ia64/linux-2.6.18-xen.hg

view kernel/rwsem.c @ 562:66faefe721eb

pvSCSI backend driver

Signed-off-by: Tomonari Horikoshi <t.horikoshi@jp.fujitsu.com>
Signed-off-by: Jun Kamada <kama@jp.fujitsu.com>
author Keir Fraser <keir.fraser@citrix.com>
date Mon Jun 02 09:58:27 2008 +0100 (2008-06-02)
parents 831230e53067
children
line source
1 /* kernel/rwsem.c: R/W semaphores, public implementation
2 *
3 * Written by David Howells (dhowells@redhat.com).
4 * Derived from asm-i386/semaphore.h
5 */
7 #include <linux/types.h>
8 #include <linux/kernel.h>
9 #include <linux/module.h>
10 #include <linux/rwsem.h>
12 #include <asm/system.h>
13 #include <asm/atomic.h>
15 /*
16 * lock for reading
17 */
18 void down_read(struct rw_semaphore *sem)
19 {
20 might_sleep();
21 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
23 __down_read(sem);
24 }
26 EXPORT_SYMBOL(down_read);
28 /*
29 * trylock for reading -- returns 1 if successful, 0 if contention
30 */
31 int down_read_trylock(struct rw_semaphore *sem)
32 {
33 int ret = __down_read_trylock(sem);
35 if (ret == 1)
36 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
37 return ret;
38 }
40 EXPORT_SYMBOL(down_read_trylock);
42 /*
43 * lock for writing
44 */
45 void down_write(struct rw_semaphore *sem)
46 {
47 might_sleep();
48 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
50 __down_write(sem);
51 }
53 EXPORT_SYMBOL(down_write);
55 /*
56 * trylock for writing -- returns 1 if successful, 0 if contention
57 */
58 int down_write_trylock(struct rw_semaphore *sem)
59 {
60 int ret = __down_write_trylock(sem);
62 if (ret == 1)
63 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
64 return ret;
65 }
67 EXPORT_SYMBOL(down_write_trylock);
69 /*
70 * release a read lock
71 */
72 void up_read(struct rw_semaphore *sem)
73 {
74 rwsem_release(&sem->dep_map, 1, _RET_IP_);
76 __up_read(sem);
77 }
79 EXPORT_SYMBOL(up_read);
81 /*
82 * release a write lock
83 */
84 void up_write(struct rw_semaphore *sem)
85 {
86 rwsem_release(&sem->dep_map, 1, _RET_IP_);
88 __up_write(sem);
89 }
91 EXPORT_SYMBOL(up_write);
93 /*
94 * downgrade write lock to read lock
95 */
96 void downgrade_write(struct rw_semaphore *sem)
97 {
98 /*
99 * lockdep: a downgraded write will live on as a write
100 * dependency.
101 */
102 __downgrade_write(sem);
103 }
105 EXPORT_SYMBOL(downgrade_write);
107 #ifdef CONFIG_DEBUG_LOCK_ALLOC
109 void down_read_nested(struct rw_semaphore *sem, int subclass)
110 {
111 might_sleep();
112 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
114 __down_read(sem);
115 }
117 EXPORT_SYMBOL(down_read_nested);
119 void down_read_non_owner(struct rw_semaphore *sem)
120 {
121 might_sleep();
123 __down_read(sem);
124 }
126 EXPORT_SYMBOL(down_read_non_owner);
128 void down_write_nested(struct rw_semaphore *sem, int subclass)
129 {
130 might_sleep();
131 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
133 __down_write_nested(sem, subclass);
134 }
136 EXPORT_SYMBOL(down_write_nested);
138 void up_read_non_owner(struct rw_semaphore *sem)
139 {
140 __up_read(sem);
141 }
143 EXPORT_SYMBOL(up_read_non_owner);
145 #endif