ia64/linux-2.6.18-xen.hg

annotate 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
rev   line source
ian@0 1 #include <linux/module.h>
ian@0 2 #include <linux/spinlock.h>
ian@0 3 #include <asm/atomic.h>
ian@0 4
ian@0 5 /*
ian@0 6 * This is an implementation of the notion of "decrement a
ian@0 7 * reference count, and return locked if it decremented to zero".
ian@0 8 *
ian@0 9 * NOTE NOTE NOTE! This is _not_ equivalent to
ian@0 10 *
ian@0 11 * if (atomic_dec_and_test(&atomic)) {
ian@0 12 * spin_lock(&lock);
ian@0 13 * return 1;
ian@0 14 * }
ian@0 15 * return 0;
ian@0 16 *
ian@0 17 * because the spin-lock and the decrement must be
ian@0 18 * "atomic".
ian@0 19 */
ian@0 20 int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
ian@0 21 {
ian@0 22 #ifdef CONFIG_SMP
ian@0 23 /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
ian@0 24 if (atomic_add_unless(atomic, -1, 1))
ian@0 25 return 0;
ian@0 26 #endif
ian@0 27 /* Otherwise do it the slow way */
ian@0 28 spin_lock(lock);
ian@0 29 if (atomic_dec_and_test(atomic))
ian@0 30 return 1;
ian@0 31 spin_unlock(lock);
ian@0 32 return 0;
ian@0 33 }
ian@0 34
ian@0 35 EXPORT_SYMBOL(_atomic_dec_and_lock);