bus: Fix timeout restarts

The code counting pending fds relied on restart of timeouts when they are
enabled. This patch adds function that ensures that such enabled timeouts
have their timekeeping data reset (and not only when timeout is
registered into event loop processing).

When timeouts weren't reset, they'd fire at rather random and mainly
incorrect moments leading to interruption of connections of dbus-daemon.

Every time we reset the interval, we also need to re-enable the timeout
and mark its end time to be recalculated by the event loop, so combine
the old set_enabled(TRUE) with set_interval() as a new restart() method.
This leaves all the set_enabled() calls having a FALSE parameter, so
remove the parameter and rename the method to disable().

[smcv: fix minor coding style issues]
[smcv: replace set_reenabled()/set_interval() pair with restart()]
[smcv: replace set_enabled(FALSE) with disable()]
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=95619
Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>

bus/connection.c

@@ -477,7 +477,7 @@ bus_connections_new (BusContext *context)
   if (connections->expire_timeout == NULL)
     goto failed_3;
 
-  _dbus_timeout_set_enabled (connections->expire_timeout, FALSE);
+  _dbus_timeout_disable (connections->expire_timeout);
 
   connections->pending_replies = bus_expire_list_new (bus_context_get_loop (context),
                                                       bus_context_get_reply_timeout (context),
@@ -683,14 +683,13 @@ check_pending_fds_cb (DBusConnection *connection)
 
   if (n_pending_unix_fds_old == 0 && n_pending_unix_fds_new > 0)
     {
-      _dbus_timeout_set_interval (d->pending_unix_fds_timeout,
+      _dbus_timeout_restart (d->pending_unix_fds_timeout,
               bus_context_get_pending_fd_timeout (d->connections->context));
-      _dbus_timeout_set_enabled (d->pending_unix_fds_timeout, TRUE);
     }
 
   if (n_pending_unix_fds_old > 0 && n_pending_unix_fds_new == 0)
     {
-      _dbus_timeout_set_enabled (d->pending_unix_fds_timeout, FALSE);
+      _dbus_timeout_disable (d->pending_unix_fds_timeout);
     }
 
 
@@ -846,7 +845,7 @@ bus_connections_setup_connection (BusConnections *connections,
   if (d->pending_unix_fds_timeout == NULL)
     goto out;
 
-  _dbus_timeout_set_enabled (d->pending_unix_fds_timeout, FALSE);
+  _dbus_timeout_disable (d->pending_unix_fds_timeout);
   if (!_dbus_loop_add_timeout (bus_context_get_loop (connections->context),
                                d->pending_unix_fds_timeout))
     goto out;

bus/expirelist.c

@@ -63,7 +63,7 @@ bus_expire_list_new (DBusLoop      *loop,
   if (list->timeout == NULL)
     goto failed;
 
-  _dbus_timeout_set_enabled (list->timeout, FALSE);
+  _dbus_timeout_disable (list->timeout);
 
   if (!_dbus_loop_add_timeout (list->loop, list->timeout))
     goto failed;
@@ -97,16 +97,14 @@ bus_expire_timeout_set_interval (DBusTimeout   *timeout,
 {
   if (next_interval >= 0)
     {
-      _dbus_timeout_set_interval (timeout,
-                                  next_interval);
-      _dbus_timeout_set_enabled (timeout, TRUE);
+      _dbus_timeout_restart (timeout, next_interval);
 
       _dbus_verbose ("Enabled an expire timeout with interval %d\n",
                      next_interval);
     }
   else if (dbus_timeout_get_enabled (timeout))
     {
-      _dbus_timeout_set_enabled (timeout, FALSE);
+      _dbus_timeout_disable (timeout);
 
       _dbus_verbose ("Disabled an expire timeout\n");
     }

dbus/dbus-mainloop.c

@@ -30,6 +30,7 @@
 #include <dbus/dbus-hash.h>
 #include <dbus/dbus-list.h>
 #include <dbus/dbus-socket-set.h>
+#include <dbus/dbus-timeout.h>
 #include <dbus/dbus-watch.h>
 
 #define MAINLOOP_SPEW 0
@@ -608,6 +609,13 @@ _dbus_loop_iterate (DBusLoop     *loop,
             {
               int msecs_remaining;
 
+              if (_dbus_timeout_needs_restart (tcb->timeout))
+                {
+                  tcb->last_tv_sec = tv_sec;
+                  tcb->last_tv_usec = tv_usec;
+                  _dbus_timeout_restarted (tcb->timeout);
+                }
+
               check_timeout (tv_sec, tv_usec, tcb, &msecs_remaining);
 
               if (timeout < 0)

dbus/dbus-timeout.c

@@ -49,6 +49,7 @@ struct DBusTimeout
   void *data;		   	               /**< Application data. */
   DBusFreeFunction free_data_function;         /**< Free the application data. */
   unsigned int enabled : 1;                    /**< True if timeout is active. */
+  unsigned int needs_restart : 1;              /**< Flag that timeout should be restarted after re-enabling. */
 };
 
