Fix T36474: Blender 2.68a crashes upon rendering

Summary:
Original issue was caused by wring detection of whether
SS modifier is being applied for render/viewport. After
recent dependency graph commit this was no longer an
issue.

But it still might have happen conflict between viewport
draw and scene_update_for_newframe() invoked from render
thread when using external engines like Cycles.

Solved by adding viewport lock while scene is being
updated and objects being exported to the render engine.

Same lock was already used for Blender Internal.

Reviewers: brecht

Reviewed By: brecht

Maniphest Tasks: T36474

Differential Revision: https://developer.blender.org/D138

1 files changed, 17 insertions, 2 deletions

diff --git a/source/blender/render/intern/source/external_engine.c b/source/blender/render/intern/source/external_engine.c
index cccfeed6e47..fa72d5f4057 100644
--- a/source/blender/render/intern/source/external_engine.c
+++ b/source/blender/render/intern/source/external_engine.c
@@ -423,6 +423,11 @@ int RE_engine_render(Render *re, int do_all)
 	if (!do_all && (type->flag & RE_USE_POSTPROCESS))
 		return 0;
 
+	/* Lock drawing in UI during data phase. */
+	if (re->draw_lock) {
+		re->draw_lock(re->dlh, 1);
+	}
+
 	/* update animation here so any render layer animation is applied before
 	 * creating the render result */
 	if ((re->r.scemode & (R_NO_FRAME_UPDATE | R_BUTS_PREVIEW)) == 0) {
@@ -476,8 +481,13 @@ int RE_engine_render(Render *re, int do_all)
 	}
 	BLI_rw_mutex_unlock(&re->resultmutex);
 
-	if (re->result == NULL)
+	if (re->result == NULL) {
+		/* Clear UI drawing locks. */
+		if (re->draw_lock) {
+			re->draw_lock(re->dlh, 0);
+		}
 		return 1;
+	}
 
 	/* set render info */
 	re->i.cfra = re->scene->r.cfra;
@@ -515,7 +525,12 @@ int RE_engine_render(Render *re, int do_all)
 
 	if (type->update)
 		type->update(engine, re->main, re->scene);
-	
+
+	/* Clear UI drawing locks. */
+	if (re->draw_lock) {
+		re->draw_lock(re->dlh, 0);
+	}
+
 	if (type->render)
 		type->render(engine, re->scene);