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

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Message-ID: <20090914202729.GB10398@elf.ucw.cz>
Date:	Mon, 14 Sep 2009 22:27:29 +0200
From:	Pavel Machek <pavel@....cz>
To:	Zdenek Kabelac <zdenek.kabelac@...il.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Chris Ball <cjb@...top.org>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Christoph Hellwig <hch@....de>,
	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

On Mon 2009-09-14 10:39:44, Zdenek Kabelac wrote:
> 2009/9/12 Rafael J. Wysocki <rjw@...k.pl>:
> > On Saturday 12 September 2009, Chris Ball wrote:
> >> Hi,
> >>
> >>    > Well system could check basic card ids if they match after resume
> >>
> >> No.  That (arguably) guarantees that it's the same card, but not that
> >> it wasn't modified in another machine during the suspend.
> >
> > Generally speaking, we'd also need to check superblocks for this to work.
> >
> >>    > if some users wants to crash his card by randomly swapping it
> >>    > during suspend/resume - I'd have no problem with that....
> >>
> >> You should have a problem with it.  Taking a card from a suspended
> >> machine and working on it with a different machine is not a bizarre
> >> thing to want to do.
> >
> > Agreed.
> 
> 
> Well - ok - so let me ask this question - if I'll replace local hard
> drive during suspend - what will happen - is this prohibited by hw
> (e.i. to switch SATA cables) ?

During _suspend_: yes. You are not expected to open your machine while
powered up.

> IMHO filesystem should be able to detect corruption of its data
> structures - (assuming fs is notified about suspend/resume
> operation)

Patch welcome.

> Also there could be one simple quick solution/hack - to require to
> have at least all remote drives unmounted - so suspend would be
> refused if it runs mounted card/usb drive -  this would be 100% better
> than current solution which effectively kills my laptop if I forget to
> unmount card in mmc reader - especially if dmesg contains message with
> the reason why my suspend fails.

It should not _kill_ your laptop -- that's a bug we want to
fix. Instead it is designed to behave as if you hot-unplugged your
card while mounted.

									Pavel

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