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// Copyright 2017 The Abseil Authors.
//
// 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
//
// https://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 "absl/synchronization/barrier.h"
#include <thread> // NOLINT(build/c++11)
#include <vector>
#include "gtest/gtest.h"
#include "absl/synchronization/mutex.h"
#include "absl/time/clock.h"
TEST(Barrier, SanityTest) {
constexpr int kNumThreads = 10;
absl::Barrier* barrier = new absl::Barrier(kNumThreads);
absl::Mutex mutex;
int counter = 0; // Guarded by mutex.
auto thread_func = [&] {
if (barrier->Block()) {
// This thread is the last thread to reach the barrier so it is
// responsible for deleting it.
delete barrier;
}
// Increment the counter.
absl::MutexLock lock(&mutex);
++counter;
};
// Start (kNumThreads - 1) threads running thread_func.
std::vector<std::thread> threads;
for (int i = 0; i < kNumThreads - 1; ++i) {
threads.push_back(std::thread(thread_func));
}
// Give (kNumThreads - 1) threads a chance to reach the barrier.
// This test assumes at least one thread will have run after the
// sleep has elapsed. Sleeping in a test is usually bad form, but we
// need to make sure that we are testing the barrier instead of some
// other synchronization method.
absl::SleepFor(absl::Seconds(1));
// The counter should still be zero since no thread should have
// been able to pass the barrier yet.
{
absl::MutexLock lock(&mutex);
EXPECT_EQ(counter, 0);
}
// Start 1 more thread. This should make all threads pass the barrier.
threads.push_back(std::thread(thread_func));
// All threads should now be able to proceed and finish.
for (auto& thread : threads) {
thread.join();
}
// All threads should now have incremented the counter.
absl::MutexLock lock(&mutex);
EXPECT_EQ(counter, kNumThreads);
}
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