trace **const trace)
1790 {
1791         int ret;
1792         struct lock_list *uninitialized_var(target_entry);
1793         struct lock_list src_entry = {
1794                 .class = hlock_class(src),
1795                 .parent = NULL,
1796         };
1797 
1798         debug_atomic_inc(nr_cyclic_checks);
1799 
1800         ret = check_path(hlock_class(target), &src_entry, &target_entry);
1801 
1802         if (unlikely(!ret)) {
1803                 if (!*trace) {
1804                         /*
1805                          * If save_trace fails here, the printing might
1806                          * trigger a WARN but because of the !nr_entries it
1807                          * should not do bad things.
1808                          */
1809                         *trace = save_trace();
1810                 }
1811 
1812                 print_circular_bug(&src_entry, target_entry, src, target);
1813         }
1814 
1815         return ret;
1816 }
1817 
1818 #ifdef CONFIG_LOCKDEP_SMALL
1819 /*
1820  * Check that the dependency graph starting at <src> can lead to
1821  * <target> or not. If it can, <src> -> <target> dependency is already
1822  * in the graph.
1823  *
1824  * Print an error and return 2 if it does or 1 if it does not.
1825  */
1826 static noinline int
1827 check_redundant(struct held_lock *src, struct held_lock *target)
1828 {
1829         int ret;
1830         struct lock_list *uninitialized_var(target_entry);
1831         struct lock_list src_entry = {
1832                 .class = hlock_class(src),
1833                 .parent = NULL,
1834         };
1835 
1836         debug_atomic_inc(nr_redundant_checks);
1837 
1838         ret = check_path(hlock_class(target), &src_entry, &target_entry);
1839 
1840         if (!ret) {
1841                 debug_atomic_inc(nr_redundant);
1842                 ret = 2;
1843         } else if (ret < 0)
1844                 ret = 0;
1845 
1846         return ret;
1847 }
1848 #endif
1849 
1850 #ifdef CONFIG_TRACE_IRQFLAGS
1851 
1852 static inline int usage_accumulate(struct lock_list *entry, void *mask)
1853 {
1854         *(unsigned long *)mask |= entry->class->usage_mask;
1855 
1856         return 0;
1857 }
1858 
1859 /*
1860  * Forwards and backwards subgraph searching, for the purposes of
1861  * proving that two subgraphs can be connected by a new dependency
1862  * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1863  */
1864 
1865 static inline int usage_match(struct lock_list *entry, void *mask)
1866 {
1867         return entry->class->usage_mask & *(unsigned long *)mask;
1868 }
1869 
1870 /*
1871  * Find a node in the forwards-direction dependency sub-graph starting
1872  * at @root->class that matches @bit.
1873  *
1874  * Return 0 if such a node exists in the subgraph, and put that node
1875  * into *@target_entry.
1876  *
1877  * Return 1 otherwise and keep *@target_entry unchanged.
1878  * Return <0 on error.
1879  */
1880 static int
1881 find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
1882                         struct lock_list **target_entry)
1883 {
1884         int result;
1885 
1886         debug_atomic_inc(nr_find_usage_forwards_checks);
1887 
1888         result = __bfs_forwards(root, &usage_mask, usage_match, target_entry);
1889 
1890         return result;
1891 }
1892 
1893 /*
1894  * Find a node in the backwards-direction dependency sub-graph starting
1895  * at @root->class that matches @bit.
1896  *
1897  * Return 0 if such a node exists in the subgraph, and put that node
1898  * into *@target_entry.
1899  *
1900  * Return 1 otherwise and keep *@target_entry unchanged.
1901  * Return <0 on error.
1902  */
1903 static int
1904 find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
1905                         struct lock_list **target_entry)
1906 {
1907         int result;
1908 
1909         debug_atomic_inc(nr_find_usage_backwards_checks);
1910 
1911         result = __bfs_backwards(root, &usage_mask, usage_match, target_entry);
1912 
1913         return result;
1914 }
1915 
1916 static void print_lock_class_header(struct lock_class *class, int depth)
1917 {
1918         int bit;
1919 
1920         printk("%*s->", depth, "");
1921         print_lock_name(class);
1922 #ifdef CONFIG_DEBUG_LOCKDEP
1923         printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
1924 #endif
1925         printk(KERN_CONT " {\n");
1926 
1927         for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1928                 if (class->usage_mask & (1 << bit)) {
1929                         int len = depth;
1930 
1931                         len += printk("%*s   %s", depth, "", usage_str[bit]);
1932                         len += printk(KERN_CONT " at:\n");
1933                         print_lock_trace(class->usage_traces[bit], len);
1934                 }
1935         }
1936         printk("%*s }\n", depth, "");
1937 
1938         printk("%*s ... key      at: [<%px>] %pS\n",
1939                 depth, "", class->key, class->key);
1940 }
1941 
1942 /*
1943  * printk the shortest lock dependencies from @start to @end in reverse order:
1944  */
1945 static void __used
1946 print_shortest_lock_dependencies(struct lock_list *leaf,
1947                                  struct lock_list *root)
1948 {
1949         struct lock_list *entry = leaf;
1950         int depth;
1951 
1952         /*compute depth from generated tree by BFS*/
1953         depth = get_lock_depth(leaf);
1954 
1955         do {
1956                 print_lock_class_header(entry->class, depth);
1957                 printk("%*s ... acquired at:\n", depth, "");
1958                 print_lock_trace(entry->trace, 2);
1959                 printk("\n");
1960 
1961                 if (depth == 0 && (entry != root)) {
1962                         printk("lockdep:%s bad path found in chain graph\n", __func__);
1963                         break;
1964                 }
1965 
1966                 entry = get_lock_parent(entry);
1967                 depth--;
1968         } while (entry && (depth >= 0));
1969 }
1970 
1971 static void
1972 print_irq_lock_scenario(struct lock_list *safe_entry,
1973                         struct lock_list *unsafe_entry,
1974                         struct lock_class *prev_class,
1975                         struct lock_class *next_class)
1976 {
1977         struct lock_class *safe_class = safe_entry->class;
1978         struct lock_class *unsafe_class = unsafe_entry->class;
1979         struct lock_class *middle_class = prev_class;
1980 
1981         if (middle_class == safe_class)
1982                 middle_class = next_class;
1983 
1984         /*
1985          * A direct locking problem where unsafe_class lock is taken
1986          * directly by safe_class lock, then all we need to show
1987          * is the deadlock scenario, as it is obvious that the
1988          * unsafe lock is taken under the safe lock.
1989          *
1990          * But if there is a chain instead, where the safe lock takes
1991          * an intermediate lock (middle_class) where this lock is
1992          * not the same as the safe lock, then the lock chain is
1993          * used to describe the problem. Otherwise we would need
1994          * to show a different CPU case for each link in the chain
1995          * from the safe_class lock to the unsafe_class lock.
1996          */
1997         if (middle_class != unsafe_class) {
1998                 printk("Chain exists of:\n  ");
1999                 __print_lock_name(safe_class);
2000                 printk(KERN_CONT " --> ");
2001                 __print_lock_name(middle_class);
2002                 printk(KERN_CONT " --> ");
2003                 __print_lock_name(unsafe_class);
2004                 printk(KERN_CONT "\n\n");
2005         }
2006 
2007         printk(" Possible interrupt unsafe locking scenario:\n\n");
2008         printk("       CPU0                    CPU1\n");
2009         printk("       ----                    ----\n");
2010         printk("  lock(");
2011         __print_lock_name(unsafe_class);
2012         printk(KERN_CONT ");\n");
2013         printk("                               local_irq_disable();\n");
2014         printk("                               lock(");
2015         __print_lock_name(safe_class);
2016         printk(KERN_CONT ");\n");
2017         printk("                               lock(");
2018         __print_lock_name(middle_class);
2019         printk(KERN_CONT ");\n");
2020         printk("  <Interrupt>\n");
2021         printk("    lock(");
2022         __print_lock_name(safe_class);
2023         printk(KERN_CONT ");\n");
2024         printk("\n *** DEADLOCK ***\n\n");
2025 }
2026 
2027 static void
2028 print_bad_irq_dependency(struct task_struct *curr,
2029                          struct lock_list *prev_root,
2030                          struct lock_list *next_root,
2031                          struct lock_list *backwards_entry,
2032                          struct lock_list *forwards_entry,
2033                          struct held_lock *prev,
2034                          struct held_lock *next,
2035                          enum lock_usage_bit bit1,
2036                          enum lock_usage_bit bit2,
2037                          const char *irqclass)
2038 {
2039         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2040                 return;
2041 
2042         pr_warn("\n");
2043         pr_warn("=====================================================\n");
2044         pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
2045                 irqclass, irqclass);
2046         print_kernel_ident();
2047         pr_warn("-----------------------------------------------------\n");
2048         pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
2049                 curr->comm, task_pid_nr(curr),
2050                 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
2051                 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
2052                 curr->hardirqs_enabled,
2053                 curr->softirqs_enabled);
2054         print_lock(next);
2055 
2056         pr_warn("\nand this task is already holding:\n");
2057         print_lock(prev);
2058         pr_warn("which would create a new lock dependency:\n");
2059         print_lock_name(hlock_class(prev));
2060         pr_cont(" ->");
2061         print_lock_name(hlock_class(next));
2062         pr_cont("\n");
2063 
2064         pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
2065                 irqclass);
2066         print_lock_name(backwards_entry->class);
2067         pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
2068 
2069         print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
2070 
2071         pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
2072         print_lock_name(forwards_entry->class);
2073         pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
2074         pr_warn("...");
2075 
2076         print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
2077 
2078         pr_warn("\nother info that might help us debug this:\n\n");
2079         print_irq_lock_scenario(backwards_entry, forwards_entry,
2080                                 hlock_class(prev), hlock_class(next));
2081 
2082         lockdep_print_held_locks(curr);
2083 
2084         pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
2085         prev_root->trace = save_trace();
2086         if (!prev_root->trace)
2087                 return;
2088         print_shortest_lock_dependencies(backwards_entry, prev_root);
2089 
2090         pr_warn("\nthe dependencies between the lock to be acquired");
2091         pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
2092         next_root->trace = save_trace();
2093         if (!next_root->trace)
2094                 return;
2095         print_shortest_lock_dependencies(forwards_entry, next_root);
2096 
2097         pr_warn("\nstack backtrace:\n");
2098         dump_stack();
2099 }
2100 
2101 static const char *state_names[] = {
2102 #define LOCKDEP_STATE(__STATE) \
2103         __stringify(__STATE),
2104 #include "lockdep_states.h"
2105 #undef LOCKDEP_STATE
2106 };
2107 
2108 static const char *state_rnames[] = {
2109 #define LOCKDEP_STATE(__STATE) \
2110         __stringify(__STATE)"-READ",
2111 #include "lockdep_states.h"
2112 #undef LOCKDEP_STATE
2113 };
2114 
2115 static inline const char *state_name(enum lock_usage_bit bit)
2116 {
2117         if (bit & LOCK_USAGE_READ_MASK)
2118                 return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
2119         else
2120                 return state_names[bit >> LOCK_USAGE_DIR_MASK];
2121 }
2122 
2123 /*
2124  * The bit number is encoded like:
2125  *
2126  *  bit0: 0 exclusive, 1 read lock
2127  *  bit1: 0 used in irq, 1 irq enabled
2128  *  bit2-n: state
2129  */
2130 static int exclusive_bit(int new_bit)
2131 {
2132         int state = new_bit & LOCK_USAGE_STATE_MASK;
2133         int dir = new_bit & LOCK_USAGE_DIR_MASK;
2134 
2135         /*
2136          * keep state, bit flip the direction and strip read.
2137          */
2138         return state | (dir ^ LOCK_USAGE_DIR_MASK);
2139 }
2140 
2141 /*
2142  * Observe that when given a bitmask where each bitnr is encoded as above, a
2143  * right shift of the mask transforms the individual bitnrs as -1 and
2144  * conversely, a left shift transforms into +1 for the individual bitnrs.
2145  *
2146  * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
2147  * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
2148  * instead by subtracting the bit number by 2, or shifting the mask right by 2.
2149  *
2150  * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
2151  *
2152  * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
2153  * all bits set) and recompose with bitnr1 flipped.
2154  */
2155 static unsigned long invert_dir_mask(unsigned long mask)
2156 {
2157         unsigned long excl = 0;
2158 
2159         /* Invert dir */
2160         excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
2161         excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
2162 
2163         return excl;
2164 }
2165 
2166 /*
2167  * As above, we clear bitnr0 (LOCK_*_READ off) with bitmask ops. First, for all
2168  * bits with bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*).
2169  * And then mask out all bitnr0.
2170  */
2171 static unsigned long exclusive_mask(unsigned long mask)
2172 {
2173         unsigned long excl = invert_dir_mask(mask);
2174 
2175         /* Strip read */
2176         excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2177         excl &= ~LOCKF_IRQ_READ;
2178 
2179         return excl;
2180 }
2181 
2182 /*
2183  * Retrieve the _possible_ original mask to which @mask is
2184  * exclusive. Ie: this is the opposite of exclusive_mask().
2185  * Note that 2 possible original bits can match an exclusive
2186  * bit: one has LOCK_USAGE_READ_MASK set, the other has it
2187  * cleared. So both are returned for each exclusive bit.
2188  */
2189 static unsigned long original_mask(unsigned long mask)
2190 {
2191         unsigned long excl = invert_dir_mask(mask);
2192 
2193         /* Include read in existing usages */
2194         excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2195 
2196         return excl;
2197 }
2198 
2199 /*
2200  * Find the first pair of bit match between an original
2201  * usage mask and an exclusive usage mask.
2202  */
2203 static int find_exclusive_match(unsigned long mask,
2204                                 unsigned long excl_mask,
2205                                 enum lock_usage_bit *bitp,
2206                                 enum lock_usage_bit *excl_bitp)
2207 {
2208         int bit, excl;
2209 
2210         for_each_set_bit(bit, &mask, LOCK_USED) {
2211                 excl = exclusive_bit(bit);
2212                 if (excl_mask & lock_flag(excl)) {
2213                         *bitp = bit;
2214                         *excl_bitp = excl;
2215                         return 0;
2216                 }
2217         }
2218         return -1;
2219 }
2220 
2221 /*
2222  * Prove that the new dependency does not connect a hardirq-safe(-read)
2223  * lock with a hardirq-unsafe lock - to achieve this we search
2224  * the backwards-subgraph starting at <prev>, and the
2225  * forwards-subgraph starting at <next>:
2226  */
2227 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
2228                            struct held_lock *next)
2229 {
2230         unsigned long usage_mask = 0, forward_mask, backward_mask;
2231         enum lock_usage_bit forward_bit = 0, backward_bit = 0;
2232         struct lock_list *uninitialized_var(target_entry1);
2233         struct lock_list *uninitialized_var(target_entry);
2234         struct lock_list this, that;
2235         int ret;
2236 
2237         /*
2238          * Step 1: gather all hard/soft IRQs usages backward in an
2239          * accumulated usage mask.
