/*

 * Copyright (c) 2005, 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 "gc/cms/concurrentMarkSweepGeneration.inline.hpp"

#include "gc/cms/concurrentMarkSweepThread.hpp"

#include "gc/cms/vmCMSOperations.hpp"

#include "gc/shared/gcLocker.inline.hpp"

#include "gc/shared/gcTimer.hpp"

#include "gc/shared/gcTraceTime.inline.hpp"

#include "gc/shared/isGCActiveMark.hpp"

#include "runtime/interfaceSupport.hpp"

#include "runtime/os.hpp"

#include "utilities/dtrace.hpp"

//////////////////////////////////////////////////////////

// Methods in abstract class VM_CMS_Operation

//////////////////////////////////////////////////////////

void VM_CMS_Operation::verify_before_gc() {

  if (VerifyBeforeGC &&

      GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {

    GCTraceTime(Info, gc, phases, verify) tm("Verify Before", _collector->_gc_timer_cm);

    HandleMark hm;

    FreelistLocker x(_collector);

    MutexLockerEx  y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);

    GenCollectedHeap::heap()->prepare_for_verify();

    Universe::verify();

  }

}

void VM_CMS_Operation::verify_after_gc() {

  if (VerifyAfterGC &&

      GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {

    GCTraceTime(Info, gc, phases, verify) tm("Verify After", _collector->_gc_timer_cm);

    HandleMark hm;

    FreelistLocker x(_collector);

    MutexLockerEx  y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);

    Universe::verify();

  }

}

bool VM_CMS_Operation::lost_race() const {

  if (CMSCollector::abstract_state() == CMSCollector::Idling) {

    // We lost a race to a foreground collection

    // -- there's nothing to do

    return true;

  }

  assert(CMSCollector::abstract_state() == legal_state(),

         "Inconsistent collector state?");

  return false;

}

bool VM_CMS_Operation::doit_prologue() {

  assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");

  assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");

  assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),

         "Possible deadlock");

  Heap_lock->lock();

  if (lost_race()) {

    assert(_prologue_succeeded == false, "Initialized in c'tor");

    Heap_lock->unlock();

  } else {

    _prologue_succeeded = true;

  }

  return _prologue_succeeded;

}

void VM_CMS_Operation::doit_epilogue() {

  assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");

  assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");

  assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),

         "Possible deadlock");

  Heap_lock->unlock();

}

//////////////////////////////////////////////////////////

// Methods in class VM_CMS_Initial_Mark

//////////////////////////////////////////////////////////

void VM_CMS_Initial_Mark::doit() {

  if (lost_race()) {

    // Nothing to do.

    return;

  }

  HS_PRIVATE_CMS_INITMARK_BEGIN();

  GCIdMark gc_id_mark(_gc_id);

  _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark");

  GenCollectedHeap* gch = GenCollectedHeap::heap();

  GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);

  VM_CMS_Operation::verify_before_gc();

  IsGCActiveMark x; // stop-world GC active

  _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause());

  VM_CMS_Operation::verify_after_gc();

  _collector->_gc_timer_cm->register_gc_pause_end();

  HS_PRIVATE_CMS_INITMARK_END();

}

//////////////////////////////////////////////////////////

// Methods in class VM_CMS_Final_Remark_Operation

//////////////////////////////////////////////////////////

void VM_CMS_Final_Remark::doit() {

  if (lost_race()) {

    // Nothing to do.

    return;

  }

  HS_PRIVATE_CMS_REMARK_BEGIN();

  GCIdMark gc_id_mark(_gc_id);

  _collector->_gc_timer_cm->register_gc_pause_start("Final Mark");

  GenCollectedHeap* gch = GenCollectedHeap::heap();

  GCCauseSetter gccs(gch, GCCause::_cms_final_remark);

  VM_CMS_Operation::verify_before_gc();

  IsGCActiveMark x; // stop-world GC active

  _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause());

  VM_CMS_Operation::verify_after_gc();

  _collector->save_heap_summary();

