From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andre Przywara Subject: Re: Hypervisor crash(!) on xl cpupool-numa-split Date: Thu, 10 Feb 2011 15:18:36 +0100 Message-ID: <4D53F3BC.4070807@amd.com> References: <4D41FD3A.5090506@amd.com> <201102021539.06664.stephan.diestelhorst@amd.com> <4D4974D1.1080503@ts.fujitsu.com> <201102021701.05665.stephan.diestelhorst@amd.com> <4D4A43B7.5040707@ts.fujitsu.com> <4D4A72D8.3020502@ts.fujitsu.com> <4D4C08B6.30600@amd.com> <4D4FE7E2.9070605@amd.com> <4D4FF452.6060508@ts.fujitsu.com> <4D50D80F.9000007@ts.fujitsu.com> <4D517051.10402@amd.com> <4D529BD9.5050200@amd.com> <4D52A2CD.9090507@ts.fujitsu.com> <4D5388DF.8040900@ts.fujitsu.com> <4D53AF27.7030909@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4D53AF27.7030909@amd.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Juergen Gross Cc: George Dunlap , "xen-devel@lists.xensource.com" , "Diestelhorst, Stephan" List-Id: xen-devel@lists.xenproject.org Andre Przywara wrote: > On 02/10/2011 07:42 AM, Juergen Gross wrote: >> On 02/09/11 15:21, Juergen Gross wrote: >>> Andre, George, >>> >>> >>> What seems to be interesting: I think the problem did always occur when >>> a new cpupool was created and the first cpu was moved to it. >>> >>> I think my previous assumption regarding the master_ticker was not too bad. >>> I think somehow the master_ticker of the new cpupool is becoming active >>> before the scheduler is really initialized properly. This could happen, if >>> enough time is spent between alloc_pdata for the cpu to be moved and the >>> critical section in schedule_cpu_switch(). >>> >>> The solution should be to activate the timers only if the scheduler is >>> ready for them. >>> >>> George, do you think the master_ticker should be stopped in suspend_ticker >>> as well? I still see potential problems for entering deep C-States. I think >>> I'll prepare a patch which will keep the master_ticker active for the >>> C-State case and migrate it for the schedule_cpu_switch() case. >> Okay, here is a patch for this. It ran on my 4-core machine without any >> problems. >> Andre, could you give it a try? > Did, but unfortunately it crashed as always. Tried twice and made sure I > booted the right kernel. Sorry. > The idea with the race between the timer and the state changing sounded > very appealing, actually that was suspicious to me from the beginning. > > I will add some code to dump the state of all cpupools to the BUG_ON to > see in which situation we are when the bug triggers. OK, here is a first try of this, the patch iterates over all CPU pools and outputs some data if the BUG_ON ((sdom->weight * sdom->active_vcpu_count) > weight_left) condition triggers: (XEN) CPU pool #0: 1 domains (SMP Credit Scheduler), mask: fffffffc003f (XEN) CPU pool #1: 0 domains (SMP Credit Scheduler), mask: fc0 (XEN) CPU pool #2: 0 domains (SMP Credit Scheduler), mask: 1000 (XEN) Xen BUG at sched_credit.c:1010 .... The masks look proper (6 cores per node), the bug triggers when the first CPU is about to be(?) inserted. HTH, Andre. -- Andre Przywara AMD-Operating System Research Center (OSRC), Dresden, Germany