// 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){	/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */	if (atomic_add_unless(atomic, -1, 1))		return 0; 	/* Otherwise do it the slow way */	spin_lock(lock);	if (atomic_dec_and_test(atomic))		return 1;	spin_unlock(lock);	return 0;} EXPORT_SYMBOL(atomic_dec_and_lock); int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,				 unsigned long *flags){	/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */	if (atomic_add_unless(atomic, -1, 1))		return 0; 	/* Otherwise do it the slow way */	spin_lock_irqsave(lock, *flags);	if (atomic_dec_and_test(atomic))		return 1;	spin_unlock_irqrestore(lock, *flags);	return 0;}EXPORT_SYMBOL(_atomic_dec_and_lock_irqsave); int atomic_dec_and_raw_lock(atomic_t *atomic, raw_spinlock_t *lock){	/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */	if (atomic_add_unless(atomic, -1, 1))		return 0; 	/* Otherwise do it the slow way */	raw_spin_lock(lock);	if (atomic_dec_and_test(atomic))		return 1;	raw_spin_unlock(lock);	return 0;}EXPORT_SYMBOL(atomic_dec_and_raw_lock); int _atomic_dec_and_raw_lock_irqsave(atomic_t *atomic, raw_spinlock_t *lock,				     unsigned long *flags){	/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */	if (atomic_add_unless(atomic, -1, 1))		return 0; 	/* Otherwise do it the slow way */	raw_spin_lock_irqsave(lock, *flags);	if (atomic_dec_and_test(atomic))		return 1;	raw_spin_unlock_irqrestore(lock, *flags);	return 0;}EXPORT_SYMBOL(_atomic_dec_and_raw_lock_irqsave);