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@xxxxxxx> _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@xxxxxxx> Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Acked-by: Nick Piggin <npiggin@xxxxxxx> Cc: Valerie Aurora <vaurora@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- 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@xxxxxxx are origin.patch linux-next.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html