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/*

 * x86 version of "atomic_dec_and_lock()" using

 * the atomic "cmpxchg" instruction.

 *

 * (For CPU's lacking cmpxchg, we use the slow

 * generic version, and this one never even gets

 * compiled).

 */

#include <linux/spinlock.h>

#include <asm/atomic.h>

int atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)

{

        int counter;

        int newcount;

repeat:

        counter = atomic_read(atomic);

        newcount = counter-1;

        if (!newcount)

                goto slow_path;

        asm volatile("lock; cmpxchgl %1,%2"

                :"=a" (newcount)

                :"r" (newcount), "m" (atomic->counter), "0" (counter));

        /* If the above failed, "eax" will have changed */

        if (newcount != counter)

                goto repeat;

        return 0;

slow_path:

        spin_lock(lock);

        if (atomic_dec_and_test(atomic))

                return 1;

        spin_unlock(lock);

        return 0;

}