linux-kernel - Re: [PATCH v3 2/3] genirq: Always limit the affinity to online CPUs

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Message-ID: <87mtgodjnh.ffs@tglx>
Date:   Thu, 14 Apr 2022 12:49:38 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marc Zyngier <maz@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        'Linux Samsung SOC' <linux-samsung-soc@...r.kernel.org>,
        John Garry <john.garry@...wei.com>,
        Xiongfeng Wang <wangxiongfeng2@...wei.com>,
        David Decotigny <ddecotig@...gle.com>,
        Krzysztof Kozlowski <krzk@...nel.org>
Subject: Re: [PATCH v3 2/3] genirq: Always limit the affinity to online CPUs

On Wed, Apr 13 2022 at 18:26, Marc Zyngier wrote:
> Marek Szyprowski <m.szyprowski@...sung.com> wrote:
>> This patch landed in linux next-20220413 as commit 33de0aa4bae9 
>> ("genirq: Always limit the affinity to online CPUs"). Unfortunately it 
>> breaks booting of most ARM 32bit Samsung Exynos based boards.
>> 
>> I don't see anything specific in the log, though. Booting just hangs at 
>> some point. The only Samsung Exynos boards that boot properly are those 
>> Exynos4412 based.
>> 
>> I assume that this is related to the Multi Core Timer IRQ configuration 
>> specific for that SoCs. Exynos4412 uses PPI interrupts, while all other 
>> Exynos SoCs have separate IRQ lines for each CPU.
>
> Can you also check that with the patch applied, it is this path that
> is taken and that it is the timer interrupts that get rejected? If
> that's the case, can you put a dump_stack() here and give me that
> stack trace? The use of irq_force_affinity() in the driver looks
> suspicious...

It's pretty clear what happens.

secondary_start_kernel()
  notify_cpu_starting(cpu);
    exynos4_mct_starting_cpu()
     irq_force_affinity() -> fail

  set_cpu_online(cpu, true);

Thanks,

        tglx