src/share/vm/utilities/ostream.hpp

*** 121,142 ****
--- 121,160 ----
  extern outputStream* tty;           // tty output
  extern outputStream* gclog_or_tty;  // stream for gc log if -Xloggc:<f>, or tty
  
  // advisory locking for the shared tty stream:
  class ttyLocker: StackObj {
+   friend class ttyUnlocker;
   private:
    intx _holder;
  
   public:
    static intx  hold_tty();                // returns a "holder" token
    static void  release_tty(intx holder);  // must witness same token
+   static bool  release_tty_if_locked();   // returns true if lock was released
    static void  break_tty_lock_for_safepoint(intx holder);
  
    ttyLocker()  { _holder = hold_tty(); }
    ~ttyLocker() { release_tty(_holder); }
  };
  
+ // Release the tty lock if it's held and reacquire it if it was
+ // locked.  Used to avoid lock ordering problems.
+ class ttyUnlocker: StackObj {
+  private:
+   bool _was_locked;
+  public:
+   ttyUnlocker()  {
+     _was_locked = ttyLocker::release_tty_if_locked();
+   }
+   ~ttyUnlocker() {
+     if (_was_locked) {
+       ttyLocker::hold_tty();
+     }
+   }
+ };
+ 
  // for writing to strings; buffer will expand automatically
  class stringStream : public outputStream {
   protected:
    char*  buffer;
    size_t buffer_pos;