/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright (c) 2008 Intel Corporation
 * Author: Matthew Wilcox <willy@linux.intel.com>
 *
 * Please see kernel/locking/semaphore.c for documentation of these functions
 */
#ifndef __LINUX_SEMAPHORE_H
#define __LINUX_SEMAPHORE_H

#include <linux/list.h>
#include <linux/spinlock.h>

/* Please don't access any members of this structure directly */
struct semaphore {
        raw_spinlock_t          lock;
        unsigned int            count;
        struct list_head        wait_list;

#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
        unsigned long           last_holder;
#endif
};

#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
#define __LAST_HOLDER_SEMAPHORE_INITIALIZER                             \
        , .last_holder = 0UL
#else
#define __LAST_HOLDER_SEMAPHORE_INITIALIZER
#endif

#define __SEMAPHORE_INITIALIZER(name, n)                                \
{                                                                       \
        .lock           = __RAW_SPIN_LOCK_UNLOCKED((name).lock),        \
        .count          = n,                                            \
        .wait_list      = LIST_HEAD_INIT((name).wait_list)              \
        __LAST_HOLDER_SEMAPHORE_INITIALIZER                             \
}

/*
 * Unlike mutexes, binary semaphores do not have an owner, so up() can
 * be called in a different thread from the one which called down().
 * It is also safe to call down_trylock() and up() from interrupt
 * context.
 */
#define DEFINE_SEMAPHORE(_name, _n)     \
        struct semaphore _name = __SEMAPHORE_INITIALIZER(_name, _n)

static inline void sema_init(struct semaphore *sem, int val)
{
        static struct lock_class_key __key;
        *sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val);
        lockdep_init_map(&sem->lock.dep_map, "semaphore->lock", &__key, 0);
}

extern void down(struct semaphore *sem);
extern int __must_check down_interruptible(struct semaphore *sem);
extern int __must_check down_killable(struct semaphore *sem);
extern int __must_check down_trylock(struct semaphore *sem);
extern int __must_check down_timeout(struct semaphore *sem, long jiffies);
extern void up(struct semaphore *sem);
extern unsigned long sem_last_holder(struct semaphore *sem);

#endif /* __LINUX_SEMAPHORE_H */