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/rt_lock.h>
  16 #include <linux/linkage.h>
  17 #include <linux/lockdep.h>
  18
  19 #include <asm/atomic.h>
  20
  21 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  22 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
  23                 , .dep_map = { .name = #lockname }
  24 #else
  25 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
  26 #endif
  27
  28 #ifdef CONFIG_PREEMPT_RT
  29
  30 #include <linux/rtmutex.h>
  31
  32 struct mutex {
  33         struct rt_mutex         lock;
  34 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  35         struct lockdep_map      dep_map;
  36 #endif
  37 };
  38
  39
  40 #define __MUTEX_INITIALIZER(mutexname)                                  \
  41         {                                                               \
  42                 .lock = __RT_MUTEX_INITIALIZER(mutexname.lock)          \
  43                 __DEP_MAP_MUTEX_INITIALIZER(mutexname)                  \
  44         }
  45
  46 #define DEFINE_MUTEX(mutexname)                                         \
  47         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
  48
  49 extern void
  50 __mutex_init(struct mutex *lock, char *name, struct lock_class_key *key);
  51
  52 extern void __lockfunc _mutex_lock(struct mutex *lock);
  53 extern int __lockfunc _mutex_lock_interruptible(struct mutex *lock);
  54 extern int __lockfunc _mutex_lock_killable(struct mutex *lock);
  55 extern void __lockfunc _mutex_lock_nested(struct mutex *lock, int subclass);
  56 extern int __lockfunc _mutex_lock_interruptible_nested(struct mutex *lock, int subclass);
  57 extern int __lockfunc _mutex_lock_killable_nested(struct mutex *lock, int subclass);
  58 extern int __lockfunc _mutex_trylock(struct mutex *lock);
  59 extern void __lockfunc _mutex_unlock(struct mutex *lock);
  60
  61 #define mutex_is_locked(l)              rt_mutex_is_locked(&(l)->lock)
  62 #define mutex_lock(l)                   _mutex_lock(l)
  63 #define mutex_lock_interruptible(l)     _mutex_lock_interruptible(l)
  64 #define mutex_lock_killable(l)          _mutex_lock_killable(l)
  65 #define mutex_trylock(l)                _mutex_trylock(l)
  66 #define mutex_unlock(l)                 _mutex_unlock(l)
  67 #define mutex_destroy(l)                rt_mutex_destroy(&(l)->lock)
  68
  69 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  70 # define mutex_lock_nested(l, s)        _mutex_lock_nested(l, s)
  71 # define mutex_lock_interruptible_nested(l, s) \
  72                                         _mutex_lock_interruptible_nested(l, s)
  73 # define mutex_lock_killable_nested(l, s) \
  74                                         _mutex_lock_killable_nested(l, s)
  75 #else
  76 # define mutex_lock_nested(l, s)        _mutex_lock(l)
  77 # define mutex_lock_interruptible_nested(l, s) \
  78                                         _mutex_lock_interruptible(l)
  79 # define mutex_lock_killable_nested(l, s) \
  80                                         _mutex_lock_killable(l)
  81 #endif
  82
  83 # define mutex_init(mutex)                              \
  84 do {                                                    \
  85         static struct lock_class_key __key;             \
  86                                                         \
  87         __mutex_init((mutex), #mutex, &__key);          \
  88 } while (0)
  89
  90 #else /* PREEMPT_RT */
  91
  92 /*
  93  * Simple, straightforward mutexes with strict semantics:
  94  *
  95  * - only one task can hold the mutex at a time
  96  * - only the owner can unlock the mutex
  97  * - multiple unlocks are not permitted
  98  * - recursive locking is not permitted
  99  * - a mutex object must be initialized via the API
 100  * - a mutex object must not be initialized via memset or copying
 101  * - task may not exit with mutex held
 102  * - memory areas where held locks reside must not be freed
 103  * - held mutexes must not be reinitialized
 104  * - mutexes may not be used in hardware or software interrupt
 105  *   contexts such as tasklets and timers
 106  *
 107  * These semantics are fully enforced when DEBUG_MUTEXES is
 108  * enabled. Furthermore, besides enforcing the above rules, the mutex
 109  * debugging code also implements a number of additional features
 110  * that make lock debugging easier and faster:
 111  *
 112  * - uses symbolic names of mutexes, whenever they are printed in debug output
 113  * - point-of-acquire tracking, symbolic lookup of function names
 114  * - list of all locks held in the system, printout of them
 115  * - owner tracking
 116  * - detects self-recursing locks and prints out all relevant info
 117  * - detects multi-task circular deadlocks and prints out all affected
