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

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Message-ID: <6b2e54d6-effa-4884-b674-2692a67e5cbc@email.android.com>
Date:	Tue, 05 Nov 2013 13:39:49 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Vivek Goyal <vgoyal@...hat.com>, Baoquan He <bhe@...hat.com>
CC:	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.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

We should, yes, if cpu 0 is available.

Vivek Goyal <vgoyal@...hat.com> 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 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

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
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