4 files changed, 59 insertions, 5 deletions

diff --git a/source/blender/modifiers/intern/MOD_laplaciandeform.c b/source/blender/modifiers/intern/MOD_laplaciandeform.c
index defd287034e..7b5b73e0f6d 100644
--- a/source/blender/modifiers/intern/MOD_laplaciandeform.c
+++ b/source/blender/modifiers/intern/MOD_laplaciandeform.c
@@ -452,6 +452,10 @@ static void laplacianDeformPreview(LaplacianSystem *sys, float (*vertexCos)[3])
 	n = sys->total_verts;
 	na = sys->total_anchors;
 
+#ifdef OPENNL_THREADING_HACK
+	modifier_opennl_lock();
+#endif
+
 	if (!sys->is_matrix_computed) {
 		nlNewContext();
 		sys->context = nlGetCurrent();
@@ -530,12 +534,9 @@ static void laplacianDeformPreview(LaplacianSystem *sys, float (*vertexCos)[3])
 			sys->has_solution = false;
 		}
 		sys->is_matrix_computed = true;
-	}
-	else {
-		if (!sys->has_solution) {
-			return;
-		}
 
+	}
+	else if (sys->has_solution) {
 		nlBegin(NL_SYSTEM);
 		nlBegin(NL_MATRIX);
 
@@ -589,6 +590,10 @@ static void laplacianDeformPreview(LaplacianSystem *sys, float (*vertexCos)[3])
 			sys->has_solution = false;
 		}
 	}
+
+#ifdef OPENNL_THREADING_HACK
+	modifier_opennl_unlock();
+#endif
 }
 
 static bool isValidVertexGroup(LaplacianDeformModifierData *lmd, Object *ob, DerivedMesh *dm)
diff --git a/source/blender/modifiers/intern/MOD_laplaciansmooth.c b/source/blender/modifiers/intern/MOD_laplaciansmooth.c
index febd81e2f1b..130013af75b 100644
--- a/source/blender/modifiers/intern/MOD_laplaciansmooth.c
+++ b/source/blender/modifiers/intern/MOD_laplaciansmooth.c
@@ -534,6 +534,11 @@ static void laplaciansmoothModifier_do(
 	sys->vert_centroid[1] = 0.0f;
 	sys->vert_centroid[2] = 0.0f;
 	memset_laplacian_system(sys, 0);
+
+#ifdef OPENNL_THREADING_HACK
+	modifier_opennl_lock();
+#endif
+
 	nlNewContext();
 	sys->context = nlGetCurrent();
 	nlSolverParameteri(NL_NB_VARIABLES, numVerts);
@@ -618,6 +623,11 @@ static void laplaciansmoothModifier_do(
 	}
 	nlDeleteContext(sys->context);
 	sys->context = NULL;
+
+#ifdef OPENNL_THREADING_HACK
+	modifier_opennl_unlock();
+#endif
+
 	delete_laplacian_system(sys);
 }
 
diff --git a/source/blender/modifiers/intern/MOD_util.c b/source/blender/modifiers/intern/MOD_util.c
index feae95bf777..0cc9b8bb77b 100644
--- a/source/blender/modifiers/intern/MOD_util.c
+++ b/source/blender/modifiers/intern/MOD_util.c
@@ -61,6 +61,10 @@
 
 #include "RE_shader_ext.h"
 
+#ifdef OPENNL_THREADING_HACK
+#include "BLI_threads.h"
+#endif
+
 void modifier_init_texture(Scene *scene, Tex *tex)
 {
 	if (!tex)
@@ -235,6 +239,24 @@ void modifier_get_vgroup(Object *ob, DerivedMesh *dm, const char *name, MDeformV
 	}
 }
 
+
+#ifdef OPENNL_THREADING_HACK
+
+static ThreadMutex opennl_context_mutex = BLI_MUTEX_INITIALIZER;
+
+void modifier_opennl_lock(void)
+{
+	BLI_mutex_lock(&opennl_context_mutex);
+}
+
+void modifier_opennl_unlock(void)
+{
+	BLI_mutex_unlock(&opennl_context_mutex);
+}
+
+#endif
+
+
 /* only called by BKE_modifier.h/modifier.c */
 void modifier_type_init(ModifierTypeInfo *types[])
 {
diff --git a/source/blender/modifiers/intern/MOD_util.h b/source/blender/modifiers/intern/MOD_util.h
index 72077b5c000..cb851a51c64 100644
--- a/source/blender/modifiers/intern/MOD_util.h
+++ b/source/blender/modifiers/intern/MOD_util.h
@@ -52,4 +52,21 @@ struct DerivedMesh *get_dm_for_modifier(struct Object *ob, ModifierApplyFlag fla
 void modifier_get_vgroup(struct Object *ob, struct DerivedMesh *dm,
                          const char *name, struct MDeformVert **dvert, int *defgrp_index);
 
+/* XXX workaround for non-threadsafe context in OpenNL (T38403)
+ * OpenNL uses global pointer for "current context", which causes
+ * conflict when multiple modifiers get evaluated in threaded depgraph.
+ * This is just a stupid hack to prevent assert failure / crash,
+ * otherwise we'd have to modify OpenNL on a large scale.
+ * OpenNL should be replaced eventually, there are other options (eigen, ceres).
+ * - lukas_t
+ */
+#ifdef WITH_OPENNL
+#define OPENNL_THREADING_HACK
+#endif
+
+#ifdef OPENNL_THREADING_HACK
+void modifier_opennl_lock(void);
+void modifier_opennl_unlock(void);
+#endif
+
 #endif /* __MOD_UTIL_H__ */