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 struct ww_acquire_ctx; 24 25 /* 26 * Simple, straightforward mutexes with strict semantics: 27 * 28 * - only one task can hold the mutex at a time 29 * - only the owner can unlock the mutex 30 * - multiple unlocks are not permitted 31 * - recursive locking is not permitted 32 * - a mutex object must be initialized via the API 33 * - a mutex object must not be initialized via memset or copying 34 * - task may not exit with mutex held 35 * - memory areas where held locks reside must not be freed 36 * - held mutexes must not be reinitialized 37 * - mutexes may not be used in hardware or software interrupt 38 * contexts such as tasklets and timers 39 * 40 * These semantics are fully enforced when DEBUG_MUTEXES is 41 * enabled. Furthermore, besides enforcing the above rules, the mutex 42 * debugging code also implements a number of additional features 43 * that make lock debugging easier and faster: 44 * 45 * - uses symbolic names of mutexes, whenever they are printed in debug output 46 * - point-of-acquire tracking, symbolic lookup of function names 47 * - list of all locks held in the system, printout of them 48 * - owner tracking 49 * - detects self-recursing locks and prints out all relevant info 50 * - detects multi-task circular deadlocks and prints out all affected 51 * locks and tasks (and only those tasks) 52 */ 53 struct mutex { 54 atomic_long_t owner; 55 spinlock_t wait_lock; 56 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER 57 struct optimistic_spin_queue osq; /* Spinner MCS lock */ 58 #endif 59 struct list_head wait_list; 60 #ifdef CONFIG_DEBUG_MUTEXES 61 void *magic; 62 #endif 63 #ifdef CONFIG_DEBUG_LOCK_ALLOC 64 struct lockdep_map dep_map; 65 #endif 66 }; 67 68 static inline struct task_struct *__mutex_owner(struct mutex *lock) 69 { 70 return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07); 71 } 72 73 /* 74 * This is the control structure for tasks blocked on mutex, 75 * which resides on the blocked task's kernel stack: 76 */ 77 struct mutex_waiter { 78 struct list_head list; 79 struct task_struct *task; 80 struct ww_acquire_ctx *ww_ctx; 81 #ifdef CONFIG_DEBUG_MUTEXES 82 void *magic; 83 #endif 84 }; 85 86 #ifdef CONFIG_DEBUG_MUTEXES 87 88 #define __DEBUG_MUTEX_INITIALIZER(lockname) \ 89 , .magic = &lockname 90 91 extern void mutex_destroy(struct mutex *lock); 92 93 #else 94 95 # define __DEBUG_MUTEX_INITIALIZER(lockname) 96 97 static inline void mutex_destroy(struct mutex *lock) {} 98 99 #endif 100 101 /** 102 * mutex_init - initialize the mutex 103 * @mutex: the mutex to be initialized 104 * 105 * Initialize the mutex to unlocked state. 106 * 107 * It is not allowed to initialize an already locked mutex. 108 */ 109 #define mutex_init(mutex) \ 110 do { \ 111 static struct lock_class_key __key; \ 112 \ 113 __mutex_init((mutex), #mutex, &__key); \ 114 } while (0) 115 116 #ifdef CONFIG_DEBUG_LOCK_ALLOC 117 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ 118 , .dep_map = { .name = #lockname } 119 #else 120 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) 121 #endif 122 123 #define __MUTEX_INITIALIZER(lockname) \ 124 { .owner = ATOMIC_LONG_INIT(0) \ 125 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \ 126 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ 127 __DEBUG_MUTEX_INITIALIZER(lockname) \ 128 __DEP_MAP_MUTEX_INITIALIZER(lockname) } 129 130 #define DEFINE_MUTEX(mutexname) \ 131 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) 132 133 extern void __mutex_init(struct mutex *lock, const char *name, 134 struct lock_class_key *key); 135 136 /** 137 * mutex_is_locked - is the mutex locked 138 * @lock: the mutex to be queried 139 * 140 * Returns 1 if the mutex is locked, 0 if unlocked. 141 */ 142 static inline int mutex_is_locked(struct mutex *lock) 143 { 144 /* 145 * XXX think about spin_is_locked 146 */ 147 return __mutex_owner(lock) != NULL; 148 } 149 150 /* 151 * See kernel/locking/mutex.c for detailed documentation of these APIs. 152 * Also see Documentation/locking/mutex-design.txt. 153 */ 154 #ifdef CONFIG_DEBUG_LOCK_ALLOC 155 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 156 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); 157 158 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, 159 unsigned int subclass); 160 extern int __must_check mutex_lock_killable_nested(struct mutex *lock, 161 unsigned int subclass); 162 163 #define mutex_lock(lock) mutex_lock_nested(lock, 0) 164 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) 165 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) 166 167 #define mutex_lock_nest_lock(lock, nest_lock) \ 168 do { \ 169 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ 170 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \ 171 } while (0) 172 173 #else 174 extern void mutex_lock(struct mutex *lock); 175 extern int __must_check mutex_lock_interruptible(struct mutex *lock); 176 extern int __must_check mutex_lock_killable(struct mutex *lock); 177 178 # define mutex_lock_nested(lock, subclass) mutex_lock(lock) 179 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) 180 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) 181 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) 182 #endif 183 184 /* 185 * NOTE: mutex_trylock() follows the spin_trylock() convention, 186 * not the down_trylock() convention! 187 * 188 * Returns 1 if the mutex has been acquired successfully, and 0 on contention. 189 */ 190 extern int mutex_trylock(struct mutex *lock); 191 extern void mutex_unlock(struct mutex *lock); 192 193 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); 194 195 /* 196 * These values are chosen such that FAIL and SUCCESS match the 197 * values of the regular mutex_trylock(). 198 */ 199 enum mutex_trylock_recursive_enum { 200 MUTEX_TRYLOCK_FAILED = 0, 201 MUTEX_TRYLOCK_SUCCESS = 1, 202 MUTEX_TRYLOCK_RECURSIVE, 203 }; 204 205 /** 206 * mutex_trylock_recursive - trylock variant that allows recursive locking 207 * @lock: mutex to be locked 208 * 209 * This function should not be used, _ever_. It is purely for hysterical GEM 210 * raisins, and once those are gone this will be removed. 211 * 212 * Returns: 213 * MUTEX_TRYLOCK_FAILED - trylock failed, 214 * MUTEX_TRYLOCK_SUCCESS - lock acquired, 215 * MUTEX_TRYLOCK_RECURSIVE - we already owned the lock. 216 */ 217 static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum 218 mutex_trylock_recursive(struct mutex *lock) 219 { 220 if (unlikely(__mutex_owner(lock) == current)) 221 return MUTEX_TRYLOCK_RECURSIVE; 222 223 return mutex_trylock(lock); 224 } 225 226 #endif /* __LINUX_MUTEX_H */ 227