Re: [patch] hibernation: utilize ACPI hardware signature

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Wednesday, 2 of January 2008, Erik Andrén wrote:
> Hi,
> 
> 2008/1/2, Shaohua Li <shaohua.li@intel.com>:
> >
> > ACPI defines a hardware signature. BIOS calculates the signature
> > according to hardware configure, if hardware changes, the signature will
> > change, in this case, S4 resume should fail.
> >
> > Signed-off-by: Shaohua Li <shaohua.li@intel.com>
> > ---
> 
> 
> Would it be possible to extend this mechanism to prevent the following
> scenario:
> 
> 1. Linux image A is suspended to disk
> 2. Linux image B is booted and various changes to the system are done.
> 3. Linux image B is shut down
> 4. Linux image A is booted, restoring the suspend to disk image.
> 5. Chaos is ensured as the file system state is changed in regard to how
> linux image A expects it.
> 
> Correct behaviour would naturally be that image A detects that changes have
> been made under its feet and proceed to perform a normal boot instead of
> resuming the stored suspend-to-disk image.

It should be possible in theory.

> Is there another mechanism preventing this?

Not at the kernel level, but you can prevent this from happening by running
mkswap on all swap spaces that refuse to come up after a fresh boot.

Greetings,
Rafael
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