summaryrefslogtreecommitdiffstats
path: root/include/linux/mutex.h
blob: f25c13423bd4774d3d602d2ec7afb561a39614d5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Mutexes: blocking mutual exclusion locks
 *
 * started by Ingo Molnar:
 *
 *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 * This file contains the main data structure and API definitions.
 */
#ifndef __LINUX_MUTEX_H
#define __LINUX_MUTEX_H

#include <asm/current.h>
#include <linux/list.h>
#include <linux/spinlock_types.h>
#include <linux/linkage.h>
#include <linux/lockdep.h>
#include <linux/atomic.h>
#include <asm/processor.h>
#include <linux/osq_lock.h>
#include <linux/debug_locks.h>

struct ww_acquire_ctx;

/*
 * Simple, straightforward mutexes with strict semantics:
 *
 * - only one task can hold the mutex at a time
 * - only the owner can unlock the mutex
 * - multiple unlocks are not permitted
 * - recursive locking is not permitted
 * - a mutex object must be initialized via the API
 * - a mutex object must not be initialized via memset or copying
 * - task may not exit with mutex held
 * - memory areas where held locks reside must not be freed
 * - held mutexes must not be reinitialized
 * - mutexes may not be used in hardware or software interrupt
 *   contexts such as tasklets and timers
 *
 * These semantics are fully enforced when DEBUG_MUTEXES is
 * enabled. Furthermore, besides enforcing the above rules, the mutex
 * debugging code also implements a number of additional features
 * that make lock debugging easier and faster:
 *
 * - uses symbolic names of mutexes, whenever they are printed in debug output
 * - point-of-acquire tracking, symbolic lookup of function names
 * - list of all locks held in the system, printout of them
 * - owner tracking
 * - detects self-recursing locks and prints out all relevant info
 * - detects multi-task circular deadlocks and prints out all affected
 *   locks and tasks (and only those tasks)
 */
struct mutex {
	atomic_long_t		owner;
	spinlock_t		wait_lock;
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
	struct optimistic_spin_queue osq; /* Spinner MCS lock */
#endif
	struct list_head	wait_list;
#ifdef CONFIG_DEBUG_MUTEXES
	void			*magic;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	struct lockdep_map	dep_map;
#endif
};

static inline struct task_struct *__mutex_owner(struct mutex *lock)
{
	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
}

/*
 * This is the control structure for tasks blocked on mutex,
 * which resides on the blocked task's kernel stack:
 */
struct mutex_waiter {
	struct list_head	list;
	struct task_struct	*task;
	struct ww_acquire_ctx	*ww_ctx;
#ifdef CONFIG_DEBUG_MUTEXES
	void			*magic;
#endif
};

#ifdef CONFIG_DEBUG_MUTEXES

#define __DEBUG_MUTEX_INITIALIZER(lockname)				\
	, .magic = &lockname

extern void mutex_destroy(struct mutex *lock);

#else

# define __DEBUG_MUTEX_INITIALIZER(lockname)

static inline void mutex_destroy(struct mutex *lock) {}

#endif

/**
 * mutex_init - initialize the mutex
 * @mutex: the mutex to be initialized
 *
 * Initialize the mutex to unlocked state.
 *
 * It is not allowed to initialize an already locked mutex.
 */
#define mutex_init(mutex)						\
do {									\
	static struct lock_class_key __key;				\
									\
	__mutex_init((mutex), #mutex, &__key);				\
} while (0)

#ifdef CONFIG_DEBUG_LOCK_ALLOC
# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
		, .dep_map = { .name = #lockname }
#else
# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
#endif

#define __MUTEX_INITIALIZER(lockname) \
		{ .owner = ATOMIC_LONG_INIT(0) \
		, .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
		, .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
		__DEBUG_MUTEX_INITIALIZER(lockname) \
		__DEP_MAP_MUTEX_INITIALIZER(lockname) }

#define DEFINE_MUTEX(mutexname) \
	struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)

extern void __mutex_init(struct mutex *lock, const char *name,
			 struct lock_class_key *key);

/**
 * mutex_is_locked - is the mutex locked
 * @lock: the mutex to be queried
 *
 * Returns true if the mutex is locked, false if unlocked.
 */
static inline bool mutex_is_locked(struct mutex *lock)
{
	/*
	 * XXX think about spin_is_locked
	 */
	return __mutex_owner(lock) != NULL;
}

/*
 * See kernel/locking/mutex.c for detailed documentation of these APIs.
 * Also see Documentation/locking/mutex-design.txt.
 */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);

extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
					unsigned int subclass);
extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
					unsigned int subclass);
extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);

#define mutex_lock(lock) mutex_lock_nested(lock, 0)
#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
#define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)

#define mutex_lock_nest_lock(lock, nest_lock)				\
do {									\
	typecheck(struct lockdep_map *, &(nest_lock)->dep_map);	\
	_mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);		\
} while (0)

#else
extern void mutex_lock(struct mutex *lock);
extern int __must_check mutex_lock_interruptible(struct mutex *lock);
extern int __must_check mutex_lock_killable(struct mutex *lock);
extern void mutex_lock_io(struct mutex *lock);

# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
# define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
# define mutex_lock_io_nested(lock, subclass) mutex_lock(lock)
#endif

/*
 * NOTE: mutex_trylock() follows the spin_trylock() convention,
 *       not the down_trylock() convention!
 *
 * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
 */
extern int mutex_trylock(struct mutex *lock);
extern void mutex_unlock(struct mutex *lock);

extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);

/*
 * These values are chosen such that FAIL and SUCCESS match the
 * values of the regular mutex_trylock().
 */
enum mutex_trylock_recursive_enum {
	MUTEX_TRYLOCK_FAILED    = 0,
	MUTEX_TRYLOCK_SUCCESS   = 1,
	MUTEX_TRYLOCK_RECURSIVE,
};

/**
 * mutex_trylock_recursive - trylock variant that allows recursive locking
 * @lock: mutex to be locked
 *
 * This function should not be used, _ever_. It is purely for hysterical GEM
 * raisins, and once those are gone this will be removed.
 *
 * Returns:
 *  - MUTEX_TRYLOCK_FAILED    - trylock failed,
 *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
 *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
 */
static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
mutex_trylock_recursive(struct mutex *lock)
{
	if (unlikely(__mutex_owner(lock) == current))
		return MUTEX_TRYLOCK_RECURSIVE;

	return mutex_trylock(lock);
}

#endif /* __LINUX_MUTEX_H */
OpenPOWER on IntegriCloud