Fix T85287: Cycles deadlock loading Blender images in some cases

intern/cycles/blender/blender_python.cpp

@@ -35,6 +35,7 @@
 #include "util/util_path.h"
 #include "util/util_string.h"
 #include "util/util_task.h"
+#include "util/util_tbb.h"
 #include "util/util_types.h"
 
 #ifdef WITH_OSL
@@ -288,9 +289,11 @@ static PyObject *render_func(PyObject * /*self*/, PyObject *args)
   RNA_pointer_create(NULL, &RNA_Depsgraph, (ID *)PyLong_AsVoidPtr(pydepsgraph), &depsgraphptr);
   BL::Depsgraph b_depsgraph(depsgraphptr);
 
+  /* Allow Blender to execute other Python scripts, and isolate TBB tasks so we
+   * don't get deadlocks with Blender threads accessing shared data like images. */
   python_thread_state_save(&session->python_thread_state);
 
-  session->render(b_depsgraph);
+  tbb::this_task_arena::isolate([&] { session->render(b_depsgraph); });
 
   python_thread_state_restore(&session->python_thread_state);
 
@@ -327,7 +330,8 @@ static PyObject *bake_func(PyObject * /*self*/, PyObject *args)
 
   python_thread_state_save(&session->python_thread_state);
 
-  session->bake(b_depsgraph, b_object, pass_type, pass_filter, width, height);
+  tbb::this_task_arena::isolate(
+      [&] { session->bake(b_depsgraph, b_object, pass_type, pass_filter, width, height); });
 
   python_thread_state_restore(&session->python_thread_state);
 
@@ -373,7 +377,7 @@ static PyObject *reset_func(PyObject * /*self*/, PyObject *args)
 
   python_thread_state_save(&session->python_thread_state);
 
-  session->reset_session(b_data, b_depsgraph);
+  tbb::this_task_arena::isolate([&] { session->reset_session(b_data, b_depsgraph); });
 
   python_thread_state_restore(&session->python_thread_state);
 
@@ -395,7 +399,7 @@ static PyObject *sync_func(PyObject * /*self*/, PyObject *args)
 
   python_thread_state_save(&session->python_thread_state);
 
-  session->synchronize(b_depsgraph);
+  tbb::this_task_arena::isolate([&] { session->synchronize(b_depsgraph); });
 
   python_thread_state_restore(&session->python_thread_state);