linux-kernel - Re: [Intel-gfx] [PATCH v3 2/4] drm/i915/pmu: Use kstat

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Message-ID: <87pn3hk12r.fsf@nanos.tec.linutronix.de>
Date:   Thu, 10 Dec 2020 18:44:44 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        linux-kernel@...r.kernel.org,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Chris Wilson <chris@...is-wilson.co.uk>
Cc:     Jason Gunthorpe <jgg@...pe.ca>,
        Peter Zijlstra <peterz@...radead.org>,
        intel-gfx@...ts.freedesktop.org,
        Matthew Garrett <mjg59@...gle.com>,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        David Airlie <airlied@...ux.ie>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        dri-devel@...ts.freedesktop.org, linux-integrity@...r.kernel.org,
        Peter Huewe <peterhuewe@....de>
Subject: Re: [Intel-gfx] [PATCH v3 2/4] drm/i915/pmu: Use kstat_irqs to get interrupt count

On Thu, Dec 10 2020 at 17:09, Tvrtko Ursulin wrote:
> On 10/12/2020 16:35, Thomas Gleixner wrote:
>> I'll send out a series addressing irq_to_desc() (ab)use all over the
>> place shortly. i915 is in there...
>
> Yep we don't need atomic, my bad. And we would care about the shared 
> interrupt line. And without atomic the extra accounting falls way below 
> noise.

You have to be careful though. If you make the accumulated counter 64
bit wide then you need to be careful vs. 32bit machines.

> So in the light of it all, it sounds best I just quickly replace our 
> abuse with private counting and then you don't have to deal with it in 
> your series.

I mostly have it. Still chewing on the 32bit vs. 64bit thing. And
keeping it in my series allows me to remove the export of irq_to_desc()
at the end without waiting for your tree to be merged.

Give me a few.

Thanks,

        tglx