[deserializer] Make large object deserialization GC safe

src/snapshot/deserializer.cc

Index: src/snapshot/deserializer.cc
diff --git a/src/snapshot/deserializer.cc b/src/snapshot/deserializer.cc
index 288308776663a389b968e8aca56f09fed65da150..38f41caa2727d77d33daf1d217d04a225bc3b097 100644
--- a/src/snapshot/deserializer.cc
+++ b/src/snapshot/deserializer.cc
@@ -54,6 +54,14 @@ void Deserializer::FlushICacheForNewCodeObjectsAndRecordEmbeddedObjects() {
   }
 }
 
+void Deserializer::RecordWritesForLargeObjects() {
+  Heap* heap = isolate_->heap();
+  if (!heap->incremental_marking()->black_allocation()) return;
+  for (HeapObject* object : deserialized_large_objects_) {
+    heap->incremental_marking()->IterateBlackObject(object);
+  }
+}
+
 bool Deserializer::ReserveSpace() {
 #ifdef DEBUG
   for (int i = NEW_SPACE; i < kNumberOfSpaces; ++i) {
@@ -171,6 +179,7 @@ MaybeHandle<HeapObject> Deserializer::DeserializeObject(Isolate* isolate) {
       VisitRootPointer(Root::kPartialSnapshotCache, &root);
       DeserializeDeferredObjects();
       FlushICacheForNewCodeObjectsAndRecordEmbeddedObjects();
+      RecordWritesForLargeObjects();

[Hannes Payer (out of office), 2017/05/09 21:19:51]

Ideally, we would move this one into RegisterReservationsForBlackAllocation and
rename RegisterReservationsForBlackAllocation to something more generic like
RegisterDeserializedObjectsForBlackAllocation.

[Jakob Kummerow, 2017/05/10 11:09:07]

Done.

       result = Handle<HeapObject>(HeapObject::cast(root));
       isolate->heap()->RegisterReservationsForBlackAllocation(reservations_);

[Hannes Payer (out of office), 2017/05/09 21:19:51]

I guess that means we never have reservations for LO? Whenever we iterate
reservations we go to LO space.

[Jakob Kummerow, 2017/05/10 11:09:07]

Correct; LO space doesn't use reservations (because it can't -- there's no way
to batch allocations for several large objects).

     }