[merged] atomic-only-take-lock-when-the-counter-drops-to-zero-on-up-as-well.patch removed from -mm tree

[merged] atomic-only-take-lock-when-the-counter-drops-to-zero-on-up-as-well.patch removed from -mm tree

[akpm]

The patch titled
     atomic: only take lock when the counter drops to zero on UP as well
has been removed from the -mm tree.  Its filename was
     atomic-only-take-lock-when-the-counter-drops-to-zero-on-up-as-well.patch

This patch was dropped because it was merged into mainline or a subsystem tree

The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
Subject: atomic: only take lock when the counter drops to zero on UP as well
From: Jan Blunck <jblunck@suse.de>

_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>
---

 lib/dec_and_lock.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff -puN lib/dec_and_lock.c~atomic-only-take-lock-when-the-counter-drops-to-zero-on-up-as-well lib/dec_and_lock.c
--- a/lib/dec_and_lock.c~atomic-only-take-lock-when-the-counter-drops-to-zero-on-up-as-well
+++ a/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))
_

Patches currently in -mm which might be from jblunck@suse.de are

origin.patch
linux-next.patch