Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 8 Dec 2020 11:54:32 +0200
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Jerry Snitselaar <jsnitsel@redhat.com>,
        linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org,
        intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Peter Huewe <peterhuewe@gmx.de>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        Matthew Garrett <mjg59@google.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v3 2/4] drm/i915/pmu: Use kstat_irqs to get interrupt
 count
Message-ID: <20201208095432.GA44672@kernel.org>
References: <20201205014340.148235-1-jsnitsel@redhat.com>
 <20201205014340.148235-3-jsnitsel@redhat.com>
 <875z5e99ez.fsf@nanos.tec.linutronix.de>
 <87o8j67h7u.fsf@nanos.tec.linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <87o8j67h7u.fsf@nanos.tec.linutronix.de>
Precedence: bulk

On Sun, Dec 06, 2020 at 10:33:09PM +0100, Thomas Gleixner wrote:
> On Sun, Dec 06 2020 at 17:38, Thomas Gleixner wrote:
> > On Fri, Dec 04 2020 at 18:43, Jerry Snitselaar wrote:
> >> Now that kstat_irqs is exported, get rid of count_interrupts in
> >> i915_pmu.c
> >
> > May I ask why this has been merged in the first place?
> >
> > Nothing in a driver has ever to fiddle with the internals of an irq
> > descriptor. We have functions for properly accessing them. Just because
> > C allows to fiddle with everything is not a justification. If the
> > required function is not exported then adding the export with a proper
> > explanation is not asked too much.
> >
> > Also this lacks protection or at least a comment why this can be called
> > safely and is not subject to a concurrent removal of the irq descriptor.
> > The same problem exists when calling kstat_irqs(). It's even documented
> > at the top of the function.
> 
> And as pointed out vs. that TPM thing this really could have been a
> trivial
> 
>     i915->irqs++;
> 
> in the interrupt handler and a read of that instead of iterating over
> all possible cpus and summing it up. Oh well...

I'm fine with that. 

> Thanks,
> 
>         tglx

/Jarkko