Cleanup: DRW: Make Open subdiv evaluator part of a DRW module

This avoids the global variable access with race condition.
Rel #134690

Pull Request: https://projects.blender.org/blender/blender/pulls/134855

source/blender/draw/DRW_engine.hh

@@ -171,11 +171,9 @@ void DRW_cache_free_old_batches(Main *bmain);
 
 namespace blender::draw {
 
+/* Free garbage collected subdivision data. */
 void DRW_cache_free_old_subdiv();
 
-/* For the OpenGL evaluators and garbage collected subdivision data. */
-void DRW_subdiv_free();
-
 }  // namespace blender::draw
 
 /* Never use this. Only for closing blender. */

source/blender/draw/intern/draw_cache_impl_subdivision.cc

@@ -2,6 +2,7 @@
  *
  * SPDX-License-Identifier: GPL-2.0-or-later */
 
+#include "draw_manager_c.hh"
 #include "draw_subdivision.hh"
 
 #include "DNA_mesh_types.h"
@@ -43,6 +44,7 @@
 #include "draw_cache_extract.hh"
 #include "draw_cache_impl.hh"
 #include "draw_cache_inline.hh"
+#include "draw_common_c.hh"
 #include "draw_shader.hh"
 #include "draw_subdiv_shader_shared.hh"
 #include "mesh_extractors/extract_mesh.hh"
@@ -1926,7 +1928,18 @@ void DRW_subdivide_loose_geom(DRWSubdivCache &subdiv_cache, const MeshBufferCach
   });
 }
 
-static OpenSubdiv_EvaluatorCache *g_evaluator_cache = nullptr;
+/**
+ * OpenSubdiv GPU evaluation module.
+ */
+struct SubdivModule {
+  OpenSubdiv_EvaluatorCache *evaluator_cache = openSubdiv_createEvaluatorCache(
+      OPENSUBDIV_EVALUATOR_GPU);
+
+  ~SubdivModule()
+  {
+    openSubdiv_deleteEvaluatorCache(evaluator_cache);
+  }
+};
 
 void DRW_create_subdivision(Object &ob,
                             Mesh &mesh,
@@ -1941,8 +1954,9 @@ void DRW_create_subdivision(Object &ob,
                             const ToolSettings *ts,
                             const bool use_hide)
 {
-  if (g_evaluator_cache == nullptr) {
-    g_evaluator_cache = openSubdiv_createEvaluatorCache(OPENSUBDIV_EVALUATOR_GPU);
+  DRWData &drw_data = *DST.vmempool;
+  if (drw_data.subdiv_module == nullptr) {
+    drw_data.subdiv_module = MEM_new<SubdivModule>("SubdivModule");
   }
 
 #undef TIME_SUBDIV
@@ -1963,7 +1977,7 @@ void DRW_create_subdivision(Object &ob,
                                             do_cage,
                                             ts,
                                             use_hide,
-                                            g_evaluator_cache))
+                                            drw_data.subdiv_module->evaluator_cache))
   {
     return;
   }
@@ -1975,16 +1989,18 @@ void DRW_create_subdivision(Object &ob,
 #endif
 }
 
-void DRW_subdiv_free()
+void DRW_subdiv_module_free(SubdivModule *subdiv_module)
 {
-  DRW_cache_free_old_subdiv();
-
-  if (g_evaluator_cache) {
-    openSubdiv_deleteEvaluatorCache(g_evaluator_cache);
-    g_evaluator_cache = nullptr;
-  }
+  MEM_delete(subdiv_module);
 }
 
+/**
+ * The `bke::subdiv::Subdiv` data is being owned the modifier.
+ * Since the modifier can be freed from any thread (e.g. from depsgraph multithreaded update)
+ * which may not have a valid GPUContext active, we move the data to discard to this free list
+ * until a codepath with a active GPUContext is hit.
+ * This is kindof garbage collection.
+ */
 static LinkNode *gpu_subdiv_free_queue = nullptr;
 static ThreadMutex gpu_subdiv_queue_mutex = BLI_MUTEX_INITIALIZER;
 

source/blender/draw/intern/draw_common_c.hh

@@ -29,6 +29,7 @@ namespace blender::draw {
 class Manager;
 struct CurvesModule;
 struct PointCloudModule;
+struct SubdivModule;
 struct VolumeModule;
 }  // namespace blender::draw
 
@@ -71,6 +72,10 @@ void DRW_pointcloud_module_free(draw::PointCloudModule *module);
 void DRW_volume_init(DRWData *drw_data = nullptr);
 void DRW_volume_module_free(draw::VolumeModule *module);
 
+/* draw_cache_impl_subdivision.cc */
+
+void DRW_subdiv_module_free(draw::SubdivModule *module);
+
 }  // namespace blender::draw
 
 /* `draw_fluid.cc` */

source/blender/draw/intern/draw_manager_c.cc

@@ -355,6 +355,7 @@ void DRW_viewport_data_free(DRWData *drw_data)
   DRW_volume_module_free(drw_data->volume_module);
   DRW_pointcloud_module_free(drw_data->pointcloud_module);
   DRW_curves_module_free(drw_data->curves_module);
+  DRW_subdiv_module_free(drw_data->subdiv_module);
   delete drw_data->default_view;
   MEM_freeN(drw_data);
 }

source/blender/draw/intern/draw_manager_c.hh

@@ -32,6 +32,7 @@ struct Object;
 struct Mesh;
 namespace blender::draw {
 struct CurvesModule;
+struct SubdivModule;
 struct VolumeModule;
 struct PointCloudModule;
 struct DRW_Attributes;
@@ -72,6 +73,7 @@ struct DRWData {
   DRWViewData *view_data[2];
   /** Module storage. */
   blender::draw::CurvesModule *curves_module;
+  blender::draw::SubdivModule *subdiv_module;
   blender::draw::VolumeModule *volume_module;
   blender::draw::PointCloudModule *pointcloud_module;
   /** Default view that feeds every engine. */

source/blender/windowmanager/intern/wm_init_exit.cc

@@ -596,7 +596,7 @@ void WM_exit_ex(bContext *C, const bool do_python_exit, const bool do_user_exit_
   /* Free the GPU subdivision data after the database to ensure that subdivision structs used by
    * the modifiers were garbage collected. */
   if (gpu_is_init) {
-    blender::draw::DRW_subdiv_free();
+    blender::draw::DRW_cache_free_old_subdiv();
   }
 
   ANIM_fcurves_copybuf_free();