On Thu, 13 May 2010, Tony Lindgren wrote:

> > > And that's why 
> > > it should be handled by runtime power management instead.
> > 
> > Runtime PM is not capable of freezing userspace and shutting down CPUs.  
> > More or less by definition -- if it could then it wouldn't be "runtime" 
> > any more, since the processor wouldn't be running.
> 
> Not true. We are already powering off CPUs and rebooting them for
> at least omaps in every idle loop using cpuidle. The memory stays on.

Okay, that's a valid point.  But is that approach usable in general 
(i.e., on non-OMAP systems)?

How do you handle situations where the CPU is currently idle but an 
event (such as I/O completion) is expected to occur in the near future?  
You don't want to power-off and reboot then, do you?

Alan Stern