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authorJan Blunck <jblunck@suse.de>2009-06-16 15:33:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:47 -0700
commit417dcdf99ec9f8d8d6917189130bdc17cb67c678 (patch)
tree4a97ab3ec286dda502ee7b3a16e0b6186cdc30d9 /lib
parenta7d932af06e8eee2163627d19898e18da5635449 (diff)
downloadvexpress-lsk-417dcdf99ec9f8d8d6917189130bdc17cb67c678.tar.gz
atomic: only take lock when the counter drops to zero on UP as well
_atomic_dec_and_lock() should not unconditionally take the lock before calling atomic_dec_and_test() in the UP case. For consistency reasons it should behave exactly like in the SMP case. Besides that this works around the problem that with CONFIG_DEBUG_SPINLOCK this spins in __spin_lock_debug() if the lock is already taken even if the counter doesn't drop to 0. Signed-off-by: Jan Blunck <jblunck@suse.de> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Nick Piggin <npiggin@suse.de> Cc: Valerie Aurora <vaurora@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/dec_and_lock.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c
index a65c3145554..e73822aa6e9 100644
--- a/lib/dec_and_lock.c
+++ b/lib/dec_and_lock.c
@@ -19,11 +19,10 @@
*/
int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
{
-#ifdef CONFIG_SMP
/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
if (atomic_add_unless(atomic, -1, 1))
return 0;
-#endif
+
/* Otherwise do it the slow way */
spin_lock(lock);
if (atomic_dec_and_test(atomic))