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From: Parav Pandit <parav@nvidia.com>
To: =?utf-8?B?5byg5bm/6L6J?= <zhang.guanghui@cestc.cn>,
        Roi Dayan <roid@nvidia.com>,
        Saeed Mahameed <saeedm@nvidia.com>,
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CC: "linux-kernel " <linux-kernel@vger.kernel.org>,
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Subject: RE: Fix a devlink AB-BA deadlock on net namespace deletion
Thread-Topic: Fix a devlink AB-BA deadlock on net namespace deletion
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Date: Mon, 25 Apr 2022 02:24:10 +0000
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Did you audit if it is safe to not hold the pernet_ops_rwsem when traversin=
g the pernet_list list?
Last time several months back when I reviewed this area for this issue, it =
appeared that pernet_ops_rwsem must be held while traversing pernet_list.

You also need to fix the mail client to send text only patches.


From: =E5=BC=A0=E5=B9=BF=E8=BE=89 <zhang.guanghui@cestc.cn>=20
Sent: Sunday, April 24, 2022 2:02 AM
To: =E5=BC=A0=E5=B9=BF=E8=BE=89 <zhang.guanghui@cestc.cn>; Roi Dayan <roid@=
nvidia.com>; Saeed Mahameed <saeedm@nvidia.com>; Parav Pandit <parav@nvidia=
.com>; Jason Gunthorpe <jgg@nvidia.com>; gregkh <gregkh@linuxfoundation.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>; stable <stable@vger.kernel=
.org>
Subject: Fix a devlink AB-BA deadlock on net namespace deletion


=EF=BB=BFHi=C2=A0 all

Deleting a netns holds pernet_ops_rwsem and then takes devlink_mutex.=C2=A0
at that time changing mode to switchdev, holds the devlink_mutex, unregiste=
red to netdevice notifier and then takes pernet_ops_rwsem.=C2=A0
So AB-BA deadlock problem can happen. I have made a patch to fix the deadlo=
ck problem, it work well.=C2=A0please help with the review.=C2=A0Thanks=C2=
=A0


=C2=A0Example sequence is:=C2=A0
\$ ip netns add foo
\$ ip netns del foo &=C2=A0
\$ devlink=C2=A0 dev eswitch set pci/0000:af:00.1 mode switchdev

Process A:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 P=
rocess B:
cleanup_net()=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0genl_family_rcv_msg_doit=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0
=C2=A0=C2=A0down_read(&pernet_ops_rwsem);=C2=A0<-=C2=A0first=C2=A0sem=C2=A0=
acquired=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0ops_pre_exit_list()=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0pre_doit=C2=A0
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0devlink_nl_pre_doit=C2=A0mutex_lock(&devlink_mutex);=C2=
=A0<-first=C2=A0devlink_mutex=C2=A0acquired
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0pre_exit()
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0devlink_pernet_pre_ex=
it()=C2=A0mutex_lock(&devlink_mutex);<-first=C2=A0devlink_mutex=C2=A0acquir=
ed
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0dev=
link_nl_cmd_eswitch_set_doit
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0mlx5_devlink_eswitch_mode_set=C2=A0
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0mlx5_lag_disable_change
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0mlx5_disable_lag
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0mlx5_rescan_drivers_locked
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0device_del
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0...
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0unregister_netdevice_notifier=C2=
=A0
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0down_write(&pernet_op=
s_rwsem);<-=C2=A0first=C2=A0sem=C2=A0acquired
=C2=A0

