Merge branch 'postloop_callbacks_2'

3 files changed, 51 insertions, 48 deletions

diff --git a/src/or/connection_edge.c b/src/or/connection_edge.c
index 948c8722bf..955f942c50 100644
--- a/src/or/connection_edge.c
+++ b/src/or/connection_edge.c
@@ -611,6 +611,12 @@ static smartlist_t *pending_entry_connections = NULL;
 
 static int untried_pending_connections = 0;
 
+/**
+ * Mainloop event to tell us to scan for pending connections that can
+ * be attached.
+ */
+static mainloop_event_t *attach_pending_entry_connections_ev = NULL;
+
 /** Common code to connection_(ap|exit)_about_to_close. */
 static void
 connection_edge_about_to_close(edge_connection_t *edge_conn)
@@ -956,6 +962,14 @@ connection_ap_attach_pending(int retry)
   untried_pending_connections = 0;
 }
 
+static void
+attach_pending_entry_connections_cb(mainloop_event_t *ev, void *arg)
+{
+  (void)ev;
+  (void)arg;
+  connection_ap_attach_pending(0);
+}
+
 /** Mark <b>entry_conn</b> as needing to get attached to a circuit.
  *
  * And <b>entry_conn</b> must be in AP_CONN_STATE_CIRCUIT_WAIT,
@@ -973,9 +987,13 @@ connection_ap_mark_as_pending_circuit_(entry_connection_t *entry_conn,
   if (conn->marked_for_close)
     return;
 
-  if (PREDICT_UNLIKELY(NULL == pending_entry_connections))
+  if (PREDICT_UNLIKELY(NULL == pending_entry_connections)) {
     pending_entry_connections = smartlist_new();
-
+  }
+  if (PREDICT_UNLIKELY(NULL == attach_pending_entry_connections_ev)) {
+    attach_pending_entry_connections_ev = mainloop_event_postloop_new(
+                                  attach_pending_entry_connections_cb, NULL);
+  }
   if (PREDICT_UNLIKELY(smartlist_contains(pending_entry_connections,
                                           entry_conn))) {
     log_warn(LD_BUG, "What?? pending_entry_connections already contains %p! "
@@ -999,14 +1017,7 @@ connection_ap_mark_as_pending_circuit_(entry_connection_t *entry_conn,
   untried_pending_connections = 1;
   smartlist_add(pending_entry_connections, entry_conn);
 
-  /* Work-around for bug 19969: we handle pending_entry_connections at
-   * the end of run_main_loop_once(), but in many cases that function will
-   * take a very long time, if ever, to finish its call to event_base_loop().
-   *
-   * So the fix is to tell it right now that it ought to finish its loop at
-   * its next available opportunity.
-   */
-  tell_event_loop_to_run_external_code();
+  mainloop_event_activate(attach_pending_entry_connections_ev);
 }
 
 /** Mark <b>entry_conn</b> as no longer waiting for a circuit. */
@@ -4165,5 +4176,6 @@ connection_edge_free_all(void)
   untried_pending_connections = 0;
   smartlist_free(pending_entry_connections);
   pending_entry_connections = NULL;
+  mainloop_event_free(attach_pending_entry_connections_ev);
 }
 
diff --git a/src/or/main.c b/src/or/main.c
index 0e67ea6f68..30f00ae342 100644
--- a/src/or/main.c
+++ b/src/or/main.c
@@ -410,6 +410,27 @@ connection_unlink(connection_t *conn)
   connection_free(conn);
 }
 
+/**
+ * Callback: used to activate read events for all linked connections, so
+ * libevent knows to call their read callbacks.  This callback run as a
+ * postloop event, so that the events _it_ activates don't happen until
+ * Libevent has a chance to check for other events.
+ */
+static void
+schedule_active_linked_connections_cb(mainloop_event_t *event, void *arg)
+{
+  (void)event;
+  (void)arg;
+
+  /* All active linked conns should get their read events activated,
+   * so that libevent knows to run their callbacks. */
+  SMARTLIST_FOREACH(active_linked_connection_lst, connection_t *, conn,
+                    event_active(conn->read_event, EV_READ, 1));
+}
+
+/** Event that invokes schedule_active_linked_connections_cb. */
+static mainloop_event_t *schedule_active_linked_connections_event = NULL;
+
 /** Initialize the global connection list, closeable connection list,
  * and active connection list. */
 STATIC void
@@ -710,20 +731,6 @@ connection_should_read_from_linked_conn(connection_t *conn)
   return 0;
 }
 
