ia64/linux-2.6.18-xen.hg

view lib/dec_and_lock.c @ 847:ad4d307bf9ce

net sfc: Update sfc and sfc_resource driver to latest release

...and update sfc_netfront, sfc_netback, sfc_netutil for any API changes

sfc_netback: Fix asymmetric use of SFC buffer table alloc and free
sfc_netback: Clean up if no SFC accel device found
sfc_netback: Gracefully handle case where page grant fails
sfc_netback: Disable net acceleration if the physical link goes down
sfc_netfront: Less verbose error messages, more verbose counters for
rx discard errors
sfc_netfront: Gracefully handle case where SFC netfront fails during
initialisation

Signed-off-by: Kieran Mansley <kmansley@solarflare.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Mar 31 11:59:10 2009 +0100 (2009-03-31)
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);