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 */
63 struct 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
83 extern void mutex_destroy(struct mutex *lock);
84
85 #else
86
87 # define __DEBUG_MUTEX_INITIALIZER(lockname)
88
mutex_destroy(struct mutex * lock)89 static 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) \
102 do { \
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
118 extern 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 */
127 extern 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
135 struct 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
151 extern void __mutex_rt_init(struct mutex *lock, const char *name,
152 struct lock_class_key *key);
153 extern int mutex_trylock(struct mutex *lock);
154
mutex_destroy(struct mutex * lock)155 static 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) \
160 do { \
161 rt_mutex_base_init(&(mutex)->rtmutex); \
162 __mutex_rt_init((mutex), name, key); \
163 } while (0)
164
165 #define mutex_init(mutex) \
166 do { \
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
178 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
179 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
180
181 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
182 unsigned int subclass);
183 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
184 unsigned int subclass);
185 extern 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) \
193 do { \
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
199 extern void mutex_lock(struct mutex *lock);
200 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
201 extern int __must_check mutex_lock_killable(struct mutex *lock);
202 extern 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 */
217 extern int mutex_trylock(struct mutex *lock);
218 extern void mutex_unlock(struct mutex *lock);
219
220 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
221
222 #endif /* __LINUX_MUTEX_H */
223
