1 /* rwsem-spinlock.h: fallback C implementation
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
8 #ifndef _LINUX_RWSEM_SPINLOCK_H
9 #define _LINUX_RWSEM_SPINLOCK_H
11 #ifndef _LINUX_RWSEM_H
12 #error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
15 #include <linux/spinlock.h>
16 #include <linux/list.h>
20 #include <linux/types.h>
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
34 struct list_head wait_list;
37 #define __RWSEM_INITIALIZER(name) \
38 { 0, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) }
40 #define DECLARE_RWSEM(name) \
41 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
43 extern void FASTCALL(init_rwsem(struct rw_semaphore *sem));
44 extern void FASTCALL(__down_read(struct rw_semaphore *sem));
45 extern int FASTCALL(__down_read_trylock(struct rw_semaphore *sem));
46 extern void FASTCALL(__down_write(struct rw_semaphore *sem));
47 extern int FASTCALL(__down_write_trylock(struct rw_semaphore *sem));
48 extern void FASTCALL(__up_read(struct rw_semaphore *sem));
49 extern void FASTCALL(__up_write(struct rw_semaphore *sem));
50 extern void FASTCALL(__downgrade_write(struct rw_semaphore *sem));
52 static inline int rwsem_is_locked(struct rw_semaphore *sem)
54 return (sem->activity != 0);
57 #endif /* __KERNEL__ */
58 #endif /* _LINUX_RWSEM_SPINLOCK_H */