Re: [PATCH] arm64: fix a migrating irq bug when hotplug cpu

[Yang Yingliang]

å 2015/8/31 20:20, Marc Zyngier åé:
> On Sun, 30 Aug 2015 21:15:56 +0800
> Hanjun Guo <hanjun.guo@xxxxxxxxxx> wrote:
>
> > On 08/30/2015 02:12 AM, Marc Zyngier wrote:
> > > On 2015-08-29 16:12, Jiang Liu wrote:
> > > > On 2015/8/29 21:00, Yang Yingliang wrote:
> > > > > From: Yang Yingliang <yangyingliang@xxxxxxxxxx>
> > > > >
> > > > > When cpu is disabled, all irqs will be migratged to another cpu.
> > > > > In some cases, a new affinity is different, it needed to be coppied
> > > > > to irq's affinity. But if the type of irq is LPI, it's affinity will
> > > > > not be coppied because of irq_set_affinity's return value.
> > > > > So copy the affinity, when the return value is IRQ_SET_MASK_OK_DONE.
> > > > Hi Yingliang,
> > > >      If irq_set_affinity callback returns IRQ_SET_MASK_OK_DONE,
> > > > it means that irq_set_affinity has copied the new CPU mask to irq
> > > > affinity mask. It would be better to change irq_set_affinity for LPI
> > > > to follow this rule.
> > >
> > > The main issue here seems to be that we do not call irq_set_affinity, but
> > > that we directly call into the top-level irqchip method, which relies on
> > > the core code to do the copy (see irq_do_set_affinity). Too bad.
> > >
> > > It feels like the arm/arm64 code would probably be better consolidated into
> > > kernel/irq/migration.c, which already deals with some of this for x86
> > > and ia64. It would save us the duplication and will make sure we don't
> > > miss things next time we add a new return code, as irq_do_set_affinity
> > > would handle this properly.
> > >
> > > Thoughts?
> >
> > I agree. In arch/arm64/kernel/irq.c the irq migrate code is the same
> > as ARM32, and it's duplicate. But this is a bugfix, can we fix it in
> > a simple way, and refactor the code later?
>
> I'm not buying this.
>
> I really can't see how adding more duplication can be beneficial. It is
> not so much that there is duplication between arm and arm64 that
> bothers me (as if that was the only thing...). The real issue is that
> there is duplication between the arch code and the core code.
>
> Migrating interrupts is a core code matter, and that's were it should
> be handled IMHO. Plus, we're in the merge window, and there is plenty
> of time to get this fixed the proper way.

Got it. I'm trying to move the irq migrate code to kernel/irq/migration.c

Regards
Yang

> Thanks,
>
> 	M.

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