On Fri, Apr 10, 2009 at 06:13:57PM +0200, Jan Blunck wrote:I think it is wrong to unconditionally take the lock before calling
atomic_dec_and_test() in _atomic_dec_and_lock(). This will deadlock in
situation where it is known that the counter will not reach zero (e.g. holding
another reference to the same object) but the lock is already taken.
The thought of calling _atomic_dec_and_lock() when you already hold the
lock really really scares me.
Could you please give an example where you need to do this?
Thanx, Paul--
Signed-off-by: Jan Blunck <jblunck@xxxxxxx>
---
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))
--
1.6.0.2