xen-netfront: Fix hang on device removal
BugLink: http://bugs.launchpad.net/bugs/1768429 commit c2d2e673 upstream. 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: 5b5971df ("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> Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Juerg Haefliger <juergh@canonical.com> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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