8004903: VMThread::execute() calls Thread::check_for_valid_safepoint_state() on concurrent VM ops

Summary: check_for_valid_safepoint_state() only applies to blocking VM ops
Reviewed-by: acorn, dholmes, dice, sspitsyn
Contributed-by: karen.kinnear@oracle.com

src/share/vm/runtime/vmThread.cpp

 /*
- * Copyright (c) 1998, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -570,7 +570,11 @@ void VMThread::execute(VM_Operation* op) {
   if (!t->is_VM_thread()) {
     SkipGCALot sgcalot(t);    // avoid re-entrant attempts to gc-a-lot
     // JavaThread or WatcherThread
+    bool concurrent = op->evaluate_concurrently();
+    // only blocking VM operations need to verify the caller's safepoint state:
+    if (!concurrent) {
       t->check_for_valid_safepoint_state(true);
+    }
 
     // New request from Java thread, evaluate prologue
     if (!op->doit_prologue()) {
@@ -582,7 +586,6 @@ void VMThread::execute(VM_Operation* op) {
 
     // It does not make sense to execute the epilogue, if the VM operation object is getting
     // deallocated by the VM thread.
-    bool concurrent     = op->evaluate_concurrently();
     bool execute_epilog = !op->is_cheap_allocated();
     assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated");