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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 <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 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
163 
164 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
165 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
166 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
167 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
168 
169 #define mutex_lock_nest_lock(lock, nest_lock)                           \
170 do {                                                                    \
171         typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
172         _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);             \
173 } while (0)
174 
175 #else
176 extern void mutex_lock(struct mutex *lock);
177 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
178 extern int __must_check mutex_lock_killable(struct mutex *lock);
179 extern void mutex_lock_io(struct mutex *lock);
180 
181 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
182 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
183 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
184 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
185 # define mutex_lock_io_nested(lock, subclass) mutex_lock(lock)
186 #endif
187 
188 /*
189  * NOTE: mutex_trylock() follows the spin_trylock() convention,
190  *       not the down_trylock() convention!
191  *
192  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
193  */
194 extern int mutex_trylock(struct mutex *lock);
195 extern void mutex_unlock(struct mutex *lock);
196 
197 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
198 
199 /*
200  * These values are chosen such that FAIL and SUCCESS match the
201  * values of the regular mutex_trylock().
202  */
203 enum mutex_trylock_recursive_enum {
204         MUTEX_TRYLOCK_FAILED    = 0,
205         MUTEX_TRYLOCK_SUCCESS   = 1,
206         MUTEX_TRYLOCK_RECURSIVE,
207 };
208 
209 /**
210  * mutex_trylock_recursive - trylock variant that allows recursive locking
211  * @lock: mutex to be locked
212  *
213  * This function should not be used, _ever_. It is purely for hysterical GEM
214  * raisins, and once those are gone this will be removed.
215  *
216  * Returns:
217  *  MUTEX_TRYLOCK_FAILED    - trylock failed,
218  *  MUTEX_TRYLOCK_SUCCESS   - lock acquired,
219  *  MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
220  */
221 static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
222 mutex_trylock_recursive(struct mutex *lock)
223 {
224         if (unlikely(__mutex_owner(lock) == current))
225                 return MUTEX_TRYLOCK_RECURSIVE;
226 
227         return mutex_trylock(lock);
228 }
229 
230 #endif /* __LINUX_MUTEX_H */
231 

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