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 #include <linux/android_vendor.h>
23
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 ANDROID_OEM_DATA_ARRAY(1, 2);
68 };
69
70 struct ww_class;
71 struct ww_acquire_ctx;
72
73 struct ww_mutex {
74 struct mutex base;
75 struct ww_acquire_ctx *ctx;
76 #ifdef CONFIG_DEBUG_MUTEXES
77 struct ww_class *ww_class;
78 #endif
79 };
80
81 /*
82 * This is the control structure for tasks blocked on mutex,
83 * which resides on the blocked task's kernel stack:
84 */
85 struct mutex_waiter {
86 struct list_head list;
87 struct task_struct *task;
88 struct ww_acquire_ctx *ww_ctx;
89 #ifdef CONFIG_DEBUG_MUTEXES
90 void *magic;
91 #endif
92 };
93
94 #ifdef CONFIG_DEBUG_MUTEXES
95
96 #define __DEBUG_MUTEX_INITIALIZER(lockname) \
97 , .magic = &lockname
98
99 extern void mutex_destroy(struct mutex *lock);
100
101 #else
102
103 # define __DEBUG_MUTEX_INITIALIZER(lockname)
104
mutex_destroy(struct mutex * lock)105 static inline void mutex_destroy(struct mutex *lock) {}
106
107 #endif
108
109 /**
110 * mutex_init - initialize the mutex
111 * @mutex: the mutex to be initialized
112 *
113 * Initialize the mutex to unlocked state.
114 *
115 * It is not allowed to initialize an already locked mutex.
116 */
117 #define mutex_init(mutex) \
118 do { \
119 static struct lock_class_key __key; \
120 \
121 __mutex_init((mutex), #mutex, &__key); \
122 } while (0)
123
124 #ifdef CONFIG_DEBUG_LOCK_ALLOC
125 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
126 , .dep_map = { \
127 .name = #lockname, \
128 .wait_type_inner = LD_WAIT_SLEEP, \
129 }
130 #else
131 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
132 #endif
133
134 #define __MUTEX_INITIALIZER(lockname) \
135 { .owner = ATOMIC_LONG_INIT(0) \
136 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
137 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
138 __DEBUG_MUTEX_INITIALIZER(lockname) \
139 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
140
141 #define DEFINE_MUTEX(mutexname) \
142 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
143
144 extern void __mutex_init(struct mutex *lock, const char *name,
145 struct lock_class_key *key);
146
147 /**
148 * mutex_is_locked - is the mutex locked
149 * @lock: the mutex to be queried
150 *
151 * Returns true if the mutex is locked, false if unlocked.
152 */
153 extern bool mutex_is_locked(struct mutex *lock);
154
155 /*
156 * See kernel/locking/mutex.c for detailed documentation of these APIs.
157 * Also see Documentation/locking/mutex-design.rst.
158 */
159 #ifdef CONFIG_DEBUG_LOCK_ALLOC
160 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
161 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
162
163 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
164 unsigned int subclass);
165 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
166 unsigned int subclass);
167 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
168
169 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
170 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
171 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
172 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
173
174 #define mutex_lock_nest_lock(lock, nest_lock) \
175 do { \
176 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
177 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \
178 } while (0)
179
180 #else
181 extern void mutex_lock(struct mutex *lock);
182 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
183 extern int __must_check mutex_lock_killable(struct mutex *lock);
184 extern void mutex_lock_io(struct mutex *lock);
185
186 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
187 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
188 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
189 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
190 # define mutex_lock_io_nested(lock, subclass) mutex_lock_io(lock)
191 #endif
192
193 /*
194 * NOTE: mutex_trylock() follows the spin_trylock() convention,
195 * not the down_trylock() convention!
196 *
197 * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
198 */
199 extern int mutex_trylock(struct mutex *lock);
200 extern void mutex_unlock(struct mutex *lock);
201
202 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
203
204 /*
205 * These values are chosen such that FAIL and SUCCESS match the
206 * values of the regular mutex_trylock().
207 */
208 enum mutex_trylock_recursive_enum {
209 MUTEX_TRYLOCK_FAILED = 0,
210 MUTEX_TRYLOCK_SUCCESS = 1,
211 MUTEX_TRYLOCK_RECURSIVE,
212 };
213
214 /**
215 * mutex_trylock_recursive - trylock variant that allows recursive locking
216 * @lock: mutex to be locked
217 *
218 * This function should not be used, _ever_. It is purely for hysterical GEM
219 * raisins, and once those are gone this will be removed.
220 *
221 * Returns:
222 * - MUTEX_TRYLOCK_FAILED - trylock failed,
223 * - MUTEX_TRYLOCK_SUCCESS - lock acquired,
224 * - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
225 */
226 extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
227 mutex_trylock_recursive(struct mutex *lock);
228
229 #endif /* __LINUX_MUTEX_H */
230