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 struct ww_class;
24 struct 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 */
54 struct 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
69 struct 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 */
81 struct 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
95 extern void mutex_destroy(struct mutex *lock);
96
97 #else
98
99 # define __DEBUG_MUTEX_INITIALIZER(lockname)
100
mutex_destroy(struct mutex * lock)101 static 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) \
114 do { \
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
140 extern 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 */
149 extern 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
156 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
157 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
158
159 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
160 unsigned int subclass);
161 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
162 unsigned int subclass);
163 extern 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) \
171 do { \
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
177 extern void mutex_lock(struct mutex *lock);
178 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
179 extern int __must_check mutex_lock_killable(struct mutex *lock);
180 extern 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 */
195 extern int mutex_trylock(struct mutex *lock);
196 extern void mutex_unlock(struct mutex *lock);
197
198 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
199
200 #endif /* __LINUX_MUTEX_H */
201