LXR linux/include/linux/mutex.h

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