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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 | ||
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12 | #ifdef __KERNEL__ |
13 | ||
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14 | #include <linux/types.h> |
15 | #include <linux/kernel.h> | |
16 | #include <asm/system.h> | |
17 | #include <asm/atomic.h> | |
18 | ||
19 | struct rw_semaphore; | |
20 | ||
21 | #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK | |
22 | #include <linux/rwsem-spinlock.h> /* use a generic implementation */ | |
23 | #else | |
24 | #include <asm/rwsem.h> /* use an arch-specific implementation */ | |
25 | #endif | |
26 | ||
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27 | /* |
28 | * lock for reading | |
29 | */ | |
4ea2176d | 30 | extern void down_read(struct rw_semaphore *sem); |
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31 | |
32 | /* | |
33 | * trylock for reading -- returns 1 if successful, 0 if contention | |
34 | */ | |
4ea2176d | 35 | extern int down_read_trylock(struct rw_semaphore *sem); |
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36 | |
37 | /* | |
38 | * lock for writing | |
39 | */ | |
4ea2176d | 40 | extern void down_write(struct rw_semaphore *sem); |
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41 | |
42 | /* | |
43 | * trylock for writing -- returns 1 if successful, 0 if contention | |
44 | */ | |
4ea2176d | 45 | extern int down_write_trylock(struct rw_semaphore *sem); |
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46 | |
47 | /* | |
48 | * release a read lock | |
49 | */ | |
4ea2176d | 50 | extern void up_read(struct rw_semaphore *sem); |
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51 | |
52 | /* | |
53 | * release a write lock | |
54 | */ | |
4ea2176d | 55 | extern void up_write(struct rw_semaphore *sem); |
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56 | |
57 | /* | |
58 | * downgrade write lock to read lock | |
59 | */ | |
4ea2176d IM |
60 | extern void downgrade_write(struct rw_semaphore *sem); |
61 | ||
62 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
63 | /* | |
64 | * nested locking: | |
65 | */ | |
66 | extern void down_read_nested(struct rw_semaphore *sem, int subclass); | |
67 | extern void down_write_nested(struct rw_semaphore *sem, int subclass); | |
68 | /* | |
69 | * Take/release a lock when not the owner will release it: | |
70 | */ | |
71 | extern void down_read_non_owner(struct rw_semaphore *sem); | |
72 | extern void up_read_non_owner(struct rw_semaphore *sem); | |
73 | #else | |
74 | # define down_read_nested(sem, subclass) down_read(sem) | |
75 | # define down_write_nested(sem, subclass) down_write(sem) | |
76 | # define down_read_non_owner(sem) down_read(sem) | |
77 | # define up_read_non_owner(sem) up_read(sem) | |
78 | #endif | |
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79 | |
80 | #endif /* __KERNEL__ */ | |
81 | #endif /* _LINUX_RWSEM_H */ |