Clean VM thread shutdown:

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 116 matching lines @@
   isolate->MakeCurrentThreadMutator(thread);
   isolate->set_vm_tag(VMTag::kVMTagId);
   ASSERT(thread->store_buffer_block_ == NULL);
   thread->store_buffer_block_ = isolate->store_buffer()->PopNonFullBlock();
   ASSERT(isolate->heap() != NULL);
   thread->heap_ = isolate->heap();
   thread->Schedule(isolate);
   ASSERT(thread->thread_state() == NULL);
   InterruptableThreadState* thread_state =
       ThreadInterrupter::GetCurrentThreadState();
-#if defined(DEBUG)
-  thread->set_thread_state(NULL);  // Exclude thread itself from the dupe check.
-  Isolate::CheckForDuplicateThreadState(thread_state);
-  thread->set_thread_state(thread_state);
-#endif
+  // TODO(koda): Calling Isolate::CheckForDuplicateThreadState(thread_state)
+  // here can lead to deadlock. Evaluate doing this check some other way.
   ASSERT(thread_state != NULL);
   // TODO(koda): Migrate profiler interface to use Thread.
   Profiler::BeginExecution(isolate);
 }
 
 
 void Thread::ExitIsolate() {
   Thread* thread = Thread::Current();
   // TODO(koda): Audit callers; they should know whether they're in an isolate.
   if (thread == NULL || thread->isolate() == NULL) return;
@@ skipping 107 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