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From: Don Zickus <dzickus@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
	uobergfe@redhat.com, Don Zickus <dzickus@redhat.com>
Subject: [PATCH 6/9] watchdog: implement error handling for failure to set up hardware perf events
Date: Tue,  4 Nov 2014 11:20:21 -0500	[thread overview]
Message-ID: <1415118024-194247-7-git-send-email-dzickus@redhat.com> (raw)
In-Reply-To: <1415118024-194247-1-git-send-email-dzickus@redhat.com>

From: Ulrich Obergfell <uobergfe@redhat.com>

If watchdog_nmi_enable() fails to set up the hardware perf event
of one CPU, the entire hard lockup detector is deemed unreliable.
Hence, disable the hard lockup detector and shut down the hardware
perf events on all CPUs.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
---
 kernel/watchdog.c |   18 ++++++++++++++++++
 1 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 2897a5e..86ba5e5 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -502,6 +502,15 @@ static void watchdog(unsigned int cpu)
 	__this_cpu_write(soft_lockup_hrtimer_cnt,
 			 __this_cpu_read(hrtimer_interrupts));
 	__touch_watchdog();
+
+	/*
+	 * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
+	 * failure path. Check for failures that can occur asynchronously -
+	 * for example, when CPUs are on-lined - and shut down the hardware
+	 * perf event on each CPU accordingly.
+	 */
+	if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
+		watchdog_nmi_disable(cpu);
 }
 
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
@@ -552,6 +561,15 @@ handle_err:
 		goto out_save;
 	}
 
+	/*
+	 * Disable the hard lockup detector if _any_ CPU fails to set up
+	 * set up the hardware perf event. The watchdog() function checks
+	 * the NMI_WATCHDOG_ENABLED bit periodically.
+	 */
+	smp_mb__before_atomic();
+	clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
+	smp_mb__after_atomic();
+
 	/* skip displaying the same error again */
 	if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
 		return PTR_ERR(event);
-- 
1.7.1


  parent reply	other threads:[~2014-11-04 16:22 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-04 16:20 [PATCH 0/9] watchdog: internally split softlockup and hardlockup Don Zickus
2014-11-04 16:20 ` [PATCH 1/9] watchdog: new definitions and variables, initialization Don Zickus
2014-11-04 16:20 ` [PATCH 2/9] watchdog: introduce the proc_watchdog_update() function Don Zickus
2014-11-04 16:20 ` [PATCH 3/9] watchdog: move definition of 'watchdog_proc_mutex' outside of proc_dowatchdog() Don Zickus
2014-11-04 16:20 ` [PATCH 4/9] watchdog: introduce the proc_watchdog_common() function Don Zickus
2014-11-04 16:20 ` [PATCH 5/9] watchdog: introduce separate handlers for parameters in /proc/sys/kernel Don Zickus
2014-11-04 16:20 ` Don Zickus [this message]
2014-11-04 16:20 ` [PATCH 7/9] watchdog: enable the new user interface of the watchdog mechanism Don Zickus
2014-11-04 16:20 ` [PATCH 8/9] watchdog: clean up some function names and arguments Don Zickus
2014-11-04 16:20 ` [PATCH 9/9] watchdog: introduce the hardlockup_detector_disable() function Don Zickus
2014-12-17 21:25 ` [PATCH 0/9] watchdog: internally split softlockup and hardlockup Don Zickus
2015-01-21 14:15 ` Don Zickus
2015-01-21 22:23   ` Andrew Morton
2015-02-05 20:40 Don Zickus
2015-02-05 20:40 ` [PATCH 6/9] watchdog: implement error handling for failure to set up hardware perf events Don Zickus
2015-02-23 21:17   ` Andrew Morton
2015-02-24 15:39     ` Don Zickus
2015-03-02 19:06     ` Don Zickus

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