linux-kernel - Re: [PATCH v3 16/16] ARM: Remove custom IRQ stat accounting

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Message-ID: <3cd270a8-ddff-b3aa-5d7f-e7224deefbcc@collabora.com>
Date:   Thu, 24 Sep 2020 14:09:06 +0100
From:   Guillaume Tucker <guillaume.tucker@...labora.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Valentin Schneider <valentin.schneider@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Sumit Garg <sumit.garg@...aro.org>, kernel-team@...roid.com,
        Florian Fainelli <f.fainelli@...il.com>,
        Russell King <linux@....linux.org.uk>,
        Jason Cooper <jason@...edaemon.net>,
        Saravana Kannan <saravanak@...gle.com>,
        Andrew Lunn <andrew@...n.ch>,
        Catalin Marinas <catalin.marinas@....com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, kernelci-results@...ups.io
Subject: Re: [PATCH v3 16/16] ARM: Remove custom IRQ stat accounting

On 24/09/2020 10:29, Marc Zyngier wrote:
> Hi Guillaume,
> 
> On Thu, 24 Sep 2020 10:00:09 +0100,
> Guillaume Tucker <guillaume.tucker@...labora.com> wrote:
>>
>> Hi Marc,
>>
>> On 01/09/2020 15:43, Marc Zyngier wrote:
>>> Let's switch the arm code to the core accounting, which already
>>> does everything we need.
>>>
>>> Reviewed-by: Valentin Schneider <valentin.schneider@....com>
>>> Signed-off-by: Marc Zyngier <maz@...nel.org>
>>> ---
>>>  arch/arm/include/asm/hardirq.h | 17 -----------------
>>>  arch/arm/kernel/smp.c          | 20 ++++----------------
>>>  2 files changed, 4 insertions(+), 33 deletions(-)
>>
>> This appears to be causing a NULL pointer dereference on
>> beaglebone-black, it got bisected automatically several times.
>> None of the other platforms in the KernelCI labs appears to be
>> affected.
> 
> Hmm. My bet is that because this is a UP machine running an SMP
> kernel, and I fell into the trap of forgetting about this 32bit
> configuration.
> 
> I expect the following patch to fix it. Please give it a go if you can
> (I'm away at the moment and can't test much, and do not have any
> physical 32bit machine to test this on).

OK thanks, that worked:

  https://lava.baylibre.com/scheduler/job/143170

I've added this fix to the kernel branch used on
staging.kernelci.org which is based on linux-next, so it will get
fully verified a bit later today.

Guillaume


> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 00327fa74b01..b4e3d336dc33 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -531,7 +531,12 @@ void show_ipi_list(struct seq_file *p, int prec)
>  	unsigned int cpu, i;
>  
>  	for (i = 0; i < NR_IPI; i++) {
> -		unsigned int irq = irq_desc_get_irq(ipi_desc[i]);
> +		unsigned int irq;
> +
> +		if (!ipi_desc[i])
> +			continue;
> +
> +		irq = irq_desc_get_irq(ipi_desc[i]);
>  		seq_printf(p, "%*s%u: ", prec - 1, "IPI", i);
>  
>  		for_each_online_cpu(cpu)
> 
> Thanks,
> 
> 	M.
>