/*

 * Copyright (c) 1997, 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.

 *

 * 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.

 *

 */

#ifndef SHARE_RUNTIME_SAFEPOINT_HPP

#define SHARE_RUNTIME_SAFEPOINT_HPP

#include "memory/allocation.hpp"

#include "runtime/os.hpp"

#include "runtime/thread.hpp"

#include "runtime/vmOperations.hpp"

#include "utilities/ostream.hpp"

#include "utilities/waitBarrier.hpp"

//

// Safepoint synchronization

////

// The VMThread uses the SafepointSynchronize::begin/end

// methods to enter/exit a safepoint region. The begin method will roll

// all JavaThreads forward to a safepoint.

//

// JavaThreads must use the ThreadSafepointState abstraction (defined in

// thread.hpp) to indicate that that they are at a safepoint.

//

// The Mutex/Condition variable and ObjectLocker classes calls the enter/

// exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/

// exit points *must* be at a safepoint.

class ThreadSafepointState;

//

// Implements roll-forward to safepoint (safepoint synchronization)

//

class SafepointSynchronize : AllStatic {

 public:

  enum SynchronizeState {

      _not_synchronized = 0,                   // Threads not synchronized at a safepoint. Keep this value 0.

      _synchronizing    = 1,                   // Synchronizing in progress

      _synchronized     = 2                    // All Java threads are running in native, blocked in OS or stopped at safepoint.

                                               // VM thread and any NonJavaThread may be running.

  };

  // The enums are listed in the order of the tasks when done serially.

  enum SafepointCleanupTasks {

    SAFEPOINT_CLEANUP_DEFLATE_MONITORS,

    SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES,

    SAFEPOINT_CLEANUP_COMPILATION_POLICY,

    SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH,

    SAFEPOINT_CLEANUP_STRING_TABLE_REHASH,

    SAFEPOINT_CLEANUP_CLD_PURGE,

    SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE,

    // Leave this one last.

    SAFEPOINT_CLEANUP_NUM_TASKS

  };

 private:

  friend class SafepointMechanism;

  friend class ThreadSafepointState;

  friend class HandshakeState;

  // Threads might read this flag directly, without acquiring the Threads_lock:

  static volatile SynchronizeState _state;

  // Number of threads we are waiting for to block:

  static int              _waiting_to_block;

  // Counts the number of active critical natives during the safepoint:

  static int              _current_jni_active_count;

  // This counter is used for fast versions of jni_Get<Primitive>Field.

  // An even value means there are no ongoing safepoint operations.

  // The counter is incremented ONLY at the beginning and end of each

  // safepoint.

  static volatile uint64_t _safepoint_counter;

  // JavaThreads that need to block for the safepoint will stop on the

  // _wait_barrier, where they can quickly be started again.

  static WaitBarrier* _wait_barrier;

  static long         _end_of_last_safepoint;     // Time of last safepoint in milliseconds

  static julong       _coalesced_vmop_count;     // coalesced vmop count

  // For debug long safepoint

  static void print_safepoint_timeout();

  // Helper methods for safepoint procedure:

  static void arm_safepoint();

  static int synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running);

  static void disarm_safepoint();

  static void increment_jni_active_count();

  static void decrement_waiting_to_block();

  // Used in safepoint_safe to do a stable load of the thread state.

  static bool try_stable_load_state(JavaThreadState *state,

                                    JavaThread *thread,

                                    uint64_t safepoint_count);

  // Called when a thread voluntarily blocks

  static void block(JavaThread *thread);

  // Called from VMThread during handshakes.

  // If true the VMThread may safely process the handshake operation for the JavaThread.

  static bool handshake_safe(JavaThread *thread);

public:

  static void init(Thread* vmthread);

  // Roll all threads forward to safepoint. Must be called by the VMThread.

  static void begin();

  static void end();                    // Start all suspended threads again...

