YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.

//  This source code is licensed under the BSD-style license found in the

//  LICENSE file in the root directory of this source tree. An additional grant

//  of patent rights can be found in the PATENTS file in the same directory.

//

// The following only applies to changes made to this file as part of YugaByte development.

//

// Portions Copyright (c) YugaByte, Inc.

//

// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except

// in compliance with the License.  You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software distributed under the License

// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express

// or implied.  See the License for the specific language governing permissions and limitations

// under the License.

//

#include "yb/rocksdb/db/flush_scheduler.h"

#include <cassert>

#include "yb/rocksdb/db/column_family.h"

namespace rocksdb {

void FlushScheduler::ScheduleFlush(ColumnFamilyData* cfd) {

#ifndef NDEBUG

  {

    std::lock_guard<std::mutex> lock(checking_mutex_);

    assert(checking_set_.count(cfd) == 0);

    checking_set_.insert(cfd);

  }

#endif  // NDEBUG

  cfd->Ref();

  Node* node = new Node{cfd, head_.load(std::memory_order_relaxed)};

  while (!head_.compare_exchange_strong(

      node->next, node, std::memory_order_relaxed, std::memory_order_relaxed)) {

    // failing CAS updates the first param, so we are already set for

    // retry.  TakeNextColumnFamily won't happen until after another

    // inter-thread synchronization, so we don't even need release

    // semantics for this CAS

  }

}

ColumnFamilyData* FlushScheduler::TakeNextColumnFamily() {

  while (true) {

    if (Empty()) {

      return nullptr;

    }

    // dequeue the head

    Node* node = head_.load(std::memory_order_relaxed);

    head_.store(node->next, std::memory_order_relaxed);

    ColumnFamilyData* cfd = node->column_family;

    delete node;

#ifndef NDEBUG

    {

      auto iter = checking_set_.find(cfd);

      assert(iter != checking_set_.end());

      checking_set_.erase(iter);

    }

#endif  // NDEBUG

    if (!cfd->IsDropped()) {

      // success

      return cfd;

    }

    // no longer relevant, retry

    if (cfd->Unref()) {

      delete cfd;

    }

  }

}

bool FlushScheduler::Empty() {

  auto rv = head_.load(std::memory_order_relaxed) == nullptr;

  assert(rv == checking_set_.empty());

  return rv;

}

void FlushScheduler::Clear() {

  ColumnFamilyData* cfd;

  while ((cfd = TakeNextColumnFamily()) != nullptr) {

    if (cfd->Unref()) {

      delete cfd;

    }

  }

  assert(Empty());

}

}  // namespace rocksdb