/*

 * Copyright (c) 2001, 2009, 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

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

class VoidClosure;

// A SuspendibleThreadSet is (obviously) a set of threads that can be

// suspended.  A thread can join and later leave the set, and periodically

// yield.  If some thread (not in the set) requests, via suspend_all, that

// the threads be suspended, then the requesting thread is blocked until

// all the threads in the set have yielded or left the set.  (Threads may

// not enter the set when an attempted suspension is in progress.)  The

// suspending thread later calls resume_all, allowing the suspended threads

// to continue.

class SuspendibleThreadSet {

  Monitor* _m;

  int      _async;

  bool     _async_stop;

  int      _async_stopped;

  bool     _initialized;

  double   _suspend_all_start;

  void initialize_work();

 public:

  SuspendibleThreadSet() : _initialized(false) {}

  // Add the current thread to the set.  May block if a suspension

  // is in progress.

  void join();

  // Removes the current thread from the set.

  void leave();

  // Returns "true" iff an suspension is in progress.

  bool should_yield() { return _async_stop; }

  // Suspends the current thread if a suspension is in progress (for

  // the duration of the suspension.)

  void yield(const char* id);

  // Return when all threads in the set are suspended.

  void suspend_all();

  // Allow suspended threads to resume.

  void resume_all();

  // Redundant initializations okay.

  void initialize() {

    // Double-check dirty read idiom.

    if (!_initialized) initialize_work();

  }

};

class ConcurrentGCThread: public NamedThread {

  friend class VMStructs;

protected:

  bool _should_terminate;

  bool _has_terminated;

  enum CGC_flag_type {

    CGC_nil           = 0x0,

    CGC_dont_suspend  = 0x1,

    CGC_CGC_safepoint = 0x2,

    CGC_VM_safepoint  = 0x4

  };

  static int _CGC_flag;

  static bool CGC_flag_is_set(int b)       { return (_CGC_flag & b) != 0; }

  static int set_CGC_flag(int b)           { return _CGC_flag |= b; }

  static int reset_CGC_flag(int b)         { return _CGC_flag &= ~b; }

  void stopWorldAndDo(VoidClosure* op);

  // All instances share this one set.

  static SuspendibleThreadSet _sts;

  // Create and start the thread (setting it's priority high.)

  void create_and_start();

  // Do initialization steps in the thread: record stack base and size,

  // init thread local storage, set JNI handle block.

  void initialize_in_thread();

  // Wait until Universe::is_fully_initialized();

  void wait_for_universe_init();

  // Record that the current thread is terminating, and will do more

  // concurrent work.

  void terminate();

public:

  // Constructor

  ConcurrentGCThread();

  ~ConcurrentGCThread() {} // Exists to call NamedThread destructor.

  // Tester

  bool is_ConcurrentGC_thread() const          { return true;       }

  static void safepoint_synchronize();

  static void safepoint_desynchronize();

  // All overridings should probably do _sts::yield, but we allow

  // overriding for distinguished debugging messages.  Default is to do

  // nothing.

  virtual void yield() {}

  bool should_yield() { return _sts.should_yield(); }

  // they are prefixed by sts since there are already yield() and

  // should_yield() (non-static) methods in this class and it was an

  // easy way to differentiate them.

  static void stsYield(const char* id);

  static bool stsShouldYield();

  static void stsJoin();

  static void stsLeave();

};

// The SurrogateLockerThread is used by concurrent GC threads for

// manipulating Java monitors, in particular, currently for

// manipulating the pending_list_lock. XXX

class SurrogateLockerThread: public JavaThread {

  friend class VMStructs;

 public:

  enum SLT_msg_type {

    empty = 0,           // no message

    acquirePLL,          // acquire pending list lock

    releaseAndNotifyPLL  // notify and release pending list lock

  };

 private:

  // the following are shared with the CMSThread

  SLT_msg_type  _buffer;  // communication buffer

  Monitor       _monitor; // monitor controlling buffer

  BasicLock     _basicLock; // used for PLL locking

 public:

  static SurrogateLockerThread* make(TRAPS);

  SurrogateLockerThread();

  bool is_hidden_from_external_view() const     { return true; }

  void loop(); // main method

  void manipulatePLL(SLT_msg_type msg);

};