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Date: Tue, 21 Oct 2014 15:12:25 -0600
From: Kevin Fenzi <kevin@scrye.com>
To: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: localed stuck in recent 3.18 git in copy_net_ns?
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On Mon, 20 Oct 2014 14:53:59 -0600
Kevin Fenzi <kevin@scrye.com> wrote:

> On Mon, 20 Oct 2014 16:43:26 -0400
> Dave Jones <davej@redhat.com> wrote:
>=20
> > I've seen similar soft lockup traces from the sys_unshare path when
> > running my fuzz tester.  It seems that if you create enough network
> > namespaces, it can take a huge amount of time for them to be
> > iterated. (Running trinity with '-c unshare' you can see the slow
> > down happen. In some cases, it takes so long that the watchdog
> > process kills it -- though the SIGKILL won't get delivered until
> > the unshare() completes)
> >=20
> > Any idea what this machine had been doing prior to this that may
> > have involved creating lots of namespaces ?
>=20
> That was right after boot. ;)=20
>=20
> This is my main rawhide running laptop.
>=20
> A 'ip netns list' shows nothing.

Some more information:=20

The problem started between:=20

v3.17-7872-g5ff0b9e1a1da and v3.17-8307-gf1d0d14120a8

(I can try and do a bisect, but have to head out on a trip tomorrow)

In all the kernels with the problem, there is a kworker process in D.=20

sysrq-t says:=20
                                            Showing all locks held in the s=
ystem:
Oct 21 15:06:31 voldemort.scrye.com kernel: 4 locks held by kworker/u16:0/6:
Oct 21 15:06:31 voldemort.scrye.com kernel:  #0:  ("%s""netns"){.+.+.+}, at=
: [<ffffffff810ccbff>] process_one_work+0x17f/0x850
Oct 21 15:06:31 voldemort.scrye.com kernel:  #1:  (net_cleanup_work){+.+.+.=
}, at: [<ffffffff810ccbff>] process_one_work+0x17f/0x850
Oct 21 15:06:31 voldemort.scrye.com kernel:  #2:  (net_mutex){+.+.+.}, at: =
[<ffffffff817069fc>] cleanup_net+0x8c/0x1f0
Oct 21 15:06:31 voldemort.scrye.com kernel:  #3:
(rcu_sched_state.barrier_mutex){+.+...}, at: [<ffffffff8112a395>]
_rcu_barrier+0x35/0x200

On first running any of the systemd units that use PrivateNetwork, then
run ok, but they are also set to timeout after a minute. On sucessive
runs they hang in D also.

kevin

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