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

Nigel Cunningham
2008-11-06T02:03:06Z

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