=C2=A0deleting netns trace:
[=C2=A0 248.061947] INFO: task kworker/u160:3:1179 blocked for more than 12=
2 seconds.
[=C2=A0 248.061953]=C2=A0 =C2=A0 =C2=A0 =C2=A0Not tainted 5.15.13-0.el9.x86=
_64 #1
[=C2=A0 248.061955] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disa=
bles this message.
[=C2=A0 248.061956] task:kworker/u160:3=C2=A0 state:D stack:=C2=A0 =C2=A0 0=
 pid: 1179 ppid:=C2=A0 =C2=A0 =C2=A02 flags:0x00004000
[=C2=A0 248.061962] Workqueue: netns cleanup_net
[=C2=A0 248.061970] Call Trace:
[=C2=A0 248.061972]=C2=A0 <TASK>
[=C2=A0 248.061975]=C2=A0 __schedule+0x200/0x540
[=C2=A0 248.061982]=C2=A0 schedule+0x44/0xa0
[=C2=A0 248.061984]=C2=A0 schedule_preempt_disabled+0xa/0x10
[=C2=A0 248.061986]=C2=A0 __mutex_lock.constprop.0+0x212/0x400
[=C2=A0 248.061989]=C2=A0 devlink_pernet_pre_exit+0x2a/0x140
[=C2=A0 248.061994]=C2=A0 cleanup_net+0x1d2/0x3a0
[=C2=A0 248.061997]=C2=A0 process_one_work+0x1e8/0x390
[=C2=A0 248.062003]=C2=A0 worker_thread+0x53/0x3c0
[=C2=A0 248.062005]=C2=A0 ? process_one_work+0x390/0x390
[=C2=A0 248.062007]=C2=A0 kthread+0x10c/0x130
[=C2=A0 248.062011]=C2=A0 ? set_kthread_struct+0x40/0x40
[=C2=A0 248.062014]=C2=A0 ret_from_fork+0x1f/0x30
[=C2=A0 248.062020]=C2=A0 </TASK>

changing mode to switchdev trace:

