Re: [Xen-devel] 3.8.0-rc0 on xen-unstable: RCU Stall during boot as dom0 kernel after IOAPIC

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Dec 17, 2012 at 10:35:58PM +0100, Sander Eikelenboom wrote:
> 
> Monday, December 17, 2012, 10:12:40 PM, you wrote:
> 
> > On Mon, Dec 17, 2012 at 03:46:34PM -0500, Konrad Rzeszutek Wilk wrote:
> >> On Mon, Dec 17, 2012 at 09:32:17PM +0100, Sander Eikelenboom wrote:
> >> > 
> >> > Sunday, December 16, 2012, 6:38:24 PM, you wrote:
> >> > 
> >> > > On Fri, Dec 14, 2012 at 04:55:57PM +0100, Sander Eikelenboom wrote:
> >> > >> Hi Konrad,
> >> > >> 
> >> > >> I just tried to boot a 3.8.0-rc0 kernel (last commit: 
> >> > >> 7313264b899bbf3988841296265a6e0e8a7b6521) as dom0 on my machine with 
> >> > >> current xen-unstable.
> >> > 
> >> > > Yeah, saw it over the Dec 11->Dec 12 merges and was out on
> >> > > vacation during that time (just got back).
> >> > 
> >> > > Did you by any chance try to do a git bisect to narrow down
> >> > > which merge it was?
> >> > 
> >> > Hi Konrad,
> >> 
> >> Hey Sander,
> >> 
> >> Thank you for doing the bisection.
> >> 
> >> Fenghua - any ideas what might be amiss in the Xen subsystem?
> >> I hadn't looked at the patchset of the CPU0 offlining/onlining
> >> so I am not completly up to speed on the particulars of the patches.
> 
> >> > 30106c174311b8cfaaa3186c7f6f9c36c62d17da is the first bad commit
> >> > commit 30106c174311b8cfaaa3186c7f6f9c36c62d17da
> >> > Author: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> >> > Date:   Tue Nov 13 11:32:41 2012 -0800
> >> > 
> >> >     x86, hotplug: Support functions for CPU0 online/offline
> >> > 
> >> >     Add smp_store_boot_cpu_info() to store cpu info for BSP during boot 
> >> > time.
> >> > 
> >> >     Now smp_store_cpu_info() stores cpu info for bringing up BSP or AP 
> >> > after
> >> >     it's offline.
> >> > 
> >> >     Continue to online CPU0 in native_cpu_up().
> >> > 
> >> >     Continue to offline CPU0 in native_cpu_disable().
> >> > 
> >> >     Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> >> >     Link: 
> >> > http://lkml.kernel.org/r/1352835171-3958-5-git-send-email-fenghua.yu@xxxxxxxxx
> >> >     Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
> >> > 
> 
> > This patch:
> 
> 
> > diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> > index 353c50f..4f7d259 100644
> > --- a/arch/x86/xen/smp.c
> > +++ b/arch/x86/xen/smp.c
> > @@ -254,7 +254,7 @@ static void __init xen_smp_prepare_cpus(unsigned int 
> > max_cpus)
> >         }
> >         xen_init_lock_cpu(0);
> >  
> > -       smp_store_cpu_info(0);
> > +       smp_store_boot_cpu_info();
> >         cpu_data(0).x86_max_cores = 1;
> >  
> >         for_each_possible_cpu(i) {
> 
> > Would do the corresponding change in the Xen subsystem that the above
> > mentioned commit did. Perhaps that is all that is needed? I am going to
> > be able to test this and look in more details tomorrow.
> 
> Seems like it, don't know if there are other things still lurking, but with 
> your patch it boots again as dom0 :-)

Excellent. And it seems that it also fixes it on my test machine. Great.
I am going to stick Reported-and-Tested-by: Sander Eikelenboom
and push it to Linus shortly. Thanks!

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