linux-kernel - Re: [PATCH v2] genirq: move clear of kstat_irqs to free

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Message-ID: <874iopg9pl.ffs@tglx>
Date: Tue, 13 Jan 2026 10:09:42 +0100
From: Thomas Gleixner <tglx@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>, Luigi Rizzo <lrizzo@...gle.com>
Cc: maz@...nel.org, rizzo.unipi@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] genirq: move clear of kstat_irqs to free_desc()

On Mon, Jan 12 2026 at 21:18, Eric Dumazet wrote:
>> -       scoped_guard(raw_spinlock_irqsave, &desc->lock)
>> +       scoped_guard(raw_spinlock_irqsave, &desc->lock) {
>>                 desc_set_defaults(irq, desc, irq_desc_get_node(desc), NULL, NULL);
>> +               for_each_possible_cpu(cpu)
>> +                       *per_cpu_ptr(desc->kstat_irqs, cpu) = (struct irqstat) { };
>> +       }
>
>
> It seems that for_each_possible_cpu(cpu) could be done outside of the
> desc->lock protection.
>
> This would shorten hard-irq blocking by N cache line misses.

Right, though it really does not matter unless you deeply care about:

alpha, arc, hexagon, m68k, mips, parisc, sparc, xtensa and random old
ARM32 platforms :)