[Bf-blender-cvs] [91368f7b7dc] universal-scene-description: USD import: fix crash adding event notifiers.

[Michael Kowalski]

Commit: 91368f7b7dc5ec29a4f28d64ff59faf4ee575d01
Author: Michael Kowalski
Date:   Wed Dec 28 15:53:07 2022 -0500
Branches: universal-scene-description
https://developer.blender.org/rB91368f7b7dc5ec29a4f28d64ff59faf4ee575d01

USD import: fix crash adding event notifiers.

Fixed crash due to race condition adding event notifiers
when converting materials when the importer is invoked
in a background job.  Now acquiring the main thread lock
before reading object data, to avoid possible crashes
when event notifiers are added by timers for progress
updates in the main thread.

===================================================================

M	source/blender/io/usd/intern/usd_capi_import.cc

===================================================================

diff --git a/source/blender/io/usd/intern/usd_capi_import.cc b/source/blender/io/usd/intern/usd_capi_import.cc
index b0913db3d0f..ced906149f0 100644
--- a/source/blender/io/usd/intern/usd_capi_import.cc
+++ b/source/blender/io/usd/intern/usd_capi_import.cc
@@ -284,8 +284,25 @@ struct ImportJobData {
   bool was_canceled;
   bool import_ok;
   timeit::TimePoint start_time;
+
+  wmJob *wm_job;
 };
 
+static void main_thread_lock_acquire(ImportJobData *data)
+{
+  if (data->wm_job) {
+    WM_job_main_thread_lock_acquire(data->wm_job);
+  }
+}
+
+static void main_thread_lock_release(ImportJobData *data)
+{
+  if (data->wm_job) {
+    WM_job_main_thread_lock_release(data->wm_job);
+  }
+}
+
+
 static CacheFile *create_cache_file(const ImportJobData *data)
 {
   if (!data) {
@@ -505,6 +522,17 @@ static void import_startjob(void *customdata, bool *stop, bool *do_update, float
     }
   }
 
+  *data->do_update = true;
+  *data->progress = 0.5f;
+
+  /* Reading materials may trigger adding event notifiers, which
+   * isn't thread safe when the importer is invoked in a background
+   * job.  We therefore acquire the main thread lock before reading
+   * object data, to avoid possible crashes when events are added
+   * in job timers for progress updates in the main thread.
+   * (See wm_jobs_timer()). */
+  main_thread_lock_acquire(data);
+
   /* Setup parenthood and read actual object data. */
   i = 0;
   for (USDPrimReader *reader : archive->readers()) {
@@ -528,15 +556,22 @@ static void import_startjob(void *customdata, bool *stop, bool *do_update, float
       ob->parent = parent->object();
     }
 
-    *data->progress = 0.5f + 0.5f * (++i / size);
-    *data->do_update = true;
+    if ((++i & 255) == 0) {
+      main_thread_lock_release(data);
+      *data->progress = 0.5f + 0.5f * (i / size);
+      *data->do_update = true;
+      main_thread_lock_acquire(data);
+    }
 
     if (G.is_break) {
       data->was_canceled = true;
+      main_thread_lock_release(data);
       return;
     }
   }
 
+  main_thread_lock_release(data);
+
   if (data->params.import_skeletons) {
     archive->process_armature_modifiers();
   }
@@ -708,6 +743,8 @@ bool USD_import(struct bContext *C,
                                 WM_JOB_PROGRESS,
                                 WM_JOB_TYPE_ALEMBIC);
 
+    job->wm_job = wm_job;
+
     /* setup job */
     WM_jobs_customdata_set(wm_job, job, import_freejob);
     WM_jobs_timer(wm_job, 0.1, NC_SCENE, NC_SCENE);