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Message-ID: <2439ff9afd9a98d850ddd0d39b881fcbc7f6b7ac.camel@amazon.com>
Date: Thu, 8 Jun 2023 12:12:34 +0000
From: "Gowans, James" <jgowans@...zon.com>
To: "maz@...nel.org" <maz@...nel.org>
CC: "tglx@...utronix.de" <tglx@...utronix.de>,
"Raslan, KarimAllah" <karahmed@...zon.com>,
"liaochang1@...wei.com" <liaochang1@...wei.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"zouyipeng@...wei.com" <zouyipeng@...wei.com>,
"chris.zjh@...wei.com" <chris.zjh@...wei.com>
Subject: Re: [PATCH v3 2/2] genirq: fasteoi supports resend on concurrent
invoke
On Wed, 2023-06-07 at 14:13 +0100, Marc Zyngier wrote:
> On 2023-06-07 13:21, Gowans, James wrote:
> > On Tue, 2023-06-06 at 18:05 +0100, Marc Zyngier wrote:
> > > On Mon, 05 Jun 2023 16:57:23 +0100,
> > > James Gowans <jgowans@...zon.com> wrote:
> > > > ... and enable that functionality for GIC-v3 only.
> > >
> > > nit: drop the multi-line subject.
> >
> > Would you prefer two commits - one to introduce the functionality and
> > one
> > to enable it for GIC-v3?
>
> I'd prefer that. It is in general better to decouple driver stuff from
> core code.
Done, new rev with cover letter here:
https://lore.kernel.org/lkml/20230608120021.3273400-1-jgowans@amazon.com/
Also added detailed testing data to the cover - I hope that's
useful/correct.
Just one more thing: I've been thinking about it more and admit to still
being unsure of the justification for when we specifically *don't* want
the resend functionality to happen: the justification for gating it behind
a flag. The example you gave was for a wake-up source where it's not
desirable for a wakeup source to be resent. But I don't see how that case
can happen in practice: either that interrupt would never get to the
handle_fast_eoi() handler (there's probably no handler to run for it?) or
if it did it would likely use different struct irq_desc per CPU - this
race would be hit all the time if wakeup sources ran handlers and shared
irq_desc.
We have something that works now so I'm happy to go with this - I just
want to point out that I'm still struggling to see when it would actually
be wrong to apply this resend logic to a user of handle_fast_eoi().
JG
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