Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753532AbaLGX3D (ORCPT ); Sun, 7 Dec 2014 18:29:03 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:27126 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752223AbaLGX3A (ORCPT ); Sun, 7 Dec 2014 18:29:00 -0500 Message-ID: <5484E2AB.1070503@oracle.com> Date: Sun, 07 Dec 2014 18:28:43 -0500 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Linus Torvalds , Dave Jones , Chris Mason , =?windows-1252?Q?D=E2niel_Fraga?= , Linux Kernel Mailing List Subject: Re: frequent lockups in 3.18rc4 References: <20141201230339.GA20487@ret.masoncoding.com> <20141202193252.GB17595@redhat.com> <547E4C14.6040509@oracle.com> <54813C03.8040009@oracle.com> <5481C92E.6020805@oracle.com> <54846B06.8050906@oracle.com> <20141207182420.GG25340@linux.vnet.ibm.com> <20141207194304.GA17810@linux.vnet.ibm.com> In-Reply-To: <20141207194304.GA17810@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/07/2014 02:43 PM, Paul E. McKenney wrote: > On Sun, Dec 07, 2014 at 10:24:20AM -0800, Paul E. McKenney wrote: >> On Sun, Dec 07, 2014 at 09:58:14AM -0500, Sasha Levin wrote: >>> On 12/05/2014 01:15 PM, Linus Torvalds wrote: >>>> On Fri, Dec 5, 2014 at 7:03 AM, Sasha Levin wrote: >>>>> >>>>> Yes, it's going to a serial line, but it's only about 100 lines/second on >>>>> average. I wouldn't expect it to cause anything to hang! >>>> >>>> A regular 16650 serial chip? Running at 115kbps, I assume? So that's >>>> about 11kB/s. >>>> >>>> And the serial console is polling, since it can't sleep or depend on interrupts. >>>> >>>> At a average line length of what, 40 characters? At less than 300 >>>> lines/s, you'd be using up 100% of one CPU. And since the printouts >>>> are serialized, that would be all other CPU's too.. >>>> >>>> 100 lines/s _average_ means that I can easily see it be 300lines/s for a while. >>>> >>>> So yeah. The serial console is simply not designed to handle >>>> continuous output. It's for the "occasional" stuff. >>>> >>>> The fact that your rcu lockups go away when you make the fault >>>> injection be quiet makes me really suspect this is related. >>> >>> The lockups themselves "go away", but looking closer at the log >>> without those extra prints, I'm seeing: >>> >>> [ 1458.700070] INFO: rcu_preempt detected stalls on CPUs/tasks: >>> [ 1458.700133] (detected by 19, t=30502 jiffies, g=12293, c=12292, q=0) >>> [ 1458.702764] INFO: Stall ended before state dump start >>> >>> Quite often. >>> >>> Maybe the extra prints were just a catalyst? >> >> Is anything else being printed about the time that these message show >> up? Or is this the only output for the 40,000 jiffies preceding this >> message? There's actually nothing going on (beyond fuzzing noise) before/after: [ 756.618342] kexec-bzImage64: Not a bzImage [ 762.381734] kexec-bzImage64: Not a bzImage [ 765.129612] Unable to find swap-space signature [ 771.022304] Unable to find swap-space signature [ 793.434417] kexec-bzImage64: Not a bzImage [ 797.978210] => alloc_cpumask_var: failed! [ 800.253116] kexec-bzImage64: Not a bzImage [ 818.280056] INFO: rcu_sched detected stalls on CPUs/tasks: [ 818.280056] (detected by 11, t=30503 jiffies, g=-295, c=-296, q=0) [ 818.283400] INFO: Stall ended before state dump start [ 829.523992] audit: type=1326 audit(39.680:47): auid=4294967295 uid=2385760256 gid=2214330370 ses=4294967295 pid=13307 comm="trinity-c353" exe="/trinity/trinity" sig=9 arch=c000003e syscall=96 compat=0 ip=0x7fffcb7bee47 code=0x0 [ 830.890841] audit: type=1326 audit(41.010:48): auid=4294967295 uid=310902784 gid=201841673 ses=4294967295 pid=13294 comm="trinity-c350" exe="/trinity/trinity" sig=9 arch=c000003e syscall=96 compat=0 ip=0x7fffcb7bee47 code=0x0 > And could you please build with CONFIG_RCU_CPU_STALL_INFO=y and try > this again? I already have it set: $ grep STALL_INFO .config CONFIG_RCU_CPU_STALL_INFO=y Thanks, Sasha -- 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/