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

source code of linux/include/linux/mutex.h