/*

 * Copyright 1998-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

# include "incls/_precompiled.incl"

# include "incls/_vmThread.cpp.incl"

// Dummy VM operation to act as first element in our circular double-linked list

class VM_Dummy: public VM_Operation {

  VMOp_Type type() const { return VMOp_Dummy; }

  void  doit() {};

};

VMOperationQueue::VMOperationQueue() {

  // The queue is a circular doubled-linked list, which always contains

  // one element (i.e., one element means empty).

  for(int i = 0; i < nof_priorities; i++) {

    _queue_length[i] = 0;

    _queue_counter = 0;

    _queue[i] = new VM_Dummy();

    _queue[i]->set_next(_queue[i]);

    _queue[i]->set_prev(_queue[i]);

  }

  _drain_list = NULL;

}

bool VMOperationQueue::queue_empty(int prio) {

  // It is empty if there is exactly one element

  bool empty = (_queue[prio] == _queue[prio]->next());

  assert( (_queue_length[prio] == 0 && empty) ||

          (_queue_length[prio] > 0  && !empty), "sanity check");

  return _queue_length[prio] == 0;

}

// Inserts an element to the right of the q element

void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) {

  assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");

  n->set_prev(q);

  n->set_next(q->next());

  q->next()->set_prev(n);

  q->set_next(n);

}

void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) {

  _queue_length[prio]++;

  insert(_queue[prio]->next(), op);

}

void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) {

  _queue_length[prio]++;

  insert(_queue[prio]->prev(), op);

}

void VMOperationQueue::unlink(VM_Operation* q) {

  assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");

  q->prev()->set_next(q->next());

  q->next()->set_prev(q->prev());

}

VM_Operation* VMOperationQueue::queue_remove_front(int prio) {

  if (queue_empty(prio)) return NULL;

  assert(_queue_length[prio] >= 0, "sanity check");

  _queue_length[prio]--;

  VM_Operation* r = _queue[prio]->next();

  assert(r != _queue[prio], "cannot remove base element");

  unlink(r);

  return r;

}

VM_Operation* VMOperationQueue::queue_drain(int prio) {

  if (queue_empty(prio)) return NULL;

  DEBUG_ONLY(int length = _queue_length[prio];);

  assert(length >= 0, "sanity check");

  _queue_length[prio] = 0;

  VM_Operation* r = _queue[prio]->next();

  assert(r != _queue[prio], "cannot remove base element");

  // remove links to base element from head and tail

  r->set_prev(NULL);

  _queue[prio]->prev()->set_next(NULL);

  // restore queue to empty state

  _queue[prio]->set_next(_queue[prio]);

  _queue[prio]->set_prev(_queue[prio]);

  assert(queue_empty(prio), "drain corrupted queue")

#ifdef DEBUG

  int len = 0;

  VM_Operation* cur;

  for(cur = r; cur != NULL; cur=cur->next()) len++;

  assert(len == length, "drain lost some ops");

#endif

  return r;

}

void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) {

  VM_Operation* cur = _queue[queue];

  cur = cur->next();

  while (cur != _queue[queue]) {

    cur->oops_do(f);

    cur = cur->next();

  }

}

void VMOperationQueue::drain_list_oops_do(OopClosure* f) {

  VM_Operation* cur = _drain_list;

  while (cur != NULL) {

    cur->oops_do(f);

    cur = cur->next();

  }

}

//-----------------------------------------------------------------

// High-level interface

bool VMOperationQueue::add(VM_Operation *op) {

  // Encapsulates VM queue policy. Currently, that

  // only involves putting them on the right list

  if (op->evaluate_at_safepoint()) {

    queue_add_back(SafepointPriority, op);

    return true;

  }

  queue_add_back(MediumPriority, op);

  return true;

}

VM_Operation* VMOperationQueue::remove_next() {

  // Assuming VMOperation queue is two-level priority queue. If there are

  // more than two priorities, we need a different scheduling algorithm.

  assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2,

         "current algorithm does not work");

