Do not block for safepoint when transitioning from generated code to VM, otherwise the result may n…

runtime/vm/safepoint.h

 // Copyright (c) 2016, 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.
 
 #ifndef VM_SAFEPOINT_H_
 #define VM_SAFEPOINT_H_
 
 #include "vm/globals.h"
 #include "vm/lockers.h"
 #include "vm/thread.h"
@@ skipping 291 matching lines @@
   }
 
   ~TransitionToGenerated() {
     ASSERT(thread()->execution_state() == Thread::kThreadInGenerated);
     if (execution_state_ == Thread::kThreadInNative) {
       thread()->set_execution_state(Thread::kThreadInNative);
       thread()->EnterSafepoint();
     } else {
       ASSERT(execution_state_ == Thread::kThreadInVM);
       thread()->set_execution_state(Thread::kThreadInVM);
-      // Fast check to see if a safepoint is requested or not.
-      // We do the more expensive operation of blocking the thread
-      // only if a safepoint is requested.
-      if (thread()->IsSafepointRequested()) {
-        handler()->BlockForSafepoint(thread());
-      }
     }
   }
 
  private:
   int16_t execution_state_;
   DISALLOW_COPY_AND_ASSIGN(TransitionToGenerated);
 };
 
 }  // namespace dart
 
 #endif  // VM_SAFEPOINT_H_