Comment 11 for bug 1494351

Reviewed: https://review.openstack.org/223123
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=d755f7248d324bb4c44b3efc9d200f8eb075066d
Submitter: Jenkins
Branch: master

commit d755f7248d324bb4c44b3efc9d200f8eb075066d
Author: Pavel Bondar <email address hidden>
Date: Tue Oct 20 19:11:30 2015 +0300

    Use compare-and-swap for IpamAvailabilityRange

    Existing locking mechanism 'select for update' causes
    deadlocks with galera multi-writers.
    Replaced locking rows with compare-and-swap approach.

    Compare-and-swap verifies that row is not changed by
    another thread before updating/deleting it.
    Filter-and-update and filter-and-delete are used.
    They return count of affected rows.
    If count of affected row is less than expected,
    then another thread already changed our row
    and RetryRequest is raised.

    Change-Id: I514cae0fa43033433ec2982bcf3726e02e6692bf
    Closes-Bug: #1494351