Messages in this thread Patch in this message | | | Date | Mon, 15 Jun 2009 14:11:13 -0400 | From | Valerie Aurora <> | Subject | [PATCH] atomic: Fix _atomic_dec_and_lock() deadlock on UP |
| |
From: Jan Blunck <jblunck@suse.de>
_atomic_dec_and_lock() can deadlock on UP with spinlock debugging enabled. Currently, on UP we unconditionally spin_lock() first, which calls __spin_lock_debug(), which takes the lock unconditionally even on UP. This will deadlock in situations in which we call atomic_dec_and_lock() knowing that the counter won't go to zero (because we hold another reference) and that we already hold the lock. Instead, we should use the SMP code path which only takes the lock if necessary.
Signed-off-by: Jan Blunck <jblunck@suse.de> Signed-off-by: Valerie Aurora (Henson) <vaurora@redhat.com> --- lib/dec_and_lock.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-)
diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c index a65c314..e73822a 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)) -- 1.6.0.6
| |