Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932516AbaJXPoE (ORCPT ); Fri, 24 Oct 2014 11:44:04 -0400 Received: from e8.ny.us.ibm.com ([32.97.182.138]:57055 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751630AbaJXPoB (ORCPT ); Fri, 24 Oct 2014 11:44:01 -0400 Date: Fri, 24 Oct 2014 08:40:06 -0700 From: "Paul E. McKenney" To: Yanko Kaneti Cc: Josh Boyer , "Eric W. Biederman" , Cong Wang , Kevin Fenzi , netdev , "Linux-Kernel@Vger. Kernel. Org" , jay.vosburgh@canonical.com, mroos@linux.ee Subject: Re: localed stuck in recent 3.18 git in copy_net_ns? Message-ID: <20141024154006.GP4977@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20141022224032.GA1240@declera.com> <20141022232421.GN4977@linux.vnet.ibm.com> <1414044566.2031.1.camel@declera.com> <20141023122750.GP4977@linux.vnet.ibm.com> <20141023153333.GA19278@linux.vnet.ibm.com> <20141023195159.GA2331@declera.com> <20141023200507.GC4977@linux.vnet.ibm.com> <1414100740.2065.2.camel@declera.com> <20141023220406.GJ4977@linux.vnet.ibm.com> <20141024090857.GA4083@declera.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141024090857.GA4083@declera.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14102415-0029-0000-0000-000000E10B19 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 24, 2014 at 12:08:57PM +0300, Yanko Kaneti wrote: > On Thu-10/23/14-2014 15:04, Paul E. McKenney wrote: > > On Fri, Oct 24, 2014 at 12:45:40AM +0300, Yanko Kaneti wrote: > > > > > > On Thu, 2014-10-23 at 13:05 -0700, Paul E. McKenney wrote: > > > > On Thu, Oct 23, 2014 at 10:51:59PM +0300, Yanko Kaneti wrote: [ . . . ] > > > > > Indeed, c847f14217d5 it is. > > > > > > > > > > Much to my embarrasment I just noticed that in addition to the > > > > > rcu merge, triggering the bug "requires" my specific Fedora > > > > > rawhide network > > > > > setup. Booting in single mode and modprobe ppp_generic is fine. > > > > > The bug > > > > > appears when starting with my regular fedora network setup, which > > > > > in my case > > > > > includes 3 ethernet adapters and a libvirt birdge+nat setup. > > > > > > > > > > Hope that helps. > > > > > > > > > > I am attaching the config. > > > > > > > > It does help a lot, thank you!!! > > > > > > > > The following patch is a bit of a shot in the dark, and assumes that > > > > commit 1772947bd012 (rcu: Handle NOCB callbacks from irq-disabled > > > > idle > > > > code) introduced the problem. Does this patch fix things up? > > > > > > Unfortunately not, This is linus-tip + patch > > > > OK. Can't have everything, I guess. > > > > > INFO: task kworker/u16:6:96 blocked for more than 120 seconds. > > > Not tainted 3.18.0-rc1+ #4 > > > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > > kworker/u16:6 D ffff8800ca84cec0 11168 96 2 0x00000000 > > > Workqueue: netns cleanup_net > > > ffff8802218339e8 0000000000000096 ffff8800ca84cec0 00000000001d5f00 > > > ffff880221833fd8 00000000001d5f00 ffff880223264ec0 ffff8800ca84cec0 > > > ffffffff82c52040 7fffffffffffffff ffffffff81ee2658 ffffffff81ee2650 > > > Call Trace: > > > [] schedule+0x29/0x70 > > > [] schedule_timeout+0x26c/0x410 > > > [] ? native_sched_clock+0x2a/0xa0 > > > [] ? mark_held_locks+0x7c/0xb0 > > > [] ? _raw_spin_unlock_irq+0x30/0x50 > > > [] ? trace_hardirqs_on_caller+0x15d/0x200 > > > [] wait_for_completion+0x10c/0x150 > > > [] ? wake_up_state+0x20/0x20 > > > [] _rcu_barrier+0x159/0x200 > > > [] rcu_barrier+0x15/0x20 > > > [] netdev_run_todo+0x6f/0x310 > > > [] ? rollback_registered_many+0x265/0x2e0 > > > [] rtnl_unlock+0xe/0x10 > > > [] default_device_exit_batch+0x156/0x180 > > > [] ? abort_exclusive_wait+0xb0/0xb0 > > > [] ops_exit_list.isra.1+0x53/0x60 > > > [] cleanup_net+0x100/0x1f0 > > > [] process_one_work+0x218/0x850 > > > [] ? process_one_work+0x17f/0x850 > > > [] ? worker_thread+0xe7/0x4a0 > > > [] worker_thread+0x6b/0x4a0 > > > [] ? process_one_work+0x850/0x850 > > > [] kthread+0x10b/0x130 > > > [] ? sched_clock+0x9/0x10 > > > [] ? kthread_create_on_node+0x250/0x250 > > > [] ret_from_fork+0x7c/0xb0 > > > [] ? kthread_create_on_node+0x250/0x250 > > > 4 locks held by kworker/u16:6/96: > > > #0: ("%s""netns"){.+.+.+}, at: [] process_one_work+0x17f/0x850 > > > #1: (net_cleanup_work){+.+.+.}, at: [] process_one_work+0x17f/0x850 > > > #2: (net_mutex){+.+.+.}, at: [] cleanup_net+0x8c/0x1f0 > > > #3: (rcu_sched_state.barrier_mutex){+.+...}, at: [] _rcu_barrier+0x35/0x200 > > > INFO: task modprobe:1045 blocked for more than 120 seconds. > > > Not tainted 3.18.0-rc1+ #4 > > > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > > modprobe D ffff880218343480 12920 1045 1044 0x00000080 > > > ffff880218353bf8 0000000000000096 ffff880218343480 00000000001d5f00 > > > ffff880218353fd8 00000000001d5f00 ffffffff81e1b580 ffff880218343480 > > > ffff880218343480 ffffffff81f8f748 0000000000000246 ffff880218343480 > > > Call Trace: > > > [] schedule_preempt_disabled+0x31/0x80 > > > [] mutex_lock_nested+0x183/0x440 > > > [] ? register_pernet_subsys+0x1f/0x50 > > > [] ? register_pernet_subsys+0x1f/0x50 > > > [] ? 0xffffffffa0673000 > > > [] register_pernet_subsys+0x1f/0x50 > > > [] br_init+0x48/0xd3 [bridge] > > > [] do_one_initcall+0xd8/0x210 > > > [] load_module+0x20c2/0x2870 > > > [] ? store_uevent+0x70/0x70 > > > [] ? kernel_read+0x57/0x90 > > > [] SyS_finit_module+0xa6/0xe0 > > > [] system_call_fastpath+0x12/0x17 > > > 1 lock held by modprobe/1045: > > > #0: (net_mutex){+.+.+.}, at: [] register_pernet_subsys+0x1f/0x50 > > > > Presumably the kworker/u16:6 completed, then modprobe hung? > > > > If not, I have some very hard questions about why net_mutex can be > > held by two tasks concurrently, given that it does not appear to be a > > reader-writer lock... > > > > Either way, my patch assumed that 39953dfd4007 (rcu: Avoid misordering in > > __call_rcu_nocb_enqueue()) would work and that 1772947bd012 (rcu: Handle > > NOCB callbacks from irq-disabled idle code) would fail. Is that the case? > > If not, could you please bisect the commits between 11ed7f934cb8 (rcu: > > Make nocb leader kthreads process pending callbacks after spawning) > > and c847f14217d5 (rcu: Avoid misordering in nocb_leader_wait())? > > Ok, unless I've messsed up something major, bisecting points to: > > 35ce7f29a44a rcu: Create rcuo kthreads only for onlined CPUs > > Makes any sense ? Good question. ;-) Are any of your online CPUs missing rcuo kthreads? There should be kthreads named rcuos/0, rcuos/1, rcuos/2, and so on for each online CPU. > Another thing I noticed is that in failure mode the libvirtd bridge actually > doesn't show up. So maybe ppp is just the first thing to try that bumps up > into whatever libvirtd is failing to do to setup those. > > Truly hope this is not something with random timing dependency.... Me too. ;-) Thanx, Paul > --Yanko > -- > 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/ > -- 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/