linux-kernel - Re: [RFC PATCH] Bug during kexec...not all cpus are stopped

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Date:	Tue, 12 Oct 2010 18:17:17 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Alok Kataria <akataria@...are.com>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	Haren Myneni <hbabu@...ibm.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Daniel Hecht <dhecht@...are.com>, jeremy@...source.com
Subject: Re: [RFC PATCH] Bug during kexec...not all cpus are stopped

On Mon, Oct 11, 2010 at 03:10:11PM -0700, Eric W. Biederman wrote:
> Vivek Goyal <vgoyal@...hat.com> writes:
> 
> > On Mon, Oct 11, 2010 at 12:41:23PM -0700, Alok Kataria wrote:
> 
> > I don't think that kdump path uses smp_send_stop().
> 
> It doesn't.
> 
> > IIUC, on x86, we directly send NMI to other cpus.
> >
> > native_machine_crash_shutdown()
> >   kdump_nmi_shootdown_cpus()
> >         nmi_shootdown_cpus()
> >            smp_send_nmi_allbutself
> >                 apic->send_IPI_allbutself(NMI_VECTOR);
> >
> > So above description should be limited to only panic() path.
> 
> Is it actually confusing?  With respect to documenting the line
> of thinking it seems reasonable.
> 

No, just wanted to point out that let us modify the changelog to remove
keyword "kdump" from it. 

> > On a side note, I am wondering why panic() and kdump path can't share the
> > shutdown routine.
> 
> Hysterical raisins.  Andi's change to smp_send_stop says that NMIs not
> working on some boxes.  When someone wants to weed through all of the
> insanity it would probably be good to get the panic and the kdump paths
> sharing code.  For now simply separating panic and reboot should be
> enough, and it lets the code evolve where it needs to.
> 

Ok. Agreed that atleast conceptually kdump and panic() path should share
the code. But that's a different problem altogether and this patch can go in.

Thanks
Vivek
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