Dec 15 2009

drivers/cpuidle: Move dereference after NULL test 

Author: Julia Lawall <julia@diku.dk>

It does not seem possible that ldev can be NULL, so drop the unnecessary
test.  If ldev can somehow be NULL, then the initialization of last_idx
should be moved below the test.

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

// 
@match exists@
expression x, E;
identifier fld;
@@

* x->fld
  ... when != \(x = E\|&x\)
* x == NULL
// 

Signed-off-by: Julia Lawall 
Acked-by: Arjan van de Ven 
Cc: Ingo Molnar 
Cc: Venkatesh Pallipadi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 

---
 drivers/cpuidle/governors/ladder.c | 3 ---
 1 file changed, 3 deletions(-)
 
diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
index a4bec3f..1c1ceb4 100644
--- a/drivers/cpuidle/governors/ladder.c
+++ b/drivers/cpuidle/governors/ladder.c
@@ -69,9 +69,6 @@ static int ladder_select_state(struct cpuidle_device *dev)
 	int last_residency, last_idx = ldev->last_state_idx;
 	int latency_req = pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY);
 
-	if (unlikely(!ldev))
-		return 0;
-
 	/* Special case when user has set very strict latency requirement */
 	if (unlikely(latency_req == 0)) {
 		ladder_do_selection(ldev, last_idx, 0);

qlambert