Comment 7 for bug 1155748

Reviewed: https://review.openstack.org/25085
Committed: http://github.com/openstack/quantum/commit/4c53186e5a5349caa0fd3c5f21c1dd8c98debec2
Submitter: Jenkins
Branch: milestone-proposed

commit 4c53186e5a5349caa0fd3c5f21c1dd8c98debec2
Author: Aaron Rosen <email address hidden>
Date: Wed Mar 20 18:19:04 2013 -0700

    Fix race condition in dhcp agent

    This patch fixes a race condition that can happen in the dhcp agent when
    a subnet is created and then a host route is then immediately added to that
    subnet following a subnet.update.end notification. The race condition occurs
    in refresh_dhcp_helper() where self.enable_dhcp_helper() gets called twice
    since the first call had not completed self.cache.put(network). This same race
    condition can also occur in the other events so lockutils.synchronized() is
    added to synchronize those code segments as well.

    Fixes bug 1155748

    Change-Id: I2ff52adc3dfebddd6d9c15d5dc79aa65be107179