/*

 * Copyright (c) 1998, 2019, 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 "compiler/compileBroker.hpp"

#include "gc/shared/collectedHeap.hpp"

#include "jfr/jfrEvents.hpp"

#include "jfr/support/jfrThreadId.hpp"

#include "logging/log.hpp"

#include "logging/logStream.hpp"

#include "logging/logConfiguration.hpp"

#include "memory/resourceArea.hpp"

#include "memory/universe.hpp"

#include "oops/method.hpp"

#include "oops/oop.inline.hpp"

#include "oops/verifyOopClosure.hpp"

#include "runtime/atomic.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/interfaceSupport.inline.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/os.hpp"

#include "runtime/safepoint.hpp"

#include "runtime/thread.inline.hpp"

#include "runtime/vmThread.hpp"

#include "runtime/vmOperations.hpp"

#include "services/runtimeService.hpp"

#include "utilities/dtrace.hpp"

#include "utilities/events.hpp"

#include "utilities/vmError.hpp"

#include "utilities/xmlstream.hpp"

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]->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);

}

  _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 ASSERT

  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

void VMOperationQueue::add(VM_Operation *op) {

  HOTSPOT_VMOPS_REQUEST(

                   (char *) op->name(), strlen(op->name()),

  // Encapsulates VM queue policy. Currently, that

  // only involves putting them on the right list

}

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);

}

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

// Timeout machinery

void VMOperationTimeoutTask::task() {

  assert(AbortVMOnVMOperationTimeout, "only if enabled");

  if (is_armed()) {

    jlong delay = (os::javaTimeMillis() - _arm_time);

    if (delay > AbortVMOnVMOperationTimeoutDelay) {

      fatal("VM operation took too long: " JLONG_FORMAT " ms (timeout: " INTX_FORMAT " ms)",

            delay, AbortVMOnVMOperationTimeoutDelay);

    }

  }

}

bool VMOperationTimeoutTask::is_armed() {

  return Atomic::load_acquire(&_armed) != 0;

}

void VMOperationTimeoutTask::arm() {

  _arm_time = os::javaTimeMillis();

  Atomic::release_store_fence(&_armed, 1);

}

void VMOperationTimeoutTask::disarm() {

  Atomic::release_store_fence(&_armed, 0);

}

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

// 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;

uint64_t          VMThread::_coalesced_count = 0;

VMOperationTimeoutTask* VMThread::_timeout_task = NULL;

void VMThread::create() {

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

  _vm_thread = new VMThread();

  if (AbortVMOnVMOperationTimeout) {

    // Make sure we call the timeout task frequently enough, but not too frequent.

    // Try to make the interval 10% of the timeout delay, so that we miss the timeout

    // by those 10% at max. Periodic task also expects it to fit min/max intervals.

    size_t interval = (size_t)AbortVMOnVMOperationTimeoutDelay / 10;

    interval = interval / PeriodicTask::interval_gran * PeriodicTask::interval_gran;

    interval = MAX2<size_t>(interval, PeriodicTask::min_interval);

    interval = MIN2<size_t>(interval, PeriodicTask::max_interval);

    _timeout_task = new VMOperationTimeoutTask(interval);

    _timeout_task->enroll();

  } else {

    assert(_timeout_task == NULL, "sanity");

  }

  // Create VM operation queue

  _vm_queue = new VMOperationQueue();

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

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

                                Monitor::_safepoint_check_never);

  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() : NamedThread() {

  set_name("VM Thread");

}

void VMThread::destroy() {

  _vm_thread = NULL;      // VM thread is gone

}

static VM_None halt_op("Halt");

void VMThread::run() {

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

  // 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

  _cur_vm_operation = &halt_op;

  SafepointSynchronize::begin();

  if (VerifyBeforeExit) {

    HandleMark hm(VMThread::vm_thread());

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

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

    // Silent verification so as not to pollute normal output,

    // unless we really asked for it.

