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From: Thomas Gleixner <tglx@linutronix.de>
To: Kan Liang <kan.liang@intel.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	dzickus@redhat.com, Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	babu.moger@oracle.com, atomlin@redhat.com,
	Prarit Bhargava <prarit@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	eranian@google.com, Arnaldo Carvalho de Melo <acme@redhat.com>,
	ak@linux.intel.com, stable@vger.kernel.org
Subject: Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups
Date: Thu, 22 Jun 2017 17:33:02 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.20.1706221730520.1885@nanos> (raw)
In-Reply-To: <alpine.DEB.2.20.1706212235550.2152@nanos>

On Wed, 21 Jun 2017, Thomas Gleixner wrote:

> On Wed, 21 Jun 2017, kan.liang@intel.com wrote:
> > We now have more and more systems where the Turbo range is wide enough
> > that the NMI watchdog expires faster than the soft watchdog timer that
> > updates the interrupt tick the NMI watchdog relies on.
> > 
> > This problem was originally added by commit 58687acba592
> > ("lockup_detector: Combine nmi_watchdog and softlockup detector").
> > Previously the NMI watchdog would always check jiffies, which were
> > ticking fast enough. But now the backing is quite slow so the expire
> > time becomes more sensitive.
> 
> And slapping a factor 3 on the NMI period is the wrong answer to the
> problem. The simple solution would be to increase the hrtimer frequency,
> but that's not really desired either.

Thinking a bit more about it. Increasing the hrtimer frequency and
maintaining the current frequency of softlockup_watchdog wakeups, would be
probably the most trivial workaround for now.

Thanks,

	tglx

  reply	other threads:[~2017-06-22 15:33 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-21 14:41 [PATCH V2] kernel/watchdog: fix spurious hard lockups kan.liang
2017-06-21 15:12 ` Thomas Gleixner
2017-06-21 15:47   ` Liang, Kan
2017-06-21 17:40     ` Prarit Bhargava
2017-06-21 17:07   ` Andi Kleen
2017-06-21 19:59     ` Thomas Gleixner
2017-06-21 21:53 ` Thomas Gleixner
2017-06-22 15:33   ` Thomas Gleixner [this message]
2017-06-22 15:44   ` Don Zickus
2017-06-22 15:48     ` Liang, Kan
2017-06-23  8:01     ` Thomas Gleixner
2017-06-23 16:29       ` Don Zickus
2017-06-23 21:50         ` Thomas Gleixner
2017-06-26 20:19           ` Don Zickus
2017-06-26 20:30             ` Thomas Gleixner
2017-06-27 20:12             ` Don Zickus
2017-06-27 20:49               ` Liang, Kan
2017-06-27 21:09                 ` Don Zickus
2017-06-27 23:48                 ` Andi Kleen
2017-06-28 19:00                   ` Don Zickus
2017-06-28 20:14                     ` Andi Kleen
2017-06-29 15:44                       ` Don Zickus
2017-06-29 16:12                         ` Andi Kleen
2017-06-29 16:26                           ` Don Zickus
2017-06-29 16:36                             ` Andi Kleen
2017-07-17  1:24               ` Liang, Kan
2017-07-17  7:14                 ` Thomas Gleixner
2017-07-17 12:18                   ` Liang, Kan
2017-07-17 13:13                     ` Thomas Gleixner
2017-07-17 14:46                       ` Liang, Kan
2017-07-17 15:00                         ` Thomas Gleixner
2017-07-17 14:46                 ` Don Zickus
2017-08-15  1:16                   ` Liang, Kan
2017-08-15  1:28                     ` Linus Torvalds
2017-08-15  7:50                     ` Thomas Gleixner
2017-08-17 15:45                       ` Liang, Kan
2017-08-18 10:39                       ` [tip:core/urgent] kernel/watchdog: Prevent false positives with turbo modes tip-bot for Thomas Gleixner

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