linux-kernel - Re: Suspend to RAM

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Message-ID: <20131008144704.GA29729@xo-6d-61-c0.localdomain>
Date:	Tue, 8 Oct 2013 16:47:04 +0200
From:	Pavel Machek <pavel@....cz>
To:	Radek Pilar <mrkva@...va.eu>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Suspend to RAM - freeze & sync

Hi!
> I'm trying to implement feature that removes cryptsetup keys from RAM on
> suspend to RAM: mounts ramfs, unpacks initramfs to ramfs, moves /proc
> /dev and /sys to ramfs, chroots, calls luksSuspend, suspends system
> using /sys/power/state, after resume calls luksResume and cleans up.
> However, there is a small issue I wasn't able to solve: after calling
> luksSuspend, all attempts to access suspended device blocks - so most
> likely some processes won't be able to freeze. The same issue will be
> with sync just before suspend - if there are some data to be written,
> sync() blocks. If I comment out freeze and sync from the suspend code,
> it suspends (and wakes up) just fine - however, that patch will never be
> accepted.
> Is there any *correct* way to do this? (Skip freeze/sync on demand)?

Maybe uswsusp interface is powerful enough to do this?
									Pavel


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