[pango] More thread-safety

[Behdad Esfahbod <behdad src gnome org>]

commit f160843b9afab5d8f39654580d7583cf49b0c242
Author: Behdad Esfahbod <behdad behdad org>
Date:   Mon Aug 27 23:31:02 2012 -0400

    More thread-safety

 pango/pango-context.c      |    2 +-
 pango/pango-engine.c       |    2 +-
 pango/pangocairo-fcfont.c  |    2 +-
 pango/pangocairo-fontmap.c |   16 ++++++++++------
 pango/pangofc-fontmap.c    |    6 +++---
 5 files changed, 16 insertions(+), 12 deletions(-)
---
diff --git a/pango/pango-context.c b/pango/pango-context.c
index cdb6a53..97cb278 100644
--- a/pango/pango-context.c
+++ b/pango/pango-context.c
@@ -1366,7 +1366,7 @@ itemize_state_update_for_new_run (ItemizeState *state)
 static const char *
 string_from_script (PangoScript script)
 {
-  static GEnumClass *class = NULL;
+  static GEnumClass *class = NULL; /* MT-safe */
   GEnumValue *value;
   if (g_once_init_enter ((gsize*)&class))
     g_once_init_leave((gsize*)&class, (gsize)g_type_class_ref (PANGO_TYPE_SCRIPT));
diff --git a/pango/pango-engine.c b/pango/pango-engine.c
index eb75dd0..7b2c2fd 100644
--- a/pango/pango-engine.c
+++ b/pango/pango-engine.c
@@ -197,7 +197,7 @@ pango_fallback_engine_class_init (PangoFallbackEngineClass *class)
 PangoEngineShape *
 _pango_get_fallback_shaper (void)
 {
-  static PangoEngineShape *fallback_shaper = NULL;
+  static PangoEngineShape *fallback_shaper = NULL; /* MT-safe */
   if (g_once_init_enter ((gsize*)&fallback_shaper))
     g_once_init_leave((gsize*)&fallback_shaper, (gsize)g_object_new (pango_fallback_engine_get_type (), NULL));
 
diff --git a/pango/pangocairo-fcfont.c b/pango/pangocairo-fcfont.c
index 6e4fcd9..ee82675 100644
--- a/pango/pangocairo-fcfont.c
+++ b/pango/pangocairo-fcfont.c
@@ -185,7 +185,7 @@ get_font_size (const FcPattern *pattern)
 static gpointer
 get_gravity_class (void)
 {
-  static GEnumClass *class = NULL;
+  static GEnumClass *class = NULL; /* MT-safe */
 
   if (g_once_init_enter ((gsize*)&class))
     g_once_init_leave((gsize*)&class, (gsize)g_type_class_ref (PANGO_TYPE_GRAVITY));
diff --git a/pango/pangocairo-fontmap.c b/pango/pangocairo-fontmap.c
index cfc658f..1c235ac 100644
--- a/pango/pangocairo-fontmap.c
+++ b/pango/pangocairo-fontmap.c
@@ -124,7 +124,7 @@ pango_cairo_font_map_new_for_font_type (cairo_font_type_t fonttype)
   }
 }
 
-static PangoFontMap *default_font_map = NULL;
+static PangoFontMap *default_font_map = NULL; /* MT-safe */
 
 /**
  * pango_cairo_font_map_get_default:
@@ -174,17 +174,21 @@ pango_cairo_font_map_get_default (void)
 void
 pango_cairo_font_map_set_default (PangoCairoFontMap *fontmap)
 {
+  PangoCairoFontMap *def;
+
   g_return_if_fail (fontmap == NULL || PANGO_IS_CAIRO_FONT_MAP (fontmap));
 
-  if ((PangoFontMap *) fontmap == default_font_map)
-    return;
+retry:
+  def = g_atomic_pointer_get (&default_font_map);
 
-  if (default_font_map)
-    g_object_unref (default_font_map);
+  if (!g_atomic_pointer_compare_and_exchange (&default_font_map, def, fontmap))
+    goto retry;
 
   if (fontmap)
     g_object_ref (fontmap);
-  default_font_map = (PangoFontMap *) fontmap;
+
+  if (def)
+    g_object_unref (def);
 }
 
 /**
diff --git a/pango/pangofc-fontmap.c b/pango/pangofc-fontmap.c
index 4f053c9..8315b6b 100644
--- a/pango/pangofc-fontmap.c
+++ b/pango/pangofc-fontmap.c
@@ -235,10 +235,10 @@ static FcPattern *uniquify_pattern (PangoFcFontMap *fcfontmap,
 static gpointer
 get_gravity_class (void)
 {
-  static GEnumClass *class = NULL;
+  static GEnumClass *class = NULL; /* MT-safe */
 
-  if (G_UNLIKELY (!class))
-    class = g_type_class_ref (PANGO_TYPE_GRAVITY);
+  if (g_once_init_enter ((gsize*)&class))
+    g_once_init_leave ((gsize*)&class, (gsize)g_type_class_ref (PANGO_TYPE_GRAVITY));
 
   return class;
 }