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1da177e4 LT |
1 | /* rwsem.h: R/W semaphores, public interface |
2 | * | |
3 | * Written by David Howells (dhowells@redhat.com). | |
4 | * Derived from asm-i386/semaphore.h | |
5 | */ | |
6 | ||
7 | #ifndef _LINUX_RWSEM_H | |
8 | #define _LINUX_RWSEM_H | |
9 | ||
10 | #include <linux/linkage.h> | |
11 | ||
1da177e4 LT |
12 | #include <linux/types.h> |
13 | #include <linux/kernel.h> | |
c16a87ce TG |
14 | #include <linux/list.h> |
15 | #include <linux/spinlock.h> | |
60063497 | 16 | #include <linux/atomic.h> |
d4799608 | 17 | #include <linux/err.h> |
5db6c6fe | 18 | #ifdef CONFIG_RWSEM_SPIN_ON_OWNER |
90631822 | 19 | #include <linux/osq_lock.h> |
5db6c6fe | 20 | #endif |
1da177e4 LT |
21 | |
22 | struct rw_semaphore; | |
23 | ||
24 | #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK | |
25 | #include <linux/rwsem-spinlock.h> /* use a generic implementation */ | |
8ee62b18 | 26 | #define __RWSEM_INIT_COUNT(name) .count = RWSEM_UNLOCKED_VALUE |
1da177e4 | 27 | #else |
1c8ed640 TG |
28 | /* All arch specific implementations share the same struct */ |
29 | struct rw_semaphore { | |
8ee62b18 | 30 | atomic_long_t count; |
4fc828e2 | 31 | struct list_head wait_list; |
ce069fc9 | 32 | raw_spinlock_t wait_lock; |
5db6c6fe | 33 | #ifdef CONFIG_RWSEM_SPIN_ON_OWNER |
ce069fc9 | 34 | struct optimistic_spin_queue osq; /* spinner MCS lock */ |
4fc828e2 DB |
35 | /* |
36 | * Write owner. Used as a speculative check to see | |
37 | * if the owner is running on the cpu. | |
38 | */ | |
39 | struct task_struct *owner; | |
4fc828e2 | 40 | #endif |
1c8ed640 TG |
41 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
42 | struct lockdep_map dep_map; | |
43 | #endif | |
44 | }; | |
45 | ||
d1233754 TG |
46 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); |
47 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); | |
d4799608 | 48 | extern struct rw_semaphore *rwsem_down_write_failed_killable(struct rw_semaphore *sem); |
d1233754 TG |
49 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *); |
50 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); | |
aac72277 | 51 | |
1c8ed640 TG |
52 | /* Include the arch specific part */ |
53 | #include <asm/rwsem.h> | |
41e5887f TG |
54 | |
55 | /* In all implementations count != 0 means locked */ | |
56 | static inline int rwsem_is_locked(struct rw_semaphore *sem) | |
57 | { | |
8ee62b18 | 58 | return atomic_long_read(&sem->count) != 0; |
41e5887f TG |
59 | } |
60 | ||
8ee62b18 | 61 | #define __RWSEM_INIT_COUNT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE) |
1da177e4 LT |
62 | #endif |
63 | ||
12249b34 TG |
64 | /* Common initializer macros and functions */ |
65 | ||
66 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
67 | # define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname } | |
68 | #else | |
69 | # define __RWSEM_DEP_MAP_INIT(lockname) | |
70 | #endif | |
71 | ||
5db6c6fe | 72 | #ifdef CONFIG_RWSEM_SPIN_ON_OWNER |
ce069fc9 | 73 | #define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL |
4fc828e2 | 74 | #else |
ce069fc9 | 75 | #define __RWSEM_OPT_INIT(lockname) |
4fc828e2 | 76 | #endif |
12249b34 | 77 | |
ce069fc9 | 78 | #define __RWSEM_INITIALIZER(name) \ |
8ee62b18 | 79 | { __RWSEM_INIT_COUNT(name), \ |
ce069fc9 JL |
80 | .wait_list = LIST_HEAD_INIT((name).wait_list), \ |
81 | .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \ | |
82 | __RWSEM_OPT_INIT(name) \ | |
83 | __RWSEM_DEP_MAP_INIT(name) } | |
84 | ||
12249b34 TG |
85 | #define DECLARE_RWSEM(name) \ |
86 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
87 | ||
88 | extern void __init_rwsem(struct rw_semaphore *sem, const char *name, | |
89 | struct lock_class_key *key); | |
90 | ||
91 | #define init_rwsem(sem) \ | |
92 | do { \ | |
93 | static struct lock_class_key __key; \ | |
94 | \ | |
95 | __init_rwsem((sem), #sem, &__key); \ | |
96 | } while (0) | |
97 | ||
4a444b1f JB |
98 | /* |
99 | * This is the same regardless of which rwsem implementation that is being used. | |
