I've also seen this in n-api logs when attaching a volume:
http://logs.openstack.org/50/435050/1/check/gate-tempest-dsvm-cells-ubuntu-xenial/af9d60d/logs/screen-n-cpu.txt.gz?level=TRACE#_2017-02-17_00_11_17_422
I've also seen this in n-api logs when attaching a volume:
http:// logs.openstack. org/50/ 435050/ 1/check/ gate-tempest- dsvm-cells- ubuntu- xenial/ af9d60d/ logs/screen- n-cpu.txt. gz?level= TRACE#_ 2017-02- 17_00_11_ 17_422