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 <[email protected]> 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 */ 48 struct 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 */ 67 struct 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) \ 81 do { \ 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) 105 106 extern 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 */ 115 static inline int 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 125 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 126 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, 127 unsigned int subclass); 128 extern int __must_check mutex_lock_killable_nested(struct mutex *lock, 129 unsigned int subclass); 130 131 #define mutex_lock(lock) mutex_lock_nested(lock, 0) 132 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) 133 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) 134 #else 135 extern void mutex_lock(struct mutex *lock); 136 extern int __must_check mutex_lock_interruptible(struct mutex *lock); 137 extern int __must_check mutex_lock_killable(struct mutex *lock); 138 139 # define mutex_lock_nested(lock, subclass) mutex_lock(lock) 140 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) 141 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) 142 #endif 143 144 /* 145 * NOTE: mutex_trylock() follows the spin_trylock() convention, 146 * not the down_trylock() convention! 147 */ 148 extern int mutex_trylock(struct mutex *lock); 149 extern void mutex_unlock(struct mutex *lock); 150 151 #endif 152