Revision ecd68853b852cdafb138f9c437f3a751fe7dc381 authored by Linus Torvalds on 26 May 2006, 22:13:33 UTC, committed by Linus Torvalds on 26 May 2006, 22:13:33 UTC
* master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6: [NET]: dev.c comment fixes [IPV6] ROUTE: Don't try less preferred routes for on-link routes. [IRDA]: *_DONGLE should depend on IRTTY_SIR [MAINTAINERS]: Add entry for netem
dec_and_lock.c
#include <linux/module.h>
#include <linux/spinlock.h>
#include <asm/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)
{
#ifdef CONFIG_SMP
/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
if (atomic_add_unless(atomic, -1, 1))
return 0;
#endif
/* 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);
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