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 (at) 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/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 irq contexts 33 * 34 * These semantics are fully enforced when DEBUG_MUTEXES is 35 * enabled. Furthermore, besides enforcing the above rules, the mutex 36 * debugging code also implements a number of additional features 37 * that make lock debugging easier and faster: 38 * 39 * - uses symbolic names of mutexes, whenever they are printed in debug output 40 * - point-of-acquire tracking, symbolic lookup of function names 41 * - list of all locks held in the system, printout of them 42 * - owner tracking 43 * - detects self-recursing locks and prints out all relevant info 44 * - detects multi-task circular deadlocks and prints out all affected 45 * locks and tasks (and only those tasks) 46 */ 47 struct mutex { 48 /* 1: unlocked, 0: locked, negative: locked, possible waiters */ 49 atomic_t count; 50 spinlock_t wait_lock; 51 struct list_head wait_list; 52 #ifdef CONFIG_DEBUG_MUTEXES 53 struct thread_info *owner; 54 const char *name; 55 void *magic; 56 #endif 57 #ifdef CONFIG_DEBUG_LOCK_ALLOC 58 struct lockdep_map dep_map; 59 #endif 60 }; 61 62 /* 63 * This is the control structure for tasks blocked on mutex, 64 * which resides on the blocked task's kernel stack: 65 */ 66 struct mutex_waiter { 67 struct list_head list; 68 struct task_struct *task; 69 #ifdef CONFIG_DEBUG_MUTEXES 70 struct mutex *lock; 71 void *magic; 72 #endif 73 }; 74 75 #ifdef CONFIG_DEBUG_MUTEXES 76 # include <linux/mutex-debug.h> 77 #else 78 # define __DEBUG_MUTEX_INITIALIZER(lockname) 79 # define mutex_init(mutex) \ 80 do { \ 81 static struct lock_class_key __key; \ 82 \ 83 __mutex_init((mutex), #mutex, &__key); \ 84 } while (0) 85 # define mutex_destroy(mutex) do { } while (0) 86 #endif 87 88 #ifdef CONFIG_DEBUG_LOCK_ALLOC 89 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ 90 , .dep_map = { .name = #lockname } 91 #else 92 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) 93 #endif 94 95 #define __MUTEX_INITIALIZER(lockname) \ 96 { .count = ATOMIC_INIT(1) \ 97 , .wait_lock = SPIN_LOCK_UNLOCKED \ 98 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ 99 __DEBUG_MUTEX_INITIALIZER(lockname) \ 100 __DEP_MAP_MUTEX_INITIALIZER(lockname) } 101 102 #define DEFINE_MUTEX(mutexname) \ 103 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) 104 105 extern void __mutex_init(struct mutex *lock, const char *name, 106 struct lock_class_key *key); 107 108 /*** 109 * mutex_is_locked - is the mutex locked 110 * @lock: the mutex to be queried 111 * 112 * Returns 1 if the mutex is locked, 0 if unlocked. 113 */ 114 static inline int fastcall mutex_is_locked(struct mutex *lock) 115 { 116 return atomic_read(&lock->count) != 1; 117 } 118 119 /* 120 * See kernel/mutex.c for detailed documentation of these APIs. 121 * Also see Documentation/mutex-design.txt. 122 */ 123 extern void fastcall mutex_lock(struct mutex *lock); 124 extern int fastcall mutex_lock_interruptible(struct mutex *lock); 125 126 #ifdef CONFIG_DEBUG_LOCK_ALLOC 127 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 128 #else 129 # define mutex_lock_nested(lock, subclass) mutex_lock(lock) 130 #endif 131 132 /* 133 * NOTE: mutex_trylock() follows the spin_trylock() convention, 134 * not the down_trylock() convention! 135 */ 136 extern int fastcall mutex_trylock(struct mutex *lock); 137 extern void fastcall mutex_unlock(struct mutex *lock); 138 139 #endif 140
