diff --git a/src/app/main/subsysmgr.c b/src/app/main/subsysmgr.c
index 5807cbbaa4..4913949e2c 100644
--- a/src/app/main/subsysmgr.c
+++ b/src/app/main/subsysmgr.c
@@ -293,6 +293,19 @@ subsystems_thread_cleanup(void)
   }
 }
 
+/**
+ * Dump a human- and machine-readable list of all the subsystems to stdout,
+ * in their initialization order, prefixed with their level.
+ **/
+void
+subsystems_dump_list(void)
+{
+  for (unsigned i = 0; i < n_tor_subsystems - 1; ++i) {
+    const subsys_fns_t *sys = tor_subsystems[i];
+    printf("% 4d\t%s\n", sys->level, sys->name);
+  }
+}
+
 /**
  * Register all subsystem-declared options formats in <b>mgr</b>.
  *
diff --git a/src/app/main/subsysmgr.h b/src/app/main/subsysmgr.h
index 35635a756e..ae0b3df469 100644
--- a/src/app/main/subsysmgr.h
+++ b/src/app/main/subsysmgr.h
@@ -31,6 +31,8 @@ void subsystems_prefork(void);
 void subsystems_postfork(void);
 void subsystems_thread_cleanup(void);
 
+void subsystems_dump_list(void);
+
 struct config_mgr_t;
 int subsystems_register_options_formats(struct config_mgr_t *mgr);
 int subsystems_register_state_formats(struct config_mgr_t *mgr);