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