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
mutex_destroy(struct mutex * lock)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_io(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