linux-kernel - Re: 3.8.0-rc0 on xen-unstable: RCU Stall during boot as dom0 kernel after IOAPIC

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Date:	Mon, 17 Dec 2012 22:35:58 +0100
From:	Sander Eikelenboom <linux@...elenboom.it>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	fenghua.yu@...el.com, xen-devel <xen-devel@...ts.xen.org>,
	<linux-kernel@...r.kernel.org>, <hpa@...ux.intel.com>
Subject: Re: 3.8.0-rc0 on xen-unstable: RCU Stall during boot as dom0 kernel after IOAPIC


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@...el.com>
>> > 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@...el.com>
>> >     Link: http://lkml.kernel.org/r/1352835171-3958-5-git-send-email-fenghua.yu@intel.com
>> >     Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
>> > 

> 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 :-)

Thx !

--
Sander


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