linux-kernel - [PATCH 7/9] drivers/rtc: correct error-handling code

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Date:	Tue, 28 Jul 2009 17:55:33 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	p_gortmaker@...oo.com, a.zummo@...ertech.it,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [PATCH 7/9] drivers/rtc: correct error-handling code

From: Julia Lawall <julia@...u.dk>

This code is not executed before ds1307->rtc has been successfully
initialized to the result of calling rtc_device_register.  Thus the test
that ds1307->rtc is not NULL is always true.

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

// <smpl>
@match exists@
expression x, E;
statement S1, S2;
@@

x = rtc_device_register(...)
... when != x = E
(
*  if (x == NULL || ...) S1 else S2
|
*  if (x == NULL && ...) S1 else S2
)
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>

---
 drivers/rtc/rtc-ds1307.c            |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 47a93c0..eb99ee4 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -896,8 +896,7 @@ read_rtc:
 	return 0;
 
 exit_irq:
-	if (ds1307->rtc)
-		rtc_device_unregister(ds1307->rtc);
+	rtc_device_unregister(ds1307->rtc);
 exit_free:
 	kfree(ds1307);
 	return err;
--
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