 118  *   locks and tasks (and only those tasks)
 119  */
 120 struct mutex {
 121         /* 1: unlocked, 0: locked, negative: locked, possible waiters */
 122         atomic_t                count;
 123         spinlock_t              wait_lock;
 124         struct list_head        wait_list;
 125 #if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP)
 126         struct thread_info      *owner;
 127 #endif
 128 #ifdef CONFIG_DEBUG_MUTEXES
 129         const char              *name;
 130         void                    *magic;
 131 #endif
 132 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 133         struct lockdep_map      dep_map;
 134 #endif
 135 };
 136
 137 /*
 138  * This is the control structure for tasks blocked on mutex,
 139  * which resides on the blocked task's kernel stack:
 140  */
 141 struct mutex_waiter {
 142         struct list_head        list;
 143         struct task_struct      *task;
 144 #ifdef CONFIG_DEBUG_MUTEXES
 145         void                    *magic;
 146 #endif
 147 };
 148
 149 #ifdef CONFIG_DEBUG_MUTEXES
 150 # include <linux/mutex-debug.h>
 151 #else
 152 # define __DEBUG_MUTEX_INITIALIZER(lockname)
 153 # define mutex_init(mutex) \
 154 do {                                                    \
 155         static struct lock_class_key __key;             \
 156                                                         \
 157         __mutex_init((mutex), #mutex, &__key);          \
 158 } while (0)
 159 # define mutex_destroy(mutex)                           do { } while (0)
 160 #endif
 161
 162 #define __MUTEX_INITIALIZER(lockname) \
 163                 { .count = ATOMIC_INIT(1) \
 164                 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
 165                 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
 166                 __DEBUG_MUTEX_INITIALIZER(lockname) \
 167                 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
 168
 169 #define DEFINE_MUTEX(mutexname) \
 170         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 171
 172 extern void __mutex_init(struct mutex *lock, const char *name,
 173                          struct lock_class_key *key);
 174
 175 /**
 176  * mutex_is_locked - is the mutex locked
 177  * @lock: the mutex to be queried
 178  *
 179  * Returns 1 if the mutex is locked, 0 if unlocked.
 180  */
 181 static inline int mutex_is_locked(struct mutex *lock)
 182 {
 183         return atomic_read(&lock->count) != 1;
 184 }
 185
 186 /*
 187  * See kernel/mutex.c for detailed documentation of these APIs.
 188  * Also see Documentation/mutex-design.txt.
 189  */
 190 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 191 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
 192 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
 193                                         unsigned int subclass);
 194 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
 195                                         unsigned int subclass);
 196
 197 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
 198 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
 199 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
 200 #else
 201 extern void mutex_lock(struct mutex *lock);
 202 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
 203 extern int __must_check mutex_lock_killable(struct mutex *lock);
 204
 205 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
 206 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
 207 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
 208 #endif
 209
 210 /*
 211  * NOTE: mutex_trylock() follows the spin_trylock() convention,
 212  *       not the down_trylock() convention!
 213  *
 214  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
 215  */
 216 extern int mutex_trylock(struct mutex *lock);
 217 extern void mutex_unlock(struct mutex *lock);
 218
 219 #endif /* !PREEMPT_RT */
 220
 221 /**
 222  * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
 223  * @cnt: the atomic which we are to dec
 224  * @lock: the mutex to return holding if we dec to 0
 225  *
 226  * return true and hold lock if we dec to 0, return false otherwise
 227  */
 228 static inline int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
 229 {
 230         /* dec if we can't possibly hit 0 */
 231         if (atomic_add_unless(cnt, -1, 1))
 232                 return 0;
 233         /* we might hit 0, so take the lock */
 234         mutex_lock(lock);
 235         if (!atomic_dec_and_test(cnt)) {
 236                 /* when we actually did the dec, we didn't hit 0 */
 237                 mutex_unlock(lock);
 238                 return 0;
 239         }
 240         /* we hit 0, and we hold the lock */
 241         return 1;
 242 }
 243
 244 #endif