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 <linux/list.h>
  14#include <linux/spinlock_types.h>
  15#include <linux/linkage.h>
  16#include <linux/lockdep.h>
  17
  18#include <asm/atomic.h>
  19
  20/*
  21 * Simple, straightforward mutexes with strict semantics:
  22 *
  23 * - only one task can hold the mutex at a time
  24 * - only the owner can unlock the mutex
  25 * - multiple unlocks are not permitted
  26 * - recursive locking is not permitted
  27 * - a mutex object must be initialized via the API
  28 * - a mutex object must not be initialized via memset or copying
  29 * - task may not exit with mutex held
  30 * - memory areas where held locks reside must not be freed
  31 * - held mutexes must not be reinitialized
  32 * - mutexes may not be used in hardware or software interrupt
  33 *   contexts such as tasklets and timers
  34 *
  35 * These semantics are fully enforced when DEBUG_MUTEXES is
  36 * enabled. Furthermore, besides enforcing the above rules, the mutex
  37 * debugging code also implements a number of additional features
  38 * that make lock debugging easier and faster:
  39 *
  40 * - uses symbolic names of mutexes, whenever they are printed in debug output
  41 * - point-of-acquire tracking, symbolic lookup of function names
  42 * - list of all locks held in the system, printout of them
  43 * - owner tracking
  44 * - detects self-recursing locks and prints out all relevant info
  45 * - detects multi-task circular deadlocks and prints out all affected
  46 *   locks and tasks (and only those tasks)
  47 */
  48struct mutex {
  49        /* 1: unlocked, 0: locked, negative: locked, possible waiters */
  50        atomic_t                count;
  51        spinlock_t              wait_lock;
  52        struct list_head        wait_list;
  53#ifdef CONFIG_DEBUG_MUTEXES
  54        struct thread_info      *owner;
  55        const char              *name;
  56        void                    *magic;
  57#endif
  58#ifdef CONFIG_DEBUG_LOCK_ALLOC
  59        struct lockdep_map      dep_map;
  60#endif
  61};
  62
  63/*
  64 * This is the control structure for tasks blocked on mutex,
  65 * which resides on the blocked task's kernel stack:
  66 */
  67struct mutex_waiter {
  68        struct list_head        list;
  69        struct task_struct      *task;
  70#ifdef CONFIG_DEBUG_MUTEXES
  71        struct mutex            *lock;
  72        void                    *magic;
  73#endif
  74};
  75
  76#ifdef CONFIG_DEBUG_MUTEXES
  77# include <linux/mutex-debug.h>
  78#else
  79# define __DEBUG_MUTEX_INITIALIZER(lockname)
  80# define mutex_init(mutex) \
  81do {                                                    \
  82        static struct lock_class_key __key;             \
  83                                                        \
  84        __mutex_init((mutex), #mutex, &__key);          \
  85} while (0)
  86# define mutex_destroy(mutex)                           do { } while (0)
  87#endif
  88
  89#ifdef CONFIG_DEBUG_LOCK_ALLOC
  90# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
  91                , .dep_map = { .name = #lockname }
  92#else
  93# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
  94#endif
  95
  96#define __MUTEX_INITIALIZER(lockname) \
  97                { .count = ATOMIC_INIT(1) \
  98                , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
  99                , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
 100                __DEBUG_MUTEX_INITIALIZER(lockname) \
 101                __DEP_MAP_MUTEX_INITIALIZER(lockname) }
 102
 103#define DEFINE_MUTEX(mutexname) \
 104        struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 105
 106extern void __mutex_init(struct mutex *lock, const char *name,
 107                         struct lock_class_key *key);
 108
 109/**
 110 * mutex_is_locked - is the mutex locked
 111 * @lock: the mutex to be queried
 112 *
 113 * Returns 1 if the mutex is locked, 0 if unlocked.
 114 */
 115static inline int fastcall mutex_is_locked(struct mutex *lock)
 116{
 117        return atomic_read(&lock->count) != 1;
 118}
 119
 120/*
 121 * See kernel/mutex.c for detailed documentation of these APIs.
 122 * Also see Documentation/mutex-design.txt.
 123 */
 124#ifdef CONFIG_DEBUG_LOCK_ALLOC
 125extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
 126extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
 127                                        unsigned int subclass);
 128
 129#define mutex_lock(lock) mutex_lock_nested(lock, 0)
 130#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
 131#else
 132extern void fastcall mutex_lock(struct mutex *lock);
 133extern int __must_check fastcall mutex_lock_interruptible(struct mutex *lock);
 134
 135# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
 136# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
 137#endif
 138
 139/*
 140 * NOTE: mutex_trylock() follows the spin_trylock() convention,
 141 *       not the down_trylock() convention!
 142 */
 143extern int fastcall mutex_trylock(struct mutex *lock);
 144extern void fastcall mutex_unlock(struct mutex *lock);
 145
 146#endif
 147