linux-kernel - Re: [PATCH] ARM: socfpga: add smp_ops.cpu

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Date:	Tue, 2 Jun 2015 09:38:04 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	hiraku.toyooka.gu@...achi.com
Cc:	dinguyen@...nsource.altera.com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: socfpga: add smp_ops.cpu_kill to make kexec/kdump
 available

On Tue, Jun 02, 2015 at 02:32:19PM +0900, hiraku.toyooka.gu@...achi.com wrote:
> Before kexec soft reboot, secondary CPU's IRQs except for per-cpu twd are
> migrated from a CPU going offline to CPU0 by migrate_irqs(). The twd is
> stopped by twd_timer_cpu_notify(). As a result, secondary CPU has no
> interrupt source before entering WFI loop.

I wasn't thinking of SPIs and PPIs, but SGIs - the IPI interrupts coming
from the boot CPU.

> After staring kexec'd kernel, all interrupts are sent to CPU0 by default
> and CPU0 resets the secondary CPUs in socfpga_boot_secondary().
> I think it's the reason why kexec in socfpga succeeds.

If you have a way to reset CPU0, why are you not using this for hotplug
when a CPU is hot-unplugged?

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