dmeventd: Include shutdown threads in responses.

When responding to DM_EVENT_CMD_GET_REGISTERED_DEVICE no longer
ignore threads that have already been unregistered but which
are still present.

This means the caller can unregister a device and poll dmeventd
to ensure the monitoring thread has gone away before removing
the device.  If a device was registered and unregistered in quick
succession and then removed, WAITEVENT could run in parallel with
the REMOVE.

Threads are moved to the _thread_registry_unused list when they
are unregistered.

2 files changed, 13 insertions, 0 deletions

diff --git a/WHATS_NEW b/WHATS_NEW
index 3914392f4..6c76fa97c 100644
--- a/WHATS_NEW
+++ b/WHATS_NEW
@@ -1,5 +1,6 @@
 Version 2.02.112 - 
 =====================================
+  Include threads being shutdown in dmeventd device registration responses.
   Inital support for external users of thin pools based on transaction_id.
   Report some basic percentage info for cache pools.
   Introduce size_mb_arg_with_percent() for advanced size arg reading.
diff --git a/daemons/dmeventd/dmeventd.c b/daemons/dmeventd/dmeventd.c
index faae5ba78..1b950cfe7 100644
--- a/daemons/dmeventd/dmeventd.c
+++ b/daemons/dmeventd/dmeventd.c
@@ -1177,6 +1177,18 @@ static int _get_registered_dev(struct message_data *message_data, int next)
 	if (hit && !next)
 		goto reg;
 
+	/*
+	 * If we didn't get a match, try the threads waiting to be deleted.
+	 * FIXME Do something similar if 'next' is set.
+	 */
+	if (!hit && !next)
+		dm_list_iterate_items(thread, &_thread_registry_unused)
+			if (_want_registered_device(message_data->dso_name,
+						    message_data->device_uuid, thread)) {
+				hit = thread;
+				goto reg;
+			}
+
 	if (!hit)
 		goto out;