From: "Liang, Kan" <kan.liang@intel.com>
To: Don Zickus <dzickus@redhat.com>, Thomas Gleixner <tglx@linutronix.de>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"mingo@kernel.org" <mingo@kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"babu.moger@oracle.com" <babu.moger@oracle.com>,
"atomlin@redhat.com" <atomlin@redhat.com>,
"prarit@redhat.com" <prarit@redhat.com>,
"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
"peterz@infradead.org" <peterz@infradead.org>,
"eranian@google.com" <eranian@google.com>,
"acme@redhat.com" <acme@redhat.com>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [PATCH V2] kernel/watchdog: fix spurious hard lockups
Date: Mon, 17 Jul 2017 01:24:23 +0000 [thread overview]
Message-ID: <37D7C6CF3E00A74B8858931C1DB2F0775371D43E@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <20170627201249.ll34ecwhpme3vh2u@redhat.com>
> On Mon, Jun 26, 2017 at 04:19:27PM -0400, Don Zickus wrote:
> > On Fri, Jun 23, 2017 at 11:50:25PM +0200, Thomas Gleixner wrote:
> > > On Fri, 23 Jun 2017, Don Zickus wrote:
> > > > Hmm, all this work for a temp fix. Kan, how much longer until the
> > > > real fix of having perf count the right cycles?
> > >
> > > Quite a while. The approach is wilfully breaking the user space ABI,
> > > which is not going to happen.
> > >
> > > And there is a simpler solution as well, as I said here:
> > >
> > >
> > > http://lkml.kernel.org/r/alpine.DEB.2.20.1706221730520.1885@nanos
> >
> > Hi Thomas,
> >
> > So, you are saying instead of slowing down the perf counter, speed up
> > the hrtimer to sample more frequently like so:
> >
> > diff --git a/kernel/watchdog.c b/kernel/watchdog.c index
> > 03e0b69..8ff49de 100644
> > --- a/kernel/watchdog.c
> > +++ b/kernel/watchdog.c
> > @@ -160,7 +160,7 @@ static void set_sample_period(void)
> > * and hard thresholds) to increment before the
> > * hardlockup detector generates a warning
> > */
> > - sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
> > + sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC /
> 10);
> > }
>
> Hi Kan,
>
> Will the above patch work for you?
Hi Don & Thomas,
Sorry for the late response. We just finished the tests for all proposed patches.
There are three proposed patches so far.
Patch 1: The patch as above which speed up the hrtimer.
Patch 2: Thomas's first proposal.
https://patchwork.kernel.org/patch/9803033/
https://patchwork.kernel.org/patch/9805903/
Patch 3: my original proposal which increase the NMI watchdog timeout by 3X
https://patchwork.kernel.org/patch/9802053/
According to our test, only patch 3 works well.
The other two patches will hang the system eventually.
For patch 1, the system hang after running our test case for ~1 hour.
For patch 2, the system hang in running the overnight test.
There is no error message shown when the system hang. So I don't know the
root cause yet.
BTW: We set 1 to watchdog_thresh when we did the test.
It's believed that can speed up the failure.
Thanks,
Kan
next prev parent reply other threads:[~2017-07-17 1:24 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
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 [this message]
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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