Re: [linux-pm] [PATCH] PM: runtime PM + idle: allow usage when interrupts are disabled

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

On Thursday, August 19, 2010, Kevin Hilman wrote:
> "Rafael J. Wysocki" <rjw@sisk.pl> writes:
> 
> > On Tuesday, August 10, 2010, Kevin Hilman wrote:
> >> When using runtime PM in combination with CPUidle, the runtime PM
> >> transtions of some devices may be triggered during the idle path.
> >> Late in the idle sequence, interrupts will likely be disabled when
> >> runtime PM for these devices is initiated.
> >> 
> >> Currently, the runtime PM core assumes methods are called with
> >> interrupts enabled.  However, if it is called with interrupts
> >> disabled, the internal locking unconditionally enables interrupts, for
> >> example:
> >> 
> >> pm_runtime_put_sync()
> >
> > Please don't use that from interrupt context.  
> 
> I'm not using this in interrupt context.  I'm using it in process
> context where interrupts are disabled, specifically, the idle thread.
> 
> > There's pm_runtime_put() exactly for this purpose that puts the
> > _idle() call into a workqueue.
> 
> If I'm in my CPU's idle path, I don't want to activate a workqueue
> because then I'll no longer be idle.

Well, what about:

-> idle
   -> check if devices have been suspended
       - enter idle if so
       - call pm_request_idle() for devices

The workqueue will activate and put the devices into low-power states and
then your idle callback will be called again, with the devices suspended.

Thanks,
Rafael