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Message-ID: <b647ffbd0802011444n366c1537m7fb44acf0b848941@mail.gmail.com>
Date: Fri, 1 Feb 2008 23:44:12 +0100
From: "Dmitry Adamushko" <dmitry.adamushko@gmail.com>
To: "Ingo Molnar" <mingo@elte.hu>
Subject: Re: [Regression] 2.6.24-git3: Major annoyance during suspend/hibernation on x86-64 (bisected)
Cc: "Peter Zijlstra" <a.p.zijlstra@chello.nl>,
       "Rafael J. Wysocki" <rjw@sisk.pl>,
       "Steven Rostedt" <srostedt@redhat.com>,
       "Andrew Morton" <akpm@linux-foundation.org>,
       "Linus Torvalds" <torvalds@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>
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On 01/02/2008, Dmitry Adamushko <dmitry.adamushko@gmail.com> wrote:
> On 01/02/2008, Ingo Molnar <mingo@elte.hu> wrote:
> >
> > thanks - i cannot reproduce it on my usual suspend/resume testbox
> > because e1000 broke on it, and this is a pretty annoying regression.
> > We'll have to undo the hung-tasks detection feature if it's not fixed
> > quickly. (there's no point in debugging features that _add_ bugs)
>
> I can reproduce it and Peter's patch does fix it for me.
>
> e.g.
> root@earth:/sys/devices/system/cpu/cpu1# time echo 0 > online
> real    0m6.743s
> root@earth:/sys/devices/system/cpu/cpu1# time echo 0 > online
> real    0m7.770s
>
> I've observed delays from ~3 s. up to ~8 s. (out of ~20 tests) so the
> 10s. delay of msleep_interruptible() might be related but
> I'm still looking for the reason why this fix helps (and what goes
> wrong with the current code).
>

heh... it's pretty obvious indeed. What's msleep_interruptible() is
all about? :-)

"sleep waiting for signals"

so the 'watchdog' thread gets woken up

[ as a result of cpu_callback(action = CPU_DEAD) --> kthread_stop() ]

just to be immediately scheduled out again for as long as the
remaining timeout > 0.

So it should work if we substitute msleep_interruptible() with
schedule_timeout_interruptible().


-- 
Best regards,
Dmitry Adamushko