linux-kernel - [PATCH] watchdog: Disable nmi perf event in the error path of enabling watchdog

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Date:	Thu, 21 Apr 2011 04:22:36 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hillf Danton <dhillf@...il.com>,
	Don Zickus <dzickus@...hat.com>
Subject: [PATCH] watchdog: Disable nmi perf event in the error path of enabling watchdog

From: Hillf Danton <dhillf@...il.com>

In corner cases where softlockup watchdog is not setup successfully,
the relevant nmi perf event for hardlockup watchdog could be disabled,
then the status of the underlying hardware remains unchanged.

[ also if the kthread doesn't start, the hrtimer won't run and the
  hardlockup detector will falsely fire ]

Signed-off-by: Hillf Danton <dhillf@...il.com>
Signed-off-by: Don Zickus <dzickus@...hat.com>
---
 kernel/watchdog.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 140dce7..14733d4 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -430,9 +430,12 @@ static int watchdog_enable(int cpu)
 		p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
 		if (IS_ERR(p)) {
 			printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
-			if (!err)
+			if (!err) {
 				/* if hardlockup hasn't already set this */
 				err = PTR_ERR(p);
+				/* and disable the perf event */
+				watchdog_nmi_disable(cpu);
+			}
 			goto out;
 		}
 		kthread_bind(p, cpu);
-- 
1.7.4.2

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