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

[Stephan Diestelhorst <stephan.diestelhorst@amd.com>]

On Monday 02 August 2010, 23:38:05 Rafael J. Wysocki wrote:
> On Monday, August 02, 2010, Stephan Diestelhorst wrote:
> > 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?
> 
> It surely isn't.
> 
> > 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?
> 
> Well, I didn't try suspending with a number of parallel dd's with oflag=direct
> in the background, but otherwise I'm not reproducing the issue with
> the patch applied.

Mhmhm, I have tried to reproduce my issue again, and also added some
dev_printk's around your code to understand where the delay is
happening.

However, I have not been able to reproduce the issue (with and without
the debug output) anymore, and I am happy to report that for now your
patch helps.

I'd like to keep this under observation for a little while longer,
though.

Many thanks,
  Stephan

-- 
Stephan Diestelhorst, AMD Operating System Research Center
stephan.diestelhorst@amd.com, Tel. +49 (0)351 448 356 719

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