include/linux/semaphore.h

   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 */