Fix T39997: Multiple boolean modifiers sharing the same right operand crashes

The issue was caused by the temporary CD layers being allocated for subsurf
meshes, same as we've got back in 881fb43.

In the long run this temporary storage is to be re-considered, but it'll also
imply re-considering of the Derivedmesh interaction as well. For now let's
use a simpler solution which is forbidding modifiers to call getArray for other
objects' derivedMeshes but use an API calls which would allocate local copy of
the data preventing race condition of shared data in DM.

1 files changed, 19 insertions, 5 deletions

diff --git a/source/blender/blenkernel/intern/subsurf_ccg.c b/source/blender/blenkernel/intern/subsurf_ccg.c
index 16d21827f73..a9eba54128a 100644
--- a/source/blender/blenkernel/intern/subsurf_ccg.c
+++ b/source/blender/blenkernel/intern/subsurf_ccg.c
@@ -53,6 +53,7 @@
 #include "BLI_edgehash.h"
 #include "BLI_math.h"
 #include "BLI_memarena.h"
+#include "BLI_threads.h"
 
 #include "BKE_pbvh.h"
 #include "BKE_ccg.h"
@@ -80,6 +81,9 @@
 
 extern GLubyte stipple_quarttone[128]; /* glutil.c, bad level data */
 
+static ThreadRWMutex loops_cache_rwlock = BLI_RWLOCK_INITIALIZER;
+static ThreadRWMutex origindex_cache_rwlock = BLI_RWLOCK_INITIALIZER;
+
 static CCGDerivedMesh *getCCGDerivedMesh(CCGSubSurf *ss,
                                          int drawInteriorEdges,
                                          int useSubsurfUv,
@@ -1326,16 +1330,21 @@ static void ccgDM_copyFinalLoopArray(DerivedMesh *dm, MLoop *mloop)
 	/* DMFlagMat *faceFlags = ccgdm->faceFlags; */ /* UNUSED */
 
 	if (!ccgdm->ehash) {
-		MEdge *medge;
+		BLI_rw_mutex_lock(&loops_cache_rwlock, THREAD_LOCK_WRITE);
+		if (!ccgdm->ehash) {
+			MEdge *medge;
 
-		ccgdm->ehash = BLI_edgehash_new_ex(__func__, ccgdm->dm.numEdgeData);
-		medge = ccgdm->dm.getEdgeArray((DerivedMesh *)ccgdm);
+			ccgdm->ehash = BLI_edgehash_new_ex(__func__, ccgdm->dm.numEdgeData);
+			medge = ccgdm->dm.getEdgeArray((DerivedMesh *)ccgdm);
 
-		for (i = 0; i < ccgdm->dm.numEdgeData; i++) {
-			BLI_edgehash_insert(ccgdm->ehash, medge[i].v1, medge[i].v2, SET_INT_IN_POINTER(i));
+			for (i = 0; i < ccgdm->dm.numEdgeData; i++) {
+				BLI_edgehash_insert(ccgdm->ehash, medge[i].v1, medge[i].v2, SET_INT_IN_POINTER(i));
+			}
 		}
+		BLI_rw_mutex_unlock(&loops_cache_rwlock);
 	}
 
+	BLI_rw_mutex_lock(&loops_cache_rwlock, THREAD_LOCK_READ);
 	totface = ccgSubSurf_getNumFaces(ss);
 	mv = mloop;
 	for (index = 0; index < totface; index++) {
@@ -1378,6 +1387,7 @@ static void ccgDM_copyFinalLoopArray(DerivedMesh *dm, MLoop *mloop)
 			}
 		}
 	}
+	BLI_rw_mutex_unlock(&loops_cache_rwlock);
 }
 
 static void ccgDM_copyFinalPolyArray(DerivedMesh *dm, MPoly *mpoly)
@@ -2903,11 +2913,14 @@ static void *ccgDM_get_vert_data_layer(DerivedMesh *dm, int type)
 		int a, index, totnone, totorig;
 
 		/* Avoid re-creation if the layer exists already */
+		BLI_rw_mutex_lock(&origindex_cache_rwlock, THREAD_LOCK_READ);
 		origindex = DM_get_vert_data_layer(dm, CD_ORIGINDEX);
+		BLI_rw_mutex_unlock(&origindex_cache_rwlock);
 		if (origindex) {
 			return origindex;
 		}
 
+		BLI_rw_mutex_lock(&origindex_cache_rwlock, THREAD_LOCK_WRITE);
 		DM_add_vert_layer(dm, CD_ORIGINDEX, CD_CALLOC, NULL);
 		origindex = DM_get_vert_data_layer(dm, CD_ORIGINDEX);
 
@@ -2922,6 +2935,7 @@ static void *ccgDM_get_vert_data_layer(DerivedMesh *dm, int type)
 			CCGVert *v = ccgdm->vertMap[index].vert;
 			origindex[a] = ccgDM_getVertMapIndex(ccgdm->ss, v);
 		}
+		BLI_rw_mutex_unlock(&origindex_cache_rwlock);
 
 		return origindex;
 	}