2240          */
2241         this.parent = NULL;
2242         this.class = hlock_class(prev);
2243 
2244         ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, NULL);
2245         if (ret < 0) {
2246                 print_bfs_bug(ret);
2247                 return 0;
2248         }
2249 
2250         usage_mask &= LOCKF_USED_IN_IRQ_ALL;
2251         if (!usage_mask)
2252                 return 1;
2253 
2254         /*
2255          * Step 2: find exclusive uses forward that match the previous
2256          * backward accumulated mask.
2257          */
2258         forward_mask = exclusive_mask(usage_mask);
2259 
2260         that.parent = NULL;
2261         that.class = hlock_class(next);
2262 
2263         ret = find_usage_forwards(&that, forward_mask, &target_entry1);
2264         if (ret < 0) {
2265                 print_bfs_bug(ret);
2266                 return 0;
2267         }
2268         if (ret == 1)
2269                 return ret;
2270 
2271         /*
2272          * Step 3: we found a bad match! Now retrieve a lock from the backward
2273          * list whose usage mask matches the exclusive usage mask from the
2274          * lock found on the forward list.
2275          */
2276         backward_mask = original_mask(target_entry1->class->usage_mask);
2277 
2278         ret = find_usage_backwards(&this, backward_mask, &target_entry);
2279         if (ret < 0) {
2280                 print_bfs_bug(ret);
2281                 return 0;
2282         }
2283         if (DEBUG_LOCKS_WARN_ON(ret == 1))
2284                 return 1;
2285 
2286         /*
2287          * Step 4: narrow down to a pair of incompatible usage bits
2288          * and report it.
2289          */
2290         ret = find_exclusive_match(target_entry->class->usage_mask,
2291                                    target_entry1->class->usage_mask,
2292                                    &backward_bit, &forward_bit);
2293         if (DEBUG_LOCKS_WARN_ON(ret == -1))
2294                 return 1;
2295 
2296         print_bad_irq_dependency(curr, &this, &that,
2297                                  target_entry, target_entry1,
2298                                  prev, next,
2299                                  backward_bit, forward_bit,
2300                                  state_name(backward_bit));
2301 
2302         return 0;
2303 }
2304 
2305 static void inc_chains(void)
2306 {
2307         if (current->hardirq_context)
2308                 nr_hardirq_chains++;
2309         else {
2310                 if (current->softirq_context)
2311                         nr_softirq_chains++;
2312                 else
2313                         nr_process_chains++;
2314         }
2315 }
2316 
2317 #else
2318 
2319 static inline int check_irq_usage(struct task_struct *curr,
2320                                   struct held_lock *prev, struct held_lock *next)
2321 {
2322         return 1;
2323 }
2324 
2325 static inline void inc_chains(void)
2326 {
2327         nr_process_chains++;
2328 }
2329 
2330 #endif /* CONFIG_TRACE_IRQFLAGS */
2331 
2332 static void
2333 print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
2334 {
2335         struct lock_class *next = hlock_class(nxt);
2336         struct lock_class *prev = hlock_class(prv);
2337 
2338         printk(" Possible unsafe locking scenario:\n\n");
2339         printk("       CPU0\n");
2340         printk("       ----\n");
2341         printk("  lock(");
2342         __print_lock_name(prev);
2343         printk(KERN_CONT ");\n");
2344         printk("  lock(");
2345         __print_lock_name(next);
2346         printk(KERN_CONT ");\n");
2347         printk("\n *** DEADLOCK ***\n\n");
2348         printk(" May be due to missing lock nesting notation\n\n");
2349 }
2350 
2351 static void
2352 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
2353                    struct held_lock *next)
2354 {
2355         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2356                 return;
2357 
2358         pr_warn("\n");
2359         pr_warn("============================================\n");
2360         pr_warn("WARNING: possible recursive locking detected\n");
2361         print_kernel_ident();
2362         pr_warn("--------------------------------------------\n");
2363         pr_warn("%s/%d is trying to acquire lock:\n",
2364                 curr->comm, task_pid_nr(curr));
2365         print_lock(next);
2366         pr_warn("\nbut task is already holding lock:\n");
2367         print_lock(prev);
2368 
2369         pr_warn("\nother info that might help us debug this:\n");
2370         print_deadlock_scenario(next, prev);
2371         lockdep_print_held_locks(curr);
2372 
2373         pr_warn("\nstack backtrace:\n");
2374         dump_stack();
2375 }
2376 
2377 /*
2378  * Check whether we are holding such a class already.
2379  *
2380  * (Note that this has to be done separately, because the graph cannot
2381  * detect such classes of deadlocks.)
2382  *
2383  * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
2384  */
2385 static int
2386 check_deadlock(struct task_struct *curr, struct held_lock *next)
2387 {
2388         struct held_lock *prev;
2389         struct held_lock *nest = NULL;
2390         int i;
2391 
2392         for (i = 0; i < curr->lockdep_depth; i++) {
2393                 prev = curr->held_locks + i;
2394 
2395                 if (prev->instance == next->nest_lock)
2396                         nest = prev;
2397 
2398                 if (hlock_class(prev) != hlock_class(next))
2399                         continue;
2400 
2401                 /*
2402                  * Allow read-after-read recursion of the same
2403                  * lock class (i.e. read_lock(lock)+read_lock(lock)):
2404                  */
2405                 if ((next->read == 2) && prev->read)
2406                         return 2;
2407 
2408                 /*
2409                  * We're holding the nest_lock, which serializes this lock's
2410                  * nesting behaviour.
2411                  */
2412                 if (nest)
2413                         return 2;
2414 
2415                 print_deadlock_bug(curr, prev, next);
2416                 return 0;
2417         }
2418         return 1;
2419 }
2420 
2421 /*
2422  * There was a chain-cache miss, and we are about to add a new dependency
2423  * to a previous lock. We validate the following rules:
2424  *
2425  *  - would the adding of the <prev> -> <next> dependency create a
2426  *    circular dependency in the graph? [== circular deadlock]
2427  *
2428  *  - does the new prev->next dependency connect any hardirq-safe lock
2429  *    (in the full backwards-subgraph starting at <prev>) with any
2430  *    hardirq-unsafe lock (in the full forwards-subgraph starting at
2431  *    <next>)? [== illegal lock inversion with hardirq contexts]
2432  *
2433  *  - does the new prev->next dependency connect any softirq-safe lock
2434  *    (in the full backwards-subgraph starting at <prev>) with any
2435  *    softirq-unsafe lock (in the full forwards-subgraph starting at
2436  *    <next>)? [== illegal lock inversion with softirq contexts]
2437  *
2438  * any of these scenarios could lead to a deadlock.
2439  *
2440  * Then if all the validations pass, we add the forwards and backwards
2441  * dependency.
2442  */
2443 static int
2444 check_prev_add(struct task_struct *curr, struct held_lock *prev,
2445                struct held_lock *next, int distance,
2446                struct lock_trace **const trace)
2447 {
2448         struct lock_list *entry;
2449         int ret;
2450 
2451         if (!hlock_class(prev)->key || !hlock_class(next)->key) {
2452                 /*
2453                  * The warning statements below may trigger a use-after-free
2454                  * of the class name. It is better to trigger a use-after free
2455                  * and to have the class name most of the time instead of not
2456                  * having the class name available.
2457                  */
2458                 WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
2459                           "Detected use-after-free of lock class %px/%s\n",
2460                           hlock_class(prev),
2461                           hlock_class(prev)->name);
2462                 WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
2463                           "Detected use-after-free of lock class %px/%s\n",
2464                           hlock_class(next),
2465                           hlock_class(next)->name);
2466                 return 2;
2467         }
2468 
2469         /*
2470          * Prove that the new <prev> -> <next> dependency would not
2471          * create a circular dependency in the graph. (We do this by
2472          * a breadth-first search into the graph starting at <next>,
2473          * and check whether we can reach <prev>.)
2474          *
2475          * The search is limited by the size of the circular queue (i.e.,
2476          * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
2477          * in the graph whose neighbours are to be checked.
2478          */
2479         ret = check_noncircular(next, prev, trace);
2480         if (unlikely(ret <= 0))
2481                 return 0;
2482 
2483         if (!check_irq_usage(curr, prev, next))
2484                 return 0;
2485 
2486         /*
2487          * For recursive read-locks we do all the dependency checks,
2488          * but we dont store read-triggered dependencies (only
2489          * write-triggered dependencies). This ensures that only the
2490          * write-side dependencies matter, and that if for example a
2491          * write-lock never takes any other locks, then the reads are
2492          * equivalent to a NOP.
2493          */
2494         if (next->read == 2 || prev->read == 2)
2495                 return 1;
2496         /*
2497          * Is the <prev> -> <next> dependency already present?
2498          *
2499          * (this may occur even though this is a new chain: consider
2500          *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
2501          *  chains - the second one will be new, but L1 already has
2502          *  L2 added to its dependency list, due to the first chain.)
2503          */
2504         list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
2505                 if (entry->class == hlock_class(next)) {
2506                         if (distance == 1)
2507                                 entry->distance = 1;
2508                         return 1;
2509                 }
2510         }
2511 
2512 #ifdef CONFIG_LOCKDEP_SMALL
2513         /*
2514          * Is the <prev> -> <next> link redundant?
2515          */
2516         ret = check_redundant(prev, next);
2517         if (ret != 1)
2518                 return ret;
2519 #endif
2520 
2521         if (!*trace) {
2522                 *trace = save_trace();
2523                 if (!*trace)
2524                         return 0;
2525         }
2526 
2527         /*
2528          * Ok, all validations passed, add the new lock
2529          * to the previous lock's dependency list:
2530          */
2531         ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
2532                                &hlock_class(prev)->locks_after,
2533                                next->acquire_ip, distance, *trace);
2534 
2535         if (!ret)
2536                 return 0;
2537 
2538         ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
2539                                &hlock_class(next)->locks_before,
2540                                next->acquire_ip, distance, *trace);
2541         if (!ret)
2542                 return 0;
2543 
2544         return 2;
2545 }
2546 
2547 /*
2548  * Add the dependency to all directly-previous locks that are 'relevant'.
2549  * The ones that are relevant are (in increasing distance from curr):
2550  * all consecutive trylock entries and the final non-trylock entry - or
2551  * the end of this context's lock-chain - whichever comes first.
2552  */
2553 static int
2554 check_prevs_add(struct task_struct *curr, struct held_lock *next)
2555 {
2556         struct lock_trace *trace = NULL;
2557         int depth = curr->lockdep_depth;
2558         struct held_lock *hlock;
2559 
2560         /*
2561          * Debugging checks.
2562          *
2563          * Depth must not be zero for a non-head lock:
2564          */
2565         if (!depth)
2566                 goto out_bug;
2567         /*
2568          * At least two relevant locks must exist for this
2569          * to be a head:
2570          */
2571         if (curr->held_locks[depth].irq_context !=
2572                         curr->held_locks[depth-1].irq_context)
2573                 goto out_bug;
2574 
2575         for (;;) {
2576                 int distance = curr->lockdep_depth - depth + 1;
2577                 hlock = curr->held_locks + depth - 1;
2578 
2579                 /*
2580                  * Only non-recursive-read entries get new dependencies
2581                  * added:
2582                  */
2583                 if (hlock->read != 2 && hlock->check) {
2584                         int ret = check_prev_add(curr, hlock, next, distance,
2585                                                  &trace);
2586                         if (!ret)
2587                                 return 0;
2588 
2589                         /*
2590                          * Stop after the first non-trylock entry,
2591                          * as non-trylock entries have added their
2592                          * own direct dependencies already, so this
2593                          * lock is connected to them indirectly:
2594                          */
2595                         if (!hlock->trylock)
2596                                 break;
2597                 }
2598 
2599                 depth--;
2600                 /*
2601                  * End of lock-stack?
2602                  */
2603                 if (!depth)
2604                         break;
2605                 /*
2606                  * Stop the search if we cross into another context:
2607                  */
2608                 if (curr->held_locks[depth].irq_context !=
2609                                 curr->held_locks[depth-1].irq_context)
2610                         break;
2611         }
2612         return 1;
2613 out_bug:
2614         if (!debug_locks_off_graph_unlock())
2615                 return 0;
2616 
2617         /*
2618          * Clearly we all shouldn't be here, but since we made it we
2619          * can reliable say we messed up our state. See the above two
2620          * gotos for reasons why we could possibly end up here.
2621          */
2622         WARN_ON(1);
2623 
2624         return 0;
2625 }
2626 
2627 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
2628 static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
2629 int nr_chain_hlocks;
2630 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
2631 
2632 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
2633 {
2634         return lock_classes + chain_hlocks[chain->base + i];
2635 }
2636 
2637 /*
2638  * Returns the index of the first held_lock of the current chain
2639  */
2640 static inline int get_first_held_lock(struct task_struct *curr,
2641                                         struct held_lock *hlock)
2642 {
2643         int i;
2644         struct held_lock *hlock_curr;
2645 
2646         for (i = curr->lockdep_depth - 1; i >= 0; i--) {
2647                 hlock_curr = curr->held_locks + i;
2648                 if (hlock_curr->irq_context != hlock->irq_context)
2649                         break;
2650 
2651         }
2652 
2653         return ++i;
2654 }
2655 
2656 #ifdef CONFIG_DEBUG_LOCKDEP
2657 /*
2658  * Returns the next chain_key iteration
2659  */
2660 static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
2661 {
2662         u64 new_chain_key = iterate_chain_key(chain_key, class_idx);
2663 
2664         printk(" class_idx:%d -> chain_key:%016Lx",
2665                 class_idx,
2666                 (unsigned long long)new_chain_key);
2667         return new_chain_key;
2668 }
2669 
2670 static void
2671 print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
2672 {
2673         struct held_lock *hlock;
2674         u64 chain_key = INITIAL_CHAIN_KEY;
2675         int depth = curr->lockdep_depth;
2676         int i = get_first_held_lock(curr, hlock_next);
2677 
2678         printk("depth: %u (irq_context %u)\n", depth - i + 1,
2679                 hlock_next->irq_context);
2680         for (; i < depth; i++) {
2681                 hlock = curr->held_locks + i;
2682                 chain_key = print_chain_key_iteration(hlock->class_idx, chain_key);
2683 
2684                 print_lock(hlock);
2685         }
2686 
2687         print_chain_key_iteration(hlock_next->class_idx, chain_key);
2688         print_lock(hlock_next);
2689 }
2690 
2691 static void print_chain_keys_chain(struct lock_chain *chain)
2692 {
2693         int i;
2694         u64 chain_key = INITIAL_CHAIN_KEY;
2695         int class_id;
2696 
2697         printk("depth: %u\n", chain->depth);
2698         for (i = 0; i < chain->depth; i++) {
2699                 class_id = chain_hlocks[chain->base + i];
2700                 chain_key = print_chain_key_iteration(class_id, chain_key);
2701 
2702                 print_lock_name(lock_classes + class_id);
2703                 printk("\n");
2704         }
2705 }
2706 
2707 static void print_collision(struct task_struct *curr,
2708                         struct held_lock *hlock_next,
2709                         struct lock_chain *chain)
2710 {
2711         pr_warn("\n");
2712         pr_warn("============================\n");
2713         pr_warn("WARNING: chain_key collision\n");
2714         print_kernel_ident();
2715         pr_warn("----------------------------\n");
2716         pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
2717         pr_warn("Hash chain already cached but the contents don't match!\n");
2718 
2719         pr_warn("Held locks:");
2720         print_chain_keys_held_locks(curr, hlock_next);
2721 
2722         pr_warn("Locks in cached chain:");
2723         print_chain_keys_chain(chain);
2724 
2725         pr_warn("\nstack backtrace:\n");
2726         dump_stack();
2727 }
2728 #endif
2729 
2730 /*
2731  * Checks whether the chain and the current held locks are consistent
2732  * in depth and also in content. If they are not it most likely means
2733  * that there was a collision during the calculation of the chain_key.
