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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#include <linux/cleanup.h>
23
24#ifdef CONFIG_DEBUG_LOCK_ALLOC
25# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
26 , .dep_map = { \
27 .name = #lockname, \
28 .wait_type_inner = LD_WAIT_SLEEP, \
29 }
30#else
31# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
32#endif
33
34#ifndef CONFIG_PREEMPT_RT
35
36/*
37 * Simple, straightforward mutexes with strict semantics:
38 *
39 * - only one task can hold the mutex at a time
40 * - only the owner can unlock the mutex
41 * - multiple unlocks are not permitted
42 * - recursive locking is not permitted
43 * - a mutex object must be initialized via the API
44 * - a mutex object must not be initialized via memset or copying
45 * - task may not exit with mutex held
46 * - memory areas where held locks reside must not be freed
47 * - held mutexes must not be reinitialized
48 * - mutexes may not be used in hardware or software interrupt
49 * contexts such as tasklets and timers
50 *
51 * These semantics are fully enforced when DEBUG_MUTEXES is
52 * enabled. Furthermore, besides enforcing the above rules, the mutex
53 * debugging code also implements a number of additional features
54 * that make lock debugging easier and faster:
55 *
56 * - uses symbolic names of mutexes, whenever they are printed in debug output
57 * - point-of-acquire tracking, symbolic lookup of function names
58 * - list of all locks held in the system, printout of them
59 * - owner tracking
60 * - detects self-recursing locks and prints out all relevant info
61 * - detects multi-task circular deadlocks and prints out all affected
62 * locks and tasks (and only those tasks)
63 */
64struct mutex {
65 atomic_long_t owner;
66 raw_spinlock_t wait_lock;
67#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
68 struct optimistic_spin_queue osq; /* Spinner MCS lock */
69#endif
70 struct list_head wait_list;
71#ifdef CONFIG_DEBUG_MUTEXES
72 void *magic;
73#endif
74#ifdef CONFIG_DEBUG_LOCK_ALLOC
75 struct lockdep_map dep_map;
76#endif
77};
78
79#ifdef CONFIG_DEBUG_MUTEXES
80
81#define __DEBUG_MUTEX_INITIALIZER(lockname) \
82 , .magic = &lockname
83
84extern void mutex_destroy(struct mutex *lock);
85
86#else
87
88# define __DEBUG_MUTEX_INITIALIZER(lockname)
89
90static inline void mutex_destroy(struct mutex *lock) {}
91
92#endif
93
94/**
95 * mutex_init - initialize the mutex
96 * @mutex: the mutex to be initialized
97 *
98 * Initialize the mutex to unlocked state.
99 *
100 * It is not allowed to initialize an already locked mutex.
101 */
102#define mutex_init(mutex) \
103do { \
104 static struct lock_class_key __key; \
105 \
106 __mutex_init((mutex), #mutex, &__key); \
107} while (0)
108
109#define __MUTEX_INITIALIZER(lockname) \
110 { .owner = ATOMIC_LONG_INIT(0) \
111 , .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
112 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
113 __DEBUG_MUTEX_INITIALIZER(lockname) \
114 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
115
116#define DEFINE_MUTEX(mutexname) \
117 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
118
119extern void __mutex_init(struct mutex *lock, const char *name,
120 struct lock_class_key *key);
121
122/**
123 * mutex_is_locked - is the mutex locked
124 * @lock: the mutex to be queried
125 *
126 * Returns true if the mutex is locked, false if unlocked.
127 */
128extern bool mutex_is_locked(struct mutex *lock);
129
130#else /* !CONFIG_PREEMPT_RT */
131/*
132 * Preempt-RT variant based on rtmutexes.
133 */
134#include <linux/rtmutex.h>
135
136struct mutex {
137 struct rt_mutex_base rtmutex;
138#ifdef CONFIG_DEBUG_LOCK_ALLOC
139 struct lockdep_map dep_map;
140#endif
141};
142
143#define __MUTEX_INITIALIZER(mutexname) \
144{ \
145 .rtmutex = __RT_MUTEX_BASE_INITIALIZER(mutexname.rtmutex) \
146 __DEP_MAP_MUTEX_INITIALIZER(mutexname) \
147}
148
149#define DEFINE_MUTEX(mutexname) \
150 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
151
152extern void __mutex_rt_init(struct mutex *lock, const char *name,
153 struct lock_class_key *key);
154extern int mutex_trylock(struct mutex *lock);
155
156static inline void mutex_destroy(struct mutex *lock) { }
157
158#define mutex_is_locked(l) rt_mutex_base_is_locked(&(l)->rtmutex)
159
160#define __mutex_init(mutex, name, key) \
161do { \
162 rt_mutex_base_init(&(mutex)->rtmutex); \
163 __mutex_rt_init((mutex), name, key); \
164} while (0)
165
166#define mutex_init(mutex) \
167do { \
168 static struct lock_class_key __key; \
169 \
170 __mutex_init((mutex), #mutex, &__key); \
171} while (0)
172#endif /* CONFIG_PREEMPT_RT */
173
174/*
175 * See kernel/locking/mutex.c for detailed documentation of these APIs.
176 * Also see Documentation/locking/mutex-design.rst.
177 */
178#ifdef CONFIG_DEBUG_LOCK_ALLOC
179extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
180extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
181
182extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
183 unsigned int subclass);
184extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
185 unsigned int subclass);
186extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
187
188#define mutex_lock(lock) mutex_lock_nested(lock, 0)
189#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
190#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
191#define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
192
193#define mutex_lock_nest_lock(lock, nest_lock) \
194do { \
195 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
196 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \
197} while (0)
198
199#else
200extern void mutex_lock(struct mutex *lock);
201extern int __must_check mutex_lock_interruptible(struct mutex *lock);
202extern int __must_check mutex_lock_killable(struct mutex *lock);
203extern void mutex_lock_io(struct mutex *lock);
204
205# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
206# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
207# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
208# define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
209# define mutex_lock_io_nested(lock, subclass) mutex_lock_io(lock)
210#endif
211
212/*
213 * NOTE: mutex_trylock() follows the spin_trylock() convention,
214 * not the down_trylock() convention!
215 *
216 * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
217 */
218extern int mutex_trylock(struct mutex *lock);
219extern void mutex_unlock(struct mutex *lock);
220
221extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
222
223DEFINE_GUARD(mutex, struct mutex *, mutex_lock(_T), mutex_unlock(_T))
224DEFINE_FREE(mutex, struct mutex *, if (_T) mutex_unlock(_T))
225
226#endif /* __LINUX_MUTEX_H */