linux-kernel - Re: [Regression] 2.6.24-git3: Major annoyance during suspend/hibernation on x86-64 (bisected)

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Date:	Mon, 28 Jan 2008 17:08:47 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Steven Rostedt" <srostedt@...hat.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Subject: Re: [Regression] 2.6.24-git3: Major annoyance during suspend/hibernation on x86-64 (bisected)

On Monday, 28 of January 2008, Dmitry Adamushko wrote:
> On 28/01/2008, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > On Sunday, 27 of January 2008, Ingo Molnar wrote:
> > >
> > > * Rafael J. Wysocki <rjw@...k.pl> wrote:
> > >
> > > > Hi,
> > > >
> > > > 2.6.24-git3 adds a 5 - 10 sec delay to the suspend and hibernation
> > > > code paths (probably related to the disabling of nonboot CPUs), which
> > > > is !@...^&*() annoying.
> > > >
> > > > It's 100% reproducible on my HP nx6325 and bisection idendified the
> > > > following commit as the first bad one:
> > > >
> > > > commit 764a9d6fe4b52995c8aba277e3634385699354f4
> > > > Author: Steven Rostedt <srostedt@...hat.com>
> > > > Date:   Fri Jan 25 21:08:04 2008 +0100
> > > >
> > > >     sched: track highest prio task queued
> > >
> > > hm, this patch is a NOP, so it's weird that it has an effect.
> > >
> > > Do you have serial logging enabled perhaps? If the following WARN_ON()
> > > triggers:
> > >
> > > +               WARN_ON(p->prio < rq->rt.highest_prio);
> > >
> > > then perhaps that can cause a 5-10 seconds delay. (that's how much time
> > > it takes to printk a warning on the slowest serial settings)
> > >
> > > but if you use suspend, then any such printks would be preserved in the
> > > dmesg, right? If the WARN_ON() triggers, and if you remove it, do things
> > > get faster?
> >
> > 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@...e.hu>
> > Date:   Fri Jan 25 21:08:02 2008 +0100
> >
> >     softlockup: automatically detect hung TASK_UNINTERRUPTIBLE tasks
> >
> > Reverting this commit (it reverts with some minor modifications) fixes the
> > problem for me.
> 
> What if you use the same kernel that triggers a problem and just disable
> this new 'softlockup' functionality:
> 
> echo 0 > /proc/sys/kernel/hung_task_timeout_secs
> 
> does the problem disapear?

No, it doesn't.  The setting doesn't seem to have any effect on it.

Thanks,
Rafael
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