2734  * Returns: 0 not passed, 1 passed
2735  */
2736 static int check_no_collision(struct task_struct *curr,
2737                         struct held_lock *hlock,
2738                         struct lock_chain *chain)
2739 {
2740 #ifdef CONFIG_DEBUG_LOCKDEP
2741         int i, j, id;
2742 
2743         i = get_first_held_lock(curr, hlock);
2744 
2745         if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
2746                 print_collision(curr, hlock, chain);
2747                 return 0;
2748         }
2749 
2750         for (j = 0; j < chain->depth - 1; j++, i++) {
2751                 id = curr->held_locks[i].class_idx;
2752 
2753                 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
2754                         print_collision(curr, hlock, chain);
2755                         return 0;
2756                 }
2757         }
2758 #endif
2759         return 1;
2760 }
2761 
2762 /*
2763  * Given an index that is >= -1, return the index of the next lock chain.
2764  * Return -2 if there is no next lock chain.
2765  */
2766 long lockdep_next_lockchain(long i)
2767 {
2768         i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
2769         return i < ARRAY_SIZE(lock_chains) ? i : -2;
2770 }
2771 
2772 unsigned long lock_chain_count(void)
2773 {
2774         return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
2775 }
2776 
2777 /* Must be called with the graph lock held. */
2778 static struct lock_chain *alloc_lock_chain(void)
2779 {
2780         int idx = find_first_zero_bit(lock_chains_in_use,
2781                                       ARRAY_SIZE(lock_chains));
2782 
2783         if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
2784                 return NULL;
2785         __set_bit(idx, lock_chains_in_use);
2786         return lock_chains + idx;
2787 }
2788 
2789 /*
2790  * Adds a dependency chain into chain hashtable. And must be called with
2791  * graph_lock held.
2792  *
2793  * Return 0 if fail, and graph_lock is released.
2794  * Return 1 if succeed, with graph_lock held.
2795  */
2796 static inline int add_chain_cache(struct task_struct *curr,
2797                                   struct held_lock *hlock,
2798                                   u64 chain_key)
2799 {
2800         struct lock_class *class = hlock_class(hlock);
2801         struct hlist_head *hash_head = chainhashentry(chain_key);
2802         struct lock_chain *chain;
2803         int i, j;
2804 
2805         /*
2806          * The caller must hold the graph lock, ensure we've got IRQs
2807          * disabled to make this an IRQ-safe lock.. for recursion reasons
2808          * lockdep won't complain about its own locking errors.
2809          */
2810         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2811                 return 0;
2812 
2813         chain = alloc_lock_chain();
2814         if (!chain) {
2815                 if (!debug_locks_off_graph_unlock())
2816                         return 0;
2817 
2818                 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
2819                 dump_stack();
2820                 return 0;
2821         }
2822         chain->chain_key = chain_key;
2823         chain->irq_context = hlock->irq_context;
2824         i = get_first_held_lock(curr, hlock);
2825         chain->depth = curr->lockdep_depth + 1 - i;
2826 
2827         BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
2828         BUILD_BUG_ON((1UL << 6)  <= ARRAY_SIZE(curr->held_locks));
2829         BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
2830 
2831         if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
2832                 chain->base = nr_chain_hlocks;
2833                 for (j = 0; j < chain->depth - 1; j++, i++) {
2834                         int lock_id = curr->held_locks[i].class_idx;
2835                         chain_hlocks[chain->base + j] = lock_id;
2836                 }
2837                 chain_hlocks[chain->base + j] = class - lock_classes;
2838                 nr_chain_hlocks += chain->depth;
2839         } else {
2840                 if (!debug_locks_off_graph_unlock())
2841                         return 0;
2842 
2843                 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
2844                 dump_stack();
2845                 return 0;
2846         }
2847 
2848         hlist_add_head_rcu(&chain->entry, hash_head);
2849         debug_atomic_inc(chain_lookup_misses);
2850         inc_chains();
2851 
2852         return 1;
2853 }
2854 
2855 /*
2856  * Look up a dependency chain. Must be called with either the graph lock or
2857  * the RCU read lock held.
2858  */
2859 static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
2860 {
2861         struct hlist_head *hash_head = chainhashentry(chain_key);
2862         struct lock_chain *chain;
2863 
2864         hlist_for_each_entry_rcu(chain, hash_head, entry) {
2865                 if (READ_ONCE(chain->chain_key) == chain_key) {
2866                         debug_atomic_inc(chain_lookup_hits);
2867                         return chain;
2868                 }
2869         }
2870         return NULL;
2871 }
2872 
2873 /*
2874  * If the key is not present yet in dependency chain cache then
2875  * add it and return 1 - in this case the new dependency chain is
2876  * validated. If the key is already hashed, return 0.
2877  * (On return with 1 graph_lock is held.)
2878  */
2879 static inline int lookup_chain_cache_add(struct task_struct *curr,
2880                                          struct held_lock *hlock,
2881                                          u64 chain_key)
2882 {
2883         struct lock_class *class = hlock_class(hlock);
2884         struct lock_chain *chain = lookup_chain_cache(chain_key);
2885 
2886         if (chain) {
2887 cache_hit:
2888                 if (!check_no_collision(curr, hlock, chain))
2889                         return 0;
2890 
2891                 if (very_verbose(class)) {
2892                         printk("\nhash chain already cached, key: "
2893                                         "%016Lx tail class: [%px] %s\n",
2894                                         (unsigned long long)chain_key,
2895                                         class->key, class->name);
2896                 }
2897 
2898                 return 0;
2899         }
2900 
2901         if (very_verbose(class)) {
2902                 printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
2903                         (unsigned long long)chain_key, class->key, class->name);
2904         }
2905 
2906         if (!graph_lock())
2907                 return 0;
2908 
2909         /*
2910          * We have to walk the chain again locked - to avoid duplicates:
2911          */
2912         chain = lookup_chain_cache(chain_key);
2913         if (chain) {
2914                 graph_unlock();
2915                 goto cache_hit;
2916         }
2917 
2918         if (!add_chain_cache(curr, hlock, chain_key))
2919                 return 0;
2920 
2921         return 1;
2922 }
2923 
2924 static int validate_chain(struct task_struct *curr,
2925                           struct held_lock *hlock,
2926                           int chain_head, u64 chain_key)
2927 {
2928         /*
2929          * Trylock needs to maintain the stack of held locks, but it
2930          * does not add new dependencies, because trylock can be done
2931          * in any order.
2932          *
2933          * We look up the chain_key and do the O(N^2) check and update of
2934          * the dependencies only if this is a new dependency chain.
2935          * (If lookup_chain_cache_add() return with 1 it acquires
2936          * graph_lock for us)
2937          */
2938         if (!hlock->trylock && hlock->check &&
2939             lookup_chain_cache_add(curr, hlock, chain_key)) {
2940                 /*
2941                  * Check whether last held lock:
2942                  *
2943                  * - is irq-safe, if this lock is irq-unsafe
2944                  * - is softirq-safe, if this lock is hardirq-unsafe
2945                  *
2946                  * And check whether the new lock's dependency graph
2947                  * could lead back to the previous lock:
2948                  *
2949                  * - within the current held-lock stack
2950                  * - across our accumulated lock dependency records
2951                  *
2952                  * any of these scenarios could lead to a deadlock.
2953                  */
2954                 /*
2955                  * The simple case: does the current hold the same lock
2956                  * already?
2957                  */
2958                 int ret = check_deadlock(curr, hlock);
2959 
2960                 if (!ret)
2961                         return 0;
2962                 /*
2963                  * Mark recursive read, as we jump over it when
2964                  * building dependencies (just like we jump over
2965                  * trylock entries):
2966                  */
2967                 if (ret == 2)
2968                         hlock->read = 2;
2969                 /*
2970                  * Add dependency only if this lock is not the head
2971                  * of the chain, and if it's not a secondary read-lock:
2972                  */
2973                 if (!chain_head && ret != 2) {
2974                         if (!check_prevs_add(curr, hlock))
2975                                 return 0;
2976                 }
2977 
2978                 graph_unlock();
2979         } else {
2980                 /* after lookup_chain_cache_add(): */
2981                 if (unlikely(!debug_locks))
2982                         return 0;
2983         }
2984 
2985         return 1;
2986 }
2987 #else
2988 static inline int validate_chain(struct task_struct *curr,
2989                                  struct held_lock *hlock,
2990                                  int chain_head, u64 chain_key)
2991 {
2992         return 1;
2993 }
2994 #endif /* CONFIG_PROVE_LOCKING */
2995 
2996 /*
2997  * We are building curr_chain_key incrementally, so double-check
2998  * it from scratch, to make sure that it's done correctly:
2999  */
3000 static void check_chain_key(struct task_struct *curr)
3001 {
3002 #ifdef CONFIG_DEBUG_LOCKDEP
3003         struct held_lock *hlock, *prev_hlock = NULL;
3004         unsigned int i;
3005         u64 chain_key = INITIAL_CHAIN_KEY;
3006 
3007         for (i = 0; i < curr->lockdep_depth; i++) {
3008                 hlock = curr->held_locks + i;
3009                 if (chain_key != hlock->prev_chain_key) {
3010                         debug_locks_off();
3011                         /*
3012                          * We got mighty confused, our chain keys don't match
3013                          * with what we expect, someone trample on our task state?
3014                          */
3015                         WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
3016                                 curr->lockdep_depth, i,
3017                                 (unsigned long long)chain_key,
3018                                 (unsigned long long)hlock->prev_chain_key);
3019                         return;
3020                 }
3021 
3022                 /*
3023                  * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
3024                  * it registered lock class index?
3025                  */
3026                 if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
3027                         return;
3028 
3029                 if (prev_hlock && (prev_hlock->irq_context !=
3030                                                         hlock->irq_context))
3031                         chain_key = INITIAL_CHAIN_KEY;
3032                 chain_key = iterate_chain_key(chain_key, hlock->class_idx);
3033                 prev_hlock = hlock;
3034         }
3035         if (chain_key != curr->curr_chain_key) {
3036                 debug_locks_off();
3037                 /*
3038                  * More smoking hash instead of calculating it, damn see these
3039                  * numbers float.. I bet that a pink elephant stepped on my memory.
