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

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Message-ID: <1b07e839-5633-3b1e-1997-b86a891b2962@invisiblethingslab.com>
Date:   Thu, 19 Apr 2018 18:10:00 +0000
From:   Simon Gaiser <simon@...isiblethingslab.com>
To:     netdev@...r.kernel.org
Cc:     Jason Andryuk <jandryuk@...il.com>, 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

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



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