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