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From: Don Zickus <dzickus@redhat.com>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Ulrich Obergfell <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: Thu,  5 Feb 2015 15:40:22 -0500	[thread overview]
Message-ID: <1423168825-156238-7-git-send-email-dzickus@redhat.com> (raw)
In-Reply-To: <1423168825-156238-1-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 26002ed..7ad8949 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:[~2015-02-05 20:40 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-05 20:40 [PATCH 0/9] watchdog: internally split softlockup and hardlockup Don Zickus
2015-02-05 20:40 ` [PATCH 1/9] watchdog: new definitions and variables, initialization Don Zickus
2015-02-05 20:40 ` [PATCH 2/9] watchdog: introduce the proc_watchdog_update() function Don Zickus
2015-02-05 20:40 ` [PATCH 3/9] watchdog: move definition of 'watchdog_proc_mutex' outside of proc_dowatchdog() Don Zickus
2015-02-05 20:40 ` [PATCH 4/9] watchdog: introduce the proc_watchdog_common() function Don Zickus
2015-02-05 20:40 ` [PATCH 5/9] watchdog: introduce separate handlers for parameters in /proc/sys/kernel Don Zickus
2015-02-05 20:40 ` Don Zickus [this message]
2015-02-23 21:17   ` [PATCH 6/9] watchdog: implement error handling for failure to set up hardware perf events Andrew Morton
2015-02-24 15:39     ` Don Zickus
2015-03-02 19:06     ` Don Zickus
2015-02-05 20:40 ` [PATCH 7/9] watchdog: enable the new user interface of the watchdog mechanism Don Zickus
2015-02-23 21:19   ` Andrew Morton
2015-02-24 15:46     ` Don Zickus
2015-03-02 19:05     ` [PATCH 7/9 UPDATE] " Don Zickus
2015-02-05 20:40 ` [PATCH 8/9] watchdog: clean up some function names and arguments Don Zickus
2015-02-05 20:40 ` [PATCH 9/9] watchdog: introduce the hardlockup_detector_disable() function Don Zickus
2015-02-05 23:22 ` [PATCH 0/9] watchdog: internally split softlockup and hardlockup Andrew Morton
2015-02-06 14:12   ` Don Zickus
  -- strict thread matches above, loose matches on Subject: below --
2014-11-04 16:20 Don Zickus
2014-11-04 16:20 ` [PATCH 6/9] watchdog: implement error handling for failure to set up hardware perf events Don Zickus

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