-/** If we called event_base_loop() and told it to never stop until it
- * runs out of events, now we've changed our mind: tell it we want it to
- * exit once the current round of callbacks is done, so that we can
- * run external code, and then return to the main loop. */
-void
-tell_event_loop_to_run_external_code(void)
-{
-  if (!called_loop_once) {
-    struct timeval tv = { 0, 0 };
-    tor_libevent_exit_loop_after_delay(tor_libevent_get_base(), &tv);
-    called_loop_once = 1; /* hack to avoid adding more exit events */
-  }
-}
-
 /** Event to run 'shutdown did not work callback'. */
 static struct event *shutdown_did_not_work_event = NULL;
 
@@ -803,10 +810,7 @@ connection_start_reading_from_linked_conn(connection_t *conn)
   if (!conn->active_on_link) {
     conn->active_on_link = 1;
     smartlist_add(active_linked_connection_lst, conn);
-    /* make sure that the event_base_loop() function exits at
-     * the end of its run through the current connections, so we can
-     * activate read events for linked connections. */
-    tell_event_loop_to_run_external_code();
+    mainloop_event_activate(schedule_active_linked_connections_event);
   } else {
     tor_assert(smartlist_contains(active_linked_connection_lst, conn));
   }
@@ -2583,6 +2587,11 @@ do_main_loop(void)
     initialize_periodic_events();
   }
 
+  if (!schedule_active_linked_connections_event) {
+    schedule_active_linked_connections_event =
+      mainloop_event_postloop_new(schedule_active_linked_connections_cb, NULL);
+  }
+
   /* initialize dns resolve map, spawn workers if needed */
   if (dns_init() < 0) {
     if (get_options()->ServerDNSAllowBrokenConfig)
@@ -2787,17 +2796,12 @@ run_main_loop_once(void)
   errno = 0;
 #endif
 
-  /* All active linked conns should get their read events activated,
-   * so that libevent knows to run their callbacks. */
-  SMARTLIST_FOREACH(active_linked_connection_lst, connection_t *, conn,
-                    event_active(conn->read_event, EV_READ, 1));
-
   if (get_options()->MainloopStats) {
     /* We always enforce that EVLOOP_ONCE is passed to event_base_loop() if we
      * are collecting main loop statistics. */
     called_loop_once = 1;
   } else {
-    called_loop_once = smartlist_len(active_linked_connection_lst) ? 1 : 0;
+    called_loop_once = 0;
   }
 
   /* Make sure we know (about) what time it is. */
@@ -2853,19 +2857,6 @@ run_main_loop_once(void)
   if (main_loop_should_exit)
     return 0;
 
-  /* And here is where we put callbacks that happen "every time the event loop
-   * runs."  They must be very fast, or else the whole Tor process will get
-   * slowed down.
-   *
-   * Note that this gets called once per libevent loop, which will make it
-   * happen once per group of events that fire, or once per second. */
-
-  /* If there are any pending client connections, try attaching them to
-   * circuits (if we can.)  This will be pretty fast if nothing new is
-   * pending.
-   */
-  connection_ap_attach_pending(0);
-
   return 1;
 }
 
@@ -3500,6 +3491,7 @@ tor_free_all(int postfork)
   tor_event_free(shutdown_did_not_work_event);
   tor_event_free(initialize_periodic_events_event);
   mainloop_event_free(directory_all_unreachable_cb_event);
+  mainloop_event_free(schedule_active_linked_connections_event);
 
 #ifdef HAVE_SYSTEMD_209
   periodic_timer_free(systemd_watchdog_timer);
diff --git a/src/or/main.h b/src/or/main.h
index 9ef5b9472f..0143973b26 100644
--- a/src/or/main.h
+++ b/src/or/main.h
@@ -45,7 +45,6 @@ int connection_is_writing(connection_t *conn);
 MOCK_DECL(void,connection_stop_writing,(connection_t *conn));
 MOCK_DECL(void,connection_start_writing,(connection_t *conn));
 
-void tell_event_loop_to_run_external_code(void);
 void tor_shutdown_event_loop_and_exit(int exitcode);
 int tor_event_loop_shutdown_is_pending(void);