 /**
@@ -79,6 +80,7 @@ _dbus_timeout_new (int                 interval,
   timeout->free_handler_data_function = free_data_function;
 
   timeout->enabled = TRUE;
+  timeout->needs_restart = FALSE;
   
   return timeout;
 }
@@ -122,25 +124,29 @@ _dbus_timeout_unref (DBusTimeout *timeout)
 }
 
 /**
- * Changes the timeout interval. Note that you have to disable and
- * re-enable the timeout using the timeout toggle function
- * (_dbus_connection_toggle_timeout_unlocked() etc.) to notify the
- * application of this change.
+ * Change the timeout interval to be interval milliseconds from now
+ * (forgetting when the timeout was initially started), and enable it.
+ *
+ * This function is only valid when used in conjunction with DBusLoop:
+ * it can be used in the message bus daemon implementation or in unit tests,
+ * but it cannot be used in conjunction with an application main loop.
  *
  * @param timeout the timeout
  * @param interval the new interval
  */
 void
-_dbus_timeout_set_interval (DBusTimeout *timeout,
-                            int          interval)
+_dbus_timeout_restart (DBusTimeout *timeout,
+                       int          interval)
 {
   _dbus_assert (interval >= 0);
   
   timeout->interval = interval;
+  timeout->enabled = TRUE;
+  timeout->needs_restart = TRUE;
 }
 
 /**
- * Changes the timeout's enabled-ness. Note that you should use
+ * Disable the timeout. Note that you should use
  * _dbus_connection_toggle_timeout_unlocked() etc. instead, if
  * the timeout is passed out to an application main loop.
  * i.e. you can't use this function in the D-Bus library, it's
@@ -150,13 +156,11 @@ _dbus_timeout_set_interval (DBusTimeout *timeout,
  * @param enabled #TRUE if timeout should be enabled.
  */
 void
-_dbus_timeout_set_enabled (DBusTimeout  *timeout,
-                           dbus_bool_t   enabled)
+_dbus_timeout_disable (DBusTimeout  *timeout)
 {
-  timeout->enabled = enabled != FALSE;
+  timeout->enabled = FALSE;
 }
 
-
 /**
  * @typedef DBusTimeoutList
  *
@@ -375,6 +379,30 @@ _dbus_timeout_list_toggle_timeout (DBusTimeoutList           *timeout_list,
                                                 timeout_list->timeout_data);
 }
 
+/**
+ * Returns whether a timeout needs restart time counting in the event loop.
+ *
+ * @param timeout the DBusTimeout object
+ * @returns #TRUE if restart is needed
+ */
+dbus_bool_t
+_dbus_timeout_needs_restart (DBusTimeout *timeout)
+{
+  return timeout->needs_restart;
+}
+
+/**
+ * Mark timeout as restarted (setting timestamps is responsibility of the event
+ * loop).
+ *
+ * @param timeout the DBusTimeout object
+ */
+void
+_dbus_timeout_restarted (DBusTimeout *timeout)
+{
+  timeout->needs_restart = FALSE;
+}
+
 /** @} */
 
 /**

dbus/dbus-timeout.h

@@ -49,11 +49,10 @@ DBusTimeout* _dbus_timeout_ref          (DBusTimeout        *timeout);
 DBUS_PRIVATE_EXPORT
 void         _dbus_timeout_unref        (DBusTimeout        *timeout);
 DBUS_PRIVATE_EXPORT
-void         _dbus_timeout_set_interval (DBusTimeout        *timeout,
+void         _dbus_timeout_restart      (DBusTimeout        *timeout,
                                          int                 interval);
 DBUS_PRIVATE_EXPORT
-void         _dbus_timeout_set_enabled  (DBusTimeout        *timeout,
-                                         dbus_bool_t         enabled);
+void         _dbus_timeout_disable      (DBusTimeout        *timeout);
 
 DBusTimeoutList *_dbus_timeout_list_new            (void);
 void             _dbus_timeout_list_free           (DBusTimeoutList           *timeout_list);
@@ -71,6 +70,10 @@ void             _dbus_timeout_list_toggle_timeout (DBusTimeoutList           *t
                                                     DBusTimeout               *timeout,
                                                     dbus_bool_t                enabled);
 
+DBUS_PRIVATE_EXPORT
+dbus_bool_t _dbus_timeout_needs_restart (DBusTimeout *timeout);
+DBUS_PRIVATE_EXPORT
+void        _dbus_timeout_restarted     (DBusTimeout *timeout);
 
 /** @} */