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Subject: Re: BUG?: kernel does not (re)set irq smp_affinity to reboot_cpu
To: Hans de Goede <hdegoede@redhat.com>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
References: <4dc8bd4c-8456-9f94-b7eb-c5d227ddc673@redhat.com>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>,
        Chen-Yu Tsai <wens@csie.org>, Russell King <linux@arm.linux.org.uk>
From: Marc Zyngier <marc.zyngier@arm.com>
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Date: Mon, 27 Jun 2016 10:13:05 +0100
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[Thanks Maxime for pointing me to this discussion, +RMK]

Hi Hans,

On 26/06/16 17:00, Hans de Goede wrote:
> Hi,
> 
> I've just spend most of my Sunday debugging a problem
> where Allwinner ARM SoC based boards will not shutdown when
> using a Fedora 24 userland, where as the exact same
> kernel works fine with Fedora 22.
> 
> It turns out that irq-balanced is to blame. In Fedora 24
> it pins the i2c controller, which talks to the pmic
> which is needed for poweroff to cpu-id 1:
> 
> [root@localhost ~]# cat /proc/irq/49/smp_affinity
> 2
> 
> Where as the reboot_cpu is cpu-id 0 and with
> cpu 1 disabled at poweroff time, the i2c transfer
> never gets past its first step leading to an i2c
> driver timeout + kernel panic due to machine_power_off()
> returning.
> 
> As a workaround I can stop irq-balanced and do:
> 
> echo 3 > /proc/irq/49/smp_affinity
> 
> Before doing poweroff and then everything works as
> expected again.
> 
> Now the question is how to fix this?

[...]

I'm wondering if that's not an effect of this patch:

https://lkml.org/lkml/2015/9/24/138

missing on the ARM side (the corresponding arm64 patch is 217d453d473c).

Otherwise, can you instrument the GIC set_affinity method and find out
if we're even trying to move this IRQ away from the CPU that is being
torn down?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...