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 #include <linux/osq_lock.h> 21 #include <linux/debug_locks.h> 22 23 /* 24 * Simple, straightforward mutexes with strict semantics: 25 * 26 * - only one task can hold the mutex at a time 27 * - only the owner can unlock the mutex 28 * - multiple unlocks are not permitted 29 * - recursive locking is not permitted 30 * - a mutex object must be initialized via the API 31 * - a mutex object must not be initialized via memset or copying 32 * - task may not exit with mutex held 33 * - memory areas where held locks reside must not be freed 34 * - held mutexes must not be reinitialized 35 * - mutexes may not be used in hardware or software interrupt 36 * contexts such as tasklets and timers 37 * 38 * These semantics are fully enforced when DEBUG_MUTEXES is 39 * enabled. Furthermore, besides enforcing the above rules, the mutex 40 * debugging code also implements a number of additional features 41 * that make lock debugging easier and faster: 42 * 43 * - uses symbolic names of mutexes, whenever they are printed in debug output 44 * - point-of-acquire tracking, symbolic lookup of function names 45 * - list of all locks held in the system, printout of them 46 * - owner tracking 47 * - detects self-recursing locks and prints out all relevant info 48 * - detects multi-task circular deadlocks and prints out all affected 49 * locks and tasks (and only those tasks) 50 */ 51 struct mutex { 52 atomic_long_t owner; 53 spinlock_t wait_lock; 54 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER 55 struct optimistic_spin_queue osq; /* Spinner MCS lock */ 56 #endif 57 struct list_head wait_list; 58 #ifdef CONFIG_DEBUG_MUTEXES 59 void *magic; 60 #endif 61 #ifdef CONFIG_DEBUG_LOCK_ALLOC 62 struct lockdep_map dep_map; 63 #endif 64 }; 65 66 static inline struct task_struct *__mutex_owner(struct mutex *lock) 67 { 68 return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x03); 69 } 70 71 /* 72 * This is the control structure for tasks blocked on mutex, 73 * which resides on the blocked task's kernel stack: 74 */ 75 struct mutex_waiter { 76 struct list_head list; 77 struct task_struct *task; 78 #ifdef CONFIG_DEBUG_MUTEXES 79 void *magic; 80 #endif 81 }; 82 83 #ifdef CONFIG_DEBUG_MUTEXES 84 85 #define __DEBUG_MUTEX_INITIALIZER(lockname) \ 86 , .magic = &lockname 87 88 extern void mutex_destroy(struct mutex *lock); 89 90 #else 91 92 # define __DEBUG_MUTEX_INITIALIZER(lockname) 93 94 static inline void mutex_destroy(struct mutex *lock) {} 95 96 #endif 97 98 /** 99 * mutex_init - initialize the mutex 100 * @mutex: the mutex to be initialized 101 * 102 * Initialize the mutex to unlocked state. 103 * 104 * It is not allowed to initialize an already locked mutex. 105 */ 106 #define mutex_init(mutex) \ 107 do { \ 108 static struct lock_class_key __key; \ 109 \ 110 __mutex_init((mutex), #mutex, &__key); \ 111 } while (0) 112 113 #ifdef CONFIG_DEBUG_LOCK_ALLOC 114 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ 115 , .dep_map = { .name = #lockname } 116 #else 117 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) 118 #endif 119 120 #define __MUTEX_INITIALIZER(lockname) \ 121 { .owner = ATOMIC_LONG_INIT(0) \ 122 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \ 123 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ 124 __DEBUG_MUTEX_INITIALIZER(lockname) \ 125 __DEP_MAP_MUTEX_INITIALIZER(lockname) } 126 127 #define DEFINE_MUTEX(mutexname) \ 128 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) 129 130 extern void __mutex_init(struct mutex *lock, const char *name, 131 struct lock_class_key *key); 132 133 /** 134 * mutex_is_locked - is the mutex locked 135 * @lock: the mutex to be queried 136 * 137 * Returns 1 if the mutex is locked, 0 if unlocked. 138 */ 139 static inline int mutex_is_locked(struct mutex *lock) 140 { 141 /* 142 * XXX think about spin_is_locked 143 */ 144 return __mutex_owner(lock) != NULL; 145 } 146 147 /* 148 * See kernel/locking/mutex.c for detailed documentation of these APIs. 149 * Also see Documentation/locking/mutex-design.txt. 150 */ 151 #ifdef CONFIG_DEBUG_LOCK_ALLOC 152 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 153 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); 154 155 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, 156 unsigned int subclass); 157 extern int __must_check mutex_lock_killable_nested(struct mutex *lock, 158 unsigned int subclass); 159 160 #define mutex_lock(lock) mutex_lock_nested(lock, 0) 161 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) 162 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) 163 164 #define mutex_lock_nest_lock(lock, nest_lock) \ 165 do { \ 166 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ 167 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \ 168 } while (0) 169 170 #else 171 extern void mutex_lock(struct mutex *lock); 172 extern int __must_check mutex_lock_interruptible(struct mutex *lock); 173 extern int __must_check mutex_lock_killable(struct mutex *lock); 174 175 # define mutex_lock_nested(lock, subclass) mutex_lock(lock) 176 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) 177 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) 178 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) 179 #endif 180 181 /* 182 * NOTE: mutex_trylock() follows the spin_trylock() convention, 183 * not the down_trylock() convention! 184 * 185 * Returns 1 if the mutex has been acquired successfully, and 0 on contention. 186 */ 187 extern int mutex_trylock(struct mutex *lock); 188 extern void mutex_unlock(struct mutex *lock); 189 190 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); 191 192 /* 193 * These values are chosen such that FAIL and SUCCESS match the 194 * values of the regular mutex_trylock(). 195 */ 196 enum mutex_trylock_recursive_enum { 197 MUTEX_TRYLOCK_FAILED = 0, 198 MUTEX_TRYLOCK_SUCCESS = 1, 199 MUTEX_TRYLOCK_RECURSIVE, 200 }; 201 202 /** 203 * mutex_trylock_recursive - trylock variant that allows recursive locking 204 * @lock: mutex to be locked 205 * 206 * This function should not be used, _ever_. It is purely for hysterical GEM 207 * raisins, and once those are gone this will be removed. 208 * 209 * Returns: 210 * MUTEX_TRYLOCK_FAILED - trylock failed, 211 * MUTEX_TRYLOCK_SUCCESS - lock acquired, 212 * MUTEX_TRYLOCK_RECURSIVE - we already owned the lock. 213 */ 214 static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum 215 mutex_trylock_recursive(struct mutex *lock) 216 { 217 if (unlikely(__mutex_owner(lock) == current)) 218 return MUTEX_TRYLOCK_RECURSIVE; 219 220 return mutex_trylock(lock); 221 } 222 223 #endif /* __LINUX_MUTEX_H */ 224