/*

 * Copyright (c) 2017, 2019, 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.

 *

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#ifndef SHARE_RUNTIME_SAFEPOINTMECHANISM_HPP

#define SHARE_RUNTIME_SAFEPOINTMECHANISM_HPP

#include "runtime/globals.hpp"

#include "utilities/globalDefinitions.hpp"

#include "utilities/macros.hpp"

#include "utilities/sizes.hpp"

// This is the abstracted interface for the safepoint implementation

class SafepointMechanism : public AllStatic {

  enum PollingType {

    _global_page_poll,

    _thread_local_poll

  };

  static PollingType _polling_type;

  static void* _poll_armed_value;

  static void* _poll_disarmed_value;

  static void set_uses_thread_local_poll()            { _polling_type     = _thread_local_poll; }

  static void* poll_armed_value()                     { return _poll_armed_value; }

  static void* poll_disarmed_value()                  { return _poll_disarmed_value; }

  static inline bool local_poll_armed(JavaThread* thread);

  static inline bool local_poll(Thread* thread);

  static inline bool global_poll();

  static void block_if_requested_slow(JavaThread *thread);

  static void default_initialize();

  static void pd_initialize() NOT_AIX({ default_initialize(); });

  // By adding 8 to the base address of the protected polling page we can differentiate

  // between the armed and disarmed value by masking out this bit.

  const static intptr_t _poll_bit = 8;

public:

  static intptr_t poll_bit() { return _poll_bit; }

  static bool uses_global_page_poll() { return _polling_type == _global_page_poll; }

  static bool uses_thread_local_poll() { return _polling_type == _thread_local_poll; }

  static bool supports_thread_local_poll() {

#ifdef THREAD_LOCAL_POLL

    return true;

#else

    return false;

#endif

  }

  // Call this method to see if this thread should block for a safepoint or process handshake.

  static inline bool should_block(Thread* thread);

  // Blocks a thread until safepoint/handshake is completed.

  static inline void block_if_requested(JavaThread* thread);

  // Caller is responsible for using a memory barrier if needed.

  static inline void arm_local_poll(JavaThread* thread);

  static inline void arm_local_poll_release(JavaThread* thread);

  // Setup the selected safepoint mechanism

  static void initialize();

  static void initialize_header(JavaThread* thread);

};

#endif // SHARE_RUNTIME_SAFEPOINTMECHANISM_HPP