[mirror_ubuntu-bionic-kernel.git] / arch / ppc / lib / dec_and_lock.c

#include <linux/module.h>
#include <linux/spinlock.h>
#include <asm/atomic.h>
#include <asm/system.h>

/*
 * This is an implementation of the notion of "decrement a
 * reference count, and return locked if it decremented to zero".
 *
 * This implementation can be used on any architecture that
 * has a cmpxchg, and where atomic->value is an int holding
 * the value of the atomic (i.e. the high bits aren't used
 * for a lock or anything like that).
 */
int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
{
	int counter;
	int newcount;

	for (;;) {
		counter = atomic_read(atomic);
		newcount = counter - 1;
		if (!newcount)
			break;		/* do it the slow way */

		newcount = cmpxchg(&atomic->counter, counter, newcount);
		if (newcount == counter)
			return 0;
	}

	spin_lock(lock);
	if (atomic_dec_and_test(atomic))
		return 1;
	spin_unlock(lock);
	return 0;
}

EXPORT_SYMBOL(_atomic_dec_and_lock);
Commit	Line	Data
1da177e4 LT	1	#include <linux/module.h>
	2	#include <linux/spinlock.h>
	3	#include <asm/atomic.h>
	4	#include <asm/system.h>
	5
	6	/*
	7	* This is an implementation of the notion of "decrement a
	8	* reference count, and return locked if it decremented to zero".
	9	*
	10	* This implementation can be used on any architecture that
	11	* has a cmpxchg, and where atomic->value is an int holding
	12	* the value of the atomic (i.e. the high bits aren't used
	13	* for a lock or anything like that).
1da177e4	14	*/
1da177e4 LT	15	int _atomic_dec_and_lock(atomic_t atomic, spinlock_t lock)
	16	{
	17	int counter;
	18	int newcount;
	19
	20	for (;;) {
	21	counter = atomic_read(atomic);
	22	newcount = counter - 1;
	23	if (!newcount)
	24	break; /* do it the slow way */
	25
	26	newcount = cmpxchg(&atomic->counter, counter, newcount);
	27	if (newcount == counter)
	28	return 0;
	29	}
	30
	31	spin_lock(lock);
	32	if (atomic_dec_and_test(atomic))
	33	return 1;
	34	spin_unlock(lock);
	35	return 0;
	36	}
	37
	38	EXPORT_SYMBOL(_atomic_dec_and_lock);