1 /*
   2  * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_RUNTIME_THREADLOCALSTORAGE_HPP
  26 #define SHARE_VM_RUNTIME_THREADLOCALSTORAGE_HPP
  27 
  28 #include "utilities/top.hpp"
  29 
  30 // forward-decl as we can't have an include cycle
  31 class Thread;
  32 
  33 // Wrapper class for library-based (as opposed to compiler-based)
  34 // thread-local storage (TLS). All platforms require this for
  35 // signal-handler based TLS access (which while not strictly async-signal
  36 // safe in theory, is and has-been for a long time, in practice).
  37 // Platforms without compiler-based TLS (ie __thread storage-class modifier)
  38 // will use this implementation for all TLS access - see thread.hpp/cpp
  39 
  40 class ThreadLocalStorage : AllStatic {
  41 
  42  // Exported API
  43  public:
  44   static Thread* thread(); // return current thread, if attached
  45   static void    set_thread(Thread* thread); // set current thread
  46   static void    init();
  47   static bool    is_initialized(); // can't use TLS prior to initialization
  48 };
  49 
  50 #endif // SHARE_VM_RUNTIME_THREADLOCALSTORAGE_HPP