avoid quadratic behavior of GMainLoop when all fd's have the same priority

https://bugzilla.gnome.org/show_bug.cgi?id=640518

diff --git a/glib/gmain.c b/glib/gmain.c
index edc5677..e5c8ca3 100644 (file)
--- a/glib/gmain.c
+++ b/glib/gmain.c
@@ -227,7 +227,7 @@ struct _GMainContext
   GSource *source_list;
   gint in_check_or_prepare;
 
-  GPollRec *poll_records;
+  GPollRec *poll_records, *poll_records_tail;
   guint n_poll_records;
   GPollFD *cached_poll_array;
   guint cached_poll_array_size;
@@ -302,6 +302,7 @@ struct _GUnixSignalWatchSource
 struct _GPollRec
 {
   GPollFD *fd;
+  GPollRec *prev;
   GPollRec *next;
   gint priority;
 };
@@ -3530,7 +3531,7 @@ g_main_context_add_poll_unlocked (GMainContext *context,
                                  gint          priority,
                                  GPollFD      *fd)
 {
-  GPollRec *lastrec, *pollrec;
+  GPollRec *prevrec, *nextrec;
   GPollRec *newrec = g_slice_new (GPollRec);
 
   /* This file descriptor may be checked before we ever poll */
@@ -3538,20 +3539,26 @@ g_main_context_add_poll_unlocked (GMainContext *context,
   newrec->fd = fd;
   newrec->priority = priority;
 
-  lastrec = NULL;
-  pollrec = context->poll_records;
-  while (pollrec && priority >= pollrec->priority)
+  prevrec = context->poll_records_tail;
+  nextrec = NULL;
+  while (prevrec && priority < prevrec->priority)
     {
-      lastrec = pollrec;
-      pollrec = pollrec->next;
+      nextrec = prevrec;
+      prevrec = prevrec->prev;
     }
-  
-  if (lastrec)
-    lastrec->next = newrec;
+
+  if (prevrec)
+    prevrec->next = newrec;
   else
     context->poll_records = newrec;
 
-  newrec->next = pollrec;
+  newrec->prev = prevrec;
+  newrec->next = nextrec;
+
+  if (nextrec)
+    nextrec->prev = newrec;
+  else 
+    context->poll_records_tail = newrec;
 
   context->n_poll_records++;
 
@@ -3590,27 +3597,33 @@ static void
 g_main_context_remove_poll_unlocked (GMainContext *context,
                                     GPollFD      *fd)
 {
-  GPollRec *pollrec, *lastrec;
+  GPollRec *pollrec, *prevrec, *nextrec;
 
-  lastrec = NULL;
+  prevrec = NULL;
   pollrec = context->poll_records;
 
   while (pollrec)
     {
+      nextrec = pollrec->next;
       if (pollrec->fd == fd)
        {
-         if (lastrec != NULL)
-           lastrec->next = pollrec->next;
+         if (prevrec != NULL)
+           prevrec->next = nextrec;
+         else
+           context->poll_records = nextrec;
+
+         if (nextrec != NULL)
+           nextrec->prev = prevrec;
          else
-           context->poll_records = pollrec->next;
+           context->poll_records_tail = prevrec;
 
          g_slice_free (GPollRec, pollrec);
 
          context->n_poll_records--;
          break;
        }
-      lastrec = pollrec;
-      pollrec = pollrec->next;
+      prevrec = pollrec;
+      pollrec = nextrec;
     }
 
 #ifdef G_THREADS_ENABLED