Update to 3.4-final.

[linux-flexiantxendom0-3.2.10.git] / lib / dec_and_lock.c

diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c
index b9d574c..e262785 100644 (file)
--- a/lib/dec_and_lock.c
+++ b/lib/dec_and_lock.c
@@ -1,12 +1,10 @@
-#include <linux/module.h>
+#include <linux/export.h>
 #include <linux/spinlock.h>
-#include <asm/atomic.h>
+#include <linux/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 +16,14 @@
  *
  * 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)
+int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
 {
+       /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
+       if (atomic_add_unless(atomic, -1, 1))
+               return 0;
+
+       /* Otherwise do it the slow way */
        spin_lock(lock);
        if (atomic_dec_and_test(atomic))
                return 1;
@@ -36,5 +31,4 @@ int atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
        return 0;
 }
 
-EXPORT_SYMBOL(atomic_dec_and_lock);
-#endif
+EXPORT_SYMBOL(_atomic_dec_and_lock);