Comment 27 for bug 1879878

Reviewed: https://review.opendev.org/751349
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=8ffaac493288c73badfa4f1ec6021ecb4f3137b7
Submitter: Zuul
Branch: stable/ussuri

commit 8ffaac493288c73badfa4f1ec6021ecb4f3137b7
Author: Stephen Finucane <email address hidden>
Date: Wed Aug 5 14:11:59 2020 +0100

    tests: Add reproducer for bug #1879878

    When one resizes a pinned instance, the instance claims host CPUs for
    pinning purposes on the destination. However, the host CPUs on the
    source are not immediately relinquished. Rather, they are held by the
    migration record, to handle the event that the resize is reverted. It is
    only when one confirms this resize that the old cores are finally
    relinquished.

    It appears there is a potential race between the resource tracker's
    periodic task and the freeing of these resources, resulting in attempts
    to unpin host cores that have already been unpinned. This test
    highlights that bug pending a fix.

    Change-Id: Ie092628ac71eb87c9dfa7220255a2953ada9e04d
    Signed-off-by: Stephen Finucane <email address hidden>
    Related-Bug: #1879878
    (cherry picked from commit 10f0a42de162c90c701f70c9c28dc31bfada87db)