Messages in this thread Patch in this message | | | Date | Thu, 23 Apr 2009 15:51:05 +0200 | From | Jan Blunck <> | Subject | [PATCH] atomic: Only take lock when the counter drops to zero on UP as well (v2) |
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_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> --- 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))
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