From: Yanko Kaneti <yaneti@declera.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Boyer <jwboyer@fedoraproject.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Cong Wang <cwang@twopensource.com>, Kevin Fenzi <kevin@scrye.com>,
netdev <netdev@vger.kernel.org>,
"Linux-Kernel@Vger. Kernel. Org" <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?
Date: Sat, 25 Oct 2014 00:25:57 +0300 [thread overview]
Message-ID: <20141024212557.GA15537@declera.com> (raw)
In-Reply-To: <20141024183226.GW4977@linux.vnet.ibm.com>
On Fri-10/24/14-2014 11:32, Paul E. McKenney wrote:
> On Fri, Oct 24, 2014 at 08:35:26PM +0300, Yanko Kaneti wrote:
> > On Fri-10/24/14-2014 10:20, Paul E. McKenney wrote:
> > > 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.
> >
> > Doesn't seem to make a difference here
>
> OK, inspection isn't cutting it, so time for tracing. Does the system
> respond to user input? If so, please enable rcu:rcu_barrier ftrace before
> the problem occurs, then dump the trace buffer after the problem occurs.
Sorry for being unresposive here, but I know next to nothing about tracing
or most things about the kernel, so I have some cathing up to do.
In the meantime some layman observations while I tried to find what exactly
triggers the problem.
- Even in runlevel 1 I can reliably trigger the problem by starting libvirtd
- libvirtd seems to be very active in using all sorts of kernel facilities
that are modules on fedora so it seems to cause many simultaneous kworker
calls to modprobe
- there are 8 kworker/u16 from 0 to 7
- one of these kworkers always deadlocks, while there appear to be two
kworker/u16:6 - the seventh
6 vs 8 as in 6 rcuos where before they were always 8
Just observations from someone who still doesn't know what the u16
kworkers are..
-- Yanko
> 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;
> > > }
> > >
> >
>
next prev parent reply other threads:[~2014-10-24 21:25 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-20 20:15 localed stuck in recent 3.18 git in copy_net_ns? Kevin Fenzi
2014-10-20 20:43 ` Dave Jones
2014-10-20 20:53 ` Kevin Fenzi
2014-10-21 21:12 ` Kevin Fenzi
2014-10-22 17:12 ` Josh Boyer
2014-10-22 17:37 ` Cong Wang
2014-10-22 17:49 ` Josh Boyer
2014-10-22 17:53 ` Eric W. Biederman
2014-10-22 18:11 ` Paul E. McKenney
2014-10-22 18:25 ` Eric W. Biederman
2014-10-22 18:55 ` Paul E. McKenney
2014-10-22 19:33 ` Josh Boyer
2014-10-22 22:40 ` Yanko Kaneti
2014-10-22 23:24 ` Paul E. McKenney
2014-10-23 6:09 ` Yanko Kaneti
2014-10-23 12:27 ` Paul E. McKenney
2014-10-23 15:33 ` Paul E. McKenney
[not found] ` <CA+5PVA4H6EAf6cBc4a_8W8x4Mgppjc5GsskKaCRry2jq+LP+FA@mail.gmail.com>
2014-10-23 16:28 ` Paul E. McKenney
2014-10-23 19:51 ` Yanko Kaneti
2014-10-23 20:05 ` Paul E. McKenney
2014-10-23 21:45 ` Yanko Kaneti
2014-10-23 22:04 ` Paul E. McKenney
2014-10-24 4:48 ` Jay Vosburgh
2014-10-24 14:50 ` Paul E. McKenney
2014-10-24 18:20 ` Jay Vosburgh
2014-10-24 18:33 ` Paul E. McKenney
2014-10-24 9:08 ` Yanko Kaneti
2014-10-24 15:40 ` Paul E. McKenney
2014-10-24 16:29 ` Yanko Kaneti
2014-10-24 16:54 ` Paul E. McKenney
2014-10-24 17:09 ` Yanko Kaneti
2014-10-24 17:20 ` Paul E. McKenney
2014-10-24 17:35 ` Yanko Kaneti
2014-10-24 18:32 ` Paul E. McKenney
2014-10-24 18:49 ` Jay Vosburgh
2014-10-24 18:57 ` Paul E. McKenney
2014-10-24 20:15 ` Paul E. McKenney
2014-10-24 21:25 ` Yanko Kaneti [this message]
2014-10-24 21:49 ` Paul E. McKenney
2014-10-24 22:02 ` Jay Vosburgh
2014-10-24 22:16 ` Paul E. McKenney
2014-10-24 22:41 ` Jay Vosburgh
2014-10-24 22:34 ` Jay Vosburgh
2014-10-24 22:59 ` Paul E. McKenney
2014-10-24 23:05 ` Paul E. McKenney
2014-10-25 0:20 ` Jay Vosburgh
2014-10-25 2:03 ` Paul E. McKenney
2014-10-25 4:33 ` Jay Vosburgh
2014-10-25 5:16 ` Paul E. McKenney
2014-10-25 16:38 ` Jay Vosburgh
2014-10-25 18:18 ` Paul E. McKenney
2014-10-27 17:45 ` Paul E. McKenney
2014-10-27 20:43 ` Jay Vosburgh
2014-10-27 21:07 ` Paul E. McKenney
2014-10-28 8:12 ` Yanko Kaneti
2014-10-28 12:50 ` Paul E. McKenney
2014-10-28 13:00 ` Yanko Kaneti
2014-10-28 15:54 ` Kevin Fenzi
2014-10-28 16:15 ` Paul E. McKenney
2014-10-25 12:09 ` Yanko Kaneti
2014-10-25 13:38 ` Paul E. McKenney
2014-10-22 17:59 ` Paul E. McKenney
2014-10-22 18:03 ` Josh Boyer
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