Re: [RFC][PATCH] irq_work

Huang Ying
2010-06-24T07:04:36Z

On Thu, 2010-06-24 at 14:58 +0800, Peter Zijlstra wrote:
> On Thu, 2010-06-24 at 14:50 +0800, Huang Ying wrote:
> > On Thu, 2010-06-24 at 14:47 +0800, Peter Zijlstra wrote:
> > > On Thu, 2010-06-24 at 14:43 +0800, Huang Ying wrote:
> > > > Hi, Peter,
> > >
> > > > I fact I uses exactly the similar method in my patches, just trigger it
> > > > with soft_irq instead of IRQ. Please take a look at
> > > > nmi_return_notifier_schedule in
> > >
> > > But then why still use softirq? Once you have this its completely
> > > useless.
> >
> > Some systems have no self interrupt, for example the system without
> > APIC. We need to provide a fallback for them. soft_irq can help here.
>
> So there's systems that don't have self-ipi but do have NMI context?

Yes. NMI is there from 8259 age.

> Can't we run the callbacks from the tick or something for such legacy
> muck? I really don't like the whole softirq mess.

That is possible. But in NO_HZ system, we have no tick to rely on.
soft_irq is better here, because it will be triggered for any interrupt.

Best Regards,
Huang Ying