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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/notification.h"
#include <thread> // NOLINT(build/c++11)
#include <vector>
#include "gtest/gtest.h"
#include "absl/synchronization/mutex.h"
namespace absl {
// A thread-safe class that holds a counter.
class ThreadSafeCounter {
public:
ThreadSafeCounter() : count_(0) {}
void Increment() {
MutexLock lock(&mutex_);
++count_;
}
int Get() const {
MutexLock lock(&mutex_);
return count_;
}
void WaitUntilGreaterOrEqual(int n) {
MutexLock lock(&mutex_);
auto cond = [this, n]() { return count_ >= n; };
mutex_.Await(Condition(&cond));
}
private:
mutable Mutex mutex_;
int count_;
};
// Runs the |i|'th worker thread for the tests in BasicTests(). Increments the
// |ready_counter|, waits on the |notification|, and then increments the
// |done_counter|.
static void RunWorker(int i, ThreadSafeCounter* ready_counter,
Notification* notification,
ThreadSafeCounter* done_counter) {
ready_counter->Increment();
notification->WaitForNotification();
done_counter->Increment();
}
// Tests that the |notification| properly blocks and awakens threads. Assumes
// that the |notification| is not yet triggered. If |notify_before_waiting| is
// true, the |notification| is triggered before any threads are created, so the
// threads never block in WaitForNotification(). Otherwise, the |notification|
// is triggered at a later point when most threads are likely to be blocking in
// WaitForNotification().
static void BasicTests(bool notify_before_waiting, Notification* notification) {
EXPECT_FALSE(notification->HasBeenNotified());
EXPECT_FALSE(
notification->WaitForNotificationWithTimeout(absl::Milliseconds(0)));
EXPECT_FALSE(notification->WaitForNotificationWithDeadline(absl::Now()));
const absl::Duration delay = absl::Milliseconds(50);
const absl::Time start = absl::Now();
EXPECT_FALSE(notification->WaitForNotificationWithTimeout(delay));
const absl::Duration elapsed = absl::Now() - start;
// Allow for a slight early return, to account for quality of implementation
// issues on various platforms.
const absl::Duration slop = absl::Microseconds(200);
EXPECT_LE(delay - slop, elapsed)
<< "WaitForNotificationWithTimeout returned " << delay - elapsed
<< " early (with " << slop << " slop), start time was " << start;
ThreadSafeCounter ready_counter;
ThreadSafeCounter done_counter;
if (notify_before_waiting) {
notification->Notify();
}
// Create a bunch of threads that increment the |done_counter| after being
// notified.
const int kNumThreads = 10;
std::vector<std::thread> workers;
for (int i = 0; i < kNumThreads; ++i) {
workers.push_back(std::thread(&RunWorker, i, &ready_counter, notification,
&done_counter));
}
if (!notify_before_waiting) {
ready_counter.WaitUntilGreaterOrEqual(kNumThreads);
// Workers have not been notified yet, so the |done_counter| should be
// unmodified.
EXPECT_EQ(0, done_counter.Get());
notification->Notify();
}
// After notifying and then joining the workers, both counters should be
// fully incremented.
notification->WaitForNotification(); // should exit immediately
EXPECT_TRUE(notification->HasBeenNotified());
EXPECT_TRUE(notification->WaitForNotificationWithTimeout(absl::Seconds(0)));
EXPECT_TRUE(notification->WaitForNotificationWithDeadline(absl::Now()));
for (std::thread& worker : workers) {
worker.join();
}
EXPECT_EQ(kNumThreads, ready_counter.Get());
EXPECT_EQ(kNumThreads, done_counter.Get());
}
TEST(NotificationTest, SanityTest) {
Notification local_notification1, local_notification2;
BasicTests(false, &local_notification1);
BasicTests(true, &local_notification2);
}
} // namespace absl
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