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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 struct ww_class;
 69 struct ww_acquire_ctx;
 70 
 71 struct ww_mutex {
 72         struct mutex base;
 73         struct ww_acquire_ctx *ctx;
 74 #ifdef CONFIG_DEBUG_MUTEXES
 75         struct ww_class *ww_class;
 76 #endif
 77 };
 78 
 79 /*
 80  * This is the control structure for tasks blocked on mutex,
 81  * which resides on the blocked task's kernel stack:
 82  */
 83 struct mutex_waiter {
 84         struct list_head        list;
 85         struct task_struct      *task;
 86         struct ww_acquire_ctx   *ww_ctx;
 87 #ifdef CONFIG_DEBUG_MUTEXES
 88         void                    *magic;
 89 #endif
 90 };
 91 
 92 #ifdef CONFIG_DEBUG_MUTEXES
 93 
 94 #define __DEBUG_MUTEX_INITIALIZER(lockname)                             \
 95         , .magic = &lockname
 96 
 97 extern void mutex_destroy(struct mutex *lock);
 98 
 99 #else
100 
101 # define __DEBUG_MUTEX_INITIALIZER(lockname)
102 
103 static inline void mutex_destroy(struct mutex *lock) {}
104 
105 #endif
106 
107 /**
108  * mutex_init - initialize the mutex
109  * @mutex: the mutex to be initialized
110  *
111  * Initialize the mutex to unlocked state.
112  *
113  * It is not allowed to initialize an already locked mutex.
114  */
115 #define mutex_init(mutex)                                               \
116 do {                                                                    \
117         static struct lock_class_key __key;                             \
118                                                                         \
119         __mutex_init((mutex), #mutex, &__key);                          \
120 } while (0)
121 
122 #ifdef CONFIG_DEBUG_LOCK_ALLOC
123 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)                  \
124                 , .dep_map = {                                  \
125                         .name = #lockname,                      \
126                         .wait_type_inner = LD_WAIT_SLEEP,       \
127                 }
128 #else
129 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
130 #endif
131 
132 #define __MUTEX_INITIALIZER(lockname) \
133                 { .owner = ATOMIC_LONG_INIT(0) \
134                 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
135                 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
136                 __DEBUG_MUTEX_INITIALIZER(lockname) \
137                 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
138 
139 #define DEFINE_MUTEX(mutexname) \
140         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
141 
142 extern void __mutex_init(struct mutex *lock, const char *name,
143                          struct lock_class_key *key);
144 
145 /**
146  * mutex_is_locked - is the mutex locked
147  * @lock: the mutex to be queried
148  *
149  * Returns true if the mutex is locked, false if unlocked.
150  */
151 extern bool mutex_is_locked(struct mutex *lock);
152 
153 /*
154  * See kernel/locking/mutex.c for detailed documentation of these APIs.
155  * Also see Documentation/locking/mutex-design.rst.
156  */
157 #ifdef CONFIG_DEBUG_LOCK_ALLOC
158 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
159 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
160 
161 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
162                                         unsigned int subclass);
163 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
164                                         unsigned int subclass);
165 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
166 
167 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
168 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
169 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
170 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
171 
172 #define mutex_lock_nest_lock(lock, nest_lock)                           \
173 do {                                                                    \
174         typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
175         _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);             \
176 } while (0)
177 
178 #else
179 extern void mutex_lock(struct mutex *lock);
180 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
181 extern int __must_check mutex_lock_killable(struct mutex *lock);
182 extern void mutex_lock_io(struct mutex *lock);
183 
184 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
185 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
186 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
187 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
188 # define mutex_lock_io_nested(lock, subclass) mutex_lock(lock)
189 #endif
190 
191 /*
192  * NOTE: mutex_trylock() follows the spin_trylock() convention,
193  *       not the down_trylock() convention!
194  *
195  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
196  */
197 extern int mutex_trylock(struct mutex *lock);
198 extern void mutex_unlock(struct mutex *lock);
199 
200 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
201 
202 /*
203  * These values are chosen such that FAIL and SUCCESS match the
204  * values of the regular mutex_trylock().
205  */
206 enum mutex_trylock_recursive_enum {
207         MUTEX_TRYLOCK_FAILED    = 0,
208         MUTEX_TRYLOCK_SUCCESS   = 1,
209         MUTEX_TRYLOCK_RECURSIVE,
210 };
211 
212 /**
213  * mutex_trylock_recursive - trylock variant that allows recursive locking
214  * @lock: mutex to be locked
215  *
216  * This function should not be used, _ever_. It is purely for hysterical GEM
217  * raisins, and once those are gone this will be removed.
218  *
219  * Returns:
220  *  - MUTEX_TRYLOCK_FAILED    - trylock failed,
221  *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
222  *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
223  */
224 extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
225 mutex_trylock_recursive(struct mutex *lock);
226 
227 #endif /* __LINUX_MUTEX_H */
228 

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