| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
| 2 | /* rwsem-spinlock.h: fallback C implementation |
| 3 | * |
| 4 | * Copyright (c) 2001 David Howells (dhowells@redhat.com). |
| 5 | * - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de> |
| 6 | * - Derived also from comments by Linus |
| 7 | */ |
| 8 | |
| 9 | #ifndef _LINUX_RWSEM_SPINLOCK_H |
| 10 | #define _LINUX_RWSEM_SPINLOCK_H |
| 11 | |
| 12 | #ifndef _LINUX_RWSEM_H |
| 13 | #error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead" |
| 14 | #endif |
| 15 | |
| 16 | #ifdef __KERNEL__ |
| 17 | /* |
| 18 | * the rw-semaphore definition |
| 19 | * - if count is 0 then there are no active readers or writers |
| 20 | * - if count is +ve then that is the number of active readers |
| 21 | * - if count is -1 then there is one active writer |
| 22 | * - if wait_list is not empty, then there are processes waiting for the semaphore |
| 23 | */ |
| 24 | struct rw_semaphore { |
| 25 | __s32 count; |
| 26 | raw_spinlock_t wait_lock; |
| 27 | struct list_head wait_list; |
| 28 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 29 | struct lockdep_map dep_map; |
| 30 | #endif |
| 31 | }; |
| 32 | |
| 33 | #define RWSEM_UNLOCKED_VALUE 0x00000000 |
| 34 | |
| 35 | extern void __down_read(struct rw_semaphore *sem); |
| 36 | extern int __must_check __down_read_killable(struct rw_semaphore *sem); |
| 37 | extern int __down_read_trylock(struct rw_semaphore *sem); |
| 38 | extern void __down_write(struct rw_semaphore *sem); |
| 39 | extern int __must_check __down_write_killable(struct rw_semaphore *sem); |
| 40 | extern int __down_write_trylock(struct rw_semaphore *sem); |
| 41 | extern void __up_read(struct rw_semaphore *sem); |
| 42 | extern void __up_write(struct rw_semaphore *sem); |
| 43 | extern void __downgrade_write(struct rw_semaphore *sem); |
| 44 | extern int rwsem_is_locked(struct rw_semaphore *sem); |
| 45 | |
| 46 | #endif /* __KERNEL__ */ |
| 47 | #endif /* _LINUX_RWSEM_SPINLOCK_H */ |