[Maverick] SRU: Reboot of linux-virtual hangs on EC2

[Brad Figg]

On 03/02/2011 06:57 AM, Stefan Bader wrote:
> SRU Justification:
>
> Impact: On reboot or shutdown the current Xen code does try to stop other
> CPUs. However the IPI communication is disabled already at that point.
> So issuing a reboot or shutdown from within an instance with multiple
> vcpus hangs.
>
> Fix: Cherry pick of an upstream patch (added around 2.6.37) removes the
> attempt to stop other CPUs.
>
> Testcase: From within an EC2 instance, call "sudo reboot". Instance never
> comes up again. With the patch applied it does.
>
> -Stefan
>
> ---
>
>  From bf8e8b6da4821b59ea162eec16e05f3a6d8a0f9a Mon Sep 17 00:00:00 2001
> From: Jeremy Fitzhardinge<jeremy.fitzhardinge at citrix.com>
> Date: Mon, 29 Nov 2010 14:16:53 -0800
> Subject: [PATCH] xen: don't bother to stop other cpus on shutdown/reboot
>
> Xen will shoot all the VCPUs when we do a shutdown hypercall, so there's
> no need to do it manually.
>
> In any case it will fail because all the IPI irqs have been pulled
> down by this point, so the cross-CPU calls will simply hang forever.
>
> Until change 76fac077db6b34e2c6383a7b4f3f4f7b7d06d8ce the function calls
> were not synchronously waited for, so this wasn't apparent.  However after
> that change the calls became synchronous leading to a hang on shutdown
> on multi-VCPU guests.
>
> Signed-off-by: Jeremy Fitzhardinge<jeremy.fitzhardinge at citrix.com>
> Cc: Stable Kernel<stable at kernel.org>
> Cc: Alok Kataria<akataria at vmware.com>
>
> BugLink: http://bugs.launchpad.net/bugs/727814
>
> (cherry-picked from commit 31e323cca9d5c8afd372976c35a5d46192f540d1 upstream)
> Signed-off-by: Stefan Bader<stefan.bader at canonical.com>
> ---
>   arch/x86/xen/enlighten.c |    4 ----
>   1 files changed, 0 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 6f6cd65..42c2d5f 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1022,10 +1022,6 @@ static void xen_reboot(int reason)
>   {
>   	struct sched_shutdown r = { .reason = reason };
>
> -#ifdef CONFIG_SMP
> -	stop_other_cpus();
> -#endif
> -
>   	if (HYPERVISOR_sched_op(SCHEDOP_shutdown,&r))
>   		BUG();
>   }

Acked-by: Brad Figg <brad.figg at canonical.com>

-- 
Brad Figg brad.figg at canonical.com http://www.canonical.com