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

From: Baoquan He <bhe@redhat.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: mwhitehe@redhat.com, x86@kernel.org, kexec@lists.infradead.org,
	linux-kernel@vger.kernel.org, davej@fedoraproject.org,
	mingo@redhat.com, holt@sgi.com, hpa@zytor.com,
	rmk+kernel@arm.linux.org.uk, tglx@linutronix.de,
	akpm@linux-foundation.org, chaowang@redhat.com
Subject: Re: [PATCH] x86: make reboot task only run on the appropriate processor
Date: Thu, 7 Nov 2013 10:20:15 +0800	[thread overview]
Message-ID: <20131107022015.GA2491@dhcp-16-105.nay.redhat.com> (raw)
In-Reply-To: <20131105202855.GD4598@redhat.com>

On 11/05/13 at 03:28pm, Vivek Goyal wrote:
> 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 was wrong, they are the same problem. With multiple CPUs, by setting
affinity to execute crash or kexec on CPUn(n!==0), they all reboot after
the same message as below and then reboot through BIOS. It should be the
BSP got a INIT IPI message and make system hang.

[    0.572119] smpboot: Booting Node   0, Processors  #   1 OK

> 
> 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@redhat.com>
> > Reported-by: Dave Young <dyoung@redhat.com>
> > Tested-by: WANG Chao <chaowang@redhat.com>
> > Signed-off-by: Baoquan He <bhe@redhat.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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