linux-kernel - RE: [PATCH] kernel/watchdog: fix spurious hard lockups

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Message-ID: <37D7C6CF3E00A74B8858931C1DB2F07753710034@SHSMSX103.ccr.corp.intel.com>
Date:   Wed, 21 Jun 2017 12:40:28 +0000
From:   "Liang, Kan" <kan.liang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dzickus@...hat.com" <dzickus@...hat.com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "babu.moger@...cle.com" <babu.moger@...cle.com>,
        "atomlin@...hat.com" <atomlin@...hat.com>,
        "prarit@...hat.com" <prarit@...hat.com>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "eranian@...gle.com" <eranian@...gle.com>,
        "acme@...hat.com" <acme@...hat.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH] kernel/watchdog: fix spurious hard lockups


> >
> > The right fix for mainline can be found here.
> > perf/x86/intel: enable CPU ref_cycles for GP counter perf/x86/intel,
> > watchdog: Switch NMI watchdog to ref cycles on x86
> > https://patchwork.kernel.org/patch/9779087/
> > https://patchwork.kernel.org/patch/9779089/
> 
> Presumably the "right fix" will later be altered to revert this one-line
> workaround?

The "right fix" itself will not touch the watchdog rate. I will modify the
changelog to notify the people who want to do the backport.

As my understanding, it's not harmful even if we don't revert the
workaround. It can still detect the hardlockup, only takes
a tiny bit longer.

Thanks,
Kan