Re: [2.6.17-rc5-mm2] crash when doing second suspend: BUG in arch/i386/kernel/nmi.c:174

[Don Zickus <dzickus@redhat.com>]

On Wed, Jun 07, 2006 at 10:05:07AM +1000, Nigel Cunningham wrote:
> Hi.
> 
> On Wednesday 07 June 2006 09:55, Don Zickus wrote:
> > > > So my question is/was what is the proper way to handle processor level
> > > > subsystems during the suspend/resume path on an SMP system.  I really
> > > > don't understand the hotplug path nor the suspend/resume path very
> > > > well.
> > >
> > > Make it work properly for CPU hotplug for individual CPU and then in
> > > suspend you take care of "global" state and the last CPU.
> >
> > So the assumption is treat all the cpus the same either all on or all off,
> > no mixed mode (some cpus on, some cpus off).  I guess I was trying to hard
> > to work on the per-cpu level.
> 
> This sounds wrong to me. Shouldn't the the effect of hotunplugging a cpu be to 
> put the driver in a state equivalent to if that cpu simply didn't exist? 
> Unplugging shouldn't assume we're going to subsequently have either a driver 
> suspend, or a replug.

This is my biggest problem or maybe my complete lack of understanding, is
that I don't know how to determine what state I am in during a hotplug
event, either a cpu removal or a suspend.  Therefore I feel like I have to
store some persistant data around _just_ in case this is a suspend event.
Also at the opposite end, how to separate a cpu insert vs. a cpu resume.
The different being initialize to a global state vs. initialize to a last
known state.  

I thought it would make more sense if a few more states were to the
hotplug event list.  For example, in addition to CPU_ONLINE and CPU_DEAD,
there could also be something like CPU_SUSPEND, CPU_FREEZE, CPU_RESUME,
and CPU_THAW.  

Anyway, I am probably complicating the matter.  I'll whip something up and
post it for review.

Cheers,
Don

> 
> Regards,
> 
> Nigel
> -- 
> Nigel, Michelle and Alisdair Cunningham
> 5 Mitchell Street
> Cobden 3266
> Victoria, Australia