Ensure helper threads get empty initial store buffer block.

runtime/vm/thread.cc

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/thread.h"
 
 #include "vm/growable_array.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
 #include "vm/object.h"
@@ skipping 155 matching lines @@
   thread->heap_ = NULL;
 }
 
 
 void Thread::EnterIsolateAsHelper(Isolate* isolate) {
   Thread* thread = Thread::Current();
   ASSERT(thread != NULL);
   ASSERT(thread->isolate() == NULL);
   thread->isolate_ = isolate;
   ASSERT(thread->store_buffer_block_ == NULL);
-  thread->StoreBufferAcquire();
+  // TODO(koda): Use StoreBufferAcquire once we properly flush before Scavenge.
+  thread->store_buffer_block_ =
+      thread->isolate()->store_buffer()->PopEmptyBlock();
   ASSERT(isolate->heap() != NULL);
   thread->heap_ = isolate->heap();
   ASSERT(thread->thread_state() == NULL);
   // Do not update isolate->mutator_thread, but perform sanity check:
   // this thread should not be both the main mutator and helper.
   ASSERT(!isolate->MutatorThreadIsCurrentThread());
   thread->Schedule(isolate);
 }
 
 
@@ skipping 83 matching lines @@
 #define COMPUTE_OFFSET(type_name, member_name, expr, default_init_value)       \
   ASSERT((expr)->IsVMHeapObject());                                            \
   if (object.raw() == expr) return Thread::member_name##offset();
 CACHED_VM_OBJECTS_LIST(COMPUTE_OFFSET)
 #undef COMPUTE_OFFSET
   UNREACHABLE();
   return -1;
 }
 
 }  // namespace dart