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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 : :
23 : : struct ww_acquire_ctx;
24 : :
25 : : /*
26 : : * Simple, straightforward mutexes with strict semantics:
27 : : *
28 : : * - only one task can hold the mutex at a time
29 : : * - only the owner can unlock the mutex
30 : : * - multiple unlocks are not permitted
31 : : * - recursive locking is not permitted
32 : : * - a mutex object must be initialized via the API
33 : : * - a mutex object must not be initialized via memset or copying
34 : : * - task may not exit with mutex held
35 : : * - memory areas where held locks reside must not be freed
36 : : * - held mutexes must not be reinitialized
37 : : * - mutexes may not be used in hardware or software interrupt
38 : : * contexts such as tasklets and timers
39 : : *
40 : : * These semantics are fully enforced when DEBUG_MUTEXES is
41 : : * enabled. Furthermore, besides enforcing the above rules, the mutex
42 : : * debugging code also implements a number of additional features
43 : : * that make lock debugging easier and faster:
44 : : *
45 : : * - uses symbolic names of mutexes, whenever they are printed in debug output
46 : : * - point-of-acquire tracking, symbolic lookup of function names
47 : : * - list of all locks held in the system, printout of them
48 : : * - owner tracking
49 : : * - detects self-recursing locks and prints out all relevant info
50 : : * - detects multi-task circular deadlocks and prints out all affected
51 : : * locks and tasks (and only those tasks)
52 : : */
53 : : struct mutex {
54 : : atomic_long_t owner;
55 : : spinlock_t wait_lock;
56 : : #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
57 : : struct optimistic_spin_queue osq; /* Spinner MCS lock */
58 : : #endif
59 : : struct list_head wait_list;
60 : : #ifdef CONFIG_DEBUG_MUTEXES
61 : : void *magic;
62 : : #endif
63 : : #ifdef CONFIG_DEBUG_LOCK_ALLOC
64 : : struct lockdep_map dep_map;
65 : : #endif
66 : : };
67 : :
68 : : /*
69 : : * This is the control structure for tasks blocked on mutex,
70 : : * which resides on the blocked task's kernel stack:
71 : : */
72 : : struct mutex_waiter {
73 : : struct list_head list;
74 : : struct task_struct *task;
75 : : struct ww_acquire_ctx *ww_ctx;
76 : : #ifdef CONFIG_DEBUG_MUTEXES
77 : : void *magic;
78 : : #endif
79 : : };
80 : :
81 : : #ifdef CONFIG_DEBUG_MUTEXES
82 : :
83 : : #define __DEBUG_MUTEX_INITIALIZER(lockname) \
84 : : , .magic = &lockname
85 : :
86 : : extern void mutex_destroy(struct mutex *lock);
87 : :
88 : : #else
89 : :
90 : : # define __DEBUG_MUTEX_INITIALIZER(lockname)
91 : :
92 [ - + # # : 325 : static inline void mutex_destroy(struct mutex *lock) {}
# # ]
93 : :
94 : : #endif
95 : :
96 : : /**
97 : : * mutex_init - initialize the mutex
98 : : * @mutex: the mutex to be initialized
99 : : *
100 : : * Initialize the mutex to unlocked state.
101 : : *
102 : : * It is not allowed to initialize an already locked mutex.
103 : : */
104 : : #define mutex_init(mutex) \
105 : : do { \
106 : : static struct lock_class_key __key; \
107 : : \
108 : : __mutex_init((mutex), #mutex, &__key); \
109 : : } while (0)
110 : :
111 : : #ifdef CONFIG_DEBUG_LOCK_ALLOC
112 : : # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
113 : : , .dep_map = { .name = #lockname }
114 : : #else
115 : : # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
116 : : #endif
117 : :
118 : : #define __MUTEX_INITIALIZER(lockname) \
119 : : { .owner = ATOMIC_LONG_INIT(0) \
120 : : , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
121 : : , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
122 : : __DEBUG_MUTEX_INITIALIZER(lockname) \
123 : : __DEP_MAP_MUTEX_INITIALIZER(lockname) }
124 : :
125 : : #define DEFINE_MUTEX(mutexname) \
126 : : struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
127 : :
128 : : extern void __mutex_init(struct mutex *lock, const char *name,
129 : : struct lock_class_key *key);
130 : :
131 : : /**
132 : : * mutex_is_locked - is the mutex locked
133 : : * @lock: the mutex to be queried
134 : : *
135 : : * Returns true if the mutex is locked, false if unlocked.
136 : : */
137 : : extern bool mutex_is_locked(struct mutex *lock);
138 : :
139 : : /*
140 : : * See kernel/locking/mutex.c for detailed documentation of these APIs.
141 : : * Also see Documentation/locking/mutex-design.rst.
142 : : */
143 : : #ifdef CONFIG_DEBUG_LOCK_ALLOC
144 : : extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
145 : : extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
146 : :
147 : : extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
148 : : unsigned int subclass);
149 : : extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
150 : : unsigned int subclass);
151 : : extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
152 : :
153 : : #define mutex_lock(lock) mutex_lock_nested(lock, 0)
154 : : #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
155 : : #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
156 : : #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
157 : :
158 : : #define mutex_lock_nest_lock(lock, nest_lock) \
159 : : do { \
160 : : typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
161 : : _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \
162 : : } while (0)
163 : :
164 : : #else
165 : : extern void mutex_lock(struct mutex *lock);
166 : : extern int __must_check mutex_lock_interruptible(struct mutex *lock);
167 : : extern int __must_check mutex_lock_killable(struct mutex *lock);
168 : : extern void mutex_lock_io(struct mutex *lock);
169 : :
170 : : # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
171 : : # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
172 : : # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
173 : : # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
174 : : # define mutex_lock_io_nested(lock, subclass) mutex_lock(lock)
175 : : #endif
176 : :
177 : : /*
178 : : * NOTE: mutex_trylock() follows the spin_trylock() convention,
179 : : * not the down_trylock() convention!
180 : : *
181 : : * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
182 : : */
183 : : extern int mutex_trylock(struct mutex *lock);
184 : : extern void mutex_unlock(struct mutex *lock);
185 : :
186 : : extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
187 : :
188 : : /*
189 : : * These values are chosen such that FAIL and SUCCESS match the
190 : : * values of the regular mutex_trylock().
191 : : */
192 : : enum mutex_trylock_recursive_enum {
193 : : MUTEX_TRYLOCK_FAILED = 0,
194 : : MUTEX_TRYLOCK_SUCCESS = 1,
195 : : MUTEX_TRYLOCK_RECURSIVE,
196 : : };
197 : :
198 : : /**
199 : : * mutex_trylock_recursive - trylock variant that allows recursive locking
200 : : * @lock: mutex to be locked
201 : : *
202 : : * This function should not be used, _ever_. It is purely for hysterical GEM
203 : : * raisins, and once those are gone this will be removed.
204 : : *
205 : : * Returns:
206 : : * - MUTEX_TRYLOCK_FAILED - trylock failed,
207 : : * - MUTEX_TRYLOCK_SUCCESS - lock acquired,
208 : : * - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
209 : : */
210 : : extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
211 : : mutex_trylock_recursive(struct mutex *lock);
212 : :
213 : : #endif /* __LINUX_MUTEX_H */
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