[=C2=A0 248.062078] task:devlink=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0state:D s=
tack:=C2=A0 =C2=A0 0 pid: 8546 ppid:=C2=A0 8542 flags:0x00004000
[=C2=A0 248.062081] Call Trace:
[=C2=A0 248.062082]=C2=A0 <TASK>
[=C2=A0 248.062083]=C2=A0 __schedule+0x200/0x540
[=C2=A0 248.062087]=C2=A0 ? free_msg+0x3f/0xb0 [mlx5_core]
[=C2=A0 248.062156]=C2=A0 schedule+0x44/0xa0
[=C2=A0 248.062158]=C2=A0 rwsem_down_write_slowpath+0x19c/0x3c0
[=C2=A0 248.062165]=C2=A0 unregister_netdevice_notifier+0x1c/0xb0
[=C2=A0 248.062168]=C2=A0 mlx5_ib_roce_cleanup+0x8a/0x110 [mlx5_ib]
[=C2=A0 248.062184]=C2=A0 mlx5r_remove+0x36/0x60 [mlx5_ib]
[=C2=A0 248.062196]=C2=A0 auxiliary_bus_remove+0x18/0x30
[=C2=A0 248.062200]=C2=A0 __device_release_driver+0x177/0x240
[=C2=A0 248.062203]=C2=A0 device_release_driver+0x24/0x30
[=C2=A0 248.062205]=C2=A0 bus_remove_device+0xd8/0x140
[=C2=A0 248.062210]=C2=A0 device_del+0x18b/0x400
[=C2=A0 248.062213]=C2=A0 mlx5_rescan_drivers_locked.part.0+0x7e/0x150 [mlx=
5_core]
[=C2=A0 248.062267]=C2=A0 mlx5_disable_lag+0x149/0x160 [mlx5_core]
[=C2=A0 248.062318]=C2=A0 mlx5_lag_disable_change+0x60/0xa0 [mlx5_core]
[=C2=A0 248.062369]=C2=A0 mlx5_devlink_eswitch_mode_set+0x4b/0x1a0 [mlx5_co=
re]
[=C2=A0 248.062436]=C2=A0 devlink_nl_cmd_eswitch_set_doit+0xc1/0x150
[=C2=A0 248.062440]=C2=A0 genl_family_rcv_msg_doit+0xe7/0x150
[=C2=A0 248.062445]=C2=A0 genl_rcv_msg+0xdc/0x1e0
[=C2=A0 248.062448]=C2=A0 ? __devlink_port_phys_port_name_get+0x1e0/0x1e0
[=C2=A0 248.062451]=C2=A0 ? genl_get_cmd+0xd0/0xd0
[=C2=A0 248.062454]=C2=A0 netlink_rcv_skb+0x4e/0xf0
[=C2=A0 248.062457]=C2=A0 genl_rcv+0x24/0x40
[=C2=A0 248.062460]=C2=A0 netlink_unicast+0x1fe/0x2d0
[=C2=A0 248.062463]=C2=A0 netlink_sendmsg+0x24f/0x4b0
[=C2=A0 248.062466]=C2=A0 sock_sendmsg+0x5b/0x60
[=C2=A0 248.062469]=C2=A0 __sys_sendto+0xf0/0x160
[=C2=A0 248.062473]=C2=A0 ? handle_mm_fault+0xbf/0x280
[=C2=A0 248.062478]=C2=A0 ? do_user_addr_fault+0x1d0/0x670
[=C2=A0 248.062482]=C2=A0 __x64_sys_sendto+0x20/0x30
[=C2=A0 248.062484]=C2=A0 do_syscall_64+0x38/0x90
[=C2=A0 248.062487]=C2=A0 entry_SYSCALL_64_after_hwframe+0x44/0xae
[=C2=A0 248.062492] RIP: 0033:0x7ff8cc469c3a
[=C2=A0 248.062494] RSP: 002b:00007ffe06025e08 EFLAGS: 00000246 ORIG_RAX: 0=
00000000000002c
[=C2=A0 248.062497] RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00007f=
f8cc469c3a
[=C2=A0 248.062499] RDX: 0000000000000038 RSI: 000055c261bf7440 RDI: 000000=
0000000003
[=C2=A0 248.062501] RBP: 0000000000000000 R08: 00007ff8cc52d200 R09: 000000=
000000000c
[=C2=A0 248.062502] R10: 0000000000000000 R11: 0000000000000246 R12: 000000=
0000000000
[=C2=A0 248.062503] R13: 000055c261bf72a0 R14: 000055c260a01d5c R15: 000055=
c261bf7440
[=C2=A0 248.062505]=C2=A0 </TASK>


the patch details:=C2=A0

diff --git a/linux/net/core/net_namespace.c b/linux/net/core/net_namespace.c
index 202fa5eac..5c872db1f 100644
--- a/linux/net/core/net_namespace.c
+++ b/linux/net/core/net_namespace.c
@@ -576,6 +576,7 @@ static void cleanup_net(struct work_struct *work)
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 list_add_tail(&net-=
>exit_list, &net_exit_list);
=C2=A0 =C2=A0 =C2=A0 =C2=A0 }

+=C2=A0 =C2=A0 =C2=A0 =C2=A0up_read(&pernet_ops_rwsem);
=C2=A0 =C2=A0 =C2=A0 =C2=A0 /* Run all of the network namespace pre_exit me=
thods */
=C2=A0 =C2=A0 =C2=A0 =C2=A0 list_for_each_entry_reverse(ops, &pernet_list, =
list)
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 ops_pre_exit_list(o=
ps, &net_exit_list);
@@ -596,7 +597,6 @@ static void cleanup_net(struct work_struct *work)
=C2=A0 =C2=A0 =C2=A0 =C2=A0 list_for_each_entry_reverse(ops, &pernet_list, =
list)
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 ops_free_list(ops, =
&net_exit_list);

-=C2=A0 =C2=A0 =C2=A0 =C2=A0up_read(&pernet_ops_rwsem);

=C2=A0 =C2=A0 =C2=A0 =C2=A0 /* Ensure there are no outstanding rcu callback=
s using this
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0* network namespace.
=C2=A0