  // simple counter based scheduling to prevent starvation of lower priority

  // queue. -- see 4390175

  int high_prio, low_prio;

  if (_queue_counter++ < 10) {

      high_prio = SafepointPriority;

      low_prio  = MediumPriority;

  } else {

      _queue_counter = 0;

      high_prio = MediumPriority;

      low_prio  = SafepointPriority;

  }

  return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio);

}

void VMOperationQueue::oops_do(OopClosure* f) {

  for(int i = 0; i < nof_priorities; i++) {

    queue_oops_do(i, f);

  }

  drain_list_oops_do(f);

}

//------------------------------------------------------------------------------------------------------------------

// Implementation of VMThread stuff

bool                VMThread::_should_terminate   = false;

bool              VMThread::_terminated         = false;

Monitor*          VMThread::_terminate_lock     = NULL;

VMThread*         VMThread::_vm_thread          = NULL;

VM_Operation*     VMThread::_cur_vm_operation   = NULL;

VMOperationQueue* VMThread::_vm_queue           = NULL;

PerfCounter*      VMThread::_perf_accumulated_vm_operation_time = NULL;

void VMThread::create() {

  assert(vm_thread() == NULL, "we can only allocate one VMThread");

  _vm_thread = new VMThread();

  // Create VM operation queue

  _vm_queue = new VMOperationQueue();

  guarantee(_vm_queue != NULL, "just checking");

  _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true);

  if (UsePerfData) {

    // jvmstat performance counters

    Thread* THREAD = Thread::current();

    _perf_accumulated_vm_operation_time =

                 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime",

                                                 PerfData::U_Ticks, CHECK);

  }

}

VMThread::VMThread() : Thread() {

  // nothing to do

}

void VMThread::destroy() {

  if (_vm_thread != NULL) {

    delete _vm_thread;

    _vm_thread = NULL;      // VM thread is gone

  }

}

void VMThread::run() {

  assert(this == vm_thread(), "check");

  this->initialize_thread_local_storage();

  this->record_stack_base_and_size();

  // Notify_lock wait checks on active_handles() to rewait in

  // case of spurious wakeup, it should wait on the last

  // value set prior to the notify

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

  {

    MutexLocker ml(Notify_lock);

    Notify_lock->notify();

  }

  // Notify_lock is destroyed by Threads::create_vm()

  int prio = (VMThreadPriority == -1)

    ? os::java_to_os_priority[NearMaxPriority]

    : VMThreadPriority;

  // Note that I cannot call os::set_priority because it expects Java

  // priorities and I am *explicitly* using OS priorities so that it's

  // possible to set the VM thread priority higher than any Java thread.

  os::set_native_priority( this, prio );

  // Wait for VM_Operations until termination

  this->loop();

  // Note the intention to exit before safepointing.

  // 6295565  This has the effect of waiting for any large tty

  // outputs to finish.

  if (xtty != NULL) {

    ttyLocker ttyl;

    xtty->begin_elem("destroy_vm");

    xtty->stamp();

    xtty->end_elem();

    assert(should_terminate(), "termination flag must be set");

  }

  // 4526887 let VM thread exit at Safepoint

  SafepointSynchronize::begin();

  if (VerifyBeforeExit) {

    HandleMark hm(VMThread::vm_thread());

    // Among other things, this ensures that Eden top is correct.

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

    os::check_heap();

    Universe::verify(true, true); // Silent verification to not polute normal output

  }

  CompileBroker::set_should_block();

  // wait for threads (compiler threads or daemon threads) in the

  // _thread_in_native state to block.

  VM_Exit::wait_for_threads_in_native_to_block();

  // signal other threads that VM process is gone

  {

    // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows

    // VM thread to enter any lock at Safepoint as long as its _owner is NULL.

    // If that happens after _terminate_lock->wait() has unset _owner

    // but before it actually drops the lock and waits, the notification below

    // may get lost and we will have a hang. To avoid this, we need to use

    // Mutex::lock_without_safepoint_check().

    MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);

    _terminated = true;

    _terminate_lock->notify();

  }

  // Deletion must be done synchronously by the JNI DestroyJavaVM thread

  // so that the VMThread deletion completes before the main thread frees

  // up the CodeHeap.

}

// Notify the VMThread that the last non-daemon JavaThread has terminated,

// and wait until operation is performed.

void VMThread::wait_for_vm_thread_exit() {

  { MutexLocker mu(VMOperationQueue_lock);

    _should_terminate = true;

    VMOperationQueue_lock->notify();

  }

  // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint

  // because this thread has been removed from the threads list. But anything

  // that could get blocked by Safepoint should not be used after this point,

  // otherwise we will hang, since there is no one can end the safepoint.

  // Wait until VM thread is terminated

  // Note: it should be OK to use Terminator_lock here. But this is called

  // at a very delicate time (VM shutdown) and we are operating in non- VM

  // thread at Safepoint. It's safer to not share lock with other threads.

  { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);

    while(!VMThread::is_terminated()) {

        _terminate_lock->wait(Mutex::_no_safepoint_check_flag);

    }

  }

}

void VMThread::print_on(outputStream* st) const {

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

  Thread::print_on(st);

  st->cr();

}

void VMThread::evaluate_operation(VM_Operation* op) {

  ResourceMark rm;

  {

    PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time());

    op->evaluate();

  }

  // Last access of info in _cur_vm_operation!

  bool c_heap_allocated = op->is_cheap_allocated();

  // Mark as completed

  if (!op->evaluate_concurrently()) {

    op->calling_thread()->increment_vm_operation_completed_count();

  }

  // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call,

  // since if it is stack allocated the calling thread might have deallocated

  if (c_heap_allocated) {

    delete _cur_vm_operation;

  }

}

void VMThread::loop() {

  assert(_cur_vm_operation == NULL, "no current one should be executing");

  while(true) {

    VM_Operation* safepoint_ops = NULL;

    //

    // Wait for VM operation

    //

    // use no_safepoint_check to get lock without attempting to "sneak"

    { MutexLockerEx mu_queue(VMOperationQueue_lock,

                             Mutex::_no_safepoint_check_flag);

      // Look for new operation

      assert(_cur_vm_operation == NULL, "no current one should be executing");

      _cur_vm_operation = _vm_queue->remove_next();

      // Stall time tracking code

      if (PrintVMQWaitTime && _cur_vm_operation != NULL &&

          !_cur_vm_operation->evaluate_concurrently()) {

        long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp();

        if (stall > 0)

          tty->print_cr("%s stall: %Ld",  _cur_vm_operation->name(), stall);

      }

      while (!should_terminate() && _cur_vm_operation == NULL) {

        // wait with a timeout to guarantee safepoints at regular intervals

        bool timedout =

          VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag,

                                      GuaranteedSafepointInterval);

        // Support for self destruction

        if ((SelfDestructTimer != 0) && !is_error_reported() &&

            (os::elapsedTime() > SelfDestructTimer * 60)) {

          tty->print_cr("VM self-destructed");

          exit(-1);

        }

        if (timedout && (SafepointALot ||

                         SafepointSynchronize::is_cleanup_needed())) {

          MutexUnlockerEx mul(VMOperationQueue_lock,

                              Mutex::_no_safepoint_check_flag);

          // Force a safepoint since we have not had one for at least

          // 'GuaranteedSafepointInterval' milliseconds.  This will run all

          // the clean-up processing that needs to be done regularly at a

          // safepoint

          SafepointSynchronize::begin();

          #ifdef ASSERT

            if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot();

          #endif

          SafepointSynchronize::end();

        }

        _cur_vm_operation = _vm_queue->remove_next();

        // If we are at a safepoint we will evaluate all the operations that

        // follow that also require a safepoint

        if (_cur_vm_operation != NULL &&

            _cur_vm_operation->evaluate_at_safepoint()) {

          safepoint_ops = _vm_queue->drain_at_safepoint_priority();

        }

      }

      if (should_terminate()) break;

    } // Release mu_queue_lock

    //

    // Execute VM operation

    //

    { HandleMark hm(VMThread::vm_thread());

      EventMark em("Executing VM operation: %s", vm_operation()->name());

      assert(_cur_vm_operation != NULL, "we should have found an operation to execute");

      // Give the VM thread an extra quantum.  Jobs tend to be bursty and this

      // helps the VM thread to finish up the job.

      // FIXME: When this is enabled and there are many threads, this can degrade

      // performance significantly.

      if( VMThreadHintNoPreempt )

        os::hint_no_preempt();

      // If we are at a safepoint we will evaluate all the operations that

      // follow that also require a safepoint

      if (_cur_vm_operation->evaluate_at_safepoint()) {

        if (PrintGCApplicationConcurrentTime) {

           gclog_or_tty->print_cr("Application time: %3.7f seconds",

                                  RuntimeService::last_application_time_sec());

        }

        _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned

        SafepointSynchronize::begin();

        evaluate_operation(_cur_vm_operation);

        // now process all queued safepoint ops, iteratively draining

        // the queue until there are none left

        do {

          _cur_vm_operation = safepoint_ops;

          if (_cur_vm_operation != NULL) {

            do {

              // evaluate_operation deletes the op object so we have

              // to grab the next op now

              VM_Operation* next = _cur_vm_operation->next();

              _vm_queue->set_drain_list(next);

              evaluate_operation(_cur_vm_operation);

              _cur_vm_operation = next;

              if (PrintSafepointStatistics) {

                SafepointSynchronize::inc_vmop_coalesced_count();

              }

            } while (_cur_vm_operation != NULL);

          }

          // There is a chance that a thread enqueued a safepoint op

          // since we released the op-queue lock and initiated the safepoint.

          // So we drain the queue again if there is anything there, as an

          // optimization to try and reduce the number of safepoints.

          // As the safepoint synchronizes us with JavaThreads we will see

          // any enqueue made by a JavaThread, but the peek will not

          // necessarily detect a concurrent enqueue by a GC thread, but

          // that simply means the op will wait for the next major cycle of the

          // VMThread - just as it would if the GC thread lost the race for

          // the lock.

          if (_vm_queue->peek_at_safepoint_priority()) {

            // must hold lock while draining queue

            MutexLockerEx mu_queue(VMOperationQueue_lock,

                                     Mutex::_no_safepoint_check_flag);

            safepoint_ops = _vm_queue->drain_at_safepoint_priority();

          } else {

            safepoint_ops = NULL;

          }

        } while(safepoint_ops != NULL);

        _vm_queue->set_drain_list(NULL);

        // Complete safepoint synchronization

        SafepointSynchronize::end();

        if (PrintGCApplicationStoppedTime) {

          gclog_or_tty->print_cr("Total time for which application threads "

                                 "were stopped: %3.7f seconds",

                                 RuntimeService::last_safepoint_time_sec());

        }

      } else {  // not a safepoint operation

        if (TraceLongCompiles) {

          elapsedTimer t;

          t.start();

          evaluate_operation(_cur_vm_operation);

          t.stop();

          double secs = t.seconds();

          if (secs * 1e3 > LongCompileThreshold) {

            // XXX - _cur_vm_operation should not be accessed after

            // the completed count has been incremented; the waiting

            // thread may have already freed this memory.

            tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs);

          }

        } else {

          evaluate_operation(_cur_vm_operation);

        }

        _cur_vm_operation = NULL;

      }

    }

    //

    //  Notify (potential) waiting Java thread(s) - lock without safepoint

    //  check so that sneaking is not possible

    { MutexLockerEx mu(VMOperationRequest_lock,

                       Mutex::_no_safepoint_check_flag);

      VMOperationRequest_lock->notify_all();

    }

    //

    // We want to make sure that we get to a safepoint regularly.

    //

    if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) {

      long interval          = SafepointSynchronize::last_non_safepoint_interval();

      bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval);

      if (SafepointALot || max_time_exceeded) {

        HandleMark hm(VMThread::vm_thread());

        SafepointSynchronize::begin();

        SafepointSynchronize::end();

      }

    }

  }

}