dlm: check if workqueues are NULL before flushing/destroying

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>

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 114ebfe309297396ce3200eac436a4ece8bad47d..3951d39b9b75991d8033404fa4e319da4c080941 100644 (file)
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -1628,8 +1628,10 @@ static void clean_writequeues(void)
 
 static void work_stop(void)
 {
-       destroy_workqueue(recv_workqueue);
-       destroy_workqueue(send_workqueue);
+       if (recv_workqueue)
+               destroy_workqueue(recv_workqueue);
+       if (send_workqueue)
+               destroy_workqueue(send_workqueue);
 }
 
 static int work_start(void)
@@ -1689,13 +1691,17 @@ static void work_flush(void)
        struct hlist_node *n;
        struct connection *con;
 
-       flush_workqueue(recv_workqueue);
-       flush_workqueue(send_workqueue);
+       if (recv_workqueue)
+               flush_workqueue(recv_workqueue);
+       if (send_workqueue)
+               flush_workqueue(send_workqueue);
        do {
                ok = 1;
                foreach_conn(stop_conn);
-               flush_workqueue(recv_workqueue);
-               flush_workqueue(send_workqueue);
+               if (recv_workqueue)
+                       flush_workqueue(recv_workqueue);
+               if (send_workqueue)
+                       flush_workqueue(send_workqueue);
                for (i = 0; i < CONN_HASH_SIZE && ok; i++) {
                        hlist_for_each_entry_safe(con, n,
                                                  &connection_hash[i], list) {