Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756676Ab2HFUeq (ORCPT ); Mon, 6 Aug 2012 16:34:46 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:59502 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756343Ab2HFUeo (ORCPT ); Mon, 6 Aug 2012 16:34:44 -0400 Message-ID: <50202A83.40705@gmail.com> Date: Mon, 06 Aug 2012 22:35:15 +0200 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120730 Thunderbird/14.0 MIME-Version: 1.0 To: John Stultz CC: Avi Kivity , paulmck@linux.vnet.ibm.com, "linux-kernel@vger.kernel.org" , mingo@kernel.org, a.p.zijlstra@chello.nl, prarit@redhat.com, tglx@linutronix.de, Dave Jones Subject: Re: rcu: INFO: rcu_preempt detected stalls on CPUs/tasks on v3.6 References: <500ED719.2010002@gmail.com> <50112D3B.4020201@redhat.com> <50127B16.5040401@gmail.com> <50153138.4020304@redhat.com> <5015A5A8.7030601@gmail.com> <50161D5E.4030009@redhat.com> <50165046.9020705@gmail.com> <501654D3.7020504@redhat.com> <50168162.4010508@gmail.com> <50168981.3000001@redhat.com> <501EA58D.4090606@gmail.com> <501FFD2A.4010905@us.ibm.com> <50200AEF.5080904@us.ibm.com> <50200CE6.70009@gmail.com> <50202987.80409@us.ibm.com> In-Reply-To: <50202987.80409@us.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1951 Lines: 34 On 08/06/2012 10:31 PM, John Stultz wrote: > On 08/06/2012 11:28 AM, Sasha Levin wrote: >> On 08/06/2012 08:20 PM, John Stultz wrote: >>> On 08/06/2012 10:21 AM, John Stultz wrote: >>>> On 08/05/2012 09:55 AM, Sasha Levin wrote: >>>>> On 07/30/2012 03:17 PM, Avi Kivity wrote: >>>>>> Possible causes: >>>>>> - the APIC calibration in the guest failed, so it is programming too >>>>>> low values into the timer >>>>>> - it actually needs 1 us wakeups and then can't keep up (esp. as kvm >>>>>> interrupt injection is slowing it down) >>>>>> >>>>>> You can try to find out by changing >>>>>> arch/x86/kvm/lapic.c:start_lapic_timer() to impose a minimum wakeup of >>>>>> (say) 20 microseconds which will let the guest live long enough for you >>>>>> to ftrace it and see what kind of timers it is programming. >>>>> I've kept trying to narrow it down, and found out It's triggerable using adjtimex(). >>> Sorry, one more question: Could you provide details on how is it trigger-able using adjtimex? >> It triggers after a while of fuzzing using trinity of just adjtimex ('./trinity --quiet -l off -cadjtimex'). >> >> Trinity is available here: http://git.codemonkey.org.uk/?p=trinity.git . >> >> Let me know if I can help further with reproducing this, I can probably copy over my testing environment to some other host if you'd like. > So far no luck. Dmesg mostly just gets filled up with trinity-child OOMs. How much memory are you running with? > > Are you running trinity as root or as some user that has CAP_SYS_TIME and can actually change values via adjtimex? Or does it trip just by reading the values? As root in a disposable vm. It triggers at a random point, not after a specific call. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/