linux-kernel - Re: Problem with freezable workqueues

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Date:	Wed, 07 Mar 2007 09:25:07 +1100
From:	Nigel Cunningham <nigel@...el.suspend2.net>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Johannes Berg <johannes@...solutions.net>,
	Pavel Machek <pavel@....cz>, Gautham R Shenoy <ego@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...sign.ru>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>
Subject: Re: Problem with freezable workqueues

Hi.

On Tue, 2007-03-06 at 21:31 +0100, Rafael J. Wysocki wrote:
> Hi,
> 
> On Tuesday, 6 March 2007 01:30, Johannes Berg wrote:
> > On Tue, 2007-02-27 at 22:51 +0100, Rafael J. Wysocki wrote:
> > 
> > > For 2.6.21-rc1 I've invented the appended workaround (works for me, waiting for
> > > Johannes to confirm it works for him too), but I think we need something better
> > > for -mm and future kernels.
> > 
> > Finally I could get back to this but after reading the thread I figured
> > it might not be necessary to test this. Please let me know ASAP if you
> > want this patch tested as well or it'll take quite a long time (going
> > skiing for a week on Saturday)
> 
> I think it won't be necessary.
> 
> For now, we have decided to make the workqueues nonfreezable (the patch for
> that has already been merged, AFAICT).
> 
> > In any case, I made the two xfs workqueues non-freezable and everything
> > on my quad powermac works again, I also couldn't detect any filesystem
> > correction.
> 
> Good, thanks for the confirmation.
> 
> > I wanted to adapt the BUG_ON(block IO not from suspend code) 
> > patch from suspend2 but haven't gotten around to it yet.
> 
> That might be a good idea for other reasons too, but I'd prefer WARN_ON()
> instead of BUG_ON() when you're at it. ;-)

I made it BUG_ON() because if Suspend2 is running any I/O coming from
another source besides Suspend2 may be I/O on a page that's been used
for the atomic copy, and in that case it would definitely be bad to
write it to disk. If swsusp is running, the BUG_ON() won't trigger IIRC.

Regards,

Nigel

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