[linux-pm] [RFD] Automatic suspend

[Rafael J. Wysocki]

On Friday 27 February 2009, Pavel Machek wrote:
> Hi!
> 
> > > > Then, the decision making logic will be able to use /sys/power/sleep whenever
> > > > it wishes to and the kernel will be able to refuse to suspend if it's not
> > > > desirable at the moment.
> > > >
> > > > It seems to be flexible enough to me.
> > > 
> > > This seems flexible enough to avoid race conditions, but it forces the
> > > user space power manager to poll when the kernel refuse suspend.
> > 
> > And if the kernel is supposed to start automatic suspend, it has to monitor
> > all of the wakelocks.  IMO, it's better to allow the power manager to poll the
> > kernel if it refuses to suspend.
> 
> polling is evil -- it keeps CPU wake up => wastes power.
> 
> Wakelocks done right are single atomic_t... and if you set it to 0,
> you just unblock "sleeper" thread or something. Zero polling and very
> simple...

Except that you have to check all of the wakelocks periodically in a loop =>
polling.  So?

Rafael