dlm: check if workqueues are NULL before flushing/destroying
[ Upstream commit
b355516f450703c9015316e429b66a93dfff0e6f ]
If the DLM lowcomms stack is shut down before any DLM
traffic can be generated, flush_workqueue() and
destroy_workqueue() can be called on empty send and/or recv
workqueues.
Insert guard conditionals to only call flush_workqueue()
and destroy_workqueue() on workqueues that are not NULL.
Signed-off-by: David Windsor <dwindsor@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>