/*

 * 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/cms/concurrentMarkSweepGeneration.inline.hpp"

#include "gc/cms/concurrentMarkSweepThread.hpp"

#include "gc/shared/gcId.hpp"

#include "gc/shared/genCollectedHeap.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/init.hpp"

#include "runtime/interfaceSupport.hpp"

#include "runtime/java.hpp"

#include "runtime/javaCalls.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/os.hpp"

#include "runtime/vmThread.hpp"

// ======= Concurrent Mark Sweep Thread ========

ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::_cmst = NULL;

CMSCollector* ConcurrentMarkSweepThread::_collector         = NULL;

int  ConcurrentMarkSweepThread::_CMS_flag                   = CMS_nil;

volatile jint ConcurrentMarkSweepThread::_pending_yields    = 0;

ConcurrentMarkSweepThread::ConcurrentMarkSweepThread(CMSCollector* collector)

  : ConcurrentGCThread() {

  assert(UseConcMarkSweepGC,  "UseConcMarkSweepGC should be set");

  assert(_cmst == NULL, "CMS thread already created");

  _cmst = this;

  assert(_collector == NULL, "Collector already set");

  _collector = collector;

  set_name("CMS Main Thread");

  // An old comment here said: "Priority should be just less

  // than that of VMThread".  Since the VMThread runs at

  // NearMaxPriority, the old comment was inaccurate, but

  // changing the default priority to NearMaxPriority-1

  // could change current behavior, so the default of

  // NearMaxPriority stays in place.

  //

  // Note that there's a possibility of the VMThread

  // starving if UseCriticalCMSThreadPriority is on.

  // That won't happen on Solaris for various reasons,

  // but may well happen on non-Solaris platforms.

  create_and_start(UseCriticalCMSThreadPriority ? CriticalPriority : NearMaxPriority);

}

void ConcurrentMarkSweepThread::run_service() {

  assert(this == cmst(), "just checking");

  if (BindCMSThreadToCPU && !os::bind_to_processor(CPUForCMSThread)) {

    log_warning(gc)("Couldn't bind CMS thread to processor " UINTX_FORMAT, CPUForCMSThread);

  }

  while (!should_terminate()) {

    sleepBeforeNextCycle();

    if (should_terminate()) break;

    GCIdMark gc_id_mark;

    GCCause::Cause cause = _collector->_full_gc_requested ?

      _collector->_full_gc_cause : GCCause::_cms_concurrent_mark;

    _collector->collect_in_background(cause);

  }

  // Check that the state of any protocol for synchronization

  // between background (CMS) and foreground collector is "clean"

  // (i.e. will not potentially block the foreground collector,

  // requiring action by us).

  verify_ok_to_terminate();

}

#ifndef PRODUCT

void ConcurrentMarkSweepThread::verify_ok_to_terminate() const {

  assert(!(CGC_lock->owned_by_self() || cms_thread_has_cms_token() ||

           cms_thread_wants_cms_token()),

         "Must renounce all worldly possessions and desires for nirvana");

  _collector->verify_ok_to_terminate();

}

#endif

// create and start a new ConcurrentMarkSweep Thread for given CMS generation

ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::start(CMSCollector* collector) {

  guarantee(_cmst == NULL, "start() called twice!");

  ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);

  assert(_cmst == th, "Where did the just-created CMS thread go?");

  return th;

}

void ConcurrentMarkSweepThread::stop_service() {

  // Now post a notify on CGC_lock so as to nudge

  // CMS thread(s) that might be slumbering in

  // sleepBeforeNextCycle.

  MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);

  CGC_lock->notify_all();

}

void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {

  assert(tc != NULL, "Null ThreadClosure");

  if (cmst() != NULL && !cmst()->has_terminated()) {

    tc->do_thread(cmst());

  }

  assert(Universe::is_fully_initialized(),

         "Called too early, make sure heap is fully initialized");

  if (_collector != NULL) {

    AbstractWorkGang* gang = _collector->conc_workers();

    if (gang != NULL) {

      gang->threads_do(tc);

    }

  }

}

void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {

  if (cmst() != NULL && !cmst()->has_terminated()) {

    cmst()->print_on(st);

    st->cr();

  }

  if (_collector != NULL) {

    AbstractWorkGang* gang = _collector->conc_workers();

    if (gang != NULL) {

      gang->print_worker_threads_on(st);

    }

  }

}

void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {

  assert(UseConcMarkSweepGC, "just checking");

  MutexLockerEx x(CGC_lock,

                  Mutex::_no_safepoint_check_flag);

  if (!is_cms_thread) {

    assert(Thread::current()->is_VM_thread(), "Not a VM thread");

    CMSSynchronousYieldRequest yr;

    while (CMS_flag_is_set(CMS_cms_has_token)) {

      // indicate that we want to get the token

      set_CMS_flag(CMS_vm_wants_token);

      CGC_lock->wait(true);

    }

    // claim the token and proceed

    clear_CMS_flag(CMS_vm_wants_token);

    set_CMS_flag(CMS_vm_has_token);

  } else {

    assert(Thread::current()->is_ConcurrentGC_thread(),

           "Not a CMS thread");

    // The following barrier assumes there's only one CMS thread.

