/*

 * Copyright (c) 2017, 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 "memory/allocation.inline.hpp"

#include "runtime/thread.inline.hpp"

#include "runtime/threadSMR.hpp"

#include "services/threadService.hpp"

// 'entries + 1' so we always have at least one entry.

ThreadsList::ThreadsList(int entries) : _length(entries), _threads(NEW_C_HEAP_ARRAY(JavaThread*, entries + 1, mtThread)), _next_list(NULL) {

  *(JavaThread**)(_threads + entries) = NULL;  // Make sure the extra entry is NULL.

}

ThreadsList::~ThreadsList() {

  FREE_C_HEAP_ARRAY(JavaThread*, _threads);

}

ThreadsListSetter::~ThreadsListSetter() {

  if (_target_needs_release) {

    // The hazard ptr in the target needs to be released.

    Threads::release_stable_list(_target);

  }

}

void ThreadsListSetter::set() {

  assert(_target->get_threads_hazard_ptr() == NULL, "hazard ptr should not already be set");

  (void) Threads::acquire_stable_list(_target, /* is_ThreadsListSetter */ true);

  _target_needs_release = true;

}

ThreadsListHandle::ThreadsListHandle(Thread *self) : _list(Threads::acquire_stable_list(self, /* is_ThreadsListSetter */ false)), _self(self) {

  assert(self == Thread::current(), "sanity check");

  if (EnableThreadSMRStatistics) {

    _timer.start();

  }

}

ThreadsListHandle::~ThreadsListHandle() {

  Threads::release_stable_list(_self);

  if (EnableThreadSMRStatistics) {

    _timer.stop();

    uint millis = (uint)_timer.milliseconds();

    Threads::inc_smr_tlh_cnt();

    Threads::add_smr_tlh_times(millis);

    Threads::update_smr_tlh_time_max(millis);

  }

}

// Convert an internal thread reference to a JavaThread found on the

// associated ThreadsList. This ThreadsListHandle "protects" the

// returned JavaThread *.

//

// If thread_oop_p is not NULL, then the caller wants to use the oop

// after this call so the oop is returned. On success, *jt_pp is set

// to the converted JavaThread * and true is returned. On error,

// returns false.

//

bool ThreadsListHandle::cv_internal_thread_to_JavaThread(jobject jthread,

                                                         JavaThread ** jt_pp,

                                                         oop * thread_oop_p) {

  assert(this->list() != NULL, "must have a ThreadsList");

  assert(jt_pp != NULL, "must have a return JavaThread pointer");

  // thread_oop_p is optional so no assert()

  // The JVM_* interfaces don't allow a NULL thread parameter; JVM/TI

  // allows a NULL thread parameter to signify "current thread" which

  // allows us to avoid calling cv_external_thread_to_JavaThread().

  // The JVM_* interfaces have no such leeway.

  oop thread_oop = JNIHandles::resolve_non_null(jthread);

  // Looks like an oop at this point.

  if (thread_oop_p != NULL) {

    // Return the oop to the caller; the caller may still want

    // the oop even if this function returns false.

    *thread_oop_p = thread_oop;

  }

  JavaThread *java_thread = java_lang_Thread::thread(thread_oop);

  if (java_thread == NULL) {

    // The java.lang.Thread does not contain a JavaThread * so it has

    // not yet run or it has died.

    return false;

  }

  // Looks like a live JavaThread at this point.

  if (java_thread != JavaThread::current()) {

    // jthread is not for the current JavaThread so have to verify

    // the JavaThread * against the ThreadsList.

    if (EnableThreadSMRExtraValidityChecks && !includes(java_thread)) {

      // Not on the JavaThreads list so it is not alive.

      return false;

    }

  }

  // Return a live JavaThread that is "protected" by the

  // ThreadsListHandle in the caller.

  *jt_pp = java_thread;

  return true;

}