YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

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

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// Portions Copyright (c) YugaByte, Inc.

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// 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

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

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

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#include <functional>

#include <thread>

#include <gtest/gtest.h>

#include "yb/util/monotime.h"

#include "yb/util/rw_semaphore.h"

#include "yb/util/shared_lock.h"

using std::vector;

namespace yb {

struct SharedState {

  SharedState() : done(false), int_var(0) {}

  bool done;

  int64_t int_var;

  rw_semaphore sem;

};

// Thread which increases the value in the shared state under the write lock.

void Writer(SharedState* state) {

  int i = 0;

  while (true) {

    std::lock_guard<rw_semaphore> l(state->sem);

    state->int_var += (i++);

    if (state->done) {

      break;

    }

  }

}

// Thread which verifies that the value in the shared state only increases.

void Reader(SharedState* state) {

  int64_t prev_val = 0;

  while (true) {

    SharedLock<rw_semaphore> l(state->sem);

    // The int var should only be seen to increase.

    CHECK_GE(state->int_var, prev_val);

    prev_val = state->int_var;

    if (state->done) {

      break;

    }

  }

}

// Test which verifies basic functionality of the semaphore.

// When run under TSAN this also verifies the barriers.

TEST(RWSemaphoreTest, TestBasicOperation) {

  SharedState s;

  vector<std::thread> threads;

  // Start 5 readers and writers.

  for (int i = 0; i < 5; i++) {

    threads.emplace_back(std::bind(Reader, &s));

    threads.emplace_back(std::bind(Writer, &s));

  }

  // Let them contend for a short amount of time.

  SleepFor(MonoDelta::FromMilliseconds(50));

  // Signal them to stop.

  {

    std::lock_guard<rw_semaphore> l(s.sem);

    s.done = true;

  }

  for (auto& t : threads) {

    t.join();

  }

}

} // namespace yb