/* 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 [31mCONFIG_DEBUG_LOCK_ALLOC[0m struct lockdep_map dep_map; #endif }; #define RWSEM_UNLOCKED_VALUE 0x00000000 extern void __down_read(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 */ |