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