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 <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 21 /* 22 * Simple, straightforward mutexes with strict semantics: 23 * 24 * - only one task can hold the mutex at a time 25 * - only the owner can unlock the mutex 26 * - multiple unlocks are not permitted 27 * - recursive locking is not permitted 28 * - a mutex object must be initialized via the API 29 * - a mutex object must not be initialized via memset or copying 30 * - task may not exit with mutex held 31 * - memory areas where held locks reside must not be freed 32 * - held mutexes must not be reinitialized 33 * - mutexes may not be used in hardware or software interrupt 34 * contexts such as tasklets and timers 35 * 36 * These semantics are fully enforced when DEBUG_MUTEXES is 37 * enabled. Furthermore, besides enforcing the above rules, the mutex 38 * debugging code also implements a number of additional features 39 * that make lock debugging easier and faster: 40 * 41 * - uses symbolic names of mutexes, whenever they are printed in debug output 42 * - point-of-acquire tracking, symbolic lookup of function names 43 * - list of all locks held in the system, printout of them 44 * - owner tracking 45 * - detects self-recursing locks and prints out all relevant info 46 * - detects multi-task circular deadlocks and prints out all affected 47 * locks and tasks (and only those tasks) 48 */ 49 struct optimistic_spin_queue; 50 struct 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 */ 74 struct 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) \ 95 do { \ 96 static struct lock_class_key __key; \ 97 \ 98 __mutex_init((mutex), #mutex, &__key); \ 99 } while (0) 100 static 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) 119 120 extern 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 */ 129 static 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 139 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 140 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); 141 142 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, 143 unsigned int subclass); 144 extern 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) \ 152 do { \ 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 158 extern void mutex_lock(struct mutex *lock); 159 extern int __must_check mutex_lock_interruptible(struct mutex *lock); 160 extern 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 */ 174 extern int mutex_trylock(struct mutex *lock); 175 extern void mutex_unlock(struct mutex *lock); 176 177 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); 178 179 #ifndef arch_mutex_cpu_relax 180 # define arch_mutex_cpu_relax() cpu_relax() 181 #endif 182 183 #endif /* __LINUX_MUTEX_H */ 184