linux-kernel - Re: Regression in suspend to ram in 2.6.31-rc kernels

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Message-ID: <20090907125130.GA1595@ucw.cz>
Date:	Mon, 7 Sep 2009 14:51:30 +0200
From:	Pavel Machek <pavel@....cz>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc:	Zdenek Kabelac <zdenek.kabelac@...il.com>,
	Christoph Hellwig <hch@....de>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mmc@...r.kernel.org, viro@...iv.linux.org.uk
Subject: Re: Regression in suspend to ram in 2.6.31-rc kernels

Hi!

> >>> Note that when you rever this patch on a current kernel you do actually
> >>> get different behvaviour than when going back to before this commit.
> >>>
> >>> In 2.6.30 we called ->write_super in the various sync functions and
> >>> then ->sync_fs, in 2.6.31-rc8 you would not call any syncing at all
> >>> anymore. ?I think this patch might just be a symptom for a situation
> >>> where the suspend code causes a sync and the mmc driver can't handle
> >>> it anymore.
> >
> > So - here is the console trace from suspend when I've added
> > dump_stack() to the fat_sync_fs()   (and also added debug prints
> > around each call in this function -so its obvious the function is
> > actually left - but then it freezes later somewhere.)
> >
> > It's interesting that 3 calls to sync happens.
> 
> It seems
> 
>     1) sync() (probabry "sync" command)
>     2) sync as part of suspend sequence
>     3) sync_filesystem() by mmc remove event
> 
> I guess the root-cause of the problem would be 3). However, it would not
> be easy to fix, at least, we would need to think about what we want to
> do for it. So, to workaround it for now, I've made this patch.

MMC driver trying to synchronize filesystems looks like ugly layering
violation to me. Why are we doing that?

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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