From 417dcdf99ec9f8d8d6917189130bdc17cb67c678 Mon Sep 17 00:00:00 2001 From: Jan Blunck Date: Tue, 16 Jun 2009 15:33:33 -0700 Subject: [PATCH] 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 Acked-by: Paul E. McKenney Acked-by: Nick Piggin Cc: Valerie Aurora Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/dec_and_lock.c | 3 +-- 1 file changed, 1 insertion(+), 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))