status: report number of active worker threads in status output

This is especially useful when dynamic load management allocates more
worker threads than active tasks, so the extra threads are effectively
invisible.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

lib/task.cc

@@ -128,6 +128,7 @@ namespace crucible {
 		static void push_back(shared_ptr<TaskState> task);
 		static void push_front(shared_ptr<TaskState> task);
 		size_t get_queue_count();
+		size_t get_thread_count();
 	};
 
 	class TaskConsumer : public enable_shared_from_this<TaskConsumer> {
@@ -324,6 +325,13 @@ namespace crucible {
 		return s_tms->m_queue.size();
 	}
 
+	size_t
+	TaskMaster::get_thread_count()
+	{
+		unique_lock<mutex> lock(s_tms->m_mutex);
+		return s_tms->m_threads.size();
+	}
+
 	ostream &
 	TaskMaster::print_queue(ostream &os)
 	{