linux-kernel - Re: [PATCH] x86: make reboot task only run on the appropriate processor

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Date:	Tue, 5 Nov 2013 15:28:56 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Baoquan He <bhe@...hat.com>
Cc:	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, akpm@...ux-foundation.org,
	holt@....com, davej@...oraproject.org, rmk+kernel@....linux.org.uk,
	chaowang@...hat.com, mwhitehe@...hat.com, kexec@...ts.infradead.org
Subject: Re: [PATCH] x86: make reboot task only run on the appropriate
 processor

On Tue, Nov 05, 2013 at 05:16:07PM +0800, Baoquan He wrote:
> Currently system always reboot after below message when execute "kexec -e".
> 
> [    0.572119] smpboot: Booting Node   0, Processors  #   1 OK
> 

So is it same problem were we reboot on non-boot cpu and sending INIT
to boot cpu in second kernel brings down the machine?

I think for x86, it makes sense to reboot on boot cpu.

Thanks
Vivek

> In commit 1b3a5d02ee070c8f9943333b9b6370f486601e0f, reboot= handling was
> moved to kerne/reboot.c. However, the code to migrate current thread to
> reboot cpu was removed. That cause this incorrect kexec behavior.
> 
> Now add that code block back.
> 
> Reported-by: Matthew Whitehead <mwhitehe@...hat.com>
> Reported-by: Dave Young <dyoung@...hat.com>
> Tested-by: WANG Chao <chaowang@...hat.com>
> Signed-off-by: Baoquan He <bhe@...hat.com>
> ---
>  arch/x86/kernel/reboot.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
> index 7e920bf..3049de9 100644
> --- a/arch/x86/kernel/reboot.c
> +++ b/arch/x86/kernel/reboot.c
> @@ -551,6 +551,21 @@ void native_machine_shutdown(void)
>  {
>  	/* Stop the cpus and apics */
>  #ifdef CONFIG_SMP
> +       /* The boot cpu is always logical cpu 0 */
> +       int reboot_cpu_id = 0;
> +
> +       /* See if there has been given a command line override */
> +       if ((reboot_cpu != -1) && (reboot_cpu < nr_cpu_ids) &&
> +               cpu_online(reboot_cpu))
> +               reboot_cpu_id = reboot_cpu;
> +
> +       /* Make certain the cpu I'm about to reboot on is online */
> +       if (!cpu_online(reboot_cpu_id))
> +               reboot_cpu_id = smp_processor_id();
> +
> +       /* Make certain I only run on the appropriate processor */
> +       set_cpus_allowed_ptr(current, cpumask_of(reboot_cpu_id));
> +
>  	/*
>  	 * Stop all of the others. Also disable the local irq to
>  	 * not receive the per-cpu timer interrupt which may trigger
> -- 
> 1.8.3.1
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