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

[Baoquan He]

On 11/10/13 at 05:44pm, Baoquan He wrote:
> On 11/08/13 at 10:14am, Vivek Goyal wrote:
> > On Tue, Nov 05, 2013 at 05:16:07PM +0800, Baoquan He wrote:
> 
> > 
> > Hi Bao,
> > 
> > This patch fixes the issue for me too. I noticed that we have generic
> > function migrate_to_reboot_cpu() to achieve what we want and rest of
> > the reboot paths are using it. So how about using that function. I 
> > wrote the new patch below. It works for me. Can you please give it
> > a try.

Hi Vivek,

Your patch works, my test script has wrong typo.

Baoquan
Thanks a lot

> 
> Seems there's something wrong with this function, that error happened
> when I executed the 2nd "kexec -e". That means executing "kexec -e" in
> kexec-ed kernel.
> 
> Tomorrow I will ask people around take more tests. We need set affinity
> to test this. E.g always execute :
> 
> taskset -c 1 -sh "kexec -e"
> 
> 
> > 
> > Thanks
> > Vivek
> > 
> > kexec: migrate to reboot cpu
> > 
> > Commit 1b3a5d02ee070c8f9943333b9b6370f486601e0f moved reboot= handling to
> > generic code. In the process it also removed the code in
> > native_machine_shutdown() which are moving reboot process to reboot_cpu/cpu0.
> > 
> > I guess that thought must have been that all reboot paths are calling
> > migrate_to_reboot_cpu(), so we don't need this special handling. But
> > kexec reboot path (kernel_kexec()) is not calling migrate_to_reboot_cpu()
> > so above change broke kexec. Now reboot can happen on non-boot cpu and when
> > INIT is sent in second kerneo to bring up BP, it brings down the machine.
> > 
> > So start calling migrate_to_reboot_cpu() in kexec reboot path to avoid
> > this problem.
> > 
> > Reported-by: Matthew Whitehead <mwhitehe at redhat.com>
> > Reported-by: Dave Young <dyoung at redhat.com>
> > Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
> > ---
> >  include/linux/reboot.h |    1 +
> >  kernel/kexec.c         |    1 +
> >  kernel/reboot.c        |    2 +-
> >  3 files changed, 3 insertions(+), 1 deletion(-)
> > 
> > Index: linux-2.6/kernel/reboot.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/reboot.c	2013-10-16 00:30:50.000000000 -0400
> > +++ linux-2.6/kernel/reboot.c	2013-11-08 21:31:03.379064848 -0500
> > @@ -104,7 +104,7 @@ int unregister_reboot_notifier(struct no
> >  }
> >  EXPORT_SYMBOL(unregister_reboot_notifier);
> >  
> > -static void migrate_to_reboot_cpu(void)
> > +void migrate_to_reboot_cpu(void)
> >  {
> >  	/* The boot cpu is always logical cpu 0 */
> >  	int cpu = reboot_cpu;
> > Index: linux-2.6/include/linux/reboot.h
> > ===================================================================
> > --- linux-2.6.orig/include/linux/reboot.h	2013-11-08 21:33:27.000000000 -0500
> > +++ linux-2.6/include/linux/reboot.h	2013-11-08 21:34:29.778073522 -0500
> > @@ -43,6 +43,7 @@ extern int unregister_reboot_notifier(st
> >   * Architecture-specific implementations of sys_reboot commands.
> >   */
> >  
> > +extern void migrate_to_reboot_cpu(void);
> >  extern void machine_restart(char *cmd);
> >  extern void machine_halt(void);
> >  extern void machine_power_off(void);
> > Index: linux-2.6/kernel/kexec.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/kexec.c	2013-10-16 00:30:50.000000000 -0400
> > +++ linux-2.6/kernel/kexec.c	2013-11-08 21:34:02.492072375 -0500
> > @@ -1676,6 +1676,7 @@ int kernel_kexec(void)
> >  #endif
> >  	{
> >  		kernel_restart_prepare(NULL);
> > +		migrate_to_reboot_cpu();
> >  		printk(KERN_EMERG "Starting new kernel\n");
> >  		machine_shutdown();
> >  	}