3040                  */
3041                 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
3042                         curr->lockdep_depth, i,
3043                         (unsigned long long)chain_key,
3044                         (unsigned long long)curr->curr_chain_key);
3045         }
3046 #endif
3047 }
3048 
3049 #ifdef CONFIG_PROVE_LOCKING
3050 static int mark_lock(struct task_struct *curr, struct held_lock *this,
3051                      enum lock_usage_bit new_bit);
3052 
3053 static void print_usage_bug_scenario(struct held_lock *lock)
3054 {
3055         struct lock_class *class = hlock_class(lock);
3056 
3057         printk(" Possible unsafe locking scenario:\n\n");
3058         printk("       CPU0\n");
3059         printk("       ----\n");
3060         printk("  lock(");
3061         __print_lock_name(class);
3062         printk(KERN_CONT ");\n");
3063         printk("  <Interrupt>\n");
3064         printk("    lock(");
3065         __print_lock_name(class);
3066         printk(KERN_CONT ");\n");
3067         printk("\n *** DEADLOCK ***\n\n");
3068 }
3069 
3070 static void
3071 print_usage_bug(struct task_struct *curr, struct held_lock *this,
3072                 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
3073 {
3074         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
3075                 return;
3076 
3077         pr_warn("\n");
3078         pr_warn("================================\n");
3079         pr_warn("WARNING: inconsistent lock state\n");
3080         print_kernel_ident();
3081         pr_warn("--------------------------------\n");
3082 
3083         pr_warn("inconsistent {%s} -> {%s} usage.\n",
3084                 usage_str[prev_bit], usage_str[new_bit]);
3085 
3086         pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
3087                 curr->comm, task_pid_nr(curr),
3088                 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
3089                 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
3090                 trace_hardirqs_enabled(curr),
3091                 trace_softirqs_enabled(curr));
3092         print_lock(this);
3093 
3094         pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
3095         print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
3096 
3097         print_irqtrace_events(curr);
3098         pr_warn("\nother info that might help us debug this:\n");
3099         print_usage_bug_scenario(this);
3100 
3101         lockdep_print_held_locks(curr);
3102 
3103         pr_warn("\nstack backtrace:\n");
3104         dump_stack();
3105 }
3106 
3107 /*
3108  * Print out an error if an invalid bit is set:
3109  */
3110 static inline int
3111 valid_state(struct task_struct *curr, struct held_lock *this,
3112             enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
3113 {
3114         if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
3115                 print_usage_bug(curr, this, bad_bit, new_bit);
3116                 return 0;
3117         }
3118         return 1;
3119 }
3120 
3121 
3122 /*
3123  * print irq inversion bug:
3124  */
3125 static void
3126 print_irq_inversion_bug(struct task_struct *curr,
3127                         struct lock_list *root, struct lock_list *other,
3128                         struct held_lock *this, int forwards,
3129                         const char *irqclass)
3130 {
3131         struct lock_list *entry = other;
3132         struct lock_list *middle = NULL;
3133         int depth;
3134 
3135         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
3136                 return;
3137 
3138         pr_warn("\n");
3139         pr_warn("========================================================\n");
3140         pr_warn("WARNING: possible irq lock inversion dependency detected\n");
3141         print_kernel_ident();
3142         pr_warn("--------------------------------------------------------\n");
3143         pr_warn("%s/%d just changed the state of lock:\n",
3144                 curr->comm, task_pid_nr(curr));
3145         print_lock(this);
3146         if (forwards)
3147                 pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
3148         else
3149                 pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
3150         print_lock_name(other->class);
3151         pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
3152 
3153         pr_warn("\nother info that might help us debug this:\n");
3154 
3155         /* Find a middle lock (if one exists) */
3156         depth = get_lock_depth(other);
3157         do {
3158                 if (depth == 0 && (entry != root)) {
3159                         pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
3160                         break;
3161                 }
3162                 middle = entry;
3163                 entry = get_lock_parent(entry);
3164                 depth--;
3165         } while (entry && entry != root && (depth >= 0));
3166         if (forwards)
3167                 print_irq_lock_scenario(root, other,
3168                         middle ? middle->class : root->class, other->class);
3169         else
3170                 print_irq_lock_scenario(other, root,
3171                         middle ? middle->class : other->class, root->class);
3172 
3173         lockdep_print_held_locks(curr);
3174 
3175         pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
3176         root->trace = save_trace();
3177         if (!root->trace)
3178                 return;
3179         print_shortest_lock_dependencies(other, root);
3180 
3181         pr_warn("\nstack backtrace:\n");
3182         dump_stack();
3183 }
3184 
3185 /*
3186  * Prove that in the forwards-direction subgraph starting at <this>
3187  * there is no lock matching <mask>:
3188  */
3189 static int
3190 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
3191                      enum lock_usage_bit bit, const char *irqclass)
3192 {
3193         int ret;
3194         struct lock_list root;
3195         struct lock_list *uninitialized_var(target_entry);
3196 
3197         root.parent = NULL;
3198         root.class = hlock_class(this);
3199         ret = find_usage_forwards(&root, lock_flag(bit), &target_entry);
3200         if (ret < 0) {
3201                 print_bfs_bug(ret);
3202                 return 0;
3203         }
3204         if (ret == 1)
3205                 return ret;
3206 
3207         print_irq_inversion_bug(curr, &root, target_entry,
3208                                 this, 1, irqclass);
3209         return 0;
3210 }
3211 
3212 /*
3213  * Prove that in the backwards-direction subgraph starting at <this>
3214  * there is no lock matching <mask>:
3215  */
3216 static int
3217 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
3218                       enum lock_usage_bit bit, const char *irqclass)
3219 {
3220         int ret;
3221         struct lock_list root;
3222         struct lock_list *uninitialized_var(target_entry);
3223 
3224         root.parent = NULL;
3225         root.class = hlock_class(this);
3226         ret = find_usage_backwards(&root, lock_flag(bit), &target_entry);
3227         if (ret < 0) {
3228                 print_bfs_bug(ret);
3229                 return 0;
3230         }
3231         if (ret == 1)
3232                 return ret;
3233 
3234         print_irq_inversion_bug(curr, &root, target_entry,
3235                                 this, 0, irqclass);
3236         return 0;
3237 }
3238 
3239 void print_irqtrace_events(struct task_struct *curr)
3240 {
3241         printk("irq event stamp: %u\n", curr->irq_events);
3242         printk("hardirqs last  enabled at (%u): [<%px>] %pS\n",
3243                 curr->hardirq_enable_event, (void *)curr->hardirq_enable_ip,
3244                 (void *)curr->hardirq_enable_ip);
3245         printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
3246                 curr->hardirq_disable_event, (void *)curr->hardirq_disable_ip,
3247                 (void *)curr->hardirq_disable_ip);
3248         printk("softirqs last  enabled at (%u): [<%px>] %pS\n",
3249                 curr->softirq_enable_event, (void *)curr->softirq_enable_ip,
3250                 (void *)curr->softirq_enable_ip);
3251         printk("softirqs last disabled at (%u): [<%px>] %pS\n",
3252                 curr->softirq_disable_event, (void *)curr->softirq_disable_ip,
3253                 (void *)curr->softirq_disable_ip);
3254 }
3255 
3256 static int HARDIRQ_verbose(struct lock_class *class)
3257 {
3258 #if HARDIRQ_VERBOSE
3259         return class_filter(class);
3260 #endif
3261         return 0;
3262 }
3263 
3264 static int SOFTIRQ_verbose(struct lock_class *class)
3265 {
3266 #if SOFTIRQ_VERBOSE
3267         return class_filter(class);
3268 #endif
3269         return 0;
3270 }
3271 
3272 #define STRICT_READ_CHECKS      1
3273 
3274 static int (*state_verbose_f[])(struct lock_class *class) = {
3275 #define LOCKDEP_STATE(__STATE) \
3276         __STATE##_verbose,
3277 #include "lockdep_states.h"
3278 #undef LOCKDEP_STATE
3279 };
3280 
3281 static inline int state_verbose(enum lock_usage_bit bit,
3282                                 struct lock_class *class)
3283 {
3284         return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
3285 }
3286 
3287 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
3288                              enum lock_usage_bit bit, const char *name);
3289 
3290 static int
3291 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
3292                 enum lock_usage_bit new_bit)
3293 {
3294         int excl_bit = exclusive_bit(new_bit);
3295         int read = new_bit & LOCK_USAGE_READ_MASK;
3296         int dir = new_bit & LOCK_USAGE_DIR_MASK;
3297 
3298         /*
3299          * mark USED_IN has to look forwards -- to ensure no dependency
3300          * has ENABLED state, which would allow recursion deadlocks.
3301          *
3302          * mark ENABLED has to look backwards -- to ensure no dependee
3303          * has USED_IN state, which, again, would allow  recursion deadlocks.
3304          */
3305         check_usage_f usage = dir ?
3306                 check_usage_backwards : check_usage_forwards;
3307 
3308         /*
3309          * Validate that this particular lock does not have conflicting
3310          * usage states.
3311          */
3312         if (!valid_state(curr, this, new_bit, excl_bit))
3313                 return 0;
3314 
3315         /*
3316          * Validate that the lock dependencies don't have conflicting usage
3317          * states.
3318          */
3319         if ((!read || STRICT_READ_CHECKS) &&
3320                         !usage(curr, this, excl_bit, state_name(new_bit & ~LOCK_USAGE_READ_MASK)))
3321                 return 0;
3322 
3323         /*
3324          * Check for read in write conflicts
3325          */
3326         if (!read) {
3327                 if (!valid_state(curr, this, new_bit, excl_bit + LOCK_USAGE_READ_MASK))
3328                         return 0;
3329 
3330                 if (STRICT_READ_CHECKS &&
3331                         !usage(curr, this, excl_bit + LOCK_USAGE_READ_MASK,
3332                                 state_name(new_bit + LOCK_USAGE_READ_MASK)))
3333                         return 0;
3334         }
3335 
3336         if (state_verbose(new_bit, hlock_class(this)))
3337                 return 2;
3338 
3339         return 1;
3340 }
3341 
3342 /*
3343  * Mark all held locks with a usage bit:
3344  */
3345 static int
3346 mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
3347 {
3348         struct held_lock *hlock;
3349         int i;
3350 
3351         for (i = 0; i < curr->lockdep_depth; i++) {
3352                 enum lock_usage_bit hlock_bit = base_bit;
3353                 hlock = curr->held_locks + i;
3354 
3355                 if (hlock->read)
3356                         hlock_bit += LOCK_USAGE_READ_MASK;
3357 
3358                 BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
3359 
3360                 if (!hlock->check)
3361                         continue;
3362 
3363                 if (!mark_lock(curr, hlock, hlock_bit))
3364                         return 0;
3365         }
3366 
3367         return 1;
3368 }
3369 
3370 /*
3371  * Hardirqs will be enabled:
3372  */
3373 static void __trace_hardirqs_on_caller(unsigned long ip)
3374 {
3375         struct task_struct *curr = current;
3376 
3377         /* we'll do an OFF -> ON transition: */
3378         curr->hardirqs_enabled = 1;
3379 
3380         /*
3381          * We are going to turn hardirqs on, so set the
3382          * usage bit for all held locks:
3383          */
3384         if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
3385                 return;
3386         /*
3387          * If we have softirqs enabled, then set the usage
3388          * bit for all held locks. (disabled hardirqs prevented
3389          * this bit from being set before)
3390          */
3391         if (curr->softirqs_enabled)
3392                 if (!mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ))
3393                         return;
3394 
3395         curr->hardirq_enable_ip = ip;
3396         curr->hardirq_enable_event = ++curr->irq_events;
3397         debug_atomic_inc(hardirqs_on_events);
3398 }
3399 
3400 void lockdep_hardirqs_on(unsigned long ip)
3401 {
3402         if (unlikely(!debug_locks || current->lockdep_recursion))
3403                 return;
3404 
3405         if (unlikely(current->hardirqs_enabled)) {
3406                 /*
3407                  * Neither irq nor preemption are disabled here
3408                  * so this is racy by nature but losing one hit
3409                  * in a stat is not a big deal.
3410                  */
3411                 __debug_atomic_inc(redundant_hardirqs_on);
3412                 return;
3413         }
3414 
3415         /*
3416          * We're enabling irqs and according to our state above irqs weren't
3417          * already enabled, yet we find the hardware thinks they are in fact
3418          * enabled.. someone messed up their IRQ state tracing.
3419          */
3420         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3421                 return;
3422 
3423         /*
3424          * See the fine text that goes along with this variable definition.
3425          */
3426         if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
3427                 return;
3428 
3429         /*
3430          * Can't allow enabling interrupts while in an interrupt handler,
3431          * that's general bad form and such. Recursion, limited stack etc..
3432          */
3433         if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
3434                 return;
3435 
3436         current->lockdep_recursion = 1;
3437         __trace_hardirqs_on_caller(ip);
3438         current->lockdep_recursion = 0;
3439 }
3440 NOKPROBE_SYMBOL(lockdep_hardirqs_on);
3441 
3442 /*
3443  * Hardirqs were disabled:
3444  */
3445 void lockdep_hardirqs_off(unsigned long ip)
3446 {
3447         struct task_struct *curr = current;
3448 
3449         if (unlikely(!debug_locks || current->lockdep_recursion))
3450                 return;
3451 
3452         /*
3453          * So we're supposed to get called after you mask local IRQs, but for
3454          * some reason the hardware doesn't quite think you did a proper job.
3455          */
3456         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3457                 return;
3458 
3459         if (curr->hardirqs_enabled) {
3460                 /*
3461                  * We have done an ON -> OFF transition:
3462                  */
3463                 curr->hardirqs_enabled = 0;
3464                 curr->hardirq_disable_ip = ip;
3465                 curr->hardirq_disable_event = ++curr->irq_events;
3466                 debug_atomic_inc(hardirqs_off_events);
3467         } else
3468                 debug_atomic_inc(redundant_hardirqs_off);
3469 }
3470 NOKPROBE_SYMBOL(lockdep_hardirqs_off);
3471 
3472 /*
3473  * Softirqs will be enabled:
3474  */
3475 void trace_softirqs_on(unsigned long ip)
3476 {
3477         struct task_struct *curr = current;
3478 
3479         if (unlikely(!debug_locks || current->lockdep_recursion))
3480                 return;
3481 
3482         /*
3483          * We fancy IRQs being disabled here, see softirq.c, avoids
3484          * funny state and nesting things.
3485          */
3486         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3487                 return;
3488 
3489         if (curr->softirqs_enabled) {
3490                 debug_atomic_inc(redundant_softirqs_on);
3491                 return;
3492         }
3493 
3494         current->lockdep_recursion = 1;
3495         /*
3496          * We'll do an OFF -> ON transition:
3497          */
3498         curr->softirqs_enabled = 1;
3499         curr->softirq_enable_ip = ip;
3500         curr->softirq_enable_event = ++curr->irq_events;
3501         debug_atomic_inc(softirqs_on_events);
3502         /*
3503          * We are going to turn softirqs on, so set the
3504          * usage bit for all held locks, if hardirqs are
3505          * enabled too:
3506          */
3507         if (curr->hardirqs_enabled)
3508                 mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
3509         current->lockdep_recursion = 0;
3510 }
3511 
3512 /*
3513  * Softirqs were disabled:
3514  */
3515 void trace_softirqs_off(unsigned long ip)
3516 {
3517         struct task_struct *curr = current;
3518 
3519         if (unlikely(!debug_locks || current->lockdep_recursion))
3520                 return;
3521 
3522         /*
3523          * We fancy IRQs being disabled here, see softirq.c
3524          */
3525         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3526                 return;
3527 
3528         if (curr->softirqs_enabled) {
3529                 /*
3530                  * We have done an ON -> OFF transition:
3531                  */
3532                 curr->softirqs_enabled = 0;
3533                 curr->softirq_disable_ip = ip;
3534                 curr->softirq_disable_event = ++curr->irq_events;
3535                 debug_atomic_inc(softirqs_off_events);
3536                 /*
3537                  * Whoops, we wanted softirqs off, so why aren't they?
