Description of problem:

In the deployment with json log format and debug enabled, when a user executes concurrent volume creation/attachment operations cinder-volume got deadlock.

The process keeps running but and subsequent volume operation gets stuck in *ing status like creating, attaching and so on.
Later the service status in "openstack volume service list" becomes down.

Version-Release number of selected component (if applicable):

How reproducible:
The issue was reproduce several times

Steps to Reproduce:
1. Deploy overcoud with json log format and debug enabled
2. Execute multiple volume creations and attachments

Actual results:
some of volume operations get stuck and status of the cinder-volume service becomes down

Expected results:
volume operations complete and cinder-volume service keeps its up status

Additional info: