[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <86r0pnwv5q.wl-maz@kernel.org>
Date: Tue, 04 Jul 2023 16:31:13 +0100
From: Marc Zyngier <maz@...nel.org>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org,
Hanks Chen <hanks.chen@...iatek.com>,
Cheng-Yuh.Wu@...iatek.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] irqchip/gic-v3: Workaround for GIC-700 erratum 2941627
On Tue, 04 Jul 2023 16:27:45 +0100,
Lorenzo Pieralisi <lpieralisi@...nel.org> wrote:
>
> On Tue, Jul 04, 2023 at 03:44:50PM +0100, Marc Zyngier wrote:
>
> [...]
>
> > > + return !((gic_irq_in_rdist(d)) || gic_irq(d) >= 8192 ||
> > > + cpumask_equal(irq_data_get_effective_affinity_mask(d),
> > > + cpumask_of(smp_processor_id())));
> >
> > I dislike this statement for multiple reasons:
> >
> > - it is written as a negation, making it harder than strictly
> > necessary to parse as it is the opposite of the comment above
> >
> > - gic_irq_in_rdist() and gic_irq(d) >= 8192 are two ways of checking
> > the interrupt range -- maybe we should just do that
> >
> > - cpumask_equal() is *slow* if you have more that 64 CPUs, something
> > that is increasingly common -- a better option would be to check
> > whether the current CPU is in the mask or not, which would be enough
> > as we only have a single affinity bit set
> >
> > - smp_processor_id() can check for preemption, which is pointless
> > here, as we're doing things under the irq_desc raw spinlock.
> >
> > I would expect something like:
> >
> > enum gic_intid_range range = get_intid_range(d);
> >
> > return (range == SGI_RANGE || range == ESPI_RANGE) &&
> > !cpumask_test_cpu(raw_smp_processor_id(),
> > irq_data_get_effective_affinity_mask(d));
> >
>
> s/SGI/SPI - just noticed, for the records.
Indeed. As you can tell, I didn't really test the damn thing...
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
Powered by blists - more mailing lists