netdev - Re: sctp netns "unregister_netdevice: waiting for lo to become free. Usage count = 1"

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Message-ID: <20180130155909.GA25399@hmswarspite.think-freely.org>
Date:   Tue, 30 Jan 2018 10:59:09 -0500
From:   Neil Horman <nhorman@...driver.com>
To:     Tommi Rantala <tommi.t.rantala@...ia.com>
Cc:     Vlad Yasevich <vyasevich@...il.com>, linux-sctp@...r.kernel.org,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: sctp netns "unregister_netdevice: waiting for lo to become free.
 Usage count = 1"

On Mon, Jan 29, 2018 at 05:55:45PM +0200, Tommi Rantala wrote:
> Hi,
> 
> When running sctp_test from lksctp-tools in netns in 4.4 and 4.9 with
> suitable arguments, the local loopback device in the netns is not getting
> destroyed after deleting the netns.
> 
> For example:
> 
> ip netns add TEST
> ip netns exec TEST ip link set lo up
> ip link add dummy0 type dummy
> ip link add dummy1 type dummy
> ip link add dummy2 type dummy
> ip link set dev dummy0 netns TEST
> ip link set dev dummy1 netns TEST
> ip link set dev dummy2 netns TEST
> ip netns exec TEST ip addr add 192.168.1.1/24 dev dummy0
> ip netns exec TEST ip link set dummy0 up
> ip netns exec TEST ip addr add 192.168.1.2/24 dev dummy1
> ip netns exec TEST ip link set dummy1 up
> ip netns exec TEST ip addr add 192.168.1.3/24 dev dummy2
> ip netns exec TEST ip link set dummy2 up
> ip netns exec TEST sctp_test -H 192.168.1.2 -P 20002 -h 192.168.1.1 -p 20000
> -s -B 192.168.1.3
> ip netns del TEST
> 
> Results to:
> 
> [  354.179591] unregister_netdevice: waiting for lo to become free. Usage
> count = 1
> [  364.419674] unregister_netdevice: waiting for lo to become free. Usage
> count = 1
> [  374.663664] unregister_netdevice: waiting for lo to become free. Usage
> count = 1
> [  384.903717] unregister_netdevice: waiting for lo to become free. Usage
> count = 1
> [  395.143724] unregister_netdevice: waiting for lo to become free. Usage
> count = 1
> [  405.383645] unregister_netdevice: waiting for lo to become free. Usage
> count = 1
> ...
> 
> Based on a quick test, 4.14 and 4.15 does not suffer from this, but its
> reproducible e.g. in 4.4.113 and 4.9.75
> 
> Any ideas?
> 
> Tommi
> 
Does the problem occur if you don't set lo up?

Neil