100 | * It is just a heuristic meant to be called by somebody alreadying holding the | |
101 | * rwsem to see if somebody from an incompatible type is wanting access to the | |
102 | * lock. | |
103 | */ | |
104 | static inline int rwsem_is_contended(struct rw_semaphore *sem) | |
105 | { | |
106 | return !list_empty(&sem->wait_list); | |
107 | } | |
108 | ||
1da177e4 LT |
109 | /* |
110 | * lock for reading | |
111 | */ | |
4ea2176d | 112 | extern void down_read(struct rw_semaphore *sem); |
1da177e4 LT |
113 | |
114 | /* | |
115 | * trylock for reading -- returns 1 if successful, 0 if contention | |
116 | */ | |
4ea2176d | 117 | extern int down_read_trylock(struct rw_semaphore *sem); |
1da177e4 LT |
118 | |
119 | /* | |
120 | * lock for writing | |
121 | */ | |
4ea2176d | 122 | extern void down_write(struct rw_semaphore *sem); |
916633a4 | 123 | extern int __must_check down_write_killable(struct rw_semaphore *sem); |
1da177e4 LT |
124 | |
125 | /* | |
126 | * trylock for writing -- returns 1 if successful, 0 if contention | |
127 | */ | |
4ea2176d | 128 | extern int down_write_trylock(struct rw_semaphore *sem); |
1da177e4 LT |
129 | |
130 | /* | |
131 | * release a read lock | |
132 | */ | |
4ea2176d | 133 | extern void up_read(struct rw_semaphore *sem); |
1da177e4 LT |
134 | |
135 | /* | |
136 | * release a write lock | |
137 | */ | |
4ea2176d | 138 | extern void up_write(struct rw_semaphore *sem); |
1da177e4 LT |
139 | |
140 | /* | |
141 | * downgrade write lock to read lock | |
142 | */ | |
4ea2176d IM |
143 | extern void downgrade_write(struct rw_semaphore *sem); |
144 | ||
145 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
146 | /* | |
5fca80e8 IM |
147 | * nested locking. NOTE: rwsems are not allowed to recurse |
148 | * (which occurs if the same task tries to acquire the same | |
149 | * lock instance multiple times), but multiple locks of the | |
150 | * same lock class might be taken, if the order of the locks | |
151 | * is always the same. This ordering rule can be expressed | |
152 | * to lockdep via the _nested() APIs, but enumerating the | |
153 | * subclasses that are used. (If the nesting relationship is | |
154 | * static then another method for expressing nested locking is | |
155 | * the explicit definition of lock class keys and the use of | |
156 | * lockdep_set_class() at lock initialization time. | |
214e0aed | 157 | * See Documentation/locking/lockdep-design.txt for more details.) |
4ea2176d IM |
158 | */ |
159 | extern void down_read_nested(struct rw_semaphore *sem, int subclass); | |
160 | extern void down_write_nested(struct rw_semaphore *sem, int subclass); | |
887bddfa | 161 | extern int down_write_killable_nested(struct rw_semaphore *sem, int subclass); |
1b963c81 JK |
162 | extern void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest_lock); |
163 | ||
164 | # define down_write_nest_lock(sem, nest_lock) \ | |
165 | do { \ | |
166 | typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ | |
167 | _down_write_nest_lock(sem, &(nest_lock)->dep_map); \ | |
168 | } while (0); | |
169 | ||
84759c6d KO |
170 | /* |
171 | * Take/release a lock when not the owner will release it. | |
172 | * | |
173 | * [ This API should be avoided as much as possible - the | |
174 | * proper abstraction for this case is completions. ] | |
175 | */ | |
176 | extern void down_read_non_owner(struct rw_semaphore *sem); | |
177 | extern void up_read_non_owner(struct rw_semaphore *sem); | |
4ea2176d IM |
178 | #else |
179 | # define down_read_nested(sem, subclass) down_read(sem) | |
e65b9ad2 | 180 | # define down_write_nest_lock(sem, nest_lock) down_write(sem) |
4ea2176d | 181 | # define down_write_nested(sem, subclass) down_write(sem) |
887bddfa | 182 | # define down_write_killable_nested(sem, subclass) down_write_killable(sem) |
84759c6d KO |
183 | # define down_read_non_owner(sem) down_read(sem) |
184 | # define up_read_non_owner(sem) up_read(sem) | |
4ea2176d | 185 | #endif |
1da177e4 | 186 | |
1da177e4 | 187 | #endif /* _LINUX_RWSEM_H */ |