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TOMOYO Linux Cross Reference
Linux/include/linux/mutex.h

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  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@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 <linux/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 #if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP)
 54         struct task_struct      *owner;
 55 #endif
 56 #ifdef CONFIG_DEBUG_MUTEXES
 57         const char              *name;
 58         void                    *magic;
 59 #endif
 60 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 61         struct lockdep_map      dep_map;
 62 #endif
 63 };
 64 
 65 /*
 66  * This is the control structure for tasks blocked on mutex,
 67  * which resides on the blocked task's kernel stack:
 68  */
 69 struct mutex_waiter {
 70         struct list_head        list;
 71         struct task_struct      *task;
 72 #ifdef CONFIG_DEBUG_MUTEXES
 73         void                    *magic;
 74 #endif
 75 };
 76 
 77 #ifdef CONFIG_DEBUG_MUTEXES
 78 # include <linux/mutex-debug.h>
 79 #else
 80 # define __DEBUG_MUTEX_INITIALIZER(lockname)
 81 /**
 82  * mutex_init - initialize the mutex
 83  * @mutex: the mutex to be initialized
 84  *
 85  * Initialize the mutex to unlocked state.
 86  *
 87  * It is not allowed to initialize an already locked mutex.
 88  */
 89 # define mutex_init(mutex) \
 90 do {                                                    \
 91         static struct lock_class_key __key;             \
 92                                                         \
 93         __mutex_init((mutex), #mutex, &__key);          \
 94 } while (0)
 95 static inline void mutex_destroy(struct mutex *lock) {}
 96 #endif
 97 
 98 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 99 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
100                 , .dep_map = { .name = #lockname }
101 #else
102 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
103 #endif
104 
105 #define __MUTEX_INITIALIZER(lockname) \
106                 { .count = ATOMIC_INIT(1) \
107                 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
108                 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
109                 __DEBUG_MUTEX_INITIALIZER(lockname) \
110                 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
111 
112 #define DEFINE_MUTEX(mutexname) \
113         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
114 
115 extern void __mutex_init(struct mutex *lock, const char *name,
116                          struct lock_class_key *key);
117 
118 /**
119  * mutex_is_locked - is the mutex locked
120  * @lock: the mutex to be queried
121  *
122  * Returns 1 if the mutex is locked, 0 if unlocked.
123  */
124 static inline int mutex_is_locked(struct mutex *lock)
125 {
126         return atomic_read(&lock->count) != 1;
127 }
128 
129 /*
130  * See kernel/mutex.c for detailed documentation of these APIs.
131  * Also see Documentation/mutex-design.txt.
132  */
133 #ifdef CONFIG_DEBUG_LOCK_ALLOC
134 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
135 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
136 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
137                                         unsigned int subclass);
138 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
139                                         unsigned int subclass);
140 
141 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
142 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
143 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
144 
145 #define mutex_lock_nest_lock(lock, nest_lock)                           \
146 do {                                                                    \
147         typecheck(struct lockdep_map *, &(nest_lock)->dep_map);         \
148         _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);             \
149 } while (0)
150 
151 #else
152 extern void mutex_lock(struct mutex *lock);
153 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
154 extern int __must_check mutex_lock_killable(struct mutex *lock);
155 
156 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
157 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
158 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
159 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
160 #endif
161 
162 /*
163  * NOTE: mutex_trylock() follows the spin_trylock() convention,
164  *       not the down_trylock() convention!
165  *
166  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
167  */
168 extern int mutex_trylock(struct mutex *lock);
169 extern void mutex_unlock(struct mutex *lock);
170 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
171 
172 #ifndef CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX
173 #define arch_mutex_cpu_relax()  cpu_relax()
174 #endif
175 
176 #endif
177 

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