src/Pure/System/progress.scala

   private var _seen: Long = 0
 
   def agent_uuid: String = synchronized { _agent_uuid }
 
   private def init(): Unit = synchronized {
-    Progress.Data.transaction_lock(db, create = true) {
+    Progress.Data.transaction_lock(db, create = true, label = "Database_Progress.init") {
       Progress.Data.read_progress_context(db, context_uuid) match {
         case Some(context) =>
           _context = context
           _agent_uuid = UUID.random().toString
         case None =>

     if (context_uuid == _agent_uuid) db.vacuum(Progress.Data.tables)
   }
 
   def exit(close: Boolean = false): Unit = synchronized {
     if (_context > 0) {
-      Progress.Data.transaction_lock(db) {
+      Progress.Data.transaction_lock(db, label = "Database_Progress.exit") {
         Progress.Data.update_agent(db, _agent_uuid, _seen, stop_now = true)
       }
       _context = 0
     }
     if (close) db.close()
   }
 
   private def sync_database[A](body: => A): A = synchronized {
     require(_context > 0)
-    Progress.Data.transaction_lock(db) {
+    Progress.Data.transaction_lock(db, label = "Database_Progress.sync") {
       val stopped_db = Progress.Data.read_progress_stopped(db, _context)
       val stopped = base_progress.stopped
 
       if (stopped_db && !stopped) base_progress.stop()
       if (stopped && !stopped_db) Progress.Data.write_progress_stopped(db, _context, true)