jdk/src/hotspot/share/runtime/threadSMR.inline.hpp

/*
 * Copyright (c) 2017, 2025, 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.
 *
 */

#ifndef SHARE_RUNTIME_THREADSMR_INLINE_HPP
#define SHARE_RUNTIME_THREADSMR_INLINE_HPP

#include "runtime/threadSMR.hpp"

#include "gc/shared/gc_globals.hpp"
#include "gc/shared/tlab_globals.hpp"
#include "memory/iterator.hpp"
#include "runtime/atomicAccess.hpp"
#include "runtime/javaThread.hpp"
#include "runtime/prefetch.inline.hpp"
#include "utilities/debug.hpp"
#include "utilities/macros.hpp"

ThreadsList::Iterator::Iterator(ThreadsList* list, uint i) :
  _thread_ptr(list->threads() + check_index(list, i))
  DEBUG_ONLY(COMMA _list(list))
{}

bool ThreadsList::Iterator::operator==(Iterator i) const {
  assert_not_singular();
  assert_same_list(i);
  return _thread_ptr == i._thread_ptr;
}

bool ThreadsList::Iterator::operator!=(Iterator i) const {
  return !operator==(i);
}

JavaThread* ThreadsList::Iterator::operator*() const {
  assert_not_singular();
  assert_dereferenceable();
  Prefetch::read(const_cast<JavaThread**>(_thread_ptr), PrefetchScanIntervalInBytes);
  return *_thread_ptr;
}

JavaThread* ThreadsList::Iterator::operator->() const {
  return operator*();
}

ThreadsList::Iterator& ThreadsList::Iterator::operator++() {
  assert_not_singular();
  assert_dereferenceable();
  ++_thread_ptr;
  return *this;
}

ThreadsList::Iterator ThreadsList::Iterator::operator++(int) {
  assert_not_singular();
  assert_dereferenceable();
  Iterator result = *this;
  ++_thread_ptr;
  return result;
}

ThreadsList::Iterator ThreadsList::begin() {
  return Iterator(this, 0);
}

ThreadsList::Iterator ThreadsList::end() {
  return Iterator(this, length());
}

// Devirtualize known thread closure types.
template <class T>
inline void ThreadsList::threads_do_dispatch(T *cl, JavaThread *const thread) const {
  cl->T::do_thread(thread);
}

template <>
inline void ThreadsList::threads_do_dispatch<ThreadClosure>(ThreadClosure *cl, JavaThread *const thread) const {
  cl->do_thread(thread);
}

template <class T>
inline void ThreadsList::threads_do(T *cl) const {
  const intx scan_interval = PrefetchScanIntervalInBytes;
  JavaThread *const *const end = _threads + _length;
  for (JavaThread *const *current_p = _threads; current_p != end; current_p++) {
    Prefetch::read((void*)current_p, scan_interval);
    JavaThread *const current = *current_p;
    threads_do_dispatch(cl, current);
  }
}

ThreadsListHandle::Iterator ThreadsListHandle::begin() { return list()->begin(); }
ThreadsListHandle::Iterator ThreadsListHandle::end() { return list()->end(); }

// These three inlines are private to ThreadsSMRSupport, but
// they are called by public inline update_tlh_stats() below:

inline void ThreadsSMRSupport::add_tlh_times(uint add_value) {
  AtomicAccess::add(&_tlh_times, add_value);
}

inline void ThreadsSMRSupport::inc_tlh_cnt() {
  AtomicAccess::inc(&_tlh_cnt);
}

inline void ThreadsSMRSupport::update_tlh_time_max(uint new_value) {
  while (true) {
    uint cur_value = _tlh_time_max;
    if (new_value <= cur_value) {
      // No need to update max value so we're done.
      break;
    }
    if (AtomicAccess::cmpxchg(&_tlh_time_max, cur_value, new_value) == cur_value) {
      // Updated max value so we're done. Otherwise try it all again.
      break;
    }
  }
}

inline ThreadsList* ThreadsSMRSupport::get_java_thread_list() {
  return (ThreadsList*)AtomicAccess::load_acquire(&_java_thread_list);
}

inline bool ThreadsSMRSupport::is_a_protected_JavaThread_with_lock(JavaThread *thread) {
  ConditionalMutexLocker ml(Threads_lock, !Threads_lock->owned_by_self());
  return is_a_protected_JavaThread(thread);
}

inline void ThreadsSMRSupport::update_tlh_stats(uint millis) {
  ThreadsSMRSupport::inc_tlh_cnt();
  ThreadsSMRSupport::add_tlh_times(millis);
  ThreadsSMRSupport::update_tlh_time_max(millis);
}

#endif // SHARE_RUNTIME_THREADSMR_INLINE_HPP