kfifo: fix kfifo_out_locked race bug

Fix a wrong optimization in include/linux/kfifo.h which could cause a race
in kfifo_out_locked.

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Reported-by: Johan Hovold <jhovold@gmail.com>
Cc: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
index 7c6b32a1421c000b33f1fa924f3f7ec43b32c551..c4ac88b3c30227f2473e026ec8fbe03a6213ee63 100644 (file)
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -228,13 +228,6 @@ static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
 
        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;