Function OverlapTest

be/src/util/cyclic-barrier-test.cc:81–98

Test where each thread calls Wait() in a tight loop, to exercise cases where calls to Wait() from different cycles can overlap. E.g. if there are two threads and a single processor, the following timing is possible: 1. Thread 1 runs, calls Wait() and blocks. 2. Thread 2 runs, calls Wait(), and notifies thread 1. 3. Thread 2 continues running, returns from Wait(), then calls Wait() again and blocks

// At step 3, thread 1 and 2 are both in Wait() but are in different cycles, hence the
// overlapping of the cycles.
void OverlapTest(int num_threads, int num_iters) {
  CyclicBarrier barrier(num_threads);
  int counter = 0;
  thread_group threads;
  for (int i = 0; i < num_threads; ++i) {
    threads.add_thread(new thread([&]() {
      for (int j = 0; j < num_iters; ++j) {
        EXPECT_OK(barrier.Wait([&counter]() {
          ++counter;
          return Status::OK();
        }));
      }
    }));
  }
  threads.join_all();
  // Counter should have been incremented by last arriving threads.
  EXPECT_EQ(num_iters, counter);
}

// Test many iterations of the barrier.
TEST(CyclicBarrierTest, Overlap) {