Message-ID: <52E16E83.6060301@intel.com>
Date: Thu, 23 Jan 2014 11:33:23 -0800
From: Dave Hansen <dave.hansen@intel.com>
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To: =?UTF-8?B?VG9yYWxmIEbDtnJzdGVy?= <toralf.foerster@gmx.de>,
        Linux Kernel <linux-kernel@vger.kernel.org>
CC: kernel@gentoo.org, kvm@vger.kernel.org, Gleb Natapov <gleb@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: 3.13 hangs when I tried to start a KVM at a 32 bit stable Gentoo
References: <52DEA270.60803@gmx.de> <52E165B7.6020506@intel.com>
In-Reply-To: <52E165B7.6020506@intel.com>
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Sender: linux-kernel-owner@vger.kernel.org

On 01/23/2014 10:55 AM, Dave Hansen wrote:
> On 01/21/2014 08:38 AM, Toralf Förster wrote:
>> Jan 21 17:18:57 n22 kernel: INFO: rcu_sched self-detected stall on CPU { 2}  (t=60001 jiffies g=18494 c=18493 q=183951)
>> Jan 21 17:18:57 n22 kernel: sending NMI to all CPUs:
>> Jan 21 17:18:57 n22 kernel: NMI backtrace for cpu 2
>> Jan 21 17:18:57 n22 kernel: CPU: 2 PID: 6779 Comm: qemu-system-x86 Not tainted 3.13.0 #3
>> Jan 21 17:18:57 n22 kernel: Hardware name: LENOVO 4180F65/4180F65, BIOS 83ET75WW (1.45 ) 05/10/2013
>> Jan 21 17:18:57 n22 kernel: task: e921c370 ti: e5f36000 task.ti: e5f36000
> 
> I'm seeing a very similar hang with an ubuntu guest and a custom kernel.
> I'm on commit 0dc3fd0249a, and it's 100% reproducible every time I run KVM.

Did a little more LKML digging and found this:

	http://marc.info/?l=linux-kernel&m=139038631607917&q=raw

Peter's fix works for me.  I'm also running a CONFIG_PREEMPT_VOLUNTARY=y
config.

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