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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * Copyright (C) 2003 Jerome Marchand, Bull S.A.
3 * Cleaned up by David Mosberger-Tang <davidm@hpl.hp.com>
4 *
5 * This file is released under the GPLv2, or at your option any later version.
6 *
7 * ia64 version of "atomic_dec_and_lock()" using the atomic "cmpxchg" instruction. This
8 * code is an adaptation of the x86 version of "atomic_dec_and_lock()".
9 */
10
11#include <linux/compiler.h>
12#include <linux/module.h>
13#include <linux/spinlock.h>
14#include <asm/atomic.h>
15
16/*
17 * Decrement REFCOUNT and if the count reaches zero, acquire the spinlock. Both of these
18 * operations have to be done atomically, so that the count doesn't drop to zero without
19 * acquiring the spinlock first.
20 */
21int
22_atomic_dec_and_lock (atomic_t *refcount, spinlock_t *lock)
23{
24 int old, new;
25
26 do {
27 old = atomic_read(refcount);
28 new = old - 1;
29
30 if (unlikely (old == 1)) {
31 /* oops, we may be decrementing to zero, do it the slow way... */
32 spin_lock(lock);
33 if (atomic_dec_and_test(refcount))
34 return 1;
35 spin_unlock(lock);
36 return 0;
37 }
38 } while (cmpxchg(&refcount->counter, old, new) != old);
39 return 0;
40}
41
42EXPORT_SYMBOL(_atomic_dec_and_lock);