1 /*
2 * Mutexes: blocking mutual exclusion locks
3 *
4 * started by Ingo Molnar:
5 *
6 * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
7 *
8 * This file contains the main data structure and API definitions.
9 */
10 #ifndef __LINUX_MUTEX_H
11 #define __LINUX_MUTEX_H
12
13 #include <linux/list.h>
14 #include <linux/spinlock_types.h>
15 #include <linux/rt_lock.h>
16 #include <linux/linkage.h>
17 #include <linux/lockdep.h>
18
19 #include <asm/atomic.h>
20
21 #ifdef CONFIG_DEBUG_LOCK_ALLOC
22 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
23 , .dep_map = { .name = #lockname }
24 #else
25 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
26 #endif
27
28 #ifdef CONFIG_PREEMPT_RT
29
30 #include <linux/rtmutex.h>
31
32 struct mutex {
33 struct rt_mutex lock;
34 #ifdef CONFIG_DEBUG_LOCK_ALLOC
35 struct lockdep_map dep_map;
36 #endif
37 };
38
39
40 #define __MUTEX_INITIALIZER(mutexname) \
41 { \
42 .lock = __RT_MUTEX_INITIALIZER(mutexname.lock) \
43 __DEP_MAP_MUTEX_INITIALIZER(mutexname) \
44 }
45
46 #define DEFINE_MUTEX(mutexname) \
47 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
48
49 extern void
50 _mutex_init(struct mutex *lock, char *name, struct lock_class_key *key);
51
52 extern void __lockfunc _mutex_lock(struct mutex *lock);
53 extern int __lockfunc _mutex_lock_interruptible(struct mutex *lock);
54 extern int __lockfunc _mutex_lock_killable(struct mutex *lock);
55 extern void __lockfunc _mutex_lock_nested(struct mutex *lock, int subclass);
56 extern int __lockfunc _mutex_lock_interruptible_nested(struct mutex *lock, int subclass);
57 extern int __lockfunc _mutex_lock_killable_nested(struct mutex *lock, int subclass);
58 extern int __lockfunc _mutex_trylock(struct mutex *lock);
59 extern void __lockfunc _mutex_unlock(struct mutex *lock);
60
61 #define mutex_is_locked(l) rt_mutex_is_locked(&(l)->lock)
62 #define mutex_lock(l) _mutex_lock(l)
63 #define mutex_lock_interruptible(l) _mutex_lock_interruptible(l)
64 #define mutex_lock_killable(l) _mutex_lock_killable(l)
65 #define mutex_trylock(l) _mutex_trylock(l)
66 #define mutex_unlock(l) _mutex_unlock(l)
67 #define mutex_destroy(l) rt_mutex_destroy(&(l)->lock)
68
69 #ifdef CONFIG_DEBUG_LOCK_ALLOC
70 # define mutex_lock_nested(l, s) _mutex_lock_nested(l, s)
71 # define mutex_lock_interruptible_nested(l, s) \
72 _mutex_lock_interruptible_nested(l, s)
73 # define mutex_lock_killable_nested(l, s) \
74 _mutex_lock_killable_nested(l, s)
75 #else
76 # define mutex_lock_nested(l, s) _mutex_lock(l)
77 # define mutex_lock_interruptible_nested(l, s) \
78 _mutex_lock_interruptible(l)
79 # define mutex_lock_killable_nested(l, s) \
80 _mutex_lock_killable(l)
81 #endif
82
83 # define mutex_init(mutex) \
84 do { \
85 static struct lock_class_key __key; \
86 \
87 _mutex_init((mutex), #mutex, &__key); \
88 } while (0)
89
90 #else
91 /*
92 * Simple, straightforward mutexes with strict semantics:
93 *
94 * - only one task can hold the mutex at a time
95 * - only the owner can unlock the mutex
96 * - multiple unlocks are not permitted
97 * - recursive locking is not permitted
98 * - a mutex object must be initialized via the API
99 * - a mutex object must not be initialized via memset or copying
100 * - task may not exit with mutex held
101 * - memory areas where held locks reside must not be freed
102 * - held mutexes must not be reinitialized
103 * - mutexes may not be used in hardware or software interrupt
104 * contexts such as tasklets and timers
105 *
106 * These semantics are fully enforced when DEBUG_MUTEXES is
107 * enabled. Furthermore, besides enforcing the above rules, the mutex
108 * debugging code also implements a number of additional features
109 * that make lock debugging easier and faster:
110 *
111 * - uses symbolic names of mutexes, whenever they are printed in debug output
112 * - point-of-acquire tracking, symbolic lookup of function names
113 * - list of all locks held in the system, printout of them
114 * - owner tracking
115 * - detects self-recursing locks and prints out all relevant info
116 * - detects multi-task circular deadlocks and prints out all affected
117 * locks and tasks (and only those tasks)
118 */
119 struct mutex {
120 /* 1: unlocked, 0: locked, negative: locked, possible waiters */
121 atomic_t count;
122 spinlock_t wait_lock;
123 struct list_head wait_list;
124 #ifdef CONFIG_DEBUG_MUTEXES
125 struct thread_info *owner;
126 const char *name;
127 void *magic;
128 #endif
129 #ifdef CONFIG_DEBUG_LOCK_ALLOC
130 struct lockdep_map dep_map;
131 #endif
132 };
133
134 /*
135 * This is the control structure for tasks blocked on mutex,
136 * which resides on the blocked task's kernel stack:
137 */
138 struct mutex_waiter {
139 struct list_head list;
140 struct task_struct *task;
141 #ifdef CONFIG_DEBUG_MUTEXES
142 struct mutex *lock;
143 void *magic;
144 #endif
145 };
146
147 #ifdef CONFIG_DEBUG_MUTEXES
148 # include <linux/mutex-debug.h>
149 #else
150 # define __DEBUG_MUTEX_INITIALIZER(lockname)
151 # define mutex_init(mutex) \
152 do { \
153 static struct lock_class_key __key; \
154 \
155 __mutex_init((mutex), #mutex, &__key); \
156 } while (0)
157 # define mutex_destroy(mutex) do { } while (0)
158 #endif
159
160 #define __MUTEX_INITIALIZER(lockname) \
161 { .count = ATOMIC_INIT(1) \
162 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
163 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
164 __DEBUG_MUTEX_INITIALIZER(lockname) \
165 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
166
167 #define DEFINE_MUTEX(mutexname) \
168 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
169
170 extern void __mutex_init(struct mutex *lock, const char *name,
171 struct lock_class_key *key);
172
173 /**
174 * mutex_is_locked - is the mutex locked
175 * @lock: the mutex to be queried
176 *
177 * Returns 1 if the mutex is locked, 0 if unlocked.
178 */
179 static inline int mutex_is_locked(struct mutex *lock)
180 {
181 return atomic_read(&lock->count) != 1;
182 }
183
184 /*
185 * See kernel/mutex.c for detailed documentation of these APIs.
186 * Also see Documentation/mutex-design.txt.
187 */
188 #ifdef CONFIG_DEBUG_LOCK_ALLOC
189 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
190 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
191 unsigned int subclass);
192 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
193 unsigned int subclass);
194
195 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
196 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
197 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
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
203 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
204 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
205 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
206 #endif
207
208 /*
209 * NOTE: mutex_trylock() follows the spin_trylock() convention,
210 * not the down_trylock() convention!
211 */
212 extern int mutex_trylock(struct mutex *lock);
213 extern void mutex_unlock(struct mutex *lock);
214
215 #endif
216 #endif
217
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