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Subject: Re: [Xen-devel] [PATCH] xen-netfront: Fix hang on device removal
To:     Jason Andryuk <jandryuk@gmail.com>, xen-devel@lists.xenproject.org,
        netdev@vger.kernel.org
Cc:     Eduardo Otubo <otubo@redhat.com>, Juergen Gross <jgross@suse.com>,
        open list <linux-kernel@vger.kernel.org>
References: <20180228122323.3914-1-jandryuk@gmail.com>
From:   Boris Ostrovsky <boris.ostrovsky@oracle.com>
Message-ID: <79cf073e-6b72-f139-46d3-79322d16209f@oracle.com>
Date:   Wed, 28 Feb 2018 10:21:07 -0500
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On 02/28/2018 07:23 AM, Jason Andryuk wrote:
> 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")
>
> Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
> Cc: Eduardo Otubo <otubo@redhat.com>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>