root/include/linux/mutex.h

INCLUDED FROM

DEFINITIONS

1. mutex_destroy

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * Mutexes: blocking mutual exclusion locks
   4  *
   5  * started by Ingo Molnar:
   6  *
   7  *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
   8  *
   9  * This file contains the main data structure and API definitions.
  10  */
  11 #ifndef __LINUX_MUTEX_H
  12 #define __LINUX_MUTEX_H
  13 
  14 #include <asm/current.h>
  15 #include <linux/list.h>
  16 #include <linux/spinlock_types.h>
  17 #include <linux/lockdep.h>
  18 #include <linux/atomic.h>
  19 #include <asm/processor.h>
  20 #include <linux/osq_lock.h>
  21 #include <linux/debug_locks.h>
  22 
  23 struct ww_acquire_ctx;
  24 
  25 /*
  26  * Simple, straightforward mutexes with strict semantics:
  27  *
  28  * - only one task can hold the mutex at a time
  29  * - only the owner can unlock the mutex
  30  * - multiple unlocks are not permitted
  31  * - recursive locking is not permitted
  32  * - a mutex object must be initialized via the API
  33  * - a mutex object must not be initialized via memset or copying
  34  * - task may not exit with mutex held
  35  * - memory areas where held locks reside must not be freed
  36  * - held mutexes must not be reinitialized
  37  * - mutexes may not be used in hardware or software interrupt
  38  *   contexts such as tasklets and timers
  39  *
  40  * These semantics are fully enforced when DEBUG_MUTEXES is
  41  * enabled. Furthermore, besides enforcing the above rules, the mutex
  42  * debugging code also implements a number of additional features
  43  * that make lock debugging easier and faster:
  44  *
  45  * - uses symbolic names of mutexes, whenever they are printed in debug output
  46  * - point-of-acquire tracking, symbolic lookup of function names
  47  * - list of all locks held in the system, printout of them
  48  * - owner tracking
  49  * - detects self-recursing locks and prints out all relevant info
  50  * - detects multi-task circular deadlocks and prints out all affected
  51  *   locks and tasks (and only those tasks)
  52  */
  53 struct mutex {
  54         atomic_long_t           owner;
  55         spinlock_t              wait_lock;
  56 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
  57         struct optimistic_spin_queue osq; /* Spinner MCS lock */
  58 #endif
  59         struct list_head        wait_list;
  60 #ifdef CONFIG_DEBUG_MUTEXES
  61         void                    *magic;
  62 #endif
  63 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  64         struct lockdep_map      dep_map;
  65 #endif
  66 };
  67 
  68 /*
  69  * This is the control structure for tasks blocked on mutex,
  70  * which resides on the blocked task's kernel stack:
  71  */
  72 struct mutex_waiter {
  73         struct list_head        list;
  74         struct task_struct      *task;
  75         struct ww_acquire_ctx   *ww_ctx;
  76 #ifdef CONFIG_DEBUG_MUTEXES
  77         void                    *magic;
  78 #endif
  79 };
  80 
  81 #ifdef CONFIG_DEBUG_MUTEXES
  82 
  83 #define __DEBUG_MUTEX_INITIALIZER(lockname)                             \
  84         , .magic = &lockname
  85 
  86 extern void mutex_destroy(struct mutex *lock);
  87 
  88 #else
  89 
  90 # define __DEBUG_MUTEX_INITIALIZER(lockname)
  91 
  92 static inline void mutex_destroy(struct mutex *lock) {}
  93 
  94 #endif
  95 
  96 /**
  97  * mutex_init - initialize the mutex
  98  * @mutex: the mutex to be initialized
  99  *
 100  * Initialize the mutex to unlocked state.
 101  *
 102  * It is not allowed to initialize an already locked mutex.
 103  */
 104 #define mutex_init(mutex)                                               \
 105 do {                                                                    \
 106         static struct lock_class_key __key;                             \
 107                                                                         \
 108         __mutex_init((mutex), #mutex, &__key);                          \
 109 } while (0)
 110 
 111 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 112 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
 113                 , .dep_map = { .name = #lockname }
 114 #else
 115 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
 116 #endif
 117 
 118 #define __MUTEX_INITIALIZER(lockname) \
 119                 { .owner = ATOMIC_LONG_INIT(0) \
 120                 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
 121                 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
 122                 __DEBUG_MUTEX_INITIALIZER(lockname) \
 123                 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
 124 
 125 #define DEFINE_MUTEX(mutexname) \
 126         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 127 
 128 extern void __mutex_init(struct mutex *lock, const char *name,
 129                          struct lock_class_key *key);
 130 
 131 /**
 132  * mutex_is_locked - is the mutex locked
 133  * @lock: the mutex to be queried
 134  *
 135  * Returns true if the mutex is locked, false if unlocked.
 136  */
 137 extern bool mutex_is_locked(struct mutex *lock);
 138 
 139 /*
 140  * See kernel/locking/mutex.c for detailed documentation of these APIs.
 141  * Also see Documentation/locking/mutex-design.rst.
 142  */
 143 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 144 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
 145 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
 146 
 147 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
 148                                         unsigned int subclass);
 149 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
 150                                         unsigned int subclass);
 151 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
 152 
 153 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
 154 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
 155 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
 156 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
 157 
 158 #define mutex_lock_nest_lock(lock, nest_lock)                           \
 159 do {                                                                    \
 160         typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
 161         _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);             \
 162 } while (0)
 163 
 164 #else
 165 extern void mutex_lock(struct mutex *lock);
 166 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
 167 extern int __must_check mutex_lock_killable(struct mutex *lock);
 168 extern void mutex_lock_io(struct mutex *lock);
 169 
 170 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
 171 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
 172 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
 173 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
 174 # define mutex_lock_io_nested(lock, subclass) mutex_lock(lock)
 175 #endif
 176 
 177 /*
 178  * NOTE: mutex_trylock() follows the spin_trylock() convention,
 179  *       not the down_trylock() convention!
 180  *
 181  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
 182  */
 183 extern int mutex_trylock(struct mutex *lock);
 184 extern void mutex_unlock(struct mutex *lock);
 185 
 186 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
 187 
 188 /*
 189  * These values are chosen such that FAIL and SUCCESS match the
 190  * values of the regular mutex_trylock().
 191  */
 192 enum mutex_trylock_recursive_enum {
 193         MUTEX_TRYLOCK_FAILED    = 0,
 194         MUTEX_TRYLOCK_SUCCESS   = 1,
 195         MUTEX_TRYLOCK_RECURSIVE,
 196 };
 197 
 198 /**
 199  * mutex_trylock_recursive - trylock variant that allows recursive locking
 200  * @lock: mutex to be locked
 201  *
 202  * This function should not be used, _ever_. It is purely for hysterical GEM
 203  * raisins, and once those are gone this will be removed.
 204  *
 205  * Returns:
 206  *  - MUTEX_TRYLOCK_FAILED    - trylock failed,
 207  *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
 208  *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
 209  */
 210 extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
 211 mutex_trylock_recursive(struct mutex *lock);
 212 
 213 #endif /* __LINUX_MUTEX_H */