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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Ingo Molnar <mingo@elte.hu>
Subject: Re: [Regression] 2.6.24-git3: Major annoyance during suspend/hibernation on x86-64 (bisected)
Date: Mon, 28 Jan 2008 17:31:36 +0100
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Cc: Steven Rostedt <srostedt@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>,
       Dmitry Adamushko <dmitry.adamushko@gmail.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>
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On Monday, 28 of January 2008, Rafael J. Wysocki wrote:
> On Monday, 28 of January 2008, Steven Rostedt wrote:
> > Rafael J. Wysocki wrote:
> > 
> > > No, this isn't the WARN_ON().
> > > 
> > >> this does have the feel of being scheduling related, but are you 
> > >> absolutely sure about the precise identity of the patch?
> > > 
> > > Actually, not quite.  That's why I have verified it and found that another
> > > patch is really responsible for the issue, namely:
> > > 
> > > commit 82a1fcb90287052aabfa235e7ffc693ea003fe69
> > > Author: Ingo Molnar <mingo@elte.hu>
> > > Date:   Fri Jan 25 21:08:02 2008 +0100
> > > 
> > >     softlockup: automatically detect hung TASK_UNINTERRUPTIBLE tasks
> > 
> > Are you getting a bunch of prints from the softlockup detector in dmesg?
> 
> No, I don't.  In fact, I don't get _any_ messages from it whatsoever.
> 
> > I wonder if the detector can detect a long timeout caused by suspend and 
> > resume and if not is triggering false positives?
> 
> I'm not sure, but the code is supposed to be suspend-aware, IIRC.  However,
> I'm seeing a similar symptom on poweroff on an SMP x86-64 box, so it may be
> more directly related to the CPU hotplug.  I'll try to verify that.

As I expected, the delay is also observable when I do:

echo 0 > /sys/devices/system/cpu/cpu1/online

(it's variable, between 3 and 30 seconds).  Again, no messages appear in dmesg
when this happens.

I suspect I'll be able to reproduce it on another x86-64 SMP machine (I'm going
to try that later today).

Thanks,
Rafael