Re: [Xen-devel] Prepping a bugfix push

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 12/04/09 07:50, Ian Campbell wrote:
> On Fri, 2009-12-04 at 07:46 +0000, Ian Campbell wrote:
>    
> > I've been doing regular suspend/resumes not checkpoint ones as Brendan
> > is doing, I did try a couple of checkpointed ones yesterday and they
> > failed, IIRC with a similar softlockup to this one.
> >      
> So what is happening is that the device event channels are getting torn
> down by the resume handler and never completely reinstated in the
> cancelled suspend (aka checkpoint) case.
>    
Hm.

> In 2.6.18 there was a separate ->suspend_cancel() callback for each
> driver, called instead of the ->resume() callback in exactly these
> circumstances. The cancel callback doesn't do any of the teardown, in
> fact for blkfront it doesn't even exist.
>
> (As a proof of concept, commenting out the entire contents of
> blkfront_resume and netfront_resume makes checkpointing work OK for me,
> at the cost of breaking regular resume, of course)
>
> pv-ops uses the generic power management infrastructure which does not
> have a concept of cancelling a suspend. Perhaps it should? Otherwise a
> different solution will be required, I'm not sure what that might be yet
> yet.
>    
Well, the obvious one is to treat it as a full suspend followed by 
immediate resume.  That is, just remove all the special case handling 
for checkpoint, and let it do the normal resume stuff when the hypercall 
returns.
I think the PM core can fail to suspend; it just resumes anything that 
has been suspended so far.
    J

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