3538                  */
3539                 DEBUG_LOCKS_WARN_ON(!softirq_count());
3540         } else
3541                 debug_atomic_inc(redundant_softirqs_off);
3542 }
3543 
3544 static int
3545 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
3546 {
3547         if (!check)
3548                 goto lock_used;
3549 
3550         /*
3551          * If non-trylock use in a hardirq or softirq context, then
3552          * mark the lock as used in these contexts:
3553          */
3554         if (!hlock->trylock) {
3555                 if (hlock->read) {
3556                         if (curr->hardirq_context)
3557                                 if (!mark_lock(curr, hlock,
3558                                                 LOCK_USED_IN_HARDIRQ_READ))
3559                                         return 0;
3560                         if (curr->softirq_context)
3561                                 if (!mark_lock(curr, hlock,
3562                                                 LOCK_USED_IN_SOFTIRQ_READ))
3563                                         return 0;
3564                 } else {
3565                         if (curr->hardirq_context)
3566                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
3567                                         return 0;
3568                         if (curr->softirq_context)
3569                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
3570                                         return 0;
3571                 }
3572         }
3573         if (!hlock->hardirqs_off) {
3574                 if (hlock->read) {
3575                         if (!mark_lock(curr, hlock,
3576                                         LOCK_ENABLED_HARDIRQ_READ))
3577                                 return 0;
3578                         if (curr->softirqs_enabled)
3579                                 if (!mark_lock(curr, hlock,
3580                                                 LOCK_ENABLED_SOFTIRQ_READ))
3581                                         return 0;
3582                 } else {
3583                         if (!mark_lock(curr, hlock,
3584                                         LOCK_ENABLED_HARDIRQ))
3585                                 return 0;
3586                         if (curr->softirqs_enabled)
3587                                 if (!mark_lock(curr, hlock,
3588                                                 LOCK_ENABLED_SOFTIRQ))
3589                                         return 0;
3590                 }
3591         }
3592 
3593 lock_used:
3594         /* mark it as used: */
3595         if (!mark_lock(curr, hlock, LOCK_USED))
3596                 return 0;
3597 
3598         return 1;
3599 }
3600 
3601 static inline unsigned int task_irq_context(struct task_struct *task)
3602 {
3603         return 2 * !!task->hardirq_context + !!task->softirq_context;
3604 }
3605 
3606 static int separate_irq_context(struct task_struct *curr,
3607                 struct held_lock *hlock)
3608 {
3609         unsigned int depth = curr->lockdep_depth;
3610 
3611         /*
3612          * Keep track of points where we cross into an interrupt context:
3613          */
3614         if (depth) {
3615                 struct held_lock *prev_hlock;
3616 
3617                 prev_hlock = curr->held_locks + depth-1;
3618                 /*
3619                  * If we cross into another context, reset the
3620                  * hash key (this also prevents the checking and the
3621                  * adding of the dependency to 'prev'):
3622                  */
3623                 if (prev_hlock->irq_context != hlock->irq_context)
3624                         return 1;
3625         }
3626         return 0;
3627 }
3628 
3629 /*
3630  * Mark a lock with a usage bit, and validate the state transition:
3631  */
3632 static int mark_lock(struct task_struct *curr, struct held_lock *this,
3633                              enum lock_usage_bit new_bit)
3634 {
3635         unsigned int new_mask = 1 << new_bit, ret = 1;
3636 
3637         if (new_bit >= LOCK_USAGE_STATES) {
3638                 DEBUG_LOCKS_WARN_ON(1);
3639                 return 0;
3640         }
3641 
3642         /*
3643          * If already set then do not dirty the cacheline,
3644          * nor do any checks:
3645          */
3646         if (likely(hlock_class(this)->usage_mask & new_mask))
3647                 return 1;
3648 
3649         if (!graph_lock())
3650                 return 0;
3651         /*
3652          * Make sure we didn't race:
3653          */
3654         if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
3655                 graph_unlock();
3656                 return 1;
3657         }
3658 
3659         hlock_class(this)->usage_mask |= new_mask;
3660 
3661         if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
3662                 return 0;
3663 
3664         switch (new_bit) {
3665         case LOCK_USED:
3666                 debug_atomic_dec(nr_unused_locks);
3667                 break;
3668         default:
3669                 ret = mark_lock_irq(curr, this, new_bit);
3670                 if (!ret)
3671                         return 0;
3672         }
3673 
3674         graph_unlock();
3675 
3676         /*
3677          * We must printk outside of the graph_lock:
3678          */
3679         if (ret == 2) {
3680                 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
3681                 print_lock(this);
3682                 print_irqtrace_events(curr);
3683                 dump_stack();
3684         }
3685 
3686         return ret;
3687 }
3688 
3689 #else /* CONFIG_PROVE_LOCKING */
3690 
3691 static inline int
3692 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
3693 {
3694         return 1;
3695 }
3696 
3697 static inline unsigned int task_irq_context(struct task_struct *task)
3698 {
3699         return 0;
3700 }
3701 
3702 static inline int separate_irq_context(struct task_struct *curr,
3703                 struct held_lock *hlock)
3704 {
3705         return 0;
3706 }
3707 
3708 #endif /* CONFIG_PROVE_LOCKING */
3709 
3710 /*
3711  * Initialize a lock instance's lock-class mapping info:
3712  */
3713 void lockdep_init_map(struct lockdep_map *lock, const char *name,
3714                       struct lock_class_key *key, int subclass)
3715 {
3716         int i;
3717 
3718         for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
3719                 lock->class_cache[i] = NULL;
3720 
3721 #ifdef CONFIG_LOCK_STAT
3722         lock->cpu = raw_smp_processor_id();
3723 #endif
3724 
3725         /*
3726          * Can't be having no nameless bastards around this place!
3727          */
3728         if (DEBUG_LOCKS_WARN_ON(!name)) {
3729                 lock->name = "NULL";
3730                 return;
3731         }
3732 
3733         lock->name = name;
3734 
3735         /*
3736          * No key, no joy, we need to hash something.
3737          */
3738         if (DEBUG_LOCKS_WARN_ON(!key))
3739                 return;
3740         /*
3741          * Sanity check, the lock-class key must either have been allocated
3742          * statically or must have been registered as a dynamic key.
3743          */
3744         if (!static_obj(key) && !is_dynamic_key(key)) {
3745                 if (debug_locks)
3746                         printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
3747                 DEBUG_LOCKS_WARN_ON(1);
3748                 return;
3749         }
3750         lock->key = key;
3751 
3752         if (unlikely(!debug_locks))
3753                 return;
3754 
3755         if (subclass) {
3756                 unsigned long flags;
3757 
3758                 if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion))
3759                         return;
3760 
3761                 raw_local_irq_save(flags);
3762                 current->lockdep_recursion = 1;
3763                 register_lock_class(lock, subclass, 1);
3764                 current->lockdep_recursion = 0;
3765                 raw_local_irq_restore(flags);
3766         }
3767 }
3768 EXPORT_SYMBOL_GPL(lockdep_init_map);
3769 
3770 struct lock_class_key __lockdep_no_validate__;
3771 EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
3772 
3773 static void
3774 print_lock_nested_lock_not_held(struct task_struct *curr,
3775                                 struct held_lock *hlock,
3776                                 unsigned long ip)
3777 {
3778         if (!debug_locks_off())
3779                 return;
3780         if (debug_locks_silent)
3781                 return;
3782 
3783         pr_warn("\n");
3784         pr_warn("==================================\n");
3785         pr_warn("WARNING: Nested lock was not taken\n");
3786         print_kernel_ident();
3787         pr_warn("----------------------------------\n");
3788 
3789         pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
3790         print_lock(hlock);
3791 
3792         pr_warn("\nbut this task is not holding:\n");
3793         pr_warn("%s\n", hlock->nest_lock->name);
3794 
3795         pr_warn("\nstack backtrace:\n");
3796         dump_stack();
3797 
3798         pr_warn("\nother info that might help us debug this:\n");
3799         lockdep_print_held_locks(curr);
3800 
3801         pr_warn("\nstack backtrace:\n");
3802         dump_stack();
3803 }
3804 
3805 static int __lock_is_held(const struct lockdep_map *lock, int read);
3806 
3807 /*
3808  * This gets called for every mutex_lock*()/spin_lock*() operation.
3809  * We maintain the dependency maps and validate the locking attempt:
3810  *
3811  * The callers must make sure that IRQs are disabled before calling it,
3812  * otherwise we could get an interrupt which would want to take locks,
3813  * which would end up in lockdep again.
3814  */
3815 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3816                           int trylock, int read, int check, int hardirqs_off,
3817                           struct lockdep_map *nest_lock, unsigned long ip,
3818                           int references, int pin_count)
3819 {
3820         struct task_struct *curr = current;
3821         struct lock_class *class = NULL;
3822         struct held_lock *hlock;
3823         unsigned int depth;
3824         int chain_head = 0;
3825         int class_idx;
3826         u64 chain_key;
3827 
3828         if (unlikely(!debug_locks))
3829                 return 0;
3830 
3831         if (!prove_locking || lock->key == &__lockdep_no_validate__)
3832                 check = 0;
3833 
3834         if (subclass < NR_LOCKDEP_CACHING_CLASSES)
3835                 class = lock->class_cache[subclass];
3836         /*
3837          * Not cached?
3838          */
3839         if (unlikely(!class)) {
3840                 class = register_lock_class(lock, subclass, 0);
3841                 if (!class)
3842                         return 0;
3843         }
3844 
3845         debug_class_ops_inc(class);
3846 
3847         if (very_verbose(class)) {
3848                 printk("\nacquire class [%px] %s", class->key, class->name);
3849                 if (class->name_version > 1)
3850                         printk(KERN_CONT "#%d", class->name_version);
3851                 printk(KERN_CONT "\n");
3852                 dump_stack();
3853         }
3854 
3855         /*
3856          * Add the lock to the list of currently held locks.
3857          * (we dont increase the depth just yet, up until the
3858          * dependency checks are done)
3859          */
3860         depth = curr->lockdep_depth;
3861         /*
3862          * Ran out of static storage for our per-task lock stack again have we?
3863          */
3864         if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
3865                 return 0;
3866 
3867         class_idx = class - lock_classes;
3868 
3869         if (depth) {
3870                 hlock = curr->held_locks + depth - 1;
3871                 if (hlock->class_idx == class_idx && nest_lock) {
3872                         if (!references)
3873                                 references++;
3874 
3875                         if (!hlock->references)
3876                                 hlock->references++;
3877 
3878                         hlock->references += references;
3879 
3880                         /* Overflow */
3881                         if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
3882                                 return 0;
3883 
3884                         return 2;
3885                 }
3886         }
3887 
3888         hlock = curr->held_locks + depth;
3889         /*
3890          * Plain impossible, we just registered it and checked it weren't no
3891          * NULL like.. I bet this mushroom I ate was good!
3892          */
3893         if (DEBUG_LOCKS_WARN_ON(!class))
3894                 return 0;
3895         hlock->class_idx = class_idx;
3896         hlock->acquire_ip = ip;
3897         hlock->instance = lock;
3898         hlock->nest_lock = nest_lock;
3899         hlock->irq_context = task_irq_context(curr);
3900         hlock->trylock = trylock;
3901         hlock->read = read;
3902         hlock->check = check;
3903         hlock->hardirqs_off = !!hardirqs_off;
3904         hlock->references = references;
3905 #ifdef CONFIG_LOCK_STAT
3906         hlock->waittime_stamp = 0;
3907         hlock->holdtime_stamp = lockstat_clock();
3908 #endif
3909         hlock->pin_count = pin_count;
3910 
3911         /* Initialize the lock usage bit */
3912         if (!mark_usage(curr, hlock, check))
3913                 return 0;
3914 
3915         /*
3916          * Calculate the chain hash: it's the combined hash of all the
3917          * lock keys along the dependency chain. We save the hash value
3918          * at every step so that we can get the current hash easily
3919          * after unlock. The chain hash is then used to cache dependency
3920          * results.
3921          *
3922          * The 'key ID' is what is the most compact key value to drive
3923          * the hash, not class->key.
3924          */
3925         /*
3926          * Whoops, we did it again.. class_idx is invalid.
3927          */
3928         if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
3929                 return 0;
3930 
3931         chain_key = curr->curr_chain_key;
3932         if (!depth) {
3933                 /*
3934                  * How can we have a chain hash when we ain't got no keys?!
3935                  */
3936                 if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
3937                         return 0;
3938                 chain_head = 1;
3939         }
3940 
3941         hlock->prev_chain_key = chain_key;
3942         if (separate_irq_context(curr, hlock)) {
3943                 chain_key = INITIAL_CHAIN_KEY;
3944                 chain_head = 1;
3945         }
3946         chain_key = iterate_chain_key(chain_key, class_idx);
3947 
3948         if (nest_lock && !__lock_is_held(nest_lock, -1)) {
3949                 print_lock_nested_lock_not_held(curr, hlock, ip);
3950                 return 0;
3951         }
3952 
3953         if (!debug_locks_silent) {
3954                 WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
3955                 WARN_ON_ONCE(!hlock_class(hlock)->key);
3956         }
3957 
3958         if (!validate_chain(curr, hlock, chain_head, chain_key))
3959                 return 0;
3960 
3961         curr->curr_chain_key = chain_key;
3962         curr->lockdep_depth++;
3963         check_chain_key(curr);
3964 #ifdef CONFIG_DEBUG_LOCKDEP
3965         if (unlikely(!debug_locks))
3966                 return 0;
3967 #endif
3968         if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
3969                 debug_locks_off();
3970                 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
3971                 printk(KERN_DEBUG "depth: %i  max: %lu!\n",
3972                        curr->lockdep_depth, MAX_LOCK_DEPTH);
3973 
3974                 lockdep_print_held_locks(current);
3975                 debug_show_all_locks();
3976                 dump_stack();
3977 
3978                 return 0;
3979         }
3980 
3981         if (unlikely(curr->lockdep_depth > max_lockdep_depth))
3982                 max_lockdep_depth = curr->lockdep_depth;
3983 
3984         return 1;
3985 }
3986 
3987 static void print_unlock_imbalance_bug(struct task_struct *curr,
3988                                        struct lockdep_map *lock,
3989                                        unsigned long ip)
3990 {
3991         if (!debug_locks_off())
3992                 return;
3993         if (debug_locks_silent)
3994                 return;
3995 
3996         pr_warn("\n");
3997         pr_warn("=====================================\n");
3998         pr_warn("WARNING: bad unlock balance detected!\n");
3999         print_kernel_ident();
4000         pr_warn("-------------------------------------\n");
4001         pr_warn("%s/%d is trying to release lock (",
4002                 curr->comm, task_pid_nr(curr));
4003         print_lockdep_cache(lock);
4004         pr_cont(") at:\n");
4005         print_ip_sym(ip);
4006         pr_warn("but there are no more locks to release!\n");
4007         pr_warn("\nother info that might help us debug this:\n");
4008         lockdep_print_held_locks(curr);
4009 
4010         pr_warn("\nstack backtrace:\n");
4011         dump_stack();
4012 }
4013 
4014 static int match_held_lock(const struct held_lock *hlock,
4015                                         const struct lockdep_map *lock)
4016 {
4017         if (hlock->instance == lock)
4018                 return 1;
4019 
4020         if (hlock->references) {
4021                 const struct lock_class *class = lock->class_cache[0];
4022 
4023                 if (!class)
4024                         class = look_up_lock_class(lock, 0);
4025 
4026                 /*
4027                  * If look_up_lock_class() failed to find a class, we're trying
4028                  * to test if we hold a lock that has never yet been acquired.
4029                  * Clearly if the lock hasn't been acquired _ever_, we're not
4030                  * holding it either, so report failure.
4031                  */
4032                 if (!class)
4033                         return 0;
4034 
4035                 /*
4036                  * References, but not a lock we're actually ref-counting?
4037                  * State got messed up, follow the sites that change ->references
4038                  * and try to make sense of it.
