From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: cpu stall and hyperthread Date: Tue, 3 Jul 2012 18:13:00 -0700 Message-ID: <20120704011300.GA2522@linux.vnet.ibm.com> References: <4FEBCDDE.60503@gmail.com> <4FF351C6.3000100@gmail.com> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-rt-users@vger.kernel.org To: Dong Liu Return-path: Received: from e35.co.us.ibm.com ([32.97.110.153]:42993 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753915Ab2GDBTp (ORCPT ); Tue, 3 Jul 2012 21:19:45 -0400 Received: from /spool/local by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 3 Jul 2012 19:19:44 -0600 Received: from d03relay01.boulder.ibm.com (d03relay01.boulder.ibm.com [9.17.195.226]) by d03dlp02.boulder.ibm.com (Postfix) with ESMTP id D3D8B3E40048 for ; Wed, 4 Jul 2012 01:19:12 +0000 (WET) Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay01.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q641JCg9302066 for ; Tue, 3 Jul 2012 19:19:12 -0600 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q641JCK6019244 for ; Tue, 3 Jul 2012 19:19:12 -0600 Content-Disposition: inline In-Reply-To: <4FF351C6.3000100@gmail.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Tue, Jul 03, 2012 at 04:10:46PM -0400, Dong Liu wrote: > Hi, > > After reading the RCU cpu stall doc. I thought that CONFIG_NO_HZ > might have something to do with this problem. And I think the NO_HZ > config is not good for RT performance, so I made a new kernel > without NO_HZ. It lasted longer but eventually cpu stalls happened > again. > > I then disable the cpu stall checking by set > > /sys/module/rcutree/parameters/rcu_cpu_stall_suppress > > to "1", but it did not solve the problem. Instead of cpu stall I had > > BUG: soft lockup - CPU#0 stuck for 279s! [swapper/0:0] > > And even I disabled Hyper-Threading, I also got cpu stall now. > > CPU stalls also occurred in KVM guest OS as well. > > But I never get cpu stall when I'm running the normal kernel without > -rt patch. > > Is the cpu stall a known issue with the rt patch? > > Thanks, > > Dong > > On 6/27/12 11:22 PM, Dong Liu wrote: > >Hi, > > > >I'm running 3.4.3-rt11 and 3.2.18-rt29 on a system with Intel I7 860, I > >noticed that with hyperthread enabled, I'm getting kernel error > > > >rcu_preempt detected stalls on CPUs/tasks: { 3} (detected by 5, t=60002 > >jiffies) Did you get stack traces with this error? And did you get repeated stall messages if you waited a few minutes after the first one? If so, the stack traces can help track down the problem. Thanx, Paul > >But with hyperthread disabled, no such error. > > > >Is preempt_rt not supposed to be used with hyperthread? > > > >Thanks, > > > >Dong > > > >P.S. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >