RE: [Xen-users] Re: [Xen-devel] Linux hangs during reboot on Jeremy's git kernel

[Mike Viau <viaum@xxxxxxxxxxxxxxx>]

> Date: Mon, 8 Feb 2010 16:07:36 -0500
> From: konrad.wilk@xxxxxxxxxx
> To: mike.viau@xxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] Re: [Xen-devel] Linux hangs during reboot on Jeremy's git kernel
> CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx
>
> > > a). Bare-metal. Boot pv-ops and shutdown. Does it do it?
> >
> > Yes oddly enough, shutdown is fine, only hangs on reboot.
> >
> > Also I'd like to note I am only using the kernel as a bare-metal kernel, so I have not loaded it as a module in grub with the hypervisor.
> >
> > > b). If it does not, try an earlier kernel or a distro supplied one.
> > >
> > > If the a) or b) don't work then you have a very unique motherboard
> > > and we will need to play a bit with 'reboot=' command line arguments.
> > > Look in arch/x86/kernel/reboot.c for details.
> > >
> >
> > I have tried using different reboot=X kernel command line arguments, but none of them have correct the rebooting issue. In fact the system hangs the same way in all cases.
>
> <scratches his head> That is most bizzare.
> Can you try to get the latest linux kernel and see how it works?
>

Well its not the 'latest' linux kernel, but I installed 2.6.30-8-amd64 from http://packages.debian.org/lenny-backports/kernel/linux-image-2.6.30-bpo.2-amd64 and the reboot hangs the same way.

That leads me to believe something in the mechanism of a system reboot has changed since 2.6.26-2-amd64.

> >
> > > Lets assume that a) or b) do work. We want to find out what it does
> > > to the machine. You can instrument the code (reboot.c?) and find out
> > > which mechanism it uses.
> > >
> >
> > I know that the system reboot fine with the Debian 2.6.26-2-amd64 kernel. Please suggest how one might compare these kernels reboot.c. Shall I simply run the diff utility. I can read C source, but to truly understand it I feel I need to have written the code... With help I believe I can find the mechanism it uses.
>
> Diff would do it. Look for shutdown.c and reboot.c file.

I don't find any shutdown.c file oddly enough. I have found multiple reboot.c though.

/usr/src/linux-2.6-xen/arch/sparc/kernel/reboot.c
/usr/src/linux-2.6-xen/arch/um/kernel/reboot.c
/usr/src/linux-2.6-xen/arch/x86/kernel/reboot.c
/usr/src/linux-2.6-xen/arch/blackfin/kernel/reboot.c
/usr/src/linux-2.6-xen/drivers/acpi/reboot.c

and

/usr/src/linux-2.6-2.6.26/arch/um/kernel/reboot.c
/usr/src/linux-2.6-2.6.26/arch/x86/kernel/reboot.c
/usr/src/linux-2.6-2.6.26/arch/x86/mach-visws/reboot.c
/usr/src/linux-2.6-2.6.26/arch/blackfin/kernel/reboot.c


Which one of these reboot.c should I diff against each other?


> ..snip ..
> > > What is weird is that your screenshot says "machine reboot" which only
> > > shows up when you are running on bare-metal. Was that screen shot taken
> > > when pv-ops was running under Xen or bare-metal?
> >
> > As mentioned previous, I was using bare-metal indeed. Should I expect the reboot functionality to work with Jeremy's kernel after using the Xen Hypervisor?
>
> Probably not. The shutdown/reboot code is similar to the upstream
> kernel. So if the upstream is not working, then this one wouldn't
> either.
>
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-M

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