/*

 * 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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 */

# include "incls/_precompiled.incl"

# include "incls/_concurrentMarkSweepThread.cpp.incl"

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

// The CMS thread is created when Concurrent Mark Sweep is used in the

// older of two generations in a generational memory system.

ConcurrentMarkSweepThread*

     ConcurrentMarkSweepThread::_cmst     = NULL;

CMSCollector* ConcurrentMarkSweepThread::_collector = NULL;

bool ConcurrentMarkSweepThread::_should_terminate = false;

int  ConcurrentMarkSweepThread::_CMS_flag         = CMS_nil;

volatile jint ConcurrentMarkSweepThread::_pending_yields      = 0;

volatile jint ConcurrentMarkSweepThread::_pending_decrements  = 0;

volatile bool ConcurrentMarkSweepThread::_icms_enabled   = false;

volatile bool ConcurrentMarkSweepThread::_should_run     = false;

// When icms is enabled, the icms thread is stopped until explicitly

// started.

volatile bool ConcurrentMarkSweepThread::_should_stop    = true;

SurrogateLockerThread*

     ConcurrentMarkSweepThread::_slt = NULL;

SurrogateLockerThread::SLT_msg_type

     ConcurrentMarkSweepThread::_sltBuffer = SurrogateLockerThread::empty;

Monitor*

     ConcurrentMarkSweepThread::_sltMonitor = NULL;

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("Concurrent Mark-Sweep GC Thread");

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

    // XXX: need to set this to low priority

    // unless "agressive mode" set; priority

    // should be just less than that of VMThread.

    os::set_priority(this, NearMaxPriority);

    if (!DisableStartThread) {

      os::start_thread(this);

    }

  }

  _sltMonitor = SLT_lock;

  set_icms_enabled(CMSIncrementalMode);

}

void ConcurrentMarkSweepThread::run() {

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

  this->record_stack_base_and_size();

  this->initialize_thread_local_storage();

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

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

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

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

    warning("Couldn't bind CMS thread to processor %u", CPUForCMSThread);

  }

  // Wait until Universe::is_fully_initialized()

  {

    CMSLoopCountWarn loopX("CMS::run", "waiting for "

                           "Universe::is_fully_initialized()", 2);

    MutexLockerEx x(CGC_lock, true);

    set_CMS_flag(CMS_cms_wants_token);

    // Wait until Universe is initialized and all initialization is completed.

    while (!is_init_completed() && !Universe::is_fully_initialized() &&

           !_should_terminate) {

      CGC_lock->wait(true, 200);

      loopX.tick();

    }

    // Wait until the surrogate locker thread that will do

    // pending list locking on our behalf has been created.

    // We cannot start the SLT thread ourselves since we need

    // to be a JavaThread to do so.

    CMSLoopCountWarn loopY("CMS::run", "waiting for SLT installation", 2);

    while (_slt == NULL && !_should_terminate) {

      CGC_lock->wait(true, 200);

      loopY.tick();

    }

    clear_CMS_flag(CMS_cms_wants_token);

  }

  while (!_should_terminate) {

    sleepBeforeNextCycle();

    if (_should_terminate) break;

    _collector->collect_in_background(false);  // !clear_all_soft_refs

  }

  assert(_should_terminate, "just checking");

  // 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();

  // Signal that it is terminated

  {

    MutexLockerEx mu(Terminator_lock,

                     Mutex::_no_safepoint_check_flag);

    assert(_cmst == this, "Weird!");

    _cmst = NULL;

    Terminator_lock->notify();

  }

  // Thread destructor usually does this..

  ThreadLocalStorage::set_thread(NULL);

}

#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) {

  if (!_should_terminate) {

    assert(cmst() == NULL, "start() called twice?");

    ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);

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

    return th;

  }

  return NULL;

}

void ConcurrentMarkSweepThread::stop() {

  if (CMSIncrementalMode) {

    // Disable incremental mode and wake up the thread so it notices the change.

    disable_icms();

    start_icms();

  }

  // it is ok to take late safepoints here, if needed

  {

    MutexLockerEx x(Terminator_lock);

    _should_terminate = true;

  }

  { // 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();

  }

  { // Now wait until (all) CMS thread(s) have exited

    MutexLockerEx x(Terminator_lock);

    while(cmst() != NULL) {

      Terminator_lock->wait();

    }

  }

}

void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {

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

  if (_cmst != NULL) {

    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_on(outputStream* st) const {

  st->print("\"%s\" ", name());

  Thread::print_on(st);

  st->cr();

}

void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {

  if (_cmst != NULL) {

    _cmst->print_on(st);

  }

  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 the next synchronous GC or a timeout, whichever is earlier.

void ConcurrentMarkSweepThread::wait_on_cms_lock(long t) {

  MutexLockerEx x(CGC_lock,

                  Mutex::_no_safepoint_check_flag);

  set_CMS_flag(CMS_cms_wants_token);   // to provoke notifies

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

  clear_CMS_flag(CMS_cms_wants_token);

  assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),

         "Should not be set");

}

void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {

  while (!_should_terminate) {

    if (CMSIncrementalMode) {

      icms_wait();

      return;

    } else {

      // Wait until the next synchronous GC or a timeout, whichever is earlier

      wait_on_cms_lock(CMSWaitDuration);

    }

    // 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

  }

}

// Incremental CMS

void ConcurrentMarkSweepThread::start_icms() {

  assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");

  MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);

  trace_state("start_icms");

  _should_run = true;

  iCMS_lock->notify_all();

}

void ConcurrentMarkSweepThread::stop_icms() {

  assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");

  MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);

  if (!_should_stop) {

    trace_state("stop_icms");

    _should_stop = true;

    _should_run = false;

    asynchronous_yield_request();

    iCMS_lock->notify_all();

  }

}

void ConcurrentMarkSweepThread::icms_wait() {

  assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");

  if (_should_stop && icms_enabled()) {

    MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);

    trace_state("pause_icms");

    _collector->stats().stop_cms_timer();

    while(!_should_run && icms_enabled()) {

      iCMS_lock->wait(Mutex::_no_safepoint_check_flag);

    }

    _collector->stats().start_cms_timer();

    _should_stop = false;

    trace_state("pause_icms end");

  }

}

// Note: this method, although exported by the ConcurrentMarkSweepThread,

// which is a non-JavaThread, can only be called by a JavaThread.

// Currently this is done at vm creation time (post-vm-init) by the

// main/Primordial (Java)Thread.

// XXX Consider changing this in the future to allow the CMS thread

// itself to create this thread?

void ConcurrentMarkSweepThread::makeSurrogateLockerThread(TRAPS) {

  assert(UseConcMarkSweepGC, "SLT thread needed only for CMS GC");

  assert(_slt == NULL, "SLT already created");

  _slt = SurrogateLockerThread::make(THREAD);

}