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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 | ||
12 | #define RWSEM_DEBUG 0 | |
13 | ||
14 | #ifdef __KERNEL__ | |
15 | ||
1da177e4 LT |
16 | #include <linux/types.h> |
17 | #include <linux/kernel.h> | |
18 | #include <asm/system.h> | |
19 | #include <asm/atomic.h> | |
20 | ||
21 | struct rw_semaphore; | |
22 | ||
23 | #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK | |
24 | #include <linux/rwsem-spinlock.h> /* use a generic implementation */ | |
25 | #else | |
26 | #include <asm/rwsem.h> /* use an arch-specific implementation */ | |
27 | #endif | |
28 | ||
29 | #ifndef rwsemtrace | |
30 | #if RWSEM_DEBUG | |
31 | extern void FASTCALL(rwsemtrace(struct rw_semaphore *sem, const char *str)); | |
32 | #else | |
33 | #define rwsemtrace(SEM,FMT) | |
34 | #endif | |
35 | #endif | |
36 | ||
37 | /* | |
38 | * lock for reading | |
39 | */ | |
40 | static inline void down_read(struct rw_semaphore *sem) | |
41 | { | |
42 | might_sleep(); | |
43 | rwsemtrace(sem,"Entering down_read"); | |
44 | __down_read(sem); | |
45 | rwsemtrace(sem,"Leaving down_read"); | |
46 | } | |
47 | ||
48 | /* | |
49 | * trylock for reading -- returns 1 if successful, 0 if contention | |
50 | */ | |
51 | static inline int down_read_trylock(struct rw_semaphore *sem) | |
52 | { | |
53 | int ret; | |
54 | rwsemtrace(sem,"Entering down_read_trylock"); | |
55 | ret = __down_read_trylock(sem); | |
56 | rwsemtrace(sem,"Leaving down_read_trylock"); | |
57 | return ret; | |
58 | } | |
59 | ||
60 | /* | |
61 | * lock for writing | |
62 | */ | |
63 | static inline void down_write(struct rw_semaphore *sem) | |
64 | { | |
65 | might_sleep(); | |
66 | rwsemtrace(sem,"Entering down_write"); | |
67 | __down_write(sem); | |
68 | rwsemtrace(sem,"Leaving down_write"); | |
69 | } | |
70 | ||
71 | /* | |
72 | * trylock for writing -- returns 1 if successful, 0 if contention | |
73 | */ | |
74 | static inline int down_write_trylock(struct rw_semaphore *sem) | |
75 | { | |
76 | int ret; | |
77 | rwsemtrace(sem,"Entering down_write_trylock"); | |
78 | ret = __down_write_trylock(sem); | |
79 | rwsemtrace(sem,"Leaving down_write_trylock"); | |
80 | return ret; | |
81 | } | |
82 | ||
83 | /* | |
84 | * release a read lock | |
85 | */ | |
86 | static inline void up_read(struct rw_semaphore *sem) | |
87 | { | |
88 | rwsemtrace(sem,"Entering up_read"); | |
89 | __up_read(sem); | |
90 | rwsemtrace(sem,"Leaving up_read"); | |
91 | } | |
92 | ||
93 | /* | |
94 | * release a write lock | |
95 | */ | |
96 | static inline void up_write(struct rw_semaphore *sem) | |
97 | { | |
98 | rwsemtrace(sem,"Entering up_write"); | |
99 | __up_write(sem); | |
100 | rwsemtrace(sem,"Leaving up_write"); | |
101 | } | |
102 | ||
103 | /* | |
104 | * downgrade write lock to read lock | |
105 | */ | |
106 | static inline void downgrade_write(struct rw_semaphore *sem) | |
107 | { | |
108 | rwsemtrace(sem,"Entering downgrade_write"); | |
109 | __downgrade_write(sem); | |
110 | rwsemtrace(sem,"Leaving downgrade_write"); | |
111 | } | |
112 | ||
113 | #endif /* __KERNEL__ */ | |
114 | #endif /* _LINUX_RWSEM_H */ |