From: Julia Lawall <julia@diku.dk>
Date: Wed, 10 Mar 2010 23:23:52 +0000 (-0800)
Subject: drivers/char/mmtimer.c: eliminate useless code
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=0fbcae222b8aa3a47034a484e02e7fc14050c783;p=openwrt%2Fstaging%2Fblogic.git

drivers/char/mmtimer.c: eliminate useless code

The variable x is initialized twice to the same (side effect-free)
expression.  Drop one initialization.

A simplified version of the semantic match that finds this problem is:
(http://coccinelle.lip6.fr/)

// <smpl>
@forall@
idexpression *x;
identifier f!=ERR_PTR;
@@

x = f(...)
... when != x
(
x = f(...,<+...x...+>,...)
|
* x = f(...)
)
// </smpl>

Stefan observed:

  The next x = rb_entry(mn->next, struct mmtimer, list); is preceded by a
  test whether mn->next is NULL.

  Unless that test is redundant too, your patch fixes a potential NULL
  pointer dereference, introduced by commit cbacdd95 "SGI Altix mmtimer:
  allow larger number of timers per node" in 2.6.26.

Signed-off-by: Julia Lawall <julia@diku.dk>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/drivers/char/mmtimer.c b/drivers/char/mmtimer.c
index 918711aa56f3..04fd0d843b3b 100644
--- a/drivers/char/mmtimer.c
+++ b/drivers/char/mmtimer.c
@@ -546,7 +546,7 @@ static void mmtimer_tasklet(unsigned long data)
 {
 	int nodeid = data;
 	struct mmtimer_node *mn = &timers[nodeid];
-	struct mmtimer *x = rb_entry(mn->next, struct mmtimer, list);
+	struct mmtimer *x;
 	struct k_itimer *t;
 	unsigned long flags;