linux-kernel - Re: No freezing of kernel threads (was: Re: [GIT PULL] libata fixes for v3.13-rc5)

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Message-ID: <2054754.LytUAbbREV@vostro.rjw.lan>
Date:	Fri, 27 Dec 2013 00:23:10 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Tejun Heo <tj@...nel.org>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	linux-ide@...r.kernel.org,
	Linux-pm mailing list <linux-pm@...r.kernel.org>
Subject: Re: No freezing of kernel threads (was: Re: [GIT PULL] libata fixes for v3.13-rc5)

On Thursday, December 26, 2013 02:01:20 PM Tejun Heo wrote:
> Hey,
> 
> On Thu, Dec 26, 2013 at 01:42:29PM -0500, Alan Stern wrote:
> > In the case of hibernation, it's not so simple.  We do need to perform 
> > I/O, in order to save the memory image.  But we also need to avoid 
> > unnecessary I/O, in order to keep the on-disk data consistent with the 
> > data in the memory image.  You probably can't accomplish this at the 
> > device driver or subsystem level.
> 
> That was what I assumed too but Rafael tells me it has nothing to do
> with hibernation.

It doesn't prevent on-disk data corruption from happening in case of a failing
hibernation.  In case of a successful hibernation it is key to keep on-disk
data in sync with the contents of the image, but relying on the freezing
for that is rather not a winning strategy, so to speak.  It would be better
to freeze filesystems instead (which has been discussed in another thread
recently).

Thanks,
Rafael

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