/*

 * Copyright (c) 2001, 2016, 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.

 *

 */

#include "precompiled.hpp"

#include "classfile/systemDictionary.hpp"

#include "gc/shared/concurrentGCThread.hpp"

#include "oops/instanceRefKlass.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/init.hpp"

#include "runtime/interfaceSupport.hpp"

#include "runtime/java.hpp"

#include "runtime/javaCalls.hpp"

#include "runtime/os.hpp"

ConcurrentGCThread::ConcurrentGCThread() :

  _should_terminate(false), _has_terminated(false) {

};

  if (os::create_thread(this, os::cgc_thread)) {

    // XXX: need to set this to low priority

    // unless "aggressive mode" set; priority

    // should be just less than that of VMThread.

    if (!_should_terminate && !DisableStartThread) {

      os::start_thread(this);

    }

  }

}

void ConcurrentGCThread::initialize_in_thread() {

  this->record_stack_base_and_size();

  this->initialize_named_thread();

  this->set_active_handles(JNIHandleBlock::allocate_block());

  // From this time Thread::current() should be working.

  assert(this == Thread::current(), "just checking");

}

void ConcurrentGCThread::wait_for_universe_init() {

  MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);

  while (!is_init_completed() && !_should_terminate) {

    CGC_lock->wait(Mutex::_no_safepoint_check_flag, 1);

  }

}

void ConcurrentGCThread::terminate() {

  assert(_should_terminate, "Should only be called on terminate request.");

  // Signal that it is terminated

  {

    MutexLockerEx mu(Terminator_lock,

                     Mutex::_no_safepoint_check_flag);

    _has_terminated = true;

    Terminator_lock->notify();

  }

}

static void _sltLoop(JavaThread* thread, TRAPS) {

  SurrogateLockerThread* slt = (SurrogateLockerThread*)thread;

  slt->loop();

}

SurrogateLockerThread::SurrogateLockerThread() :

  JavaThread(&_sltLoop),

  _monitor(Mutex::nonleaf, "SLTMonitor", false,

           Monitor::_safepoint_check_sometimes),

  _buffer(empty)

{}

SurrogateLockerThread* SurrogateLockerThread::make(TRAPS) {

  Klass* k =

    SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(),

                                      true, CHECK_NULL);

  instanceKlassHandle klass (THREAD, k);

  instanceHandle thread_oop = klass->allocate_instance_handle(CHECK_NULL);

  const char thread_name[] = "Surrogate Locker Thread (Concurrent GC)";

  Handle string = java_lang_String::create_from_str(thread_name, CHECK_NULL);

  // Initialize thread_oop to put it into the system threadGroup

  Handle thread_group (THREAD, Universe::system_thread_group());

  JavaValue result(T_VOID);

  JavaCalls::call_special(&result, thread_oop,

                          klass,

                          vmSymbols::object_initializer_name(),

                          vmSymbols::threadgroup_string_void_signature(),

                          thread_group,

                          string,

                          CHECK_NULL);

  SurrogateLockerThread* res;

  {

    MutexLocker mu(Threads_lock);

    res = new SurrogateLockerThread();

    // At this point it may be possible that no osthread was created for the

    // JavaThread due to lack of memory. We would have to throw an exception

    // in that case. However, since this must work and we do not allow

    // exceptions anyway, check and abort if this fails.

    if (res == NULL || res->osthread() == NULL) {

      vm_exit_during_initialization("java.lang.OutOfMemoryError",

                                    os::native_thread_creation_failed_msg());

    }

    java_lang_Thread::set_thread(thread_oop(), res);

    java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);

    java_lang_Thread::set_daemon(thread_oop());

    res->set_threadObj(thread_oop());

    Threads::add(res);

    Thread::start(res);

  }

  os::naked_yield(); // This seems to help with initial start-up of SLT

  return res;

}

void SurrogateLockerThread::report_missing_slt() {

  vm_exit_during_initialization(

    "GC before GC support fully initialized: "

    "SLT is needed but has not yet been created.");

  ShouldNotReachHere();

}

void SurrogateLockerThread::manipulatePLL(SLT_msg_type msg) {

  MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag);

  assert(_buffer == empty, "Should be empty");

  assert(msg != empty, "empty message");

  assert(!Heap_lock->owned_by_self(), "Heap_lock owned by requesting thread");

  _buffer = msg;

  while (_buffer != empty) {

    _monitor.notify();

    _monitor.wait(Mutex::_no_safepoint_check_flag);

  }

}

// ======= Surrogate Locker Thread =============

void SurrogateLockerThread::loop() {

  BasicLock pll_basic_lock;

  SLT_msg_type msg;

  debug_only(unsigned int owned = 0;)

  while (/* !isTerminated() */ 1) {

    {

      MutexLocker x(&_monitor);

      // Since we are a JavaThread, we can't be here at a safepoint.

      assert(!SafepointSynchronize::is_at_safepoint(),

             "SLT is a JavaThread");

      // wait for msg buffer to become non-empty

      while (_buffer == empty) {

        _monitor.notify();

        _monitor.wait();

      }

      msg = _buffer;

    }

    switch(msg) {

      case acquirePLL: {

        InstanceRefKlass::acquire_pending_list_lock(&pll_basic_lock);

        debug_only(owned++;)

        break;

      }

      case releaseAndNotifyPLL: {

        assert(owned > 0, "Don't have PLL");

        InstanceRefKlass::release_and_notify_pending_list_lock(&pll_basic_lock);

        debug_only(owned--;)

        break;

      }

      case empty:

      default: {

        guarantee(false,"Unexpected message in _buffer");

        break;

      }

    }

    {

      MutexLocker x(&_monitor);

      // Since we are a JavaThread, we can't be here at a safepoint.

      assert(!SafepointSynchronize::is_at_safepoint(),

             "SLT is a JavaThread");

      _buffer = empty;

      _monitor.notify();

    }

  }

  assert(!_monitor.owned_by_self(), "Should unlock before exit.");

}