| // 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 |
| // |
| // 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 "absl/base/call_once.h" |
| |
| #include <thread> |
| #include <vector> |
| |
| #include "gtest/gtest.h" |
| #include "absl/base/thread_annotations.h" |
| #include "absl/synchronization/mutex.h" |
| |
| namespace absl { |
| inline namespace lts_2018_12_18 { |
| namespace { |
| |
| absl::once_flag once; |
| Mutex counters_mu; |
| |
| int running_thread_count GUARDED_BY(counters_mu) = 0; |
| int call_once_invoke_count GUARDED_BY(counters_mu) = 0; |
| int call_once_finished_count GUARDED_BY(counters_mu) = 0; |
| int call_once_return_count GUARDED_BY(counters_mu) = 0; |
| bool done_blocking GUARDED_BY(counters_mu) = false; |
| |
| // Function to be called from absl::call_once. Waits for a notification. |
| void WaitAndIncrement() { |
| counters_mu.Lock(); |
| ++call_once_invoke_count; |
| counters_mu.Unlock(); |
| |
| counters_mu.LockWhen(Condition(&done_blocking)); |
| ++call_once_finished_count; |
| counters_mu.Unlock(); |
| } |
| |
| void ThreadBody() { |
| counters_mu.Lock(); |
| ++running_thread_count; |
| counters_mu.Unlock(); |
| |
| absl::call_once(once, WaitAndIncrement); |
| |
| counters_mu.Lock(); |
| ++call_once_return_count; |
| counters_mu.Unlock(); |
| } |
| |
| // Returns true if all threads are set up for the test. |
| bool ThreadsAreSetup(void*) EXCLUSIVE_LOCKS_REQUIRED(counters_mu) { |
| // All ten threads must be running, and WaitAndIncrement should be blocked. |
| return running_thread_count == 10 && call_once_invoke_count == 1; |
| } |
| |
| TEST(CallOnceTest, ExecutionCount) { |
| std::vector<std::thread> threads; |
| |
| // Start 10 threads all calling call_once on the same once_flag. |
| for (int i = 0; i < 10; ++i) { |
| threads.emplace_back(ThreadBody); |
| } |
| |
| |
| // Wait until all ten threads have started, and WaitAndIncrement has been |
| // invoked. |
| counters_mu.LockWhen(Condition(ThreadsAreSetup, nullptr)); |
| |
| // WaitAndIncrement should have been invoked by exactly one call_once() |
| // instance. That thread should be blocking on a notification, and all other |
| // call_once instances should be blocking as well. |
| EXPECT_EQ(call_once_invoke_count, 1); |
| EXPECT_EQ(call_once_finished_count, 0); |
| EXPECT_EQ(call_once_return_count, 0); |
| |
| // Allow WaitAndIncrement to finish executing. Once it does, the other |
| // call_once waiters will be unblocked. |
| done_blocking = true; |
| counters_mu.Unlock(); |
| |
| for (std::thread& thread : threads) { |
| thread.join(); |
| } |
| |
| counters_mu.Lock(); |
| EXPECT_EQ(call_once_invoke_count, 1); |
| EXPECT_EQ(call_once_finished_count, 1); |
| EXPECT_EQ(call_once_return_count, 10); |
| counters_mu.Unlock(); |
| } |
| |
| } // namespace |
| } // inline namespace lts_2018_12_18 |
| } // namespace absl |