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 * Trylock by Brian Watson (Brian.J.Watson@compaq.com). 8 */ 9 10 #ifndef _LINUX_RWSEM_SPINLOCK_H 11 #define _LINUX_RWSEM_SPINLOCK_H 12 13 #ifndef _LINUX_RWSEM_H 14 #error please dont include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead 15 #endif 16 17 #include <linux/spinlock.h> 18 #include <linux/list.h> 19 20 #ifdef __KERNEL__ 21 22 #include <linux/types.h> 23 24 struct rwsem_waiter; 25 26 /* 27 * the rw-semaphore definition 28 * - if activity is 0 then there are no active readers or writers 29 * - if activity is +ve then that is the number of active readers 30 * - if activity is -1 then there is one active writer 31 * - if wait_list is not empty, then there are processes waiting for the semaphore 32 */ 33 struct rw_semaphore { 34 __s32 activity; 35 spinlock_t wait_lock; 36 struct list_head wait_list; 37 #if RWSEM_DEBUG 38 int debug; 39 #endif 40 }; 41 42 /* 43 * initialisation 44 */ 45 #if RWSEM_DEBUG 46 #define __RWSEM_DEBUG_INIT , 0 47 #else 48 #define __RWSEM_DEBUG_INIT /* */ 49 #endif 50 51 #define __RWSEM_INITIALIZER(name) \ 52 { 0, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) __RWSEM_DEBUG_INIT } 53 54 #define DECLARE_RWSEM(name) \ 55 struct rw_semaphore name = __RWSEM_INITIALIZER(name) 56 57 extern void FASTCALL(init_rwsem(struct rw_semaphore *sem)); 58 extern void FASTCALL(__down_read(struct rw_semaphore *sem)); 59 extern int FASTCALL(__down_read_trylock(struct rw_semaphore *sem)); 60 extern void FASTCALL(__down_write(struct rw_semaphore *sem)); 61 extern int FASTCALL(__down_write_trylock(struct rw_semaphore *sem)); 62 extern void FASTCALL(__up_read(struct rw_semaphore *sem)); 63 extern void FASTCALL(__up_write(struct rw_semaphore *sem)); 64 65 #endif /* __KERNEL__ */ 66 #endif /* _LINUX_RWSEM_SPINLOCK_H */ 67