Comment 12 for bug 1755810

Reviewed: https://review.opendev.org/675878
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=09b7b2e1ea6f40cd9e6104f1c5fbef31fc3e0545
Submitter: Zuul
Branch: stable/rocky

commit 09b7b2e1ea6f40cd9e6104f1c5fbef31fc3e0545
Author: Kailun Qin <email address hidden>
Date: Wed May 1 15:50:48 2019 +0800

    Populate binding levels when concurrent ops fail

    Concurrent calls to _bind_port_if_needed may lead to a missing RPC
    notification which can cause a port stuck in a DOWN state. If the only
    caller that succeeds in the concurrency does not specify that an RPC
    notification is allowed then no RPC would be sent to the agent. The
    other caller which needs to send an RPC notification will fail since the
    resulting PortContext instance will not have any binding levels set.

    The failure has negative effects on consumers of the L2Population
    functionality because the L2Population mechanism driver will not be
    triggered to publish that a port is UP on a given compute node. Manual
    intervention is required in this case.

    This patch proposes to handle this by populating the PortContext with
    the current binding levels so that the caller can continue on and have
    an RPC notification sent out.

    Closes-Bug: #1755810
    Story: 2003922
    Change-Id: Ie2b813b2bdf181fb3c24743dbd13487ace6ee76a
    (cherry picked from commit 0dc730c7c0d3f0a49dee28d0d6e7ff9020d94443)