Re: shrinking memory for suspend?

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

On Thursday, 3 May 2007 16:34, Alan Stern wrote:
> On Thu, 3 May 2007, Rafael J. Wysocki wrote:
> 
> > On Thursday, 3 May 2007 12:34, Paul Mackerras wrote:
> > > Rafael J. Wysocki writes:
> > > 
> > > > I think that on a uniprocessor system it's quite safe, but on SMP it doesn't
> > > > seem so.  For example, imagine the situation in which one CPU is executing the
> > > > suspend code while another one is running userspace with system calls etc.
> > > > Pretty scary.
> > > 
> > > Which is why the powermac/powerbook sleep code insists on there only
> > > being one cpu active.  I have an SMP powermac which can sleep; I use a
> > > little script to take the second cpu down before sleeping and bring it
> > > back up after waking up.
> > 
> > That's quite intrusive.  Ideally, user space processes should not notice that
> > there have been a suspend at one point.
> 
> What happens without preemption enabled when a device driver's suspend() 
> method calls schedule()?
> 
> With or without preemption enabled, what happens when a user process tries
> to do I/O to a suspended device?

Yeah, right.  So much for the unforzen user space during a suspend. :-)

Greetings,
Rafael