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From: Lorenzo Pieralisi <lpieralisi@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
	Hanks Chen <hanks.chen@mediatek.com>,
	Cheng-Yuh.Wu@mediatek.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] irqchip/gic-v3: Workaround for GIC-700 erratum 2941627
Date: Tue, 4 Jul 2023 17:27:45 +0200	[thread overview]
Message-ID: <ZKQ6ce1pbYHGVIsA@lpieralisi> (raw)
In-Reply-To: <86ttujwxb1.wl-maz@kernel.org>

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.

Thanks,
Lorenzo

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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Lorenzo Pieralisi <lpieralisi@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
	Hanks Chen <hanks.chen@mediatek.com>,
	Cheng-Yuh.Wu@mediatek.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] irqchip/gic-v3: Workaround for GIC-700 erratum 2941627
Date: Tue, 4 Jul 2023 17:27:45 +0200	[thread overview]
Message-ID: <ZKQ6ce1pbYHGVIsA@lpieralisi> (raw)
In-Reply-To: <86ttujwxb1.wl-maz@kernel.org>

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.

Thanks,
Lorenzo

  parent reply	other threads:[~2023-07-04 15:28 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-04 12:34 [PATCH] irqchip/gic-v3: Workaround for GIC-700 erratum 2941627 Lorenzo Pieralisi
2023-07-04 12:34 ` Lorenzo Pieralisi
2023-07-04 14:44 ` Marc Zyngier
2023-07-04 14:44   ` Marc Zyngier
2023-07-04 15:14   ` Lorenzo Pieralisi
2023-07-04 15:14     ` Lorenzo Pieralisi
2023-07-04 15:23     ` Marc Zyngier
2023-07-04 15:23       ` Marc Zyngier
2023-07-04 15:27   ` Lorenzo Pieralisi [this message]
2023-07-04 15:27     ` Lorenzo Pieralisi
2023-07-04 15:31     ` Marc Zyngier
2023-07-04 15:31       ` Marc Zyngier
2023-07-04 15:50 ` [PATCH v2] " Lorenzo Pieralisi
2023-07-04 15:50   ` Lorenzo Pieralisi
2023-07-17 12:57   ` [irqchip: irq/irqchip-fixes] " irqchip-bot for Lorenzo Pieralisi
  -- strict thread matches above, loose matches on Subject: below --
2023-07-07 11:45 [PATCH] " Chunhui Li (李春辉)
2023-07-07 12:14 Chunhui Li (李春辉)
2023-07-09  8:20 ` Marc Zyngier
2023-07-09  8:20   ` Marc Zyngier
2023-07-10  6:00   ` Chunhui Li (李春辉)
2023-07-10  6:00     ` Chunhui Li (李春辉)
2023-07-11  2:03     ` Chunhui Li (李春辉)
2023-07-11  2:03       ` Chunhui Li (李春辉)
2023-07-12  1:40 Chunhui Li (李春辉)
2023-07-12  7:21 ` Marc Zyngier
2023-07-12  7:21   ` Marc Zyngier

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