[tip:urgent] fix kfifo_out_locked race bug

[Stefani Seibold <stefani@seibold.net>]

This patch fix a wrong optimization in include/linux/kfifo.h which could
cause a race in kfifo_out_locked.

Please apply it to the 2.6.33-rc* tree.

Signed-off-by: Stefani Seibold <stefani@seibold.net>
---
 kfifo.h |    7 -------
 1 file changed, 7 deletions(-)

--- linux-2.6.33-rc2.orig/include/linux/kfifo.h	2009-12-27
23:37:04.921185257 +0100
+++ kfifo.h	2010-01-05 14:32:31.414316321 +0100
@@ -228,13 +228,6 @@ static inline __must_check unsigned int 
 
 	ret = kfifo_out(fifo, to, n);
 
-	/*
-	 * optimization: if the FIFO is empty, set the indices to 0
-	 * so we don't wrap the next time
-	 */
-	if (kfifo_is_empty(fifo))
-		kfifo_reset(fifo);
-
 	spin_unlock_irqrestore(lock, flags);
 
 	return ret;