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