[event-loop] Add reference count to event sources

This prevents the event loop from freeing sources
early in an iteration of the loop, and then dispatching
handlers for the source later in that same iteration.

1 files changed, 57 insertions, 5 deletions

diff --git a/src/libply/ply-event-loop.c b/src/libply/ply-event-loop.c
index dacf1007..09a04924 100644
--- a/src/libply/ply-event-loop.c
+++ b/src/libply/ply-event-loop.c
@@ -56,6 +56,7 @@ typedef struct
   ply_list_t *fd_watches;
   uint32_t is_getting_polled : 1;
   uint32_t is_disconnected : 1;
+  int reference_count;
 } ply_event_source_t;
 
 typedef struct
@@ -319,6 +320,12 @@ ply_fd_watch_free (ply_fd_watch_t *watch)
   free (watch);
 }
 
+static void
+ply_event_source_take_reference (ply_event_source_t *source)
+{
+  source->reference_count++;
+}
+
 static ply_event_source_t *
 ply_event_source_new (int fd)
 {
@@ -331,6 +338,7 @@ ply_event_source_new (int fd)
   source->fd_watches = ply_list_new ();
   source->is_getting_polled = false;
   source->is_disconnected = false;
+  source->reference_count = 0;
 
   return source;
 }
@@ -349,6 +357,22 @@ ply_event_source_free (ply_event_source_t *source)
 }
 
 static void
+ply_event_source_drop_reference (ply_event_source_t *source)
+{
+  if (source == NULL)
+    return;
+
+  source->reference_count--;
+
+  assert (source->reference_count >= 0);
+
+  if (source->reference_count == 0)
+    {
+      ply_event_source_free (source);
+    }
+}
+
+static void
 ply_event_loop_update_source_event_mask (ply_event_loop_t   *loop,
                                          ply_event_source_t *source)
 {
@@ -404,6 +428,7 @@ ply_event_loop_add_destination_for_source (ply_event_loop_t        *loop,
   assert (source != NULL);
 
   destination->source = source;
+  ply_event_source_take_reference (source);
   destination_node = ply_list_append_data (source->destinations, destination);
   assert (destination_node != NULL);
   assert (destination->source == source);
@@ -412,6 +437,7 @@ ply_event_loop_add_destination_for_source (ply_event_loop_t        *loop,
 
   watch = ply_fd_watch_new (destination);
 
+  ply_event_source_take_reference (source);
   ply_list_append_data (source->fd_watches, watch);
 
   return watch;
@@ -449,6 +475,7 @@ ply_event_loop_remove_destination_by_fd_watch (ply_event_loop_t *loop,
   assert (source != NULL);
 
   ply_list_remove_data (source->destinations, destination);
+  ply_event_source_drop_reference (source);
   assert (ply_list_find_node (source->destinations, destination) == NULL);
   ply_event_loop_update_source_event_mask (loop, source);
 }
@@ -601,6 +628,7 @@ ply_event_loop_add_source (ply_event_loop_t    *loop,
 
   source->is_getting_polled = true;
 
+  ply_event_source_take_reference (source);
   ply_list_append_data (loop->sources, source);
 }
 
@@ -622,6 +650,7 @@ ply_event_loop_remove_source_node (ply_event_loop_t *loop,
     }
 
   ply_list_remove_node (loop->sources, source_node);
+  ply_event_source_drop_reference (source);
 }
 
 static void
@@ -749,6 +778,7 @@ ply_event_loop_stop_watching_fd (ply_event_loop_t *loop,
     {
       ply_trace ("source for fd %d is already disconnected", source->fd);
       ply_list_remove_data (source->fd_watches, watch);
+      ply_event_source_drop_reference (source);
       ply_fd_watch_free (watch);
       return;
     }
@@ -757,6 +787,7 @@ ply_event_loop_stop_watching_fd (ply_event_loop_t *loop,
   ply_event_loop_remove_destination_by_fd_watch (loop, watch);
 
   ply_list_remove_data (source->fd_watches, watch);
+  ply_event_source_drop_reference (source);
   ply_fd_watch_free (watch);
   ply_event_destination_free (destination);
 
@@ -764,8 +795,6 @@ ply_event_loop_stop_watching_fd (ply_event_loop_t *loop,
     {
       ply_trace ("no more destinations remaing for fd %d, removing source", source->fd);
       ply_event_loop_remove_source (loop, source);
-      ply_trace ("freeing source for fd %d", source->fd);
-      ply_event_source_free (source);
     }
 }
 
@@ -1083,6 +1112,7 @@ ply_event_loop_free_watches_for_source (ply_event_loop_t   *loop,
       assert (watch != NULL);
       ply_fd_watch_free (watch);
       ply_list_remove_node (source->fd_watches, node);
+      ply_event_source_drop_reference (source);
       node = next_node;
     }
 }
@@ -1142,6 +1172,7 @@ ply_event_loop_free_destinations_for_source (ply_event_loop_t   *loop,
       ply_event_destination_free (destination);
 
       ply_list_remove_node (source->destinations, node);
+      ply_event_source_drop_reference (source);
       node = next_node;
     }
 }
@@ -1169,9 +1200,6 @@ ply_event_loop_disconnect_source (ply_event_loop_t           *loop,
   ply_trace ("removing source with fd %d from event loop", source->fd);
   ply_event_loop_remove_source (loop, source);
   ply_trace ("done removing source with fd %d from event loop", source->fd);
-
-  ply_trace ("freeing source with fd %d", source->fd);
-  ply_event_source_free (source);
 }
 
 static void
@@ -1261,6 +1289,19 @@ ply_event_loop_process_pending_events (ply_event_loop_t *loop)
     }
   while ((number_of_received_events < 0) && ((errno == EINTR) || (errno == EAGAIN)));
 
+  /* first reference all sources, so they stay alive for the duration of this
+   * iteration of the loop
+   */
+  for (i = 0; i < number_of_received_events; i++)
+    {
+      ply_event_source_t *source;
+      source = (ply_event_source_t *) (events[i].data.ptr);
+
+      ply_event_source_take_reference (source);
+    }
+
+  /* Then process the incoming events
+   */
   for (i = 0; i < number_of_received_events; i++)
     {
       ply_event_source_t *source;
@@ -1293,6 +1334,17 @@ ply_event_loop_process_pending_events (ply_event_loop_t *loop)
       if (loop->should_exit)
         break;
     }
+
+  /* Finally, kill off any unused sources
+   */
+  for (i = 0; i < number_of_received_events; i++)
+    {
+      ply_event_source_t *source;
+
+      source = (ply_event_source_t *) (events[i].data.ptr);
+
+      ply_event_source_drop_reference (source);
+    }
 }
 
 void