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 * Trylock by Brian Watson (Brian.J.Watson@compaq.com).
7 */
8
9#ifndef _LINUX_RWSEM_H
10#define _LINUX_RWSEM_H
11
12#include <linux/linkage.h>
13
14#define RWSEM_DEBUG 0
15
16#ifdef __KERNEL__
17
18#include <linux/config.h>
19#include <linux/types.h>
20#include <linux/kernel.h>
21#include <asm/system.h>
22#include <asm/atomic.h>
23
24struct rw_semaphore;
25
26#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
27#include <linux/rwsem-spinlock.h> /* use a generic implementation */
28#else
29#include <asm/rwsem.h> /* use an arch-specific implementation */
30#endif
31
32#ifndef rwsemtrace
33#if RWSEM_DEBUG
34extern void FASTCALL(rwsemtrace(struct rw_semaphore *sem, const char *str));
35#else
36#define rwsemtrace(SEM,FMT)
37#endif
38#endif
39
40/*
41 * lock for reading
42 */
43static inline void down_read(struct rw_semaphore *sem)
44{
45	rwsemtrace(sem,"Entering down_read");
46	__down_read(sem);
47	rwsemtrace(sem,"Leaving down_read");
48}
49
50/*
51 * trylock for reading -- returns 1 if successful, 0 if contention
52 */
53static inline int down_read_trylock(struct rw_semaphore *sem)
54{
55	int ret;
56	rwsemtrace(sem,"Entering down_read_trylock");
57	ret = __down_read_trylock(sem);
58	rwsemtrace(sem,"Leaving down_read_trylock");
59	return ret;
60}
61
62/*
63 * lock for writing
64 */
65static inline void down_write(struct rw_semaphore *sem)
66{
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 */
75static 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 */
87static 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 */
97static 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#endif /* __KERNEL__ */
106#endif /* _LINUX_RWSEM_H */
107