YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you 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.

//

// 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 <mutex>

#include <string>

#include <thread>

#include <vector>

#include "yb/gutil/atomicops.h"

#include "yb/util/rwc_lock.h"

#include "yb/util/test_util.h"

#include "yb/util/locks.h"

namespace yb {

using base::subtle::NoBarrier_Load;

using base::subtle::Release_Store;

using std::string;

using std::vector;

class RWCLockTest : public YBTest {};

// Holds counters of how many threads hold the lock in each of the

// provided modes.

struct LockHoldersCount {

  LockHoldersCount()

    : num_readers(0),

      num_writers(0),

      num_committers(0) {

  }

  // Check the invariants of the lock counts.

  void CheckInvariants() {

    // At no time should we have more than one writer or committer.

    CHECK_LE(num_writers, 1);

    CHECK_LE(num_committers, 1);

    // If we have any readers, then we should not have any committers.

    if (num_readers > 0) {

      CHECK_EQ(num_committers, 0);

    }

  }

  void AdjustReaders(int delta) {

    std::lock_guard<simple_spinlock> l(lock);

    num_readers += delta;

    CheckInvariants();

  }

  void AdjustWriters(int delta) {

    std::lock_guard<simple_spinlock> l(lock);

    num_writers += delta;

    CheckInvariants();

  }

  void AdjustCommitters(int delta) {

    std::lock_guard<simple_spinlock> l(lock);

    num_committers += delta;

    CheckInvariants();

  }

  int num_readers;

  int num_writers;

  int num_committers;

  simple_spinlock lock;

};

struct SharedState {

  LockHoldersCount counts;

  RWCLock rwc_lock;

  Atomic32 stop;

};

void ReaderThread(SharedState* state) {

  while (!NoBarrier_Load(&state->stop)) {

    state->rwc_lock.ReadLock();

    state->counts.AdjustReaders(1);

    state->counts.AdjustReaders(-1);

    state->rwc_lock.ReadUnlock();

  }

}

void WriterThread(SharedState* state) {

  string local_str;

  while (!NoBarrier_Load(&state->stop)) {

    state->rwc_lock.WriteLock();

    state->counts.AdjustWriters(1);

    state->rwc_lock.UpgradeToCommitLock();

    state->counts.AdjustWriters(-1);

    state->counts.AdjustCommitters(1);

    state->counts.AdjustCommitters(-1);

    state->rwc_lock.CommitUnlock();

  }

}

TEST_F(RWCLockTest, TestCorrectBehavior) {

  SharedState state;

  Release_Store(&state.stop, 0);

  std::vector<std::thread> threads;

  const int kNumWriters = 5;

  const int kNumReaders = 5;

  for (int i = 0; i < kNumWriters; i++) {

    threads.emplace_back(std::bind(WriterThread, &state));

  }

  for (int i = 0; i < kNumReaders; i++) {

    threads.emplace_back(std::bind(ReaderThread, &state));

  }

  if (AllowSlowTests()) {

    SleepFor(MonoDelta::FromSeconds(1));

  } else {

    SleepFor(MonoDelta::FromMilliseconds(100));

  }

  Release_Store(&state.stop, 1);

  for (auto& t : threads) {

    t.join();

  }

}

} // namespace yb