Re: [PATCH 1/10] PM: Rework handling of interrupts during suspend-resume (rev. 5)

Thomas Gleixner
2009-03-11T22:48:15Z

On Wed, 11 Mar 2009, Thomas Gleixner wrote:
> On Wed, 11 Mar 2009, Rafael J. Wysocki wrote:
> > On Wednesday 11 March 2009, Thomas Gleixner wrote:
> > > > +EXPORT_SYMBOL_GPL(suspend_device_irqs);
> > >
> > > I'm not too enthusiastic about this open coded implementation of
> > > disable_irq() with slightly different semantics.
> >
> > The difference in semantics is important IMO, otherwise I woulndn't have
> > done that. In particular, IMO, the condition should be under the spinlock IMO
> > and I'd rather not synchronize all interrupts we don't really disable here.
>
> I don't say that the difference is not relevant. But the code is
> almost the same and disable_irq() could have the sync_irq optimization
> as well.

Thought more about that. Avoiding the sync_irq() for irqs which have
no action associated is fine, but you need to catch the following case
as well:

driver code calls disable_irq_nosyc() from the handler (which is
still running)

suspend code skips the sync due to depth > 0

The sync operation is not that expensive.

Thanks,

tglx