projects / linux-2.6-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 1da177e4 LT |
1 | /* 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 | ||
| 22 | struct 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 | */ | |
| 31 | struct rw_semaphore { | |
| 32 | __s32 activity; | |
| 33 | spinlock_t wait_lock; | |
| 34 | struct list_head wait_list; | |
| 1da177e4 LT |
35 | }; |
| 36 | ||
| 1da177e4 | 37 | #define __RWSEM_INITIALIZER(name) \ |
| c4e05116 | 38 | { 0, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) } |
| 1da177e4 LT |
39 | |
| 40 | #define DECLARE_RWSEM(name) \ | |
| 41 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
| 42 | ||
| 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)); | |
| 51 | ||
| eb92f4ef RVR |
52 | static inline int rwsem_is_locked(struct rw_semaphore *sem) |
| 53 | { | |
| 54 | return (sem->activity != 0); | |
| 55 | } | |
| 56 | ||
| 1da177e4 LT |
57 | #endif /* __KERNEL__ */ |
| 58 | #endif /* _LINUX_RWSEM_SPINLOCK_H */ |