Re: [linux-pm] [PATCH] hibernation should work ok with memory hotplug

[Nigel Cunningham <ncunningham@crca.org.au>]

Hi.

On Thu, 2008-11-06 at 09:53 +0900, KAMEZAWA Hiroyuki wrote:
> On Wed, 05 Nov 2008 16:28:01 -0800
> Dave Hansen <dave@linux.vnet.ibm.com> wrote:
> 
> > On Thu, 2008-11-06 at 09:14 +0900, KAMEZAWA Hiroyuki wrote:
> > > Ok, please consider "when memory hotplug happens." 
> > > 
> > > In general, it happens when
> > >   1. memory is inserted to slot.
> > >   2. the firmware notifes the system to enable already inserted memory.
> > > 
> > > To trigger "1", you have to open cover of server/pc. Do you open pc while the system
> > > starts hibernation ? for usual people, no.
> > 
> > You're right, this won't happen very often.  We're trying to close a
> > theoretical hole that hasn't ever been observed in practice.  But, we
> > don't exactly leave races in code just because we haven't observed them.
> > I think this is a classic race.
> > 
> > If we don't close it now, then someone doing some really weirdo hotplug
> > is going to run into it at some point.  Who knows what tomorrow's
> > hardware/firmware will do?
> > 
> Hmm, people tend to make crazy hardware, oh yes. the pc may fly in the sky with rocket engine.

It doesn't even have to be crazy. Just imagine someone bumping a button
on the case while plugging in the memory and that button being
configured to make the machine hibernate.

Regards,

Nigel