Prepares allocation for proper sync with mutator and bg threads.

runtime/vm/heap.cc

Index: runtime/vm/heap.cc
diff --git a/runtime/vm/heap.cc b/runtime/vm/heap.cc
index 70a34f2e325cee60f511f9601aaa712d8f2808fe..c31e008033a5a042c1864c9b8794d9407921584f 100644
--- a/runtime/vm/heap.cc
+++ b/runtime/vm/heap.cc
@@ -58,7 +58,7 @@ Heap::~Heap() {
   }
 }
 
-void Heap::FillRemainingTLAB(Thread* thread) {
+void Heap::MakeTLABIterable(Thread* thread) {
   uword start = thread->top();
   uword end = thread->end();
   ASSERT(end >= start);
@@ -67,12 +67,11 @@ void Heap::FillRemainingTLAB(Thread* thread) {
   if (size >= kObjectAlignment) {
     FreeListElement::AsElement(start, size);
     ASSERT(RawObject::FromAddr(start)->Size() == size);
-    ASSERT((start + size) == new_space_.top());
   }
 }
 
 void Heap::AbandonRemainingTLAB(Thread* thread) {
-  FillRemainingTLAB(thread);
+  MakeTLABIterable(thread);
   thread->set_top(0);
   thread->set_end(0);
 }
@@ -112,6 +111,9 @@ uword Heap::AllocateNew(intptr_t size) {
   // This call to CollectGarbage might end up "reusing" a collection spawned
   // from a different thread and will be racing to allocate the requested
   // memory with other threads being released after the collection.
+  // TODO(danunez): Ensure that once we start collecting garbage, everything
+  // stops allocating.
+  // Safepoint should be dealing with this, but we need to make sure somehow.
   CollectGarbage(kNew);
   tlab_size = CalculateTLABSize();
   uword tlab_top = new_space_.TryAllocateNewTLAB(thread, tlab_size);
@@ -630,6 +632,7 @@ bool Heap::VerifyGC(MarkExpectation mark_expectation) const {
   ObjectSet* allocated_set =
       CreateAllocatedObjectSet(stack_zone.GetZone(), mark_expectation);
   VerifyPointersVisitor visitor(isolate(), allocated_set);
+  // TODO(danunez): Need to lock and unlock for new space here.

[rmacnak, 2017/08/10 18:37:06]

This function should already be always running during a safepoint.

[danunez, 2017/08/10 20:36:46]

Done.

   VisitObjectPointers(&visitor);
 
   // Only returning a value so that Heap::Validate can be called from an ASSERT.