4039                  */
4040                 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
4041                         return 0;
4042 
4043                 if (hlock->class_idx == class - lock_classes)
4044                         return 1;
4045         }
4046 
4047         return 0;
4048 }
4049 
4050 /* @depth must not be zero */
4051 static struct held_lock *find_held_lock(struct task_struct *curr,
4052                                         struct lockdep_map *lock,
4053                                         unsigned int depth, int *idx)
4054 {
4055         struct held_lock *ret, *hlock, *prev_hlock;
4056         int i;
4057 
4058         i = depth - 1;
4059         hlock = curr->held_locks + i;
4060         ret = hlock;
4061         if (match_held_lock(hlock, lock))
4062                 goto out;
4063 
4064         ret = NULL;
4065         for (i--, prev_hlock = hlock--;
4066              i >= 0;
4067              i--, prev_hlock = hlock--) {
4068                 /*
4069                  * We must not cross into another context:
4070                  */
4071                 if (prev_hlock->irq_context != hlock->irq_context) {
4072                         ret = NULL;
4073                         break;
4074                 }
4075                 if (match_held_lock(hlock, lock)) {
4076                         ret = hlock;
4077                         break;
4078                 }
4079         }
4080 
4081 out:
4082         *idx = i;
4083         return ret;
4084 }
4085 
4086 static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
4087                                 int idx, unsigned int *merged)
4088 {
4089         struct held_lock *hlock;
4090         int first_idx = idx;
4091 
4092         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4093                 return 0;
4094 
4095         for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
4096                 switch (__lock_acquire(hlock->instance,
4097                                     hlock_class(hlock)->subclass,
4098                                     hlock->trylock,
4099                                     hlock->read, hlock->check,
4100                                     hlock->hardirqs_off,
4101                                     hlock->nest_lock, hlock->acquire_ip,
4102                                     hlock->references, hlock->pin_count)) {
4103                 case 0:
4104                         return 1;
4105                 case 1:
4106                         break;
4107                 case 2:
4108                         *merged += (idx == first_idx);
4109                         break;
4110                 default:
4111                         WARN_ON(1);
4112                         return 0;
4113                 }
4114         }
4115         return 0;
4116 }
4117 
4118 static int
4119 __lock_set_class(struct lockdep_map *lock, const char *name,
4120                  struct lock_class_key *key, unsigned int subclass,
4121                  unsigned long ip)
4122 {
4123         struct task_struct *curr = current;
4124         unsigned int depth, merged = 0;
4125         struct held_lock *hlock;
4126         struct lock_class *class;
4127         int i;
4128 
4129         if (unlikely(!debug_locks))
4130                 return 0;
4131 
4132         depth = curr->lockdep_depth;
4133         /*
4134          * This function is about (re)setting the class of a held lock,
4135          * yet we're not actually holding any locks. Naughty user!
4136          */
4137         if (DEBUG_LOCKS_WARN_ON(!depth))
4138                 return 0;
4139 
4140         hlock = find_held_lock(curr, lock, depth, &i);
4141         if (!hlock) {
4142                 print_unlock_imbalance_bug(curr, lock, ip);
4143                 return 0;
4144         }
4145 
4146         lockdep_init_map(lock, name, key, 0);
4147         class = register_lock_class(lock, subclass, 0);
4148         hlock->class_idx = class - lock_classes;
4149 
4150         curr->lockdep_depth = i;
4151         curr->curr_chain_key = hlock->prev_chain_key;
4152 
4153         if (reacquire_held_locks(curr, depth, i, &merged))
4154                 return 0;
4155 
4156         /*
4157          * I took it apart and put it back together again, except now I have
4158          * these 'spare' parts.. where shall I put them.
4159          */
4160         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
4161                 return 0;
4162         return 1;
4163 }
4164 
4165 static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
4166 {
4167         struct task_struct *curr = current;
4168         unsigned int depth, merged = 0;
4169         struct held_lock *hlock;
4170         int i;
4171 
4172         if (unlikely(!debug_locks))
4173                 return 0;
4174 
4175         depth = curr->lockdep_depth;
4176         /*
4177          * This function is about (re)setting the class of a held lock,
4178          * yet we're not actually holding any locks. Naughty user!
4179          */
4180         if (DEBUG_LOCKS_WARN_ON(!depth))
4181                 return 0;
4182 
4183         hlock = find_held_lock(curr, lock, depth, &i);
4184         if (!hlock) {
4185                 print_unlock_imbalance_bug(curr, lock, ip);
4186                 return 0;
4187         }
4188 
4189         curr->lockdep_depth = i;
4190         curr->curr_chain_key = hlock->prev_chain_key;
4191 
4192         WARN(hlock->read, "downgrading a read lock");
4193         hlock->read = 1;
4194         hlock->acquire_ip = ip;
4195 
4196         if (reacquire_held_locks(curr, depth, i, &merged))
4197                 return 0;
4198 
4199         /* Merging can't happen with unchanged classes.. */
4200         if (DEBUG_LOCKS_WARN_ON(merged))
4201                 return 0;
4202 
4203         /*
4204          * I took it apart and put it back together again, except now I have
4205          * these 'spare' parts.. where shall I put them.
4206          */
4207         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
4208                 return 0;
4209 
4210         return 1;
4211 }
4212 
4213 /*
4214  * Remove the lock to the list of currently held locks - this gets
4215  * called on mutex_unlock()/spin_unlock*() (or on a failed
4216  * mutex_lock_interruptible()).
4217  *
4218  * @nested is an hysterical artifact, needs a tree wide cleanup.
4219  */
4220 static int
4221 __lock_release(struct lockdep_map *lock, unsigned long ip)
4222 {
4223         struct task_struct *curr = current;
4224         unsigned int depth, merged = 1;
4225         struct held_lock *hlock;
4226         int i;
4227 
4228         if (unlikely(!debug_locks))
4229                 return 0;
4230 
4231         depth = curr->lockdep_depth;
4232         /*
4233          * So we're all set to release this lock.. wait what lock? We don't
4234          * own any locks, you've been drinking again?
4235          */
4236         if (depth <= 0) {
4237                 print_unlock_imbalance_bug(curr, lock, ip);
4238                 return 0;
4239         }
4240 
4241         /*
4242          * Check whether the lock exists in the current stack
4243          * of held locks:
4244          */
4245         hlock = find_held_lock(curr, lock, depth, &i);
4246         if (!hlock) {
4247                 print_unlock_imbalance_bug(curr, lock, ip);
4248                 return 0;
4249         }
4250 
4251         if (hlock->instance == lock)
4252                 lock_release_holdtime(hlock);
4253 
4254         WARN(hlock->pin_count, "releasing a pinned lock\n");
4255 
4256         if (hlock->references) {
4257                 hlock->references--;
4258                 if (hlock->references) {
4259                         /*
4260                          * We had, and after removing one, still have
4261                          * references, the current lock stack is still
4262                          * valid. We're done!
4263                          */
4264                         return 1;
4265                 }
4266         }
4267 
4268         /*
4269          * We have the right lock to unlock, 'hlock' points to it.
4270          * Now we remove it from the stack, and add back the other
4271          * entries (if any), recalculating the hash along the way:
4272          */
4273 
4274         curr->lockdep_depth = i;
4275         curr->curr_chain_key = hlock->prev_chain_key;
4276 
4277         /*
4278          * The most likely case is when the unlock is on the innermost
4279          * lock. In this case, we are done!
4280          */
4281         if (i == depth-1)
4282                 return 1;
4283 
4284         if (reacquire_held_locks(curr, depth, i + 1, &merged))
4285                 return 0;
4286 
4287         /*
4288          * We had N bottles of beer on the wall, we drank one, but now
4289          * there's not N-1 bottles of beer left on the wall...
4290          * Pouring two of the bottles together is acceptable.
4291          */
4292         DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
4293 
4294         /*
4295          * Since reacquire_held_locks() would have called check_chain_key()
4296          * indirectly via __lock_acquire(), we don't need to do it again
4297          * on return.
4298          */
4299         return 0;
4300 }
4301 
4302 static nokprobe_inline
4303 int __lock_is_held(const struct lockdep_map *lock, int read)
4304 {
4305         struct task_struct *curr = current;
4306         int i;
4307 
4308         for (i = 0; i < curr->lockdep_depth; i++) {
4309                 struct held_lock *hlock = curr->held_locks + i;
4310 
4311                 if (match_held_lock(hlock, lock)) {
4312                         if (read == -1 || hlock->read == read)
4313                                 return 1;
4314 
4315                         return 0;
4316                 }
4317         }
4318 
4319         return 0;
4320 }
4321 
4322 static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
4323 {
4324         struct pin_cookie cookie = NIL_COOKIE;
4325         struct task_struct *curr = current;
4326         int i;
4327 
4328         if (unlikely(!debug_locks))
4329                 return cookie;
4330 
4331         for (i = 0; i < curr->lockdep_depth; i++) {
4332                 struct held_lock *hlock = curr->held_locks + i;
4333 
4334                 if (match_held_lock(hlock, lock)) {
4335                         /*
4336                          * Grab 16bits of randomness; this is sufficient to not
4337                          * be guessable and still allows some pin nesting in
4338                          * our u32 pin_count.
4339                          */
4340                         cookie.val = 1 + (prandom_u32() >> 16);
4341                         hlock->pin_count += cookie.val;
4342                         return cookie;
4343                 }
4344         }
4345 
4346         WARN(1, "pinning an unheld lock\n");
4347         return cookie;
4348 }
4349 
4350 static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
4351 {
4352         struct task_struct *curr = current;
4353         int i;
4354 
4355         if (unlikely(!debug_locks))
4356                 return;
4357 
4358         for (i = 0; i < curr->lockdep_depth; i++) {
4359                 struct held_lock *hlock = curr->held_locks + i;
4360 
4361                 if (match_held_lock(hlock, lock)) {
4362                         hlock->pin_count += cookie.val;
4363                         return;
4364                 }
4365         }
4366 
4367         WARN(1, "pinning an unheld lock\n");
4368 }
4369 
4370 static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
4371 {
4372         struct task_struct *curr = current;
4373         int i;
4374 
4375         if (unlikely(!debug_locks))
4376                 return;
4377 
4378         for (i = 0; i < curr->lockdep_depth; i++) {
4379                 struct held_lock *hlock = curr->held_locks + i;
4380 
4381                 if (match_held_lock(hlock, lock)) {
4382                         if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
4383                                 return;
4384 
4385                         hlock->pin_count -= cookie.val;
4386 
4387                         if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
4388                                 hlock->pin_count = 0;
4389 
4390                         return;
4391                 }
4392         }
4393 
4394         WARN(1, "unpinning an unheld lock\n");
4395 }
4396 
4397 /*
4398  * Check whether we follow the irq-flags state precisely:
4399  */
4400 static void check_flags(unsigned long flags)
4401 {
4402 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
4403         if (!debug_locks)
4404                 return;
4405 
4406         if (irqs_disabled_flags(flags)) {
4407                 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
4408                         printk("possible reason: unannotated irqs-off.\n");
4409                 }
4410         } else {
4411                 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
4412                         printk("possible reason: unannotated irqs-on.\n");
4413                 }
4414         }
4415 
4416         /*
4417          * We dont accurately track softirq state in e.g.
4418          * hardirq contexts (such as on 4KSTACKS), so only
4419          * check if not in hardirq contexts:
4420          */
4421         if (!hardirq_count()) {
4422                 if (softirq_count()) {
4423                         /* like the above, but with softirqs */
4424                         DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
4425                 } else {
4426                         /* lick the above, does it taste good? */
4427                         DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
4428                 }
4429         }
4430 
4431         if (!debug_locks)
4432                 print_irqtrace_events(current);
4433 #endif
4434 }
4435 
4436 void lock_set_class(struct lockdep_map *lock, const char *name,
4437                     struct lock_class_key *key, unsigned int subclass,
4438                     unsigned long ip)
4439 {
4440         unsigned long flags;
4441 
4442         if (unlikely(current->lockdep_recursion))
4443                 return;
4444 
4445         raw_local_irq_save(flags);
4446         current->lockdep_recursion = 1;
4447         check_flags(flags);
4448         if (__lock_set_class(lock, name, key, subclass, ip))
4449                 check_chain_key(current);
4450         current->lockdep_recursion = 0;
4451         raw_local_irq_restore(flags);
4452 }
4453 EXPORT_SYMBOL_GPL(lock_set_class);
4454 
4455 void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
4456 {
4457         unsigned long flags;
4458 
4459         if (unlikely(current->lockdep_recursion))
4460                 return;
4461 
4462         raw_local_irq_save(flags);
4463         current->lockdep_recursion = 1;
4464         check_flags(flags);
4465         if (__lock_downgrade(lock, ip))
4466                 check_chain_key(current);
4467         current->lockdep_recursion = 0;
4468         raw_local_irq_restore(flags);
4469 }
4470 EXPORT_SYMBOL_GPL(lock_downgrade);
4471 
4472 /*
4473  * We are not always called with irqs disabled - do that here,
4474  * and also avoid lockdep recursion:
4475  */
4476 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
4477                           int trylock, int read, int check,
4478                           struct lockdep_map *nest_lock, unsigned long ip)
4479 {
4480         unsigned long flags;
4481 
4482         if (unlikely(current->lockdep_recursion))
4483                 return;
4484 
4485         raw_local_irq_save(flags);
4486         check_flags(flags);
4487 
4488         current->lockdep_recursion = 1;
4489         trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
4490         __lock_acquire(lock, subclass, trylock, read, check,
4491                        irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
4492         current->lockdep_recursion = 0;
4493         raw_local_irq_restore(flags);
4494 }
4495 EXPORT_SYMBOL_GPL(lock_acquire);
4496 
4497 void lock_release(struct lockdep_map *lock, int nested,
4498                           unsigned long ip)
4499 {
4500         unsigned long flags;
4501 
4502         if (unlikely(current->lockdep_recursion))
4503                 return;
4504 
4505         raw_local_irq_save(flags);
4506         check_flags(flags);
4507         current->lockdep_recursion = 1;
4508         trace_lock_release(lock, ip);
4509         if (__lock_release(lock, ip))
4510                 check_chain_key(current);
4511         current->lockdep_recursion = 0;
4512         raw_local_irq_restore(flags);
4513 }
4514 EXPORT_SYMBOL_GPL(lock_release);
4515 
4516 int lock_is_held_type(const struct lockdep_map *lock, int read)
4517 {
4518         unsigned long flags;
4519         int ret = 0;
4520 
4521         if (unlikely(current->lockdep_recursion))
4522                 return 1; /* avoid false negative lockdep_assert_held() */
4523 
4524         raw_local_irq_save(flags);
4525         check_flags(flags);
4526 
4527         current->lockdep_recursion = 1;
4528         ret = __lock_is_held(lock, read);
4529         current->lockdep_recursion = 0;
4530         raw_local_irq_restore(flags);
4531 
4532         return ret;
4533 }
4534 EXPORT_SYMBOL_GPL(lock_is_held_type);
4535 NOKPROBE_SYMBOL(lock_is_held_type);
4536 
4537 struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
4538 {
4539         struct pin_cookie cookie = NIL_COOKIE;
4540         unsigned long flags;
4541 
4542         if (unlikely(current->lockdep_recursion))
4543                 return cookie;
4544 
4545         raw_local_irq_save(flags);
4546         check_flags(flags);
4547 
4548         current->lockdep_recursion = 1;
4549         cookie = __lock_pin_lock(lock);
4550         current->lockdep_recursion = 0;
4551         raw_local_irq_restore(flags);
4552 
4553         return cookie;
4554 }
4555 EXPORT_SYMBOL_GPL(lock_pin_lock);
4556 
4557 void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
4558 {
4559         unsigned long flags;
4560 
4561         if (unlikely(current->lockdep_recursion))
4562                 return;
4563 
4564         raw_local_irq_save(flags);
4565         check_flags(flags);
4566 
4567         current->lockdep_recursion = 1;
4568         __lock_repin_lock(lock, cookie);
4569         current->lockdep_recursion = 0;
4570         raw_local_irq_restore(flags);
4571 }
4572 EXPORT_SYMBOL_GPL(lock_repin_lock);
4573 
4574 void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
4575 {
4576         unsigned long flags;
4577 
4578         if (unlikely(current->lockdep_recursion))
4579                 return;
4580 
4581         raw_local_irq_save(flags);
4582         check_flags(flags);
4583 
4584         current->lockdep_recursion = 1;
4585         __lock_unpin_lock(lock, cookie);
4586         current->lockdep_recursion = 0;
4587         raw_local_irq_restore(flags);
4588 }
4589 EXPORT_SYMBOL_GPL(lock_unpin_lock);
4590 
4591 #ifdef CONFIG_LOCK_STAT
4592 static void print_lock_contention_bug(struct task_struct *curr,
4593                                       struct lockdep_map *lock,
4594                                       unsigned long ip)
4595 {
4596         if (!debug_locks_off())
4597                 return;
4598         if (debug_locks_silent)
4599                 return;
4600 
4601         pr_warn("\n");
4602         pr_warn("=================================\n");
4603         pr_warn("WARNING: bad contention detected!\n");
4604         print_kernel_ident();
4605         pr_warn("---------------------------------\n");
4606         pr_warn("%s/%d is trying to contend lock (",
4607                 curr->comm, task_pid_nr(curr));
4608         print_lockdep_cache(lock);
4609         pr_cont(") at:\n");
4610         print_ip_sym(ip);
4611         pr_warn("but there are no locks held!\n");
4612         pr_warn("\nother info that might help us debug this:\n");
4613         lockdep_print_held_locks(curr);
4614 
4615         pr_warn("\nstack backtrace:\n");
4616         dump_stack();
4617 }
4618 
4619 static void
4620 __lock_contended(struct lockdep_map *lock, unsigned long ip)
4621 {
4622         struct task_struct *curr = current;
4623         struct held_lock *hlock;
4624         struct lock_class_stats *stats;
4625         unsigned int depth;
4626         int i, contention_point, contending_point;
4627 
4628         depth = curr->lockdep_depth;
4629         /*
4630          * Whee, we contended on this lock, except it seems we're not
4631          * actually trying to acquire anything much at all..