    // This will need to be modified is there are more CMS threads than one.

    while (CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token)) {

      set_CMS_flag(CMS_cms_wants_token);

      CGC_lock->wait(true);

    }

    // claim the token

    clear_CMS_flag(CMS_cms_wants_token);

    set_CMS_flag(CMS_cms_has_token);

  }

}

void ConcurrentMarkSweepThread::desynchronize(bool is_cms_thread) {

  assert(UseConcMarkSweepGC, "just checking");

  MutexLockerEx x(CGC_lock,

                  Mutex::_no_safepoint_check_flag);

  if (!is_cms_thread) {

    assert(Thread::current()->is_VM_thread(), "Not a VM thread");

    assert(CMS_flag_is_set(CMS_vm_has_token), "just checking");

    clear_CMS_flag(CMS_vm_has_token);

    if (CMS_flag_is_set(CMS_cms_wants_token)) {

      // wake-up a waiting CMS thread

      CGC_lock->notify();

    }

    assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),

           "Should have been cleared");

  } else {

    assert(Thread::current()->is_ConcurrentGC_thread(),

           "Not a CMS thread");

    assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");

    clear_CMS_flag(CMS_cms_has_token);

    if (CMS_flag_is_set(CMS_vm_wants_token)) {

      // wake-up a waiting VM thread

      CGC_lock->notify();

    }

    assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),

           "Should have been cleared");

  }

}

// Wait until any cms_lock event

void ConcurrentMarkSweepThread::wait_on_cms_lock(long t_millis) {

  MutexLockerEx x(CGC_lock,

                  Mutex::_no_safepoint_check_flag);

  if (should_terminate() || _collector->_full_gc_requested) {

    return;

  }

  set_CMS_flag(CMS_cms_wants_token);   // to provoke notifies

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

  clear_CMS_flag(CMS_cms_wants_token);

  assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),

         "Should not be set");

}

// Wait until the next synchronous GC, a concurrent full gc request,

// or a timeout, whichever is earlier.

void ConcurrentMarkSweepThread::wait_on_cms_lock_for_scavenge(long t_millis) {

  // Wait time in millis or 0 value representing infinite wait for a scavenge

  assert(t_millis >= 0, "Wait time for scavenge should be 0 or positive");

  GenCollectedHeap* gch = GenCollectedHeap::heap();

  double start_time_secs = os::elapsedTime();

  double end_time_secs = start_time_secs + (t_millis / ((double) MILLIUNITS));

  // Total collections count before waiting loop

  unsigned int before_count;

  {

    MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);

    before_count = gch->total_collections();

  }

  unsigned int loop_count = 0;

  while(!should_terminate()) {

    double now_time = os::elapsedTime();

    long wait_time_millis;

    if(t_millis != 0) {

      // New wait limit

      wait_time_millis = (long) ((end_time_secs - now_time) * MILLIUNITS);

      if(wait_time_millis <= 0) {

        // Wait time is over

        break;

      }

    } else {

      // No wait limit, wait if necessary forever

      wait_time_millis = 0;

    }

    // Wait until the next event or the remaining timeout

    {

      MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);

      if (should_terminate() || _collector->_full_gc_requested) {

        return;

      }

      set_CMS_flag(CMS_cms_wants_token);   // to provoke notifies

      assert(t_millis == 0 || wait_time_millis > 0, "Sanity");

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

      clear_CMS_flag(CMS_cms_wants_token);

      assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),

             "Should not be set");

    }

    // Extra wait time check before entering the heap lock to get the collection count

    if(t_millis != 0 && os::elapsedTime() >= end_time_secs) {

      // Wait time is over

      break;

    }

    // Total collections count after the event

    unsigned int after_count;

    {

      MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);

      after_count = gch->total_collections();

    }

    if(before_count != after_count) {

      // There was a collection - success

      break;

    }

    // Too many loops warning

    if(++loop_count == 0) {

      log_warning(gc)("wait_on_cms_lock_for_scavenge() has looped %u times", loop_count - 1);

    }

  }

}

void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {

  while (!should_terminate()) {

    if(CMSWaitDuration >= 0) {

      // Wait until the next synchronous GC, a concurrent full gc

      // request or a timeout, whichever is earlier.

      wait_on_cms_lock_for_scavenge(CMSWaitDuration);

    } else {

      // Wait until any cms_lock event or check interval not to call shouldConcurrentCollect permanently

      wait_on_cms_lock(CMSCheckInterval);

    }

    // Check if we should start a CMS collection cycle

    if (_collector->shouldConcurrentCollect()) {

      return;

    }

    // .. collection criterion not yet met, let's go back

    // and wait some more

  }

}