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

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  1 /* SPDX-License-Identifier: GPL-2.0 */
  2 /*
  3  * Mutexes: blocking mutual exclusion locks
  4  *
  5  * started by Ingo Molnar:
  6  *
  7  *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  8  *
  9  * This file contains the main data structure and API definitions.
 10  */
 11 #ifndef __LINUX_MUTEX_H
 12 #define __LINUX_MUTEX_H
 13 
 14 #include <asm/current.h>
 15 #include <linux/list.h>
 16 #include <linux/spinlock_types.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 /*
 69  * Internal helper function; C doesn't allow us to hide it :/
 70  *
 71  * DO NOT USE (outside of mutex code).
 72  */
 73 static inline struct task_struct *__mutex_owner(struct mutex *lock)
 74 {
 75         return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
 76 }
 77 
 78 /*
 79  * This is the control structure for tasks blocked on mutex,
 80  * which resides on the blocked task's kernel stack:
 81  */
 82 struct mutex_waiter {
 83         struct list_head        list;
 84         struct task_struct      *task;
 85         struct ww_acquire_ctx   *ww_ctx;
 86 #ifdef CONFIG_DEBUG_MUTEXES
 87         void                    *magic;
 88 #endif
 89 };
 90 
 91 #ifdef CONFIG_DEBUG_MUTEXES
 92 
 93 #define __DEBUG_MUTEX_INITIALIZER(lockname)                             \
 94         , .magic = &lockname
 95 
 96 extern void mutex_destroy(struct mutex *lock);
 97 
 98 #else
 99 
100 # define __DEBUG_MUTEX_INITIALIZER(lockname)
101 
102 static inline void mutex_destroy(struct mutex *lock) {}
103 
104 #endif
105 
106 /**
107  * mutex_init - initialize the mutex
108  * @mutex: the mutex to be initialized
109  *
110  * Initialize the mutex to unlocked state.
111  *
112  * It is not allowed to initialize an already locked mutex.
113  */
114 #define mutex_init(mutex)                                               \
115 do {                                                                    \
116         static struct lock_class_key __key;                             \
117                                                                         \
118         __mutex_init((mutex), #mutex, &__key);                          \
119 } while (0)
120 
121 #ifdef CONFIG_DEBUG_LOCK_ALLOC
122 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
123                 , .dep_map = { .name = #lockname }
124 #else
125 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
126 #endif
127 
128 #define __MUTEX_INITIALIZER(lockname) \
129                 { .owner = ATOMIC_LONG_INIT(0) \
130                 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
131                 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
132                 __DEBUG_MUTEX_INITIALIZER(lockname) \
133                 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
134 
135 #define DEFINE_MUTEX(mutexname) \
136         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
137 
138 extern void __mutex_init(struct mutex *lock, const char *name,
139                          struct lock_class_key *key);
140 
141 /**
142  * mutex_is_locked - is the mutex locked
143  * @lock: the mutex to be queried
144  *
145  * Returns true if the mutex is locked, false if unlocked.
146  */
147 static inline bool mutex_is_locked(struct mutex *lock)
148 {
149         return __mutex_owner(lock) != NULL;
150 }
151 
152 /*
153  * See kernel/locking/mutex.c for detailed documentation of these APIs.
154  * Also see Documentation/locking/mutex-design.txt.
155  */
156 #ifdef CONFIG_DEBUG_LOCK_ALLOC
157 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
158 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
159 
160 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
161                                         unsigned int subclass);
162 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
163                                         unsigned int subclass);
164 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
165 
166 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
167 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
168 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
169 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
170 
171 #define mutex_lock_nest_lock(lock, nest_lock)                           \
172 do {                                                                    \
173         typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
174         _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);             \
175 } while (0)
176 
177 #else
178 extern void mutex_lock(struct mutex *lock);
179 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
180 extern int __must_check mutex_lock_killable(struct mutex *lock);
181 extern void mutex_lock_io(struct mutex *lock);
182 
183 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
184 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
185 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
186 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
187 # define mutex_lock_io_nested(lock, subclass) mutex_lock(lock)
188 #endif
189 
190 /*
191  * NOTE: mutex_trylock() follows the spin_trylock() convention,
192  *       not the down_trylock() convention!
193  *
194  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
195  */
196 extern int mutex_trylock(struct mutex *lock);
197 extern void mutex_unlock(struct mutex *lock);
198 
199 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
200 
201 /*
202  * These values are chosen such that FAIL and SUCCESS match the
203  * values of the regular mutex_trylock().
204  */
205 enum mutex_trylock_recursive_enum {
206         MUTEX_TRYLOCK_FAILED    = 0,
207         MUTEX_TRYLOCK_SUCCESS   = 1,
208         MUTEX_TRYLOCK_RECURSIVE,
209 };
210 
211 /**
212  * mutex_trylock_recursive - trylock variant that allows recursive locking
213  * @lock: mutex to be locked
214  *
215  * This function should not be used, _ever_. It is purely for hysterical GEM
216  * raisins, and once those are gone this will be removed.
217  *
218  * Returns:
219  *  - MUTEX_TRYLOCK_FAILED    - trylock failed,
220  *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
221  *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
222  */
223 static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
224 mutex_trylock_recursive(struct mutex *lock)
225 {
226         if (unlikely(__mutex_owner(lock) == current))
227                 return MUTEX_TRYLOCK_RECURSIVE;
228 
229         return mutex_trylock(lock);
230 }
231 
232 #endif /* __LINUX_MUTEX_H */
233 

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