4632          */
4633         if (DEBUG_LOCKS_WARN_ON(!depth))
4634                 return;
4635 
4636         hlock = find_held_lock(curr, lock, depth, &i);
4637         if (!hlock) {
4638                 print_lock_contention_bug(curr, lock, ip);
4639                 return;
4640         }
4641 
4642         if (hlock->instance != lock)
4643                 return;
4644 
4645         hlock->waittime_stamp = lockstat_clock();
4646 
4647         contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
4648         contending_point = lock_point(hlock_class(hlock)->contending_point,
4649                                       lock->ip);
4650 
4651         stats = get_lock_stats(hlock_class(hlock));
4652         if (contention_point < LOCKSTAT_POINTS)
4653                 stats->contention_point[contention_point]++;
4654         if (contending_point < LOCKSTAT_POINTS)
4655                 stats->contending_point[contending_point]++;
4656         if (lock->cpu != smp_processor_id())
4657                 stats->bounces[bounce_contended + !!hlock->read]++;
4658 }
4659 
4660 static void
4661 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
4662 {
4663         struct task_struct *curr = current;
4664         struct held_lock *hlock;
4665         struct lock_class_stats *stats;
4666         unsigned int depth;
4667         u64 now, waittime = 0;
4668         int i, cpu;
4669 
4670         depth = curr->lockdep_depth;
4671         /*
4672          * Yay, we acquired ownership of this lock we didn't try to
4673          * acquire, how the heck did that happen?
4674          */
4675         if (DEBUG_LOCKS_WARN_ON(!depth))
4676                 return;
4677 
4678         hlock = find_held_lock(curr, lock, depth, &i);
4679         if (!hlock) {
4680                 print_lock_contention_bug(curr, lock, _RET_IP_);
4681                 return;
4682         }
4683 
4684         if (hlock->instance != lock)
4685                 return;
4686 
4687         cpu = smp_processor_id();
4688         if (hlock->waittime_stamp) {
4689                 now = lockstat_clock();
4690                 waittime = now - hlock->waittime_stamp;
4691                 hlock->holdtime_stamp = now;
4692         }
4693 
4694         trace_lock_acquired(lock, ip);
4695 
4696         stats = get_lock_stats(hlock_class(hlock));
4697         if (waittime) {
4698                 if (hlock->read)
4699                         lock_time_inc(&stats->read_waittime, waittime);
4700                 else
4701                         lock_time_inc(&stats->write_waittime, waittime);
4702         }
4703         if (lock->cpu != cpu)
4704                 stats->bounces[bounce_acquired + !!hlock->read]++;
4705 
4706         lock->cpu = cpu;
4707         lock->ip = ip;
4708 }
4709 
4710 void lock_contended(struct lockdep_map *lock, unsigned long ip)
4711 {
4712         unsigned long flags;
4713 
4714         if (unlikely(!lock_stat || !debug_locks))
4715                 return;
4716 
4717         if (unlikely(current->lockdep_recursion))
4718                 return;
4719 
4720         raw_local_irq_save(flags);
4721         check_flags(flags);
4722         current->lockdep_recursion = 1;
4723         trace_lock_contended(lock, ip);
4724         __lock_contended(lock, ip);
4725         current->lockdep_recursion = 0;
4726         raw_local_irq_restore(flags);
4727 }
4728 EXPORT_SYMBOL_GPL(lock_contended);
4729 
4730 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
4731 {
4732         unsigned long flags;
4733 
4734         if (unlikely(!lock_stat || !debug_locks))
4735                 return;
4736 
4737         if (unlikely(current->lockdep_recursion))
4738                 return;
4739 
4740         raw_local_irq_save(flags);
4741         check_flags(flags);
4742         current->lockdep_recursion = 1;
4743         __lock_acquired(lock, ip);
4744         current->lockdep_recursion = 0;
4745         raw_local_irq_restore(flags);
4746 }
4747 EXPORT_SYMBOL_GPL(lock_acquired);
4748 #endif
4749 
4750 /*
4751  * Used by the testsuite, sanitize the validator state
4752  * after a simulated failure:
4753  */
4754 
4755 void lockdep_reset(void)
4756 {
4757         unsigned long flags;
4758         int i;
4759 
4760         raw_local_irq_save(flags);
4761         lockdep_init_task(current);
4762         memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
4763         nr_hardirq_chains = 0;
4764         nr_softirq_chains = 0;
4765         nr_process_chains = 0;
4766         debug_locks = 1;
4767         for (i = 0; i < CHAINHASH_SIZE; i++)
4768                 INIT_HLIST_HEAD(chainhash_table + i);
4769         raw_local_irq_restore(flags);
4770 }
4771 
4772 /* Remove a class from a lock chain. Must be called with the graph lock held. */
4773 static void remove_class_from_lock_chain(struct pending_free *pf,
4774                                          struct lock_chain *chain,
4775                                          struct lock_class *class)
4776 {
4777 #ifdef CONFIG_PROVE_LOCKING
4778         struct lock_chain *new_chain;
4779         u64 chain_key;
4780         int i;
4781 
4782         for (i = chain->base; i < chain->base + chain->depth; i++) {
4783                 if (chain_hlocks[i] != class - lock_classes)
4784                         continue;
4785                 /* The code below leaks one chain_hlock[] entry. */
4786                 if (--chain->depth > 0) {
4787                         memmove(&chain_hlocks[i], &chain_hlocks[i + 1],
4788                                 (chain->base + chain->depth - i) *
4789                                 sizeof(chain_hlocks[0]));
4790                 }
4791                 /*
4792                  * Each lock class occurs at most once in a lock chain so once
4793                  * we found a match we can break out of this loop.
4794                  */
4795                 goto recalc;
4796         }
4797         /* Since the chain has not been modified, return. */
4798         return;
4799 
4800 recalc:
4801         chain_key = INITIAL_CHAIN_KEY;
4802         for (i = chain->base; i < chain->base + chain->depth; i++)
4803                 chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
4804         if (chain->depth && chain->chain_key == chain_key)
4805                 return;
4806         /* Overwrite the chain key for concurrent RCU readers. */
4807         WRITE_ONCE(chain->chain_key, chain_key);
4808         /*
4809          * Note: calling hlist_del_rcu() from inside a
4810          * hlist_for_each_entry_rcu() loop is safe.
4811          */
4812         hlist_del_rcu(&chain->entry);
4813         __set_bit(chain - lock_chains, pf->lock_chains_being_freed);
4814         if (chain->depth == 0)
4815                 return;
4816         /*
4817          * If the modified lock chain matches an existing lock chain, drop
4818          * the modified lock chain.
4819          */
4820         if (lookup_chain_cache(chain_key))
4821                 return;
4822         new_chain = alloc_lock_chain();
4823         if (WARN_ON_ONCE(!new_chain)) {
4824                 debug_locks_off();
4825                 return;
4826         }
4827         *new_chain = *chain;
4828         hlist_add_head_rcu(&new_chain->entry, chainhashentry(chain_key));
4829 #endif
4830 }
4831 
4832 /* Must be called with the graph lock held. */
4833 static void remove_class_from_lock_chains(struct pending_free *pf,
4834                                           struct lock_class *class)
4835 {
4836         struct lock_chain *chain;
4837         struct hlist_head *head;
4838         int i;
4839 
4840         for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
4841                 head = chainhash_table + i;
4842                 hlist_for_each_entry_rcu(chain, head, entry) {
4843                         remove_class_from_lock_chain(pf, chain, class);
4844                 }
4845         }
4846 }
4847 
4848 /*
4849  * Remove all references to a lock class. The caller must hold the graph lock.
4850  */
4851 static void zap_class(struct pending_free *pf, struct lock_class *class)
4852 {
4853         struct lock_list *entry;
4854         int i;
4855 
4856         WARN_ON_ONCE(!class->key);
4857 
4858         /*
4859          * Remove all dependencies this lock is
4860          * involved in:
4861          */
4862         for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
4863                 entry = list_entries + i;
4864                 if (entry->class != class && entry->links_to != class)
4865                         continue;
4866                 __clear_bit(i, list_entries_in_use);
4867                 nr_list_entries--;
4868                 list_del_rcu(&entry->entry);
4869         }
4870         if (list_empty(&class->locks_after) &&
4871             list_empty(&class->locks_before)) {
4872                 list_move_tail(&class->lock_entry, &pf->zapped);
4873                 hlist_del_rcu(&class->hash_entry);
4874                 WRITE_ONCE(class->key, NULL);
4875                 WRITE_ONCE(class->name, NULL);
4876                 nr_lock_classes--;
4877                 __clear_bit(class - lock_classes, lock_classes_in_use);
4878         } else {
4879                 WARN_ONCE(true, "%s() failed for class %s\n", __func__,
4880                           class->name);
4881         }
4882 
4883         remove_class_from_lock_chains(pf, class);
4884 }
4885 
4886 static void reinit_class(struct lock_class *class)
4887 {
4888         void *const p = class;
4889         const unsigned int offset = offsetof(struct lock_class, key);
4890 
4891         WARN_ON_ONCE(!class->lock_entry.next);
4892         WARN_ON_ONCE(!list_empty(&class->locks_after));
4893         WARN_ON_ONCE(!list_empty(&class->locks_before));
4894         memset(p + offset, 0, sizeof(*class) - offset);
4895         WARN_ON_ONCE(!class->lock_entry.next);
4896         WARN_ON_ONCE(!list_empty(&class->locks_after));
4897         WARN_ON_ONCE(!list_empty(&class->locks_before));
4898 }
4899 
4900 static inline int within(const void *addr, void *start, unsigned long size)
4901 {
4902         return addr >= start && addr < start + size;
4903 }
4904 
4905 static bool inside_selftest(void)
4906 {
4907         return current == lockdep_selftest_task_struct;
4908 }
4909 
4910 /* The caller must hold the graph lock. */
4911 static struct pending_free *get_pending_free(void)
4912 {
4913         return delayed_free.pf + delayed_free.index;
4914 }
4915 
4916 static void free_zapped_rcu(struct rcu_head *cb);
4917 
4918 /*
4919  * Schedule an RCU callback if no RCU callback is pending. Must be called with
4920  * the graph lock held.
4921  */
4922 static void call_rcu_zapped(struct pending_free *pf)
4923 {
4924         WARN_ON_ONCE(inside_selftest());
4925 
4926         if (list_empty(&pf->zapped))
4927                 return;
4928 
4929         if (delayed_free.scheduled)
4930                 return;
4931 
4932         delayed_free.scheduled = true;
4933 
4934         WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
4935         delayed_free.index ^= 1;
4936 
4937         call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
4938 }
4939 
4940 /* The caller must hold the graph lock. May be called from RCU context. */
4941 static void __free_zapped_classes(struct pending_free *pf)
4942 {
4943         struct lock_class *class;
4944 
4945         check_data_structures();
4946 
4947         list_for_each_entry(class, &pf->zapped, lock_entry)
4948                 reinit_class(class);
4949 
4950         list_splice_init(&pf->zapped, &free_lock_classes);
4951 
4952 #ifdef CONFIG_PROVE_LOCKING
4953         bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
4954                       pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
4955         bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
4956 #endif
4957 }
4958 
4959 static void free_zapped_rcu(struct rcu_head *ch)
4960 {
4961         struct pending_free *pf;
4962         unsigned long flags;
4963 
4964         if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
4965                 return;
4966 
4967         raw_local_irq_save(flags);
4968         arch_spin_lock(&lockdep_lock);
4969         current->lockdep_recursion = 1;
4970 
4971         /* closed head */
4972         pf = delayed_free.pf + (delayed_free.index ^ 1);
4973         __free_zapped_classes(pf);
4974         delayed_free.scheduled = false;
4975 
4976         /*
4977          * If there's anything on the open list, close and start a new callback.
4978          */
4979         call_rcu_zapped(delayed_free.pf + delayed_free.index);
4980 
4981         current->lockdep_recursion = 0;
4982         arch_spin_unlock(&lockdep_lock);
4983         raw_local_irq_restore(flags);
4984 }
4985 
4986 /*
4987  * Remove all lock classes from the class hash table and from the
4988  * all_lock_classes list whose key or name is in the address range [start,
4989  * start + size). Move these lock classes to the zapped_classes list. Must
4990  * be called with the graph lock held.
