Re: [linux-pm] [PATCH ver. 3] PM: add synchronous runtime interface for interrupt handlers

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On Thursday, November 25, 2010, Oliver Neukum wrote:
> Am Donnerstag, 25. November 2010, 16:52:39 schrieb Alan Stern:
> > When a device is declared irq-safe in this way, the PM core increments
> > the parent's usage count, so the parent will never be runtime
> > suspended.  This prevents difficult situations in which an irq-safe
> > device can't resume because it is forced to wait for its non-irq-safe
> > parent.
> 
> Shouldn't you walk further up the tree if the parent itself is irq-safe?
> It seems like a waste of power to not suspend a paren, that can be
> woken in irq.

Then we should walk up the tree if the parent's parent is irq-safe and so
on, which would make us spend uncertain amount of time in the ISR (or generally
with interrupts off).  I think it's safer not to do that.

Thanks,
Rafael
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