linux/include/linux/mutex.h
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   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#ifdef CONFIG_DEBUG_LOCK_ALLOC
  24# define __DEP_MAP_MUTEX_INITIALIZER(lockname)                  \
  25                , .dep_map = {                                  \
  26                        .name = #lockname,                      \
  27                        .wait_type_inner = LD_WAIT_SLEEP,       \
  28                }
  29#else
  30# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
  31#endif
  32
  33#ifndef CONFIG_PREEMPT_RT
  34
  35/*
  36 * Simple, straightforward mutexes with strict semantics:
  37 *
  38 * - only one task can hold the mutex at a time
  39 * - only the owner can unlock the mutex
  40 * - multiple unlocks are not permitted
  41 * - recursive locking is not permitted
  42 * - a mutex object must be initialized via the API
  43 * - a mutex object must not be initialized via memset or copying
  44 * - task may not exit with mutex held
  45 * - memory areas where held locks reside must not be freed
  46 * - held mutexes must not be reinitialized
  47 * - mutexes may not be used in hardware or software interrupt
  48 *   contexts such as tasklets and timers
  49 *
  50 * These semantics are fully enforced when DEBUG_MUTEXES is
  51 * enabled. Furthermore, besides enforcing the above rules, the mutex
  52 * debugging code also implements a number of additional features
  53 * that make lock debugging easier and faster:
  54 *
  55 * - uses symbolic names of mutexes, whenever they are printed in debug output
  56 * - point-of-acquire tracking, symbolic lookup of function names
  57 * - list of all locks held in the system, printout of them
  58 * - owner tracking
  59 * - detects self-recursing locks and prints out all relevant info
  60 * - detects multi-task circular deadlocks and prints out all affected
  61 *   locks and tasks (and only those tasks)
  62 */
  63struct mutex {
  64        atomic_long_t           owner;
  65        raw_spinlock_t          wait_lock;
  66#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
  67        struct optimistic_spin_queue osq; /* Spinner MCS lock */
  68#endif
  69        struct list_head        wait_list;
  70#ifdef CONFIG_DEBUG_MUTEXES
  71        void                    *magic;
  72#endif
  73#ifdef CONFIG_DEBUG_LOCK_ALLOC
  74        struct lockdep_map      dep_map;
  75#endif
  76};
  77
  78#ifdef CONFIG_DEBUG_MUTEXES
  79
  80#define __DEBUG_MUTEX_INITIALIZER(lockname)                             \
  81        , .magic = &lockname
  82
  83extern void mutex_destroy(struct mutex *lock);
  84
  85#else
  86
  87# define __DEBUG_MUTEX_INITIALIZER(lockname)
  88
  89static inline void mutex_destroy(struct mutex *lock) {}
  90
  91#endif
  92
  93/**
  94 * mutex_init - initialize the mutex
  95 * @mutex: the mutex to be initialized
  96 *
  97 * Initialize the mutex to unlocked state.
  98 *
  99 * It is not allowed to initialize an already locked mutex.
 100 */
 101#define mutex_init(mutex)                                               \
 102do {                                                                    \
 103        static struct lock_class_key __key;                             \
 104                                                                        \
 105        __mutex_init((mutex), #mutex, &__key);                          \
 106} while (0)
 107
 108#define __MUTEX_INITIALIZER(lockname) \
 109                { .owner = ATOMIC_LONG_INIT(0) \
 110                , .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
 111                , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
 112                __DEBUG_MUTEX_INITIALIZER(lockname) \
 113                __DEP_MAP_MUTEX_INITIALIZER(lockname) }
 114
 115#define DEFINE_MUTEX(mutexname) \
 116        struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 117
 118extern void __mutex_init(struct mutex *lock, const char *name,
 119                         struct lock_class_key *key);
 120
 121/**
 122 * mutex_is_locked - is the mutex locked
 123 * @lock: the mutex to be queried
 124 *
 125 * Returns true if the mutex is locked, false if unlocked.
 126 */
 127extern bool mutex_is_locked(struct mutex *lock);
 128
 129#else /* !CONFIG_PREEMPT_RT */
 130/*
 131 * Preempt-RT variant based on rtmutexes.
 132 */
 133#include <linux/rtmutex.h>
 134
 135struct mutex {
 136        struct rt_mutex_base    rtmutex;
 137#ifdef CONFIG_DEBUG_LOCK_ALLOC
 138        struct lockdep_map      dep_map;
 139#endif
 140};
 141
 142#define __MUTEX_INITIALIZER(mutexname)                                  \
 143{                                                                       \
 144        .rtmutex = __RT_MUTEX_BASE_INITIALIZER(mutexname.rtmutex)       \
 145        __DEP_MAP_MUTEX_INITIALIZER(mutexname)                          \
 146}
 147
 148#define DEFINE_MUTEX(mutexname)                                         \
 149        struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 150
 151extern void __mutex_rt_init(struct mutex *lock, const char *name,
 152                            struct lock_class_key *key);
 153extern int mutex_trylock(struct mutex *lock);
 154
 155static inline void mutex_destroy(struct mutex *lock) { }
 156
 157#define mutex_is_locked(l)      rt_mutex_base_is_locked(&(l)->rtmutex)
 158
 159#define __mutex_init(mutex, name, key)                  \
 160do {                                                    \
 161        rt_mutex_base_init(&(mutex)->rtmutex);          \
 162        __mutex_rt_init((mutex), name, key);            \
 163} while (0)
 164
 165#define mutex_init(mutex)                               \
 166do {                                                    \
 167        static struct lock_class_key __key;             \
 168                                                        \
 169        __mutex_init((mutex), #mutex, &__key);          \
 170} while (0)
 171#endif /* CONFIG_PREEMPT_RT */
 172
 173/*
 174 * See kernel/locking/mutex.c for detailed documentation of these APIs.
 175 * Also see Documentation/locking/mutex-design.rst.
 176 */
 177#ifdef CONFIG_DEBUG_LOCK_ALLOC
 178extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
 179extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
 180
 181extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
 182                                        unsigned int subclass);
 183extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
 184                                        unsigned int subclass);
 185extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
 186
 187#define mutex_lock(lock) mutex_lock_nested(lock, 0)
 188#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
 189#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
 190#define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
 191
 192#define mutex_lock_nest_lock(lock, nest_lock)                           \
 193do {                                                                    \
 194        typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
 195        _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);             \
 196} while (0)
 197
 198#else
 199extern void mutex_lock(struct mutex *lock);
 200extern int __must_check mutex_lock_interruptible(struct mutex *lock);
 201extern int __must_check mutex_lock_killable(struct mutex *lock);
 202extern void mutex_lock_io(struct mutex *lock);
 203
 204# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
 205# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
 206# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
 207# define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
 208# define mutex_lock_io_nested(lock, subclass) mutex_lock_io(lock)
 209#endif
 210
 211/*
 212 * NOTE: mutex_trylock() follows the spin_trylock() convention,
 213 *       not the down_trylock() convention!
 214 *
 215 * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
 216 */
 217extern int mutex_trylock(struct mutex *lock);
 218extern void mutex_unlock(struct mutex *lock);
 219
 220extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
 221
 222#endif /* __LINUX_MUTEX_H */
 223