4991  */
4992 static void __lockdep_free_key_range(struct pending_free *pf, void *start,
4993                                      unsigned long size)
4994 {
4995         struct lock_class *class;
4996         struct hlist_head *head;
4997         int i;
4998 
4999         /* Unhash all classes that were created by a module. */
5000         for (i = 0; i < CLASSHASH_SIZE; i++) {
5001                 head = classhash_table + i;
5002                 hlist_for_each_entry_rcu(class, head, hash_entry) {
5003                         if (!within(class->key, start, size) &&
5004                             !within(class->name, start, size))
5005                                 continue;
5006                         zap_class(pf, class);
5007                 }
5008         }
5009 }
5010 
5011 /*
5012  * Used in module.c to remove lock classes from memory that is going to be
5013  * freed; and possibly re-used by other modules.
5014  *
5015  * We will have had one synchronize_rcu() before getting here, so we're
5016  * guaranteed nobody will look up these exact classes -- they're properly dead
5017  * but still allocated.
5018  */
5019 static void lockdep_free_key_range_reg(void *start, unsigned long size)
5020 {
5021         struct pending_free *pf;
5022         unsigned long flags;
5023 
5024         init_data_structures_once();
5025 
5026         raw_local_irq_save(flags);
5027         arch_spin_lock(&lockdep_lock);
5028         current->lockdep_recursion = 1;
5029         pf = get_pending_free();
5030         __lockdep_free_key_range(pf, start, size);
5031         call_rcu_zapped(pf);
5032         current->lockdep_recursion = 0;
5033         arch_spin_unlock(&lockdep_lock);
5034         raw_local_irq_restore(flags);
5035 
5036         /*
5037          * Wait for any possible iterators from look_up_lock_class() to pass
5038          * before continuing to free the memory they refer to.
5039          */
5040         synchronize_rcu();
5041 }
5042 
5043 /*
5044  * Free all lockdep keys in the range [start, start+size). Does not sleep.
5045  * Ignores debug_locks. Must only be used by the lockdep selftests.
5046  */
5047 static void lockdep_free_key_range_imm(void *start, unsigned long size)
5048 {
5049         struct pending_free *pf = delayed_free.pf;
5050         unsigned long flags;
5051 
5052         init_data_structures_once();
5053 
5054         raw_local_irq_save(flags);
5055         arch_spin_lock(&lockdep_lock);
5056         __lockdep_free_key_range(pf, start, size);
5057         __free_zapped_classes(pf);
5058         arch_spin_unlock(&lockdep_lock);
5059         raw_local_irq_restore(flags);
5060 }
5061 
5062 void lockdep_free_key_range(void *start, unsigned long size)
5063 {
5064         init_data_structures_once();
5065 
5066         if (inside_selftest())
5067                 lockdep_free_key_range_imm(start, size);
5068         else
5069                 lockdep_free_key_range_reg(start, size);
5070 }
5071 
5072 /*
5073  * Check whether any element of the @lock->class_cache[] array refers to a
5074  * registered lock class. The caller must hold either the graph lock or the
5075  * RCU read lock.
5076  */
5077 static bool lock_class_cache_is_registered(struct lockdep_map *lock)
5078 {
5079         struct lock_class *class;
5080         struct hlist_head *head;
5081         int i, j;
5082 
5083         for (i = 0; i < CLASSHASH_SIZE; i++) {
5084                 head = classhash_table + i;
5085                 hlist_for_each_entry_rcu(class, head, hash_entry) {
5086                         for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
5087                                 if (lock->class_cache[j] == class)
5088                                         return true;
5089                 }
5090         }
5091         return false;
5092 }
5093 
5094 /* The caller must hold the graph lock. Does not sleep. */
5095 static void __lockdep_reset_lock(struct pending_free *pf,
5096                                  struct lockdep_map *lock)
5097 {
5098         struct lock_class *class;
5099         int j;
5100 
5101         /*
5102          * Remove all classes this lock might have:
5103          */
5104         for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
5105                 /*
5106                  * If the class exists we look it up and zap it:
5107                  */
5108                 class = look_up_lock_class(lock, j);
5109                 if (class)
5110                         zap_class(pf, class);
5111         }
5112         /*
5113          * Debug check: in the end all mapped classes should
5114          * be gone.
5115          */
5116         if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
5117                 debug_locks_off();
5118 }
5119 
5120 /*
5121  * Remove all information lockdep has about a lock if debug_locks == 1. Free
5122  * released data structures from RCU context.
5123  */
5124 static void lockdep_reset_lock_reg(struct lockdep_map *lock)
5125 {
5126         struct pending_free *pf;
5127         unsigned long flags;
5128         int locked;
5129 
5130         raw_local_irq_save(flags);
5131         locked = graph_lock();
5132         if (!locked)
5133                 goto out_irq;
5134 
5135         pf = get_pending_free();
5136         __lockdep_reset_lock(pf, lock);
5137         call_rcu_zapped(pf);
5138 
5139         graph_unlock();
5140 out_irq:
5141         raw_local_irq_restore(flags);
5142 }
5143 
5144 /*
5145  * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
5146  * lockdep selftests.
5147  */
5148 static void lockdep_reset_lock_imm(struct lockdep_map *lock)
5149 {
5150         struct pending_free *pf = delayed_free.pf;
5151         unsigned long flags;
5152 
5153         raw_local_irq_save(flags);
5154         arch_spin_lock(&lockdep_lock);
5155         __lockdep_reset_lock(pf, lock);
5156         __free_zapped_classes(pf);
5157         arch_spin_unlock(&lockdep_lock);
5158         raw_local_irq_restore(flags);
5159 }
5160 
5161 void lockdep_reset_lock(struct lockdep_map *lock)
5162 {
5163         init_data_structures_once();
5164 
5165         if (inside_selftest())
5166                 lockdep_reset_lock_imm(lock);
5167         else
5168                 lockdep_reset_lock_reg(lock);
5169 }
5170 
5171 /* Unregister a dynamically allocated key. */
5172 void lockdep_unregister_key(struct lock_class_key *key)
5173 {
5174         struct hlist_head *hash_head = keyhashentry(key);
5175         struct lock_class_key *k;
5176         struct pending_free *pf;
5177         unsigned long flags;
5178         bool found = false;
5179 
5180         might_sleep();
5181 
5182         if (WARN_ON_ONCE(static_obj(key)))
5183                 return;
5184 
5185         raw_local_irq_save(flags);
5186         if (!graph_lock())
5187                 goto out_irq;
5188 
5189         pf = get_pending_free();
5190         hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
5191                 if (k == key) {
5192                         hlist_del_rcu(&k->hash_entry);
5193                         found = true;
5194                         break;
5195                 }
5196         }
5197         WARN_ON_ONCE(!found);
5198         __lockdep_free_key_range(pf, key, 1);
5199         call_rcu_zapped(pf);
5200         graph_unlock();
5201 out_irq:
5202         raw_local_irq_restore(flags);
5203 
5204         /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
5205         synchronize_rcu();
5206 }
5207 EXPORT_SYMBOL_GPL(lockdep_unregister_key);
5208 
5209 void __init lockdep_init(void)
5210 {
5211         printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
5212 
5213         printk("... MAX_LOCKDEP_SUBCLASSES:  %lu\n", MAX_LOCKDEP_SUBCLASSES);
5214         printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
5215         printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
5216         printk("... CLASSHASH_SIZE:          %lu\n", CLASSHASH_SIZE);
5217         printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
5218         printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
5219         printk("... CHAINHASH_SIZE:          %lu\n", CHAINHASH_SIZE);
5220 
5221         printk(" memory used by lock dependency info: %zu kB\n",
5222                (sizeof(lock_classes) +
5223                 sizeof(lock_classes_in_use) +
5224                 sizeof(classhash_table) +
5225                 sizeof(list_entries) +
5226                 sizeof(list_entries_in_use) +
5227                 sizeof(chainhash_table) +
5228                 sizeof(delayed_free)
5229 #ifdef CONFIG_PROVE_LOCKING
5230                 + sizeof(lock_cq)
5231                 + sizeof(lock_chains)
5232                 + sizeof(lock_chains_in_use)
5233                 + sizeof(chain_hlocks)
5234 #endif
5235                 ) / 1024
5236                 );
5237 
5238 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
5239         printk(" memory used for stack traces: %zu kB\n",
5240                (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
5241                );
5242 #endif
5243 
5244         printk(" per task-struct memory footprint: %zu bytes\n",
5245                sizeof(((struct task_struct *)NULL)->held_locks));
5246 }
5247 
5248 static void
5249 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
5250                      const void *mem_to, struct held_lock *hlock)
5251 {
5252         if (!debug_locks_off())
5253                 return;
5254         if (debug_locks_silent)
5255                 return;
5256 
5257         pr_warn("\n");
5258         pr_warn("=========================\n");
5259         pr_warn("WARNING: held lock freed!\n");
5260         print_kernel_ident();
5261         pr_warn("-------------------------\n");
5262         pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
5263                 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
5264         print_lock(hlock);
5265         lockdep_print_held_locks(curr);
5266 
5267         pr_warn("\nstack backtrace:\n");
5268         dump_stack();
5269 }
5270 
5271 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
5272                                 const void* lock_from, unsigned long lock_len)
5273 {
5274         return lock_from + lock_len <= mem_from ||
5275                 mem_from + mem_len <= lock_from;
5276 }
5277 
5278 /*
5279  * Called when kernel memory is freed (or unmapped), or if a lock
5280  * is destroyed or reinitialized - this code checks whether there is
5281  * any held lock in the memory range of <from> to <to>:
5282  */
5283 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
5284 {
5285         struct task_struct *curr = current;
5286         struct held_lock *hlock;
5287         unsigned long flags;
5288         int i;
5289 
5290         if (unlikely(!debug_locks))
5291                 return;
5292 
5293         raw_local_irq_save(flags);
5294         for (i = 0; i < curr->lockdep_depth; i++) {
5295                 hlock = curr->held_locks + i;
5296 
5297                 if (not_in_range(mem_from, mem_len, hlock->instance,
5298                                         sizeof(*hlock->instance)))
5299                         continue;
5300 
5301                 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
5302                 break;
5303         }
5304         raw_local_irq_restore(flags);
5305 }
5306 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
5307 
5308 static void print_held_locks_bug(void)
5309 {
5310         if (!debug_locks_off())
5311                 return;
5312         if (debug_locks_silent)
5313                 return;
5314 
5315         pr_warn("\n");
5316         pr_warn("====================================\n");
5317         pr_warn("WARNING: %s/%d still has locks held!\n",
5318                current->comm, task_pid_nr(current));
5319         print_kernel_ident();
5320         pr_warn("------------------------------------\n");
5321         lockdep_print_held_locks(current);
5322         pr_warn("\nstack backtrace:\n");
5323         dump_stack();
5324 }
5325 
5326 void debug_check_no_locks_held(void)
5327 {
5328         if (unlikely(current->lockdep_depth > 0))
5329                 print_held_locks_bug();
5330 }
5331 EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
5332 
5333 #ifdef __KERNEL__
5334 void debug_show_all_locks(void)
5335 {
5336         struct task_struct *g, *p;
5337 
5338         if (unlikely(!debug_locks)) {
5339                 pr_warn("INFO: lockdep is turned off.\n");
5340                 return;
5341         }
5342         pr_warn("\nShowing all locks held in the system:\n");
5343 
5344         rcu_read_lock();
5345         for_each_process_thread(g, p) {
5346                 if (!p->lockdep_depth)
5347                         continue;
5348                 lockdep_print_held_locks(p);
5349                 touch_nmi_watchdog();
5350                 touch_all_softlockup_watchdogs();
5351         }
5352         rcu_read_unlock();
5353 
5354         pr_warn("\n");
5355         pr_warn("=============================================\n\n");
5356 }
5357 EXPORT_SYMBOL_GPL(debug_show_all_locks);
5358 #endif
5359 
5360 /*
5361  * Careful: only use this function if you are sure that
5362  * the task cannot run in parallel!
5363  */
5364 void debug_show_held_locks(struct task_struct *task)
5365 {
5366         if (unlikely(!debug_locks)) {
5367                 printk("INFO: lockdep is turned off.\n");
5368                 return;
5369         }
5370         lockdep_print_held_locks(task);
5371 }
5372 EXPORT_SYMBOL_GPL(debug_show_held_locks);
5373 
5374 asmlinkage __visible void lockdep_sys_exit(void)
5375 {
5376         struct task_struct *curr = current;
5377 
5378         if (unlikely(curr->lockdep_depth)) {
5379                 if (!debug_locks_off())
5380                         return;
5381                 pr_warn("\n");
5382                 pr_warn("================================================\n");
5383                 pr_warn("WARNING: lock held when returning to user space!\n");
5384                 print_kernel_ident();
5385                 pr_warn("------------------------------------------------\n");
5386                 pr_warn("%s/%d is leaving the kernel with locks still held!\n",
5387                                 curr->comm, curr->pid);
5388                 lockdep_print_held_locks(curr);
5389         }
5390 
5391         /*
5392          * The lock history for each syscall should be independent. So wipe the
5393          * slate clean on return to userspace.
5394          */
5395         lockdep_invariant_state(false);
5396 }
5397 
5398 void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
5399 {
5400         struct task_struct *curr = current;
5401 
5402         /* Note: the following can be executed concurrently, so be careful. */
5403         pr_warn("\n");
5404         pr_warn("=============================\n");
5405         pr_warn("WARNING: suspicious RCU usage\n");
5406         print_kernel_ident();
5407         pr_warn("-----------------------------\n");
5408         pr_warn("%s:%d %s!\n", file, line, s);
5409         pr_warn("\nother info that might help us debug this:\n\n");
5410         pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
5411                !rcu_lockdep_current_cpu_online()
5412                         ? "RCU used illegally from offline CPU!\n"
5413                         : !rcu_is_watching()
5414                                 ? "RCU used illegally from idle CPU!\n"
5415                                 : "",
5416                rcu_scheduler_active, debug_locks);
5417 
5418         /*
5419          * If a CPU is in the RCU-free window in idle (ie: in the section
5420          * between rcu_idle_enter() and rcu_idle_exit(), then RCU
5421          * considers that CPU to be in an "extended quiescent state",
5422          * which means that RCU will be completely ignoring that CPU.
5423          * Therefore, rcu_read_lock() and friends have absolutely no
5424          * effect on a CPU running in that state. In other words, even if
5425          * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
5426          * delete data structures out from under it.  RCU really has no
5427          * choice here: we need to keep an RCU-free window in idle where
5428          * the CPU may possibly enter into low power mode. This way we can
5429          * notice an extended quiescent state to other CPUs that started a grace
5430          * period. Otherwise we would delay any grace period as long as we run
5431          * in the idle task.
5432          *
5433          * So complain bitterly if someone does call rcu_read_lock(),
5434          * rcu_read_lock_bh() and so on from extended quiescent states.
5435          */
5436         if (!rcu_is_watching())
5437                 pr_warn("RCU used illegally from extended quiescent state!\n");
5438 
5439         lockdep_print_held_locks(curr);
5440         pr_warn("\nstack backtrace:\n");
5441         dump_stack();
5442 }
5443 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);