[SDB] Fix race-to-crash on runtime shutdown.

 * debugger-agent.c: Fix race-to-crash on runtime shutdown.

License: MIT/X11

mono/mini/debugger-agent.c

@@ -6939,16 +6939,18 @@ debugger_thread (void *arg)
 
 	mono_set_is_debugger_attached (FALSE);
 	
-	mono_mutex_lock (&debugger_thread_exited_mutex);
-	debugger_thread_exited = TRUE;
-	mono_cond_signal (&debugger_thread_exited_cond);
-	mono_mutex_unlock (&debugger_thread_exited_mutex);
+	if (! (vm_death_event_sent || mono_runtime_is_shutting_down ())) {
+		mono_mutex_lock (&debugger_thread_exited_mutex);
+		debugger_thread_exited = TRUE;
+		mono_cond_signal (&debugger_thread_exited_cond);
+		mono_mutex_unlock (&debugger_thread_exited_mutex);
 
-	DEBUG (1, printf ("[dbg] Debugger thread exited.\n"));
-	
-	if (command_set == CMD_SET_VM && command == CMD_VM_DISPOSE && !vm_death_event_sent && !mono_runtime_is_shutting_down ()) {
-		DEBUG (2, fprintf (log_file, "[dbg] Detached - restarting clean debugger thread.\n"));
-		start_debugger_thread ();
+		DEBUG (1, printf ("[dbg] Debugger thread exited.\n"));
+		
+		if (command_set == CMD_SET_VM && command == CMD_VM_DISPOSE) {
+			DEBUG (2, fprintf (log_file, "[dbg] Detached - restarting clean debugger thread.\n"));
+			start_debugger_thread ();
+		}
 	}
 	
 	return 0;