1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * Copyright (c) 2008 Intel Corporation 4 * Author: Matthew Wilcox <willy@linux.intel.com> 5 * 6 * Please see kernel/locking/semaphore.c for documentation of these functions 7 */ 8 #ifndef __LINUX_SEMAPHORE_H 9 #define __LINUX_SEMAPHORE_H 10 11 #include <linux/list.h> 12 #include <linux/spinlock.h> 13 14 /* Please don't access any members of this structure directly */ 15 struct semaphore { 16 raw_spinlock_t lock; 17 unsigned int count; 18 struct list_head wait_list; 19 }; 20 21 #define __SEMAPHORE_INITIALIZER(name, n) \ 22 { \ 23 .lock = __RAW_SPIN_LOCK_UNLOCKED((name).lock), \ 24 .count = n, \ 25 .wait_list = LIST_HEAD_INIT((name).wait_list), \ 26 } 27 28 /* 29 * Unlike mutexes, binary semaphores do not have an owner, so up() can 30 * be called in a different thread from the one which called down(). 31 * It is also safe to call down_trylock() and up() from interrupt 32 * context. 33 */ 34 #define DEFINE_SEMAPHORE(_name, _n) \ 35 struct semaphore _name = __SEMAPHORE_INITIALIZER(_name, _n) 36 37 static inline void sema_init(struct semaphore *sem, int val) 38 { 39 static struct lock_class_key __key; 40 *sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val); 41 lockdep_init_map(&sem->lock.dep_map, "semaphore->lock", &__key, 0); 42 } 43 44 extern void down(struct semaphore *sem); 45 extern int __must_check down_interruptible(struct semaphore *sem); 46 extern int __must_check down_killable(struct semaphore *sem); 47 extern int __must_check down_trylock(struct semaphore *sem); 48 extern int __must_check down_timeout(struct semaphore *sem, long jiffies); 49 extern void up(struct semaphore *sem); 50 51 #endif /* __LINUX_SEMAPHORE_H */ 52