Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755349AbaJWTcA (ORCPT ); Thu, 23 Oct 2014 15:32:00 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:48341 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752293AbaJWTb7 (ORCPT ); Thu, 23 Oct 2014 15:31:59 -0400 Date: Thu, 23 Oct 2014 12:28:07 -0700 From: "Paul E. McKenney" To: Dave Jones , Linux Kernel , htejun@gmail.com, oleg@redhat.com Subject: Re: rcu_preempt detected stalls. Message-ID: <20141023192807.GY4977@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20141013173504.GA27955@redhat.com> <20141023183232.GW4977@linux.vnet.ibm.com> <20141023184018.GA12274@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141023184018.GA12274@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14102319-0025-0000-0000-000000D86A0C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 23, 2014 at 02:40:18PM -0400, Dave Jones wrote: > On Thu, Oct 23, 2014 at 11:32:32AM -0700, Paul E. McKenney wrote: > > > > trinity-c225 R running task 13448 646 32295 0x00000000 > > > ffff880161ccfb28 0000000000000002 ffff880161ccfe10 ffff88000bf85e00 > > > 00000000001d4100 0000000000000003 ffff880161ccffd8 00000000001d4100 > > > ffff880030124680 ffff88000bf85e00 ffff880161ccffd8 0000000000000000 > > > Call Trace: > > > [] preempt_schedule_irq+0x52/0xb0 > > > [] retint_kernel+0x20/0x30 > > > [] ? __d_lookup_rcu+0xd1/0x1e0 > > > [] ? __d_lookup_rcu+0x166/0x1e0 > > > [] lookup_fast+0x4f/0x3d0 > > > [] link_path_walk+0x1a7/0x8a0 > > > [] ? path_lookupat+0x45/0x7b0 > > > [] path_lookupat+0x67/0x7b0 > > > [] ? trace_hardirqs_off+0xd/0x10 > > > [] ? retint_restore_args+0xe/0xe > > > [] filename_lookup+0x2b/0xc0 > > > [] user_path_at_empty+0x67/0xc0 > > > [] ? put_lock_stats.isra.27+0xe/0x30 > > > [] ? lock_release_holdtime.part.28+0xe6/0x160 > > > [] ? get_parent_ip+0xd/0x50 > > > [] user_path_at+0x11/0x20 > > > [] do_utimes+0xd1/0x180 > > > [] SyS_utime+0x7f/0xc0 > > > [] ? tracesys+0x7e/0xe2 > > > [] tracesys+0xdd/0xe2 > > > > This one will require more looking. But did you do something like > > create a pair of mutually recursive symlinks or something? ;-) > > I'm not 100% sure, but this may have been on a box that I was running > tests on NFS. So maybe the server had disappeared with the mount > still active.. > > Just a guess tbh. Another possibility might be that the box was so overloaded that tasks were getting preempted for 21 seconds as a matter of course, and sometimes within RCU read-side critical sections. Or did the box have ample idle time? Thanx, Paul -- 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/