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Subject: Re: [Xen-devel] [PATCH] xen-netfront: Fix hang on device removal
To:     netdev@vger.kernel.org
Cc:     Jason Andryuk <jandryuk@gmail.com>, xen-devel@lists.xenproject.org,
        Eduardo Otubo <otubo@redhat.com>,
        Juergen Gross <jgross@suse.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        open list <linux-kernel@vger.kernel.org>
References: <20180228122323.3914-1-jandryuk@gmail.com>
From:   Simon Gaiser <simon@invisiblethingslab.com>
Message-ID: <1b07e839-5633-3b1e-1997-b86a891b2962@invisiblethingslab.com>
Date:   Thu, 19 Apr 2018 18:10:00 +0000
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From: Simon Gaiser <simon@invisiblethingslab.com>
To: netdev@vger.kernel.org
Cc: Jason Andryuk <jandryuk@gmail.com>, xen-devel@lists.xenproject.org,
 Eduardo Otubo <otubo@redhat.com>, Juergen Gross <jgross@suse.com>,
 Boris Ostrovsky <boris.ostrovsky@oracle.com>,
 open list <linux-kernel@vger.kernel.org>
Message-ID: <1b07e839-5633-3b1e-1997-b86a891b2962@invisiblethingslab.com>
Subject: Re: [Xen-devel] [PATCH] xen-netfront: Fix hang on device removal
References: <20180228122323.3914-1-jandryuk@gmail.com>
In-Reply-To: <20180228122323.3914-1-jandryuk@gmail.com>

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Jason Andryuk:
> A toolstack may delete the vif frontend and backend xenstore entries
> while xen-netfront is in the removal code path.  In that case, the
> checks for xenbus_read_driver_state would return XenbusStateUnknown, an=
d
> xennet_remove would hang indefinitely.  This hang prevents system
> shutdown.
>=20
> xennet_remove must be able to handle XenbusStateUnknown, and
> netback_changed must also wake up the wake_queue for that state as well=
=2E
>=20
> Fixes: 5b5971df3bc2 ("xen-netfront: remove warning when unloading modul=
e")

I think this should go into stable since AFAIK the hanging network
device can only be fixed by rebooting the guest. AFAICS this affects all
4.* branches since 5b5971df3bc2 got backported to them.

Upstream commit c2d2e6738a209f0f9dffa2dc8e7292fc45360d61.

Simon


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