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Date: Fri, 8 Nov 2013 11:24:21 -0500
From: Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH] x86: make reboot task only run on the appropriate
 processor
Message-ID: <20131108162421.GC13068@redhat.com>
References: <1383642967-12595-1-git-send-email-bhe@redhat.com>
 <20131108151416.GA13068@redhat.com> <527D0D50.6010607@zytor.com>
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To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Robin Holt <robinmholt@gmail.com>, Baoquan He <bhe@redhat.com>, mwhitehe@redhat.com, x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Robin Holt <robinmholt@linux.com>, davej@fedoraproject.org, mingo@redhat.com, "Eric W. Biederman" <ebiederm@xmission.com>, rmk+kernel@arm.linux.org.uk, akpm@linux-foundation.org, tglx@linutronix.de, chaowang@redhat.com

On Fri, Nov 08, 2013 at 08:12:00AM -0800, H. Peter Anvin wrote:
> On 11/08/2013 07:14 AM, Vivek Goyal 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.
> > 
> > Thanks
> > Vivek
> > 
> 
> Is this path exercised for the kdump flow?  migrate_to_reboot_cpu() is
> unsafe in that case.

kdump path should not be affected by this change as it uses crash_kexec()
instead of kerenl_kexec() for its entry. And crash_kexec() path does not
call migrate_to_reboot_cpu().

Thanks
Vivek

> 
> > 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();
> >  	}
> > 

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