Re: Get rid of IRQF_DISABLED - (was [PATCH] genirq: warn about IRQF_SHARED|IRQF_DISABLED)

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Mon, 2009-11-30 at 22:31 +0100, Thomas Gleixner wrote:

> Are the perf events on power generally coming through the standard irq
> handler code path and/or sensitive to local_irq_disable() ?

They are in HW yes. On ppc64, we do soft-disabling, which mean that we
can still get the perf events within a local_irq_disable() region
provided we don't get another interrupt within that region that forces
us to hard disable so it would make the problem less bad I suppose.

> > I would suggest we timestamp the handlers in the core btw and warn
> if
> > they take too long so we get a chance to track down the bad guys.
> 
> The hassle is to find a time which we think is appropriate as a
> threshold which is of course depending on the cpu power of a
> system. Also I wonder whether we'd need to make such a warning thing
> aware of irq nesting.

But if we always disable interrupts while running the handlers, we don't
nest right ?

Cheers,
Ben.