/*

* Copyright (c) 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 "runtime/interfaceSupport.inline.hpp"

#include "runtime/thread.hpp"

#include "runtime/threadSMR.hpp"

#include "runtime/timerTrace.hpp"

#include "services/threadIdTable.hpp"

#include "utilities/concurrentHashTable.inline.hpp"

#include "utilities/concurrentHashTableTasks.inline.hpp"

typedef ConcurrentHashTable<ThreadIdTableConfig, mtInternal> ThreadIdTableHash;

// 2^24 is max size

static const size_t END_SIZE = 24;

// Default initial size 256

static const size_t DEFAULT_TABLE_SIZE_LOG = 8;

// Prefer short chains of avg 2

static const double PREF_AVG_LIST_LEN = 2.0;

static ThreadIdTableHash* volatile _local_table = NULL;

static volatile size_t _current_size = 0;

static volatile size_t _items_count = 0;

volatile bool ThreadIdTable::_is_initialized = false;

volatile bool ThreadIdTable::_has_work = false;

class ThreadIdTableEntry : public CHeapObj<mtInternal> {

private:

  jlong _tid;

  JavaThread* _java_thread;

public:

  ThreadIdTableEntry(jlong tid, JavaThread* java_thread) :

    _tid(tid), _java_thread(java_thread) {}

  jlong tid() const { return _tid; }

  JavaThread* thread() const { return _java_thread; }

};

class ThreadIdTableConfig : public AllStatic {

  public:

    typedef ThreadIdTableEntry* Value;

    static uintx get_hash(Value const& value, bool* is_dead) {

      jlong tid = value->tid();

      return primitive_hash(tid);

    }

    static void* allocate_node(size_t size, Value const& value) {

      ThreadIdTable::item_added();

      return AllocateHeap(size, mtInternal);

    }

    static void free_node(void* memory, Value const& value) {

      delete value;

      FreeHeap(memory);

      ThreadIdTable::item_removed();

    }

};

static size_t ceil_log2(size_t val) {

  size_t ret;

  for (ret = 1; ((size_t)1 << ret) < val; ++ret);

  return ret;

}

// Lazily creates the table and populates it with the given

// thread list

void ThreadIdTable::lazy_initialize(const ThreadsList *threads) {

  if (!_is_initialized) {

    {

      // There is no obvious benefits in allowing the thread table

      // to be concurently populated during the initalization.

      MutexLocker ml(ThreadIdTableCreate_lock);

      if (_is_initialized) {

        return;

      }

      create_table(threads->length());

      _is_initialized = true;

    }

    for (uint i = 0; i < threads->length(); i++) {

      JavaThread* thread = threads->thread_at(i);

      oop tobj = thread->threadObj();

      if (tobj != NULL) {

        jlong java_tid = java_lang_Thread::thread_id(tobj);

        MutexLocker ml(Threads_lock);

        if (!thread->is_exiting()) {

          // Must be inside the lock to ensure that we don't add a thread to the table

          // that has just passed the removal point in ThreadsSMRSupport::remove_thread()

          add_thread(java_tid, thread);

        }

      }

    }

  }

}

void ThreadIdTable::create_table(size_t size) {

  assert(_local_table == NULL, "Thread table is already created");

  size_t size_log = ceil_log2(size);

  size_t start_size_log =

      size_log > DEFAULT_TABLE_SIZE_LOG ? size_log : DEFAULT_TABLE_SIZE_LOG;

  _current_size = (size_t)1 << start_size_log;

  _local_table = new ThreadIdTableHash(start_size_log, END_SIZE);

}

void ThreadIdTable::item_added() {

  Atomic::inc(&_items_count);

  log_trace(thread, table) ("Thread entry added");

}

void ThreadIdTable::item_removed() {

  Atomic::dec(&_items_count);

  log_trace(thread, table) ("Thread entry removed");

}

double ThreadIdTable::get_load_factor() {

  return ((double)_items_count) / _current_size;

}

size_t ThreadIdTable::table_size() {

  return (size_t)1 << _local_table->get_size_log2(Thread::current());

}

void ThreadIdTable::check_concurrent_work() {

  if (_has_work) {

    return;

  }

  double load_factor = get_load_factor();

  // Resize if we have more items than preferred load factor

  if ( load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {

    log_debug(thread, table)("Concurrent work triggered, load factor: %g",

                             load_factor);

    trigger_concurrent_work();

  }

}

void ThreadIdTable::trigger_concurrent_work() {

  MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);

  _has_work = true;

  Service_lock->notify_all();

}

void ThreadIdTable::grow(JavaThread* jt) {

  ThreadIdTableHash::GrowTask gt(_local_table);

  if (!gt.prepare(jt)) {

    return;

  }

  log_trace(thread, table)("Started to grow");

  TraceTime timer("Grow", TRACETIME_LOG(Debug, membername, table, perf));

  while (gt.do_task(jt)) {

    gt.pause(jt);

    {

      ThreadBlockInVM tbivm(jt);

    }

    gt.cont(jt);

  }

  gt.done(jt);

  _current_size = table_size();

  log_info(thread, table)("Grown to size:" SIZE_FORMAT, _current_size);

}

class ThreadIdTableLookup : public StackObj {

private:

  jlong _tid;

  uintx _hash;

public:

  ThreadIdTableLookup(jlong tid)

    : _tid(tid), _hash(primitive_hash(tid)) {}

  uintx get_hash() const {

    return _hash;

  }

  bool equals(ThreadIdTableEntry** value, bool* is_dead) {

    bool equals = primitive_equals(_tid, (*value)->tid());

    if (!equals) {

      return false;

    }

    return true;

  }

};

class ThreadGet : public StackObj {

private:

  JavaThread* _return;

public:

  ThreadGet(): _return(NULL) {}

  void operator()(ThreadIdTableEntry** val) {

    _return = (*val)->thread();

  }

  JavaThread* get_res_thread() {

    return _return;

  }

};

void ThreadIdTable::do_concurrent_work(JavaThread* jt) {

  assert(_is_initialized, "Thread table is not initialized");

  _has_work = false;

  double load_factor = get_load_factor();

  log_debug(thread, table)("Concurrent work, load factor: %g", load_factor);

  if (load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {

    grow(jt);

  }

}

JavaThread* ThreadIdTable::add_thread(jlong tid, JavaThread* java_thread) {

  assert(_is_initialized, "Thread table is not initialized");

  Thread* thread = Thread::current();

  ThreadIdTableLookup lookup(tid);

  ThreadGet tg;

  while (true) {

    if (_local_table->get(thread, lookup, tg)) {

      return tg.get_res_thread();

    }

    ThreadIdTableEntry* entry = new ThreadIdTableEntry(tid, java_thread);

    // The hash table takes ownership of the ThreadTableEntry,

    // even if it's not inserted.

    if (_local_table->insert(thread, lookup, entry)) {

      check_concurrent_work();

      return java_thread;

    }

  }

}

JavaThread* ThreadIdTable::find_thread_by_tid(jlong tid) {

  assert(_is_initialized, "Thread table is not initialized");

  Thread* thread = Thread::current();

  ThreadIdTableLookup lookup(tid);

  ThreadGet tg;

  _local_table->get(thread, lookup, tg);

  return tg.get_res_thread();

}

bool ThreadIdTable::remove_thread(jlong tid) {

  assert(_is_initialized, "Thread table is not initialized");

  Thread* thread = Thread::current();

  ThreadIdTableLookup lookup(tid);

  return _local_table->remove(thread, lookup);

}