| /* rwsem-spinlock.h: fallback C implementation |
| * |
| * Copyright (c) 2001 David Howells (dhowells@redhat.com). |
| * - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de> |
| * - Derived also from comments by Linus |
| */ |
| |
| #ifndef _LINUX_RWSEM_SPINLOCK_H |
| #define _LINUX_RWSEM_SPINLOCK_H |
| |
| #ifndef _LINUX_RWSEM_H |
| #error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead" |
| #endif |
| |
| #ifdef __KERNEL__ |
| /* |
| * the rw-semaphore definition |
| * - if count is 0 then there are no active readers or writers |
| * - if count is +ve then that is the number of active readers |
| * - if count is -1 then there is one active writer |
| * - if wait_list is not empty, then there are processes waiting for the semaphore |
| */ |
| struct rw_semaphore { |
| __s32 count; |
| raw_spinlock_t wait_lock; |
| struct list_head wait_list; |
| #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| struct lockdep_map dep_map; |
| #endif |
| }; |
| |
| #define RWSEM_UNLOCKED_VALUE 0x00000000 |
| |
| extern void __down_read(struct rw_semaphore *sem); |
| extern int __must_check __down_read_killable(struct rw_semaphore *sem); |
| extern int __down_read_trylock(struct rw_semaphore *sem); |
| extern void __down_write(struct rw_semaphore *sem); |
| extern int __must_check __down_write_killable(struct rw_semaphore *sem); |
| extern int __down_write_trylock(struct rw_semaphore *sem); |
| extern void __up_read(struct rw_semaphore *sem); |
| extern void __up_write(struct rw_semaphore *sem); |
| extern void __downgrade_write(struct rw_semaphore *sem); |
| extern int rwsem_is_locked(struct rw_semaphore *sem); |
| |
| #endif /* __KERNEL__ */ |
| #endif /* _LINUX_RWSEM_SPINLOCK_H */ |