  // The value for a not set safepoint id.

  static const uint64_t InactiveSafepointCounter;

  // Query

  static bool is_at_safepoint()                   { return _state == _synchronized; }

  static bool is_synchronizing()                  { return _state == _synchronizing; }

  // Exception handling for page polling

  static void handle_polling_page_exception(JavaThread *thread);

  static bool is_cleanup_needed();

  static void do_cleanup_tasks();

  static void set_is_at_safepoint()             { _state = _synchronized; }

  static void set_is_not_at_safepoint()         { _state = _not_synchronized; }

  // Assembly support

  static address address_of_state()             { return (address)&_state; }

  // Only used for making sure that no safepoint has happened in

  // JNI_FastGetField. Therefore only the low 32-bits are needed

  // even if this is a 64-bit counter.

  static address safepoint_counter_addr() {

#ifdef VM_LITTLE_ENDIAN

    return (address)&_safepoint_counter;

#else /* BIG */

    // Return pointer to the 32 LSB:

    return (address) (((uint32_t*)(&_safepoint_counter)) + 1);

#endif

  }

};

// Some helper assert macros for safepoint checks.

#define assert_at_safepoint()                                           \

  assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint")

#define assert_at_safepoint_msg(...)                                    \

  assert(SafepointSynchronize::is_at_safepoint(), __VA_ARGS__)

#define assert_not_at_safepoint()                                       \

  assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint")

#define assert_not_at_safepoint_msg(...)                                \

  assert(!SafepointSynchronize::is_at_safepoint(), __VA_ARGS__)

// State class for a thread suspended at a safepoint

class ThreadSafepointState: public CHeapObj<mtThread> {

 private:

  // At polling page safepoint (NOT a poll return safepoint):

  volatile bool                   _at_poll_safepoint;

  JavaThread*                     _thread;

  bool                            _safepoint_safe;

  volatile uint64_t               _safepoint_id;

  ThreadSafepointState*           _next;

  void account_safe_thread();

 public:

  ThreadSafepointState(JavaThread *thread);

  // Linked list support:

  ThreadSafepointState* get_next() const { return _next; }

  void set_next(ThreadSafepointState* value) { _next = value; }

  ThreadSafepointState** next_ptr() { return &_next; }

  // examine/restart

  void examine_state_of_thread(uint64_t safepoint_count);

  void restart();

  // Query

  JavaThread*  thread() const         { return _thread; }

  bool         is_running() const     { return !_safepoint_safe; }

  uint64_t get_safepoint_id() const;

  void     reset_safepoint_id();

  void     set_safepoint_id(uint64_t sid);

  // Support for safepoint timeout (debugging)

  bool is_at_poll_safepoint()           { return _at_poll_safepoint; }

  void set_at_poll_safepoint(bool val)  { _at_poll_safepoint = val; }

  void handle_polling_page_exception();

  // debugging

  void print_on(outputStream* st) const;

  // Initialize

  static void create(JavaThread *thread);

  static void destroy(JavaThread *thread);

};

class SafepointTracing : public AllStatic {

private:

  // Absolute

  static jlong _last_safepoint_begin_time_ns;

  static jlong _last_safepoint_sync_time_ns;

  static jlong _last_safepoint_cleanup_time_ns;

  static jlong _last_safepoint_end_time_ns;

  // amount of ms since epoch

  static jlong _last_safepoint_end_time_epoch_ms;

  // Relative

  static jlong _last_app_time_ns;

  static int _nof_threads;

  static int _nof_running;

  static int _page_trap;

  static VM_Operation::VMOp_Type _current_type;

  static jlong     _max_sync_time;

  static jlong     _max_vmop_time;

  static uint64_t  _op_count[VM_Operation::VMOp_Terminating];

  static void statistics_log();

public:

  static void init();

  static void begin(VM_Operation::VMOp_Type type);

  static void synchronized(int nof_threads, int nof_running, int traps);

  static void cleanup();

  static void end();

  static void statistics_exit_log();

  static jlong time_since_last_safepoint_ms() {

    return (os::javaTimeNanos() - _last_safepoint_end_time_ns) / (NANOUNITS / MILLIUNITS);

  }

  static jlong end_of_last_safepoint_epoch_ms() {

    return _last_safepoint_end_time_epoch_ms;

  }

  static jlong start_of_safepoint() {

    return _last_safepoint_begin_time_ns;

  }

};

#endif // SHARE_RUNTIME_SAFEPOINT_HPP