ia64/linux-2.6.18-xen.hg

view lib/dec_and_lock.c @ 740:bf8b1ee634e2

balloon: Fix the build by including <linux/init.h>

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Nov 25 11:19:41 2008 +0000 (2008-11-25)
parents 831230e53067
children
line source
1 #include <linux/module.h>
2 #include <linux/spinlock.h>
3 #include <asm/atomic.h>
5 /*
6 * This is an implementation of the notion of "decrement a
7 * reference count, and return locked if it decremented to zero".
8 *
9 * NOTE NOTE NOTE! This is _not_ equivalent to
10 *
11 * if (atomic_dec_and_test(&atomic)) {
12 * spin_lock(&lock);
13 * return 1;
14 * }
15 * return 0;
16 *
17 * because the spin-lock and the decrement must be
18 * "atomic".
19 */
20 int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
21 {
22 #ifdef CONFIG_SMP
23 /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
24 if (atomic_add_unless(atomic, -1, 1))
25 return 0;
26 #endif
27 /* Otherwise do it the slow way */
28 spin_lock(lock);
29 if (atomic_dec_and_test(atomic))
30 return 1;
31 spin_unlock(lock);
32 return 0;
33 }
35 EXPORT_SYMBOL(_atomic_dec_and_lock);