LXR linux/include/linux/mutex.h

   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
  23struct ww_class;
  24struct ww_acquire_ctx;
  25
  26/*
  27 * Simple, straightforward mutexes with strict semantics:
  28 *
  29 * - only one task can hold the mutex at a time
  30 * - only the owner can unlock the mutex
  31 * - multiple unlocks are not permitted
  32 * - recursive locking is not permitted
  33 * - a mutex object must be initialized via the API
  34 * - a mutex object must not be initialized via memset or copying
  35 * - task may not exit with mutex held
  36 * - memory areas where held locks reside must not be freed
  37 * - held mutexes must not be reinitialized
  38 * - mutexes may not be used in hardware or software interrupt
  39 *   contexts such as tasklets and timers
  40 *
  41 * These semantics are fully enforced when DEBUG_MUTEXES is
  42 * enabled. Furthermore, besides enforcing the above rules, the mutex
  43 * debugging code also implements a number of additional features
  44 * that make lock debugging easier and faster:
  45 *
  46 * - uses symbolic names of mutexes, whenever they are printed in debug output
  47 * - point-of-acquire tracking, symbolic lookup of function names
  48 * - list of all locks held in the system, printout of them
  49 * - owner tracking
  50 * - detects self-recursing locks and prints out all relevant info
  51 * - detects multi-task circular deadlocks and prints out all affected
  52 *   locks and tasks (and only those tasks)
  53 */
  54struct mutex {
  55        atomic_long_t           owner;
  56        spinlock_t              wait_lock;
  57#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
  58        struct optimistic_spin_queue osq; /* Spinner MCS lock */
  59#endif
  60        struct list_head        wait_list;
  61#ifdef CONFIG_DEBUG_MUTEXES
  62        void                    *magic;
  63#endif
  64#ifdef CONFIG_DEBUG_LOCK_ALLOC
  65        struct lockdep_map      dep_map;
  66#endif
  67};
  68
  69struct ww_mutex {
  70        struct mutex base;
  71        struct ww_acquire_ctx *ctx;
  72#ifdef CONFIG_DEBUG_MUTEXES
  73        struct ww_class *ww_class;
  74#endif
  75};
  76
  77/*
  78 * This is the control structure for tasks blocked on mutex,
  79 * which resides on the blocked task's kernel stack:
  80 */
  81struct mutex_waiter {
  82        struct list_head        list;
  83        struct task_struct      *task;
  84        struct ww_acquire_ctx   *ww_ctx;
  85#ifdef CONFIG_DEBUG_MUTEXES
  86        void                    *magic;
  87#endif
  88};
  89
  90#ifdef CONFIG_DEBUG_MUTEXES
  91
  92#define __DEBUG_MUTEX_INITIALIZER(lockname)                             \
  93        , .magic = &lockname
  94
  95extern void mutex_destroy(struct mutex *lock);
  96
  97#else
  98
  99# define __DEBUG_MUTEX_INITIALIZER(lockname)
 100
 101static inline void mutex_destroy(struct mutex *lock) {}
 102
 103#endif
 104
 105/**
 106 * mutex_init - initialize the mutex
 107 * @mutex: the mutex to be initialized
 108 *
 109 * Initialize the mutex to unlocked state.
 110 *
 111 * It is not allowed to initialize an already locked mutex.
 112 */
 113#define mutex_init(mutex)                                               \
 114do {                                                                    \
 115        static struct lock_class_key __key;                             \
 116                                                                        \
 117        __mutex_init((mutex), #mutex, &__key);                          \
 118} while (0)
 119
 120#ifdef CONFIG_DEBUG_LOCK_ALLOC
 121# define __DEP_MAP_MUTEX_INITIALIZER(lockname)                  \
 122                , .dep_map = {                                  \
 123                        .name = #lockname,                      \
 124                        .wait_type_inner = LD_WAIT_SLEEP,       \
 125                }
 126#else
 127# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
 128#endif
 129
 130#define __MUTEX_INITIALIZER(lockname) \
 131                { .owner = ATOMIC_LONG_INIT(0) \
 132                , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
 133                , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
 134                __DEBUG_MUTEX_INITIALIZER(lockname) \
 135                __DEP_MAP_MUTEX_INITIALIZER(lockname) }
 136
 137#define DEFINE_MUTEX(mutexname) \
 138        struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 139
 140extern void __mutex_init(struct mutex *lock, const char *name,
 141                         struct lock_class_key *key);
 142
 143/**
 144 * mutex_is_locked - is the mutex locked
 145 * @lock: the mutex to be queried
 146 *
 147 * Returns true if the mutex is locked, false if unlocked.
 148 */
 149extern bool mutex_is_locked(struct mutex *lock);
 150
 151/*
 152 * See kernel/locking/mutex.c for detailed documentation of these APIs.
 153 * Also see Documentation/locking/mutex-design.rst.
 154 */
 155#ifdef CONFIG_DEBUG_LOCK_ALLOC
 156extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
 157extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
 158
 159extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
 160                                        unsigned int subclass);
 161extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
 162                                        unsigned int subclass);
 163extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
 164
 165#define mutex_lock(lock) mutex_lock_nested(lock, 0)
 166#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
 167#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
 168#define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
 169
 170#define mutex_lock_nest_lock(lock, nest_lock)                           \
 171do {                                                                    \
 172        typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
 173        _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);             \
 174} while (0)
 175
 176#else
 177extern void mutex_lock(struct mutex *lock);
 178extern int __must_check mutex_lock_interruptible(struct mutex *lock);
 179extern int __must_check mutex_lock_killable(struct mutex *lock);
 180extern void mutex_lock_io(struct mutex *lock);
 181
 182# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
 183# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
 184# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
 185# define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
 186# define mutex_lock_io_nested(lock, subclass) mutex_lock_io(lock)
 187#endif
 188
 189/*
 190 * NOTE: mutex_trylock() follows the spin_trylock() convention,
 191 *       not the down_trylock() convention!
 192 *
 193 * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
 194 */
 195extern int mutex_trylock(struct mutex *lock);
 196extern void mutex_unlock(struct mutex *lock);
 197
 198extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
 199
 200#endif /* __LINUX_MUTEX_H */
 201