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