  _collector->_gc_timer_cm->register_gc_pause_end();

  HS_PRIVATE_CMS_REMARK_END();

}

// VM operation to invoke a concurrent collection of a

// GenCollectedHeap heap.

void VM_GenCollectFullConcurrent::doit() {

  assert(Thread::current()->is_VM_thread(), "Should be VM thread");

  assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");

  GenCollectedHeap* gch = GenCollectedHeap::heap();

  if (_gc_count_before == gch->total_collections()) {

    // The "full" of do_full_collection call below "forces"

    // a collection; the second arg, 0, below ensures that

    // only the young gen is collected. XXX In the future,

    // we'll probably need to have something in this interface

    // to say do this only if we are sure we will not bail

    // out to a full collection in this attempt, but that's

    // for the future.

    assert(SafepointSynchronize::is_at_safepoint(),

      "We can only be executing this arm of if at a safepoint");

    GCCauseSetter gccs(gch, _gc_cause);

    gch->do_full_collection(gch->must_clear_all_soft_refs(), GenCollectedHeap::YoungGen);

  } // Else no need for a foreground young gc

  assert((_gc_count_before < gch->total_collections()) ||

         (GCLocker::is_active() /* gc may have been skipped */

          && (_gc_count_before == gch->total_collections())),

         "total_collections() should be monotonically increasing");

  MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);

  assert(_full_gc_count_before <= gch->total_full_collections(), "Error");

  if (gch->total_full_collections() == _full_gc_count_before) {

    // Nudge the CMS thread to start a concurrent collection.

    CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause);

  } else {

    assert(_full_gc_count_before < gch->total_full_collections(), "Error");

    FullGCCount_lock->notify_all();  // Inform the Java thread its work is done

  }

}

bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {

  Thread* thr = Thread::current();

  assert(thr != NULL, "Unexpected tid");

  if (!thr->is_Java_thread()) {

    assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");

    GenCollectedHeap* gch = GenCollectedHeap::heap();

    if (_gc_count_before != gch->total_collections()) {

      // No need to do a young gc, we'll just nudge the CMS thread

      // in the doit() method above, to be executed soon.

      assert(_gc_count_before < gch->total_collections(),

             "total_collections() should be monotonically increasing");

      return false;  // no need for foreground young gc

    }

  }

  return true;       // may still need foreground young gc

}

void VM_GenCollectFullConcurrent::doit_epilogue() {

  Thread* thr = Thread::current();

  assert(thr->is_Java_thread(), "just checking");

  JavaThread* jt = (JavaThread*)thr;

  Heap_lock->unlock();

  // It is fine to test whether completed collections has

  // exceeded our request count without locking because

  // the completion count is monotonically increasing;

  // this will break for very long-running apps when the

  // count overflows and wraps around. XXX fix me !!!

  // e.g. at the rate of 1 full gc per ms, this could

  // overflow in about 1000 years.

  GenCollectedHeap* gch = GenCollectedHeap::heap();

  if (_gc_cause != GCCause::_gc_locker &&

      gch->total_full_collections_completed() <= _full_gc_count_before) {

    // maybe we should change the condition to test _gc_cause ==

    // GCCause::_java_lang_system_gc or GCCause::_dcmd_gc_run,

    // instead of _gc_cause != GCCause::_gc_locker

    assert(GCCause::is_user_requested_gc(_gc_cause),

           "the only way to get here if this was a System.gc()-induced GC");

    assert(ExplicitGCInvokesConcurrent, "Error");

    // Now, wait for witnessing concurrent gc cycle to complete,

    // but do so in native mode, because we want to lock the

    // FullGCEvent_lock, which may be needed by the VM thread

    // or by the CMS thread, so we do not want to be suspended

    // while holding that lock.

    ThreadToNativeFromVM native(jt);

    MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);

    // Either a concurrent or a stop-world full gc is sufficient

    // witness to our request.

    while (gch->total_full_collections_completed() <= _full_gc_count_before) {

      FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);

    }

  }

}