[gimp] libgimp: make GimpTileBackendPlugin thread safe

[N/A <ell src gnome org>]

commit d8ae5817034582c5d41d4d0812c60dfd713d3840
Author: Ell <ell_se yahoo com>
Date:   Mon Nov 20 09:09:59 2017 -0500

    libgimp: make GimpTileBackendPlugin thread safe
    
    The entire libgimp tile code is not thread safe.  For now, do the
    easy thing, and protect GimpTileBackendPlugin with a mutex.

 libgimp/gimptilebackendplugin.c |   23 +++++++++++++++++++++--
 1 files changed, 21 insertions(+), 2 deletions(-)
---
diff --git a/libgimp/gimptilebackendplugin.c b/libgimp/gimptilebackendplugin.c
index e021e32..9791c72 100644
--- a/libgimp/gimptilebackendplugin.c
+++ b/libgimp/gimptilebackendplugin.c
@@ -34,6 +34,7 @@
 
 struct _GimpTileBackendPluginPrivate
 {
+  GMutex        mutex;
   GimpDrawable *drawable;
   gboolean      shadow;
   gint          mul;
@@ -106,6 +107,8 @@ _gimp_tile_backend_plugin_init (GimpTileBackendPlugin *backend)
                                                GimpTileBackendPluginPrivate);
 
   source->command = gimp_tile_backend_plugin_command;
+
+  g_mutex_init (&backend->priv->mutex);
 }
 
 static void
@@ -116,6 +119,8 @@ 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);
 }
 
@@ -128,26 +133,40 @@ gimp_tile_backend_plugin_command (GeglTileSource  *tile_store,
                                   gpointer         data)
 {
   GimpTileBackendPlugin *backend_plugin = GIMP_TILE_BACKEND_PLUGIN (tile_store);
+  gpointer               result         = NULL;
 
   switch (command)
     {
     case GEGL_TILE_GET:
-      return gimp_tile_read_mul (backend_plugin, x, y);
+      g_mutex_lock (&backend_plugin->priv->mutex);
+
+      result = gimp_tile_read_mul (backend_plugin, x, y);
+
+      g_mutex_unlock (&backend_plugin->priv->mutex);
+      break;
 
     case GEGL_TILE_SET:
+      g_mutex_lock (&backend_plugin->priv->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);
       break;
 
     case GEGL_TILE_FLUSH:
+      g_mutex_lock (&backend_plugin->priv->mutex);
+
       gimp_drawable_flush (backend_plugin->priv->drawable);
+
+      g_mutex_unlock (&backend_plugin->priv->mutex);
       break;
 
     default:
       g_assert (command < GEGL_TILE_LAST_COMMAND && command >= 0);
     }
 
-  return NULL;
+  return result;
 }
 
 static GeglTile *