    Universe::verify();

  }

  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().

    MonitorLocker ml(_terminate_lock, Mutex::_no_safepoint_check_flag);

    _terminated = true;

    ml.notify();

  }

  // We are now racing with the VM termination being carried out in

  // another thread, so we don't "delete this". Numerous threads don't

  // get deleted when the VM terminates

}

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

// and wait until operation is performed.

void VMThread::wait_for_vm_thread_exit() {

  assert(Thread::current()->is_Java_thread(), "Should be a JavaThread");

  assert(((JavaThread*)Thread::current())->is_terminated(), "Should be terminated");

  { MonitorLocker mu(VMOperationQueue_lock, Mutex::_no_safepoint_check_flag);

    _should_terminate = true;

    mu.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.

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

    while(!VMThread::is_terminated()) {

      ml.wait();

    }

  }

}

static void post_vm_operation_event(EventExecuteVMOperation* event, VM_Operation* op) {

  assert(event != NULL, "invariant");

  assert(event->should_commit(), "invariant");

  assert(op != NULL, "invariant");

  const bool evaluate_at_safepoint = op->evaluate_at_safepoint();

  event->set_operation(op->type());

  event->set_safepoint(evaluate_at_safepoint);

  event->set_safepointId(evaluate_at_safepoint ? SafepointSynchronize::safepoint_id() : 0);

  event->commit();

}

void VMThread::evaluate_operation(VM_Operation* op) {

  ResourceMark rm;

  {

    PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time());

    HOTSPOT_VMOPS_BEGIN(

                     (char *) op->name(), strlen(op->name()),

    EventExecuteVMOperation event;

    op->evaluate();

    if (event.should_commit()) {

      post_vm_operation_event(&event, op);

    }

    HOTSPOT_VMOPS_END(

                     (char *) op->name(), strlen(op->name()),

  }

  // Mark as completed

}

static VM_None    safepointALot_op("SafepointALot");

static VM_Cleanup cleanup_op;

class HandshakeALotTC : public ThreadClosure {

 public:

  virtual void do_thread(Thread* thread) {

#ifdef ASSERT

    assert(thread->is_Java_thread(), "must be");

    JavaThread* jt = (JavaThread*)thread;

    jt->verify_states_for_handshake();

#endif

  }

};

VM_Operation* VMThread::no_op_safepoint() {

  // Check for handshakes first since we may need to return a VMop.

  if (HandshakeALot) {

    HandshakeALotTC haltc;

    Handshake::execute(&haltc);

  }

  // Check for a cleanup before SafepointALot to keep stats correct.

  long interval_ms = SafepointTracing::time_since_last_safepoint_ms();

  bool max_time_exceeded = GuaranteedSafepointInterval != 0 &&

                           (interval_ms >= GuaranteedSafepointInterval);

    return &cleanup_op;

  }

  if (SafepointALot) {

    return &safepointALot_op;

  }

  // Nothing to be done.

  return NULL;

}

void VMThread::loop() {

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

  SafepointSynchronize::init(_vm_thread);

  while(true) {

    VM_Operation* safepoint_ops = NULL;

    //

    // Wait for VM operation

    //

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

    { MonitorLocker 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

        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

        // Support for self destruction

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

            (os::elapsedTime() > (double)SelfDestructTimer * 60.0)) {

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

          exit(-1);

        }

          // Have to unlock VMOperationQueue_lock just in case no_op_safepoint()

          MutexUnlocker mul(VMOperationQueue_lock, Mutex::_no_safepoint_check_flag);

          if ((_cur_vm_operation = VMThread::no_op_safepoint()) != NULL) {

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

            // 'GuaranteedSafepointInterval' milliseconds and we need to clean

            // something. This will run all the clean-up processing that needs

            // to be done at a safepoint.

            SafepointSynchronize::begin();

            #ifdef ASSERT

            if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot();

            #endif

            SafepointSynchronize::end();