linux-kernel - Re: [PATCH V2] genirq/affinity: Handle affinity setting on inactive interrupts correctly

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Message-ID: <874kptcc7j.fsf@nanos.tec.linutronix.de>
Date:   Mon, 27 Jul 2020 15:35:44 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marc Zyngier <maz@...nel.org>
Cc:     John Keeping <john@...anate.com>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Ben Herrenschmidt <benh@...zon.com>,
        Ali Saidi <alisaidi@...zon.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V2] genirq/affinity: Handle affinity setting on inactive interrupts correctly

Marc,

Marc Zyngier <maz@...nel.org> writes:
> On Fri, 24 Jul 2020 21:03:50 +0100,
> Thomas Gleixner <tglx@...utronix.de> wrote:
>> Right. My brain tricked me to believe that we made activation mandatory,
>> but that's not.
>> 
>> I have some ideas for a trivial generic way to solve this without
>> undoing the commit in question and without going through all the irq
>> chip drivers. So far everything I came up with is butt ugly. Maybe Marc
>> has some brilliant idea.
>
> Not really. We have contradicting behaviours here, where some
> interrupts want to see the set_affinity early (the above case), and
> some cannot handle that (x86 vectors and the GICv3 ITS). We could key
> it on the presence of an activate callback, but it feels fragile.

Yes, I thought about that briefly, but yeah, it's fragile and bound to
break in weird ways.

That said, we should make activate mandatory and actually set up the
affinity during activation correctly.

Thanks,

        tglx