76 lines
2.3 KiB
C++
76 lines
2.3 KiB
C++
// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "absl/synchronization/barrier.h"
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#include <thread> // NOLINT(build/c++11)
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#include <vector>
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#include "gtest/gtest.h"
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#include "absl/synchronization/mutex.h"
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#include "absl/time/clock.h"
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TEST(Barrier, SanityTest) {
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constexpr int kNumThreads = 10;
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absl::Barrier* barrier = new absl::Barrier(kNumThreads);
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absl::Mutex mutex;
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int counter = 0; // Guarded by mutex.
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auto thread_func = [&] {
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if (barrier->Block()) {
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// This thread is the last thread to reach the barrier so it is
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// responsible for deleting it.
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delete barrier;
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}
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// Increment the counter.
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absl::MutexLock lock(&mutex);
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++counter;
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};
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// Start (kNumThreads - 1) threads running thread_func.
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std::vector<std::thread> threads;
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for (int i = 0; i < kNumThreads - 1; ++i) {
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threads.push_back(std::thread(thread_func));
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}
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// Give (kNumThreads - 1) threads a chance to reach the barrier.
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// This test assumes at least one thread will have run after the
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// sleep has elapsed. Sleeping in a test is usually bad form, but we
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// need to make sure that we are testing the barrier instead of some
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// other synchronization method.
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absl::SleepFor(absl::Seconds(1));
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// The counter should still be zero since no thread should have
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// been able to pass the barrier yet.
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{
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absl::MutexLock lock(&mutex);
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EXPECT_EQ(counter, 0);
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}
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// Start 1 more thread. This should make all threads pass the barrier.
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threads.push_back(std::thread(thread_func));
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// All threads should now be able to proceed and finish.
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for (auto& thread : threads) {
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thread.join();
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}
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// All threads should now have incremented the counter.
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absl::MutexLock lock(&mutex);
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EXPECT_EQ(counter, kNumThreads);
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}
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