Date: Wed, 22 Jul 2015 09:52:04 -0400
From: Don Zickus <dzickus@redhat.com>
To: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: =?iso-8859-1?Q?J=F6rn?= Engel <joern@purestorage.com>,
        Spencer Baugh <sbaugh@catern.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ulrich Obergfell <uobergfe@redhat.com>, Ingo Molnar <mingo@kernel.org>,
        Andrew Jones <drjones@redhat.com>,
        chai wen <chaiw.fnst@cn.fujitsu.com>,
        Chris Metcalf <cmetcalf@ezchip.com>,
        Stephane Eranian <eranian@google.com>,
        open list <linux-kernel@vger.kernel.org>,
        Spencer Baugh <Spencer.baugh@purestorage.com>,
        Joern Engel <joern@logfs.org>
Subject: Re: [PATCH] soft lockup: kill realtime threads before panic
Message-ID: <20150722135204.GE178524@redhat.com>
References: <1437516477-30554-5-git-send-email-sbaugh@catern.com>
 <1437539790.3106.42.camel@gmail.com>
 <20150722051827.GD23662@Sligo.logfs.org>
 <1437543708.3106.70.camel@gmail.com>
 <20150722063323.GE23662@Sligo.logfs.org>
 <1437550528.3106.107.camel@gmail.com>
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On Wed, Jul 22, 2015 at 09:35:28AM +0200, Mike Galbraith wrote:
> On Tue, 2015-07-21 at 23:33 -0700, J?rn Engel wrote:
> 
> > One could argue that killing the realtime thread is even better than
> > panic, as things can restart with a blank slate even faster.  But the
> > real benefit is that we get better debug data for the failing component.
> > If we had a kernel bug, the backtrace would usually be sufficient to
> > point fingers.  With a bonkers realtime thread, not so much.
> 
> If userspace wants a watchdog, it should train a userspace dog, not turn
> the kernel watchdog into a userspace attack dog.

I agree.  The spirit of the watchdog was detection and panic (if configured
that way).  I don't think adding policy like this works well in the long
run.

Cheers,
Don
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