netdev - Re: [Xen-devel] [PATCH] xen-netfront: Fix hang on device removal

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Date:   Thu, 19 Apr 2018 14:14:43 -0400
From:   Jason Andryuk <jandryuk@...il.com>
To:     Simon Gaiser <simon@...isiblethingslab.com>
Cc:     netdev@...r.kernel.org, xen-devel@...ts.xenproject.org,
        Eduardo Otubo <otubo@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH] xen-netfront: Fix hang on device removal

On Thu, Apr 19, 2018 at 2:10 PM, Simon Gaiser
<simon@...isiblethingslab.com> wrote:
> 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, and
>> xennet_remove would hang indefinitely.  This hang prevents system
>> shutdown.
>>
>> xennet_remove must be able to handle XenbusStateUnknown, and
>> netback_changed must also wake up the wake_queue for that state as well.
>>
>> Fixes: 5b5971df3bc2 ("xen-netfront: remove warning when unloading module")
>
> 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,

Yes, I agree.  I actually submitted the request to stable earlier
today, so hopefully it gets added soon.

Have you experienced this hang?

Regards,
Jason