[PATCH] fix bad macro param in timer.c

We have

#define INDEX(N) (base->timer_jiffies >> (TVR_BITS + N * TVN_BITS)) & TVN_MASK

and it's used via

	list = varray[i + 1]->vec + (INDEX(i + 1));

So, due to underparenthesisation, this INDEX(i+1) is now a ...  (TVR_BITS + i
+ 1 * TVN_BITS)) ...

So this bugfix changes behaviour.  It worked before by sheer luck:

  "If i was anything but 0, it was broken.  But this was only used by
   s390 and arm.  Since it was for the next interrupt, could that next
   interrupt be a problem (going into the second cascade)? But it was
   probably seldom wrong.  That is, this would fail if the next
   interrupt was in the second cascade, and was wrapped.  Which may
   never of happened.  Also if it did happen, it would have just missed
   the interrupt.

   If an interrupt was missed, and no one was there to miss it, was it
   really missed :-)"

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/timer.c b/kernel/timer.c
index ee319fc69f40d7a2818485f8e76dde37d1eda76c..726caf9a0a69ca90642804d419db4229c28ba9b3 100644 (file)
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -408,7 +408,7 @@ static int cascade(tvec_base_t *base, tvec_t *tv, int index)
  * This function cascades all vectors and executes all expired timer
  * vectors.
  */
-#define INDEX(N) (base->timer_jiffies >> (TVR_BITS + N * TVN_BITS)) & TVN_MASK
+#define INDEX(N) ((base->timer_jiffies >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK)
 
 static inline void __run_timers(tvec_base_t *base)
 {