linux-kernel - Re: [PATCH] SATA / AHCI: Do not play with the link PM during suspend to RAM (was: Re: HDD not suspending properly / dead on resume)

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Message-Id: <201008022248.45135.stephan.diestelhorst@gmail.com>
Date:	Mon, 2 Aug 2010 22:48:44 +0200
From:	Stephan Diestelhorst <stephan.diestelhorst@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Stephan Diestelhorst <stephan.diestelhorst@....com>
Cc:	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	linux-ide@...r.kernel.org, linux-pm@...ts.osdl.org
Subject: Re: [PATCH] SATA / AHCI: Do not play with the link PM during suspend to RAM (was: Re: HDD not suspending properly / dead on resume)

On Wednesday 28 July 2010, 23:50:09 Rafael J. Wysocki wrote:
> On Saturday, July 10, 2010, Tejun Heo wrote:
> > On 07/10/2010 08:50 AM, Stephan Diestelhorst wrote:
> > >> I have a box where this problem is kind of reproducible, but it happens _very_
> > >> rarely.  Also I can't reproduce it on demand running suspend-resume in a tight
> > >> loop.  Are you able to reproduce it more regurarly?
> > > 
> > > For me it is much more reproducible. If I run multiple direct writing
> > > dd-s to the disk in question I trigger it rather reliably (~75% or
> > > higher). See the attached script from an earlier email.
> > > Maybe that helps triggering your case more reliabl, too?
> > 
> That didn't help, but the appended patch fixes the problem for me.

<snip>

Sorry for taking ages. Vacation and catching up after it are to blame,
as is me forgetting to build a proper initrd...

Thanks for the patch! It certainly changes behaviour, however, in a
very strange way for me. With your patch my machine does not suspend
to ram anymore (a simple echo mem > /proc/sys/state blocks), and
nothing happens in dmesg if there is a lot of write I/O while
suspending. (A number of parallel dd's with oflag=direct)

If I stop the I/O, the system eventually goes into suspend to RAM.
However, that takes a while, after the I/O has stopped, and also
from "Preparing system for suspend" log entry until it is actually
done.

Is this intentional? Let me know how I can debug this further!
Ideally I'd like to be able to suspend the machine under I/O load,
too. (E.g. during a compile job.)

Can you reproduce this at your end, too?

Many thanks,
  Stephan
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