Fix simulator with background compilation on.

runtime/vm/longjump.cc

 // Copyright (c) 2011, 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/longjump.h"
 
 #include "include/dart_api.h"
 
 #include "vm/dart_api_impl.h"
 #include "vm/isolate.h"
@@ skipping 11 matching lines @@
 }
 
 
 bool LongJumpScope::IsSafeToJump() {
   // We do not want to jump past Dart frames.  Note that this code
   // assumes the stack grows from high to low.
   Thread* thread = Thread::Current();
   uword jumpbuf_addr = Isolate::GetCurrentStackPointer();
 #if defined(USING_SIMULATOR)
   Simulator* sim = Simulator::Current();
-  uword top_exit_frame_info = sim->top_exit_frame_info();
+  // When using simulator, only mutator thread should refer to Simulator
+  // since there can be only one per isolate.
+  uword top_exit_frame_info = thread->IsMutatorThread() ?
+      sim->top_exit_frame_info() : 0;
 #else
   uword top_exit_frame_info = thread->top_exit_frame_info();
 #endif
   if (!thread->IsMutatorThread()) {
     // A helper thread does not execute Dart code, so it's safe to jump.
     ASSERT(top_exit_frame_info == 0);
     return true;
   }
   return ((top_exit_frame_info == 0) || (jumpbuf_addr < top_exit_frame_info));
 }
@@ skipping 17 matching lines @@
   // Remember the error in the sticky error of this isolate.
   thread->set_sticky_error(error);
 
   // Destruct all the active StackResource objects.
   StackResource::UnwindAbove(thread, top_);
   longjmp(environment_, value);
   UNREACHABLE();
 }
 
 }  // namespace dart