Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757069AbaJXRYG (ORCPT ); Fri, 24 Oct 2014 13:24:06 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:35611 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756100AbaJXRYD (ORCPT ); Fri, 24 Oct 2014 13:24:03 -0400 Date: Fri, 24 Oct 2014 10:20:09 -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: <20141024172009.GV4977@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <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> <20141024154006.GP4977@linux.vnet.ibm.com> <20141024162943.GA16621@declera.com> <20141024165454.GS4977@linux.vnet.ibm.com> <20141024170931.GA21849@declera.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141024170931.GA21849@declera.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14102417-0033-0000-0000-000000D56146 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 24, 2014 at 08:09:31PM +0300, Yanko Kaneti wrote: > On Fri-10/24/14-2014 09:54, Paul E. McKenney wrote: > > On Fri, Oct 24, 2014 at 07:29:43PM +0300, Yanko Kaneti wrote: > > > On Fri-10/24/14-2014 08:40, Paul E. McKenney wrote: > > > > 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: > > > > [ . . . ] > > > > > > > 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. > > > > > > Its a Phenom II X6. With 3.17 and linux-tip with 35ce7f29a44a reverted, the rcuos are 8 > > > and the modprobe ppp_generic testcase reliably works, libvirt also manages > > > to setup its bridge. > > > > > > Just with linux-tip , the rcuos are 6 but the failure is as reliable as > > > before. > > > Thank you, very interesting. Which 6 of the rcuos are present? > > Well, the rcuos are 0 to 5. Which sounds right for a 6 core CPU like this > Phenom II. Ah, you get 8 without the patch because it creates them for potential CPUs as well as real ones. OK, got it. > > > Awating instructions: :) > > > > Well, I thought I understood the problem until you found that only 6 of > > the expected 8 rcuos are present with linux-tip without the revert. ;-) > > > > I am putting together a patch for the part of the problem that I think > > I understand, of course, but it would help a lot to know which two of > > the rcuos are missing. ;-) > > Ready to test Well, if you are feeling aggressive, give the following patch a spin. I am doing sanity tests on it in the meantime. Thanx, Paul ------------------------------------------------------------------------ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 29fb23f33c18..927c17b081c7 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2546,9 +2546,13 @@ static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu) rdp->nocb_leader = rdp_spawn; if (rdp_last && rdp != rdp_spawn) rdp_last->nocb_next_follower = rdp; - rdp_last = rdp; - rdp = rdp->nocb_next_follower; - rdp_last->nocb_next_follower = NULL; + if (rdp == rdp_spawn) { + rdp = rdp->nocb_next_follower; + } else { + rdp_last = rdp; + rdp = rdp->nocb_next_follower; + rdp_last->nocb_next_follower = NULL; + } } while (rdp); rdp_spawn->nocb_next_follower = rdp_old_leader; } -- 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/