X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Fdec_and_lock.c;h=a65c314555416d9f1ea262455d1da313e1959902;hb=43bc926fffd92024b46cafaf7350d669ba9ca884;hp=6658d81e1836517107b5b8b39aa0c7e65032ec6e;hpb=cee37fe97739d85991964371c1f3a745c00dd236;p=linux-2.6.git

diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c
index 6658d81e1..a65c31455 100644
--- a/lib/dec_and_lock.c
+++ b/lib/dec_and_lock.c
@@ -3,10 +3,8 @@
 #include <asm/atomic.h>
 
 /*
- * This is an architecture-neutral, but slow,
- * implementation of the notion of "decrement
- * a reference count, and return locked if it
- * decremented to zero".
+ * This is an implementation of the notion of "decrement a
+ * reference count, and return locked if it decremented to zero".
  *
  * NOTE NOTE NOTE! This is _not_ equivalent to
  *
@@ -18,17 +16,15 @@
  *
  * because the spin-lock and the decrement must be
  * "atomic".
- *
- * This slow version gets the spinlock unconditionally,
- * and releases it if it isn't needed. Architectures
- * are encouraged to come up with better approaches,
- * this is trivially done efficiently using a load-locked
- * store-conditional approach, for example.
  */
-
-#ifndef ATOMIC_DEC_AND_LOCK
 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))
 		return 1;
@@ -37,4 +33,3 @@ int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
 }
 
 EXPORT_SYMBOL(_atomic_dec_and_lock);
-#endif