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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* rwsem-spinlock.h: fallback C implementation
2 *
3 * Copyright (c) 2001 David Howells (dhowells@redhat.com).
4 * - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de>
5 * - Derived also from comments by Linus
6 */
7
8#ifndef _LINUX_RWSEM_SPINLOCK_H
9#define _LINUX_RWSEM_SPINLOCK_H
10
11#ifndef _LINUX_RWSEM_H
12#error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
13#endif
14
15#include <linux/spinlock.h>
16#include <linux/list.h>
17
18#ifdef __KERNEL__
19
20#include <linux/types.h>
21
22struct rwsem_waiter;
23
24/*
25 * the rw-semaphore definition
26 * - if activity is 0 then there are no active readers or writers
27 * - if activity is +ve then that is the number of active readers
28 * - if activity is -1 then there is one active writer
29 * - if wait_list is not empty, then there are processes waiting for the semaphore
30 */
31struct rw_semaphore {
32 __s32 activity;
33 spinlock_t wait_lock;
34 struct list_head wait_list;
Ingo Molnar4ea21762006-07-03 00:24:53 -070035#ifdef CONFIG_DEBUG_LOCK_ALLOC
36 struct lockdep_map dep_map;
37#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -070038};
39
Ingo Molnar4ea21762006-07-03 00:24:53 -070040#ifdef CONFIG_DEBUG_LOCK_ALLOC
41# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
42#else
43# define __RWSEM_DEP_MAP_INIT(lockname)
44#endif
45
Linus Torvalds1da177e2005-04-16 15:20:36 -070046#define __RWSEM_INITIALIZER(name) \
Peter Zijlstra6cfd76a2006-12-06 20:37:22 -080047{ 0, __SPIN_LOCK_UNLOCKED(name.wait_lock), LIST_HEAD_INIT((name).wait_list) \
48 __RWSEM_DEP_MAP_INIT(name) }
Linus Torvalds1da177e2005-04-16 15:20:36 -070049
50#define DECLARE_RWSEM(name) \
51 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
52
Ingo Molnar4ea21762006-07-03 00:24:53 -070053extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
54 struct lock_class_key *key);
55
56#define init_rwsem(sem) \
57do { \
58 static struct lock_class_key __key; \
59 \
60 __init_rwsem((sem), #sem, &__key); \
61} while (0)
62
Harvey Harrisonb3c97522008-02-13 15:03:15 -080063extern void __down_read(struct rw_semaphore *sem);
64extern int __down_read_trylock(struct rw_semaphore *sem);
65extern void __down_write(struct rw_semaphore *sem);
66extern void __down_write_nested(struct rw_semaphore *sem, int subclass);
67extern int __down_write_trylock(struct rw_semaphore *sem);
68extern void __up_read(struct rw_semaphore *sem);
69extern void __up_write(struct rw_semaphore *sem);
70extern void __downgrade_write(struct rw_semaphore *sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -070071
Rik Van Rieleb92f4e2005-10-29 18:15:44 -070072static inline int rwsem_is_locked(struct rw_semaphore *sem)
73{
74 return (sem->activity != 0);
75}
76
Linus Torvalds1da177e2005-04-16 15:20:36 -070077#endif /* __KERNEL__ */
78#endif /* _LINUX_RWSEM_SPINLOCK_H */