Re: [RFC][PATCH] irq_work

From: Ingo Molnar
Date: Thu Jun 24 2010 - 07:23:54 EST

* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> On Thu, 2010-06-24 at 13:08 +0200, Andi Kleen wrote:
> > > And I really want hardirq context for perf callbacks, some code actually
> > > relies on it (I used to have the fallback in the timer softirq and that
> >
> > Surely that could be fixed? *requiring* hard irq context sounds weird.
> possibly, but there is no reason what so ever to use softirq here.
> > > broke thing at some point).
> >
> > I have one case that needs to sleep (but only when interrupting user code)
> > They key thing in it really is to switch stacks back to process.
> softirq can't sleep either, you need a trampoline anyway.

What might make sense is to offer two types of callbacks: one that is
immediate whenever an event triggers - and another that is sleepable and is
executed from process context.

Having an intermediate softirq level might be over-design indeed.


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