linux/lib/dec_and_lock.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/export.h>
#include <linux/spinlock.h>
#include <linux/atomic.h>

/*
 * This is an implementation of the notion of "decrement a
 * reference count, and return locked if it decremented to zero".
 *
 * NOTE NOTE NOTE! This is _not_ equivalent to
 *
 *	if (atomic_dec_and_test(&atomic)) {
 *		spin_lock(&lock);
 *		return 1;
 *	}
 *	return 0;
 *
 * because the spin-lock and the decrement must be
 * "atomic".
 */
int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
{ … }

EXPORT_SYMBOL(…);

int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
				 unsigned long *flags)
{ … }
EXPORT_SYMBOL(…);

int _atomic_dec_and_raw_lock(atomic_t *atomic, raw_spinlock_t *lock)
{ … }
EXPORT_SYMBOL(…);

int _atomic_dec_and_raw_lock_irqsave(atomic_t *atomic, raw_spinlock_t *lock,
				     unsigned long *flags)
{ … }
EXPORT_SYMBOL(…);