[gimp] Bug 790631 - C plug-ins instability when processing gegl graphs ...

[N/A <ell src gnome org>]

commit b6cb1d167c8f52b550df624de7fd6265e6240be2
Author: Ell <ell_se yahoo com>
Date:   Wed Nov 22 04:23:05 2017 -0500

    Bug 790631 - C plug-ins instability when processing gegl graphs ...
    
    ... with several threads
    
    Commit d8ae5817034582c5d41d4d0812c60dfd713d3840 didn't go far
    enough in protecting GimpTileBackendPlugin against race conditions.
    The underlying GimpTile cache is shared across all drawables, so we
    must use a common lock for all instances of GimpTileBackendPlugin,
    instead of one per instance.
    
    Do just that -- replace the per-instance mutex of
    GimpTileBackendPlugin with a global one.  This makes
    GimpTileBackendPlugin instances thread-safe w.r.t. themselves, and
    w.r.t other GimpTileBackendPlugin instances.  However, we don't aim
    to make GimpTileBackendPlugin thread-safe w.r.t. other libgimp
    functions at this point, since the original API has never been
    thread-safe.

 libgimp/gimptilebackendplugin.c |   20 +++++++++-----------
 1 files changed, 9 insertions(+), 11 deletions(-)
---
diff --git a/libgimp/gimptilebackendplugin.c b/libgimp/gimptilebackendplugin.c
index 9791c72..233fffc 100644
--- a/libgimp/gimptilebackendplugin.c
+++ b/libgimp/gimptilebackendplugin.c
@@ -34,7 +34,6 @@
 
 struct _GimpTileBackendPluginPrivate
 {
-  GMutex        mutex;
   GimpDrawable *drawable;
   gboolean      shadow;
   gint          mul;
@@ -85,6 +84,9 @@ G_DEFINE_TYPE (GimpTileBackendPlugin, _gimp_tile_backend_plugin,
 #define parent_class _gimp_tile_backend_plugin_parent_class
 
 
+static GMutex backend_plugin_mutex;
+
+
 static void
 _gimp_tile_backend_plugin_class_init (GimpTileBackendPluginClass *klass)
 {
@@ -107,8 +109,6 @@ _gimp_tile_backend_plugin_init (GimpTileBackendPlugin *backend)
                                                GimpTileBackendPluginPrivate);
 
   source->command = gimp_tile_backend_plugin_command;
-
-  g_mutex_init (&backend->priv->mutex);
 }
 
 static void
@@ -119,8 +119,6 @@ gimp_tile_backend_plugin_finalize (GObject *object)
   if (backend->priv->drawable) /* This also causes a flush */
     gimp_drawable_detach (backend->priv->drawable);
 
-  g_mutex_clear (&backend->priv->mutex);
-
   G_OBJECT_CLASS (parent_class)->finalize (object);
 }
 
@@ -138,28 +136,28 @@ gimp_tile_backend_plugin_command (GeglTileSource  *tile_store,
   switch (command)
     {
     case GEGL_TILE_GET:
-      g_mutex_lock (&backend_plugin->priv->mutex);
+      g_mutex_lock (&backend_plugin_mutex);
 
       result = gimp_tile_read_mul (backend_plugin, x, y);
 
-      g_mutex_unlock (&backend_plugin->priv->mutex);
+      g_mutex_unlock (&backend_plugin_mutex);
       break;
 
     case GEGL_TILE_SET:
-      g_mutex_lock (&backend_plugin->priv->mutex);
+      g_mutex_lock (&backend_plugin_mutex);
 
       gimp_tile_write_mul (backend_plugin, x, y, gegl_tile_get_data (data));
       gegl_tile_mark_as_stored (data);
 
-      g_mutex_unlock (&backend_plugin->priv->mutex);
+      g_mutex_unlock (&backend_plugin_mutex);
       break;
 
     case GEGL_TILE_FLUSH:
-      g_mutex_lock (&backend_plugin->priv->mutex);
+      g_mutex_lock (&backend_plugin_mutex);
 
       gimp_drawable_flush (backend_plugin->priv->drawable);
 
-      g_mutex_unlock (&backend_plugin->priv->mutex);
+      g_mutex_unlock (&backend_plugin_mutex);
       break;
 
     default: