linux-kernel - Re: [PATCH] powerpc/pasemi: Fix crash on reboot

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Date:	Mon, 21 Jan 2013 23:01:06 -0800
From:	Olof Johansson <olof@...om.net>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Shawn Guo <shawn.guo@...aro.org>
Subject: Re: [PATCH] powerpc/pasemi: Fix crash on reboot

Hi,

On Mon, Jan 21, 2013 at 7:23 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> commit f96972f2dc "kernel/sys.c: call disable_nonboot_cpus() in
> kernel_restart()"
>
> added a call to disable_nonboot_cpus() on kernel_restart(), which tries
> to shutdown all the CPUs except the first one. The issue with the PA
> Semi, is that it does not support CPU hotplug.
>
> When the call is made to __cpu_down(), it calls the notifiers
> CPU_DOWN_PREPARE, and then tries to take the CPU down.
>
> One of the notifiers to the CPU hotplug code, is the cpufreq. The
> DOWN_PREPARE will call __cpufreq_remove_dev() which calls
> cpufreq_driver->exit. The PA Semi exit handler unmaps regions of I/O
> that is used by an interrupt that goes off constantly
> (system_reset_common, but it goes off during normal system operations
> too). I'm not sure exactly what this interrupt does.

On this version of the power architecture, the system comes back
through the reset vector when returning from some of the lower-power
idle states, which should be why you see those exceptions go off.

Thanks for catching this. I have a system that I try booting a few
times every release cycle, but I must have missed checking if reboots
still work. Glad to see you're keeping yours alive, it's becoming a
collectible. :-)

[...]

> Cc: Olof Johansson <olof@...om.net>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>

Acked-by: Olof Johansson <olof@...om.net>

Ben, please apply for 3.8.


-Olof
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