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/*
* Copyright 2020 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "rtc_base/synchronization/mutex.h"
#include <stddef.h>
#include <stdint.h>
#include <atomic>
#include <memory>
#include <type_traits>
#include <utility>
#include <vector>
#include "benchmark/benchmark.h"
#include "rtc_base/checks.h"
#include "rtc_base/event.h"
#include "rtc_base/platform_thread.h"
#include "rtc_base/synchronization/yield.h"
#include "rtc_base/thread.h"
#include "test/gtest.h"
namespace webrtc {
namespace {
using ::rtc::Event;
using ::rtc::Thread;
constexpr int kNumThreads = 16;
template <class MutexType>
class RTC_LOCKABLE RawMutexLocker {
public:
explicit RawMutexLocker(MutexType& mutex) : mutex_(mutex) {}
void Lock() RTC_EXCLUSIVE_LOCK_FUNCTION() { mutex_.Lock(); }
void Unlock() RTC_UNLOCK_FUNCTION() { mutex_.Unlock(); }
private:
MutexType& mutex_;
};
class RTC_LOCKABLE RawMutexTryLocker {
public:
explicit RawMutexTryLocker(Mutex& mutex) : mutex_(mutex) {}
void Lock() RTC_EXCLUSIVE_LOCK_FUNCTION() {
while (!mutex_.TryLock()) {
YieldCurrentThread();
}
}
void Unlock() RTC_UNLOCK_FUNCTION() { mutex_.Unlock(); }
private:
Mutex& mutex_;
};
template <class MutexType, class MutexLockType>
class MutexLockLocker {
public:
explicit MutexLockLocker(MutexType& mutex) : mutex_(mutex) {}
void Lock() { lock_ = std::make_unique<MutexLockType>(&mutex_); }
void Unlock() { lock_ = nullptr; }
private:
MutexType& mutex_;
std::unique_ptr<MutexLockType> lock_;
};
template <class MutexType, class MutexLocker>
class LockRunner {
public:
template <typename... Args>
explicit LockRunner(Args... args)
: threads_active_(0),
start_event_(true, false),
done_event_(true, false),
shared_value_(0),
mutex_(args...),
locker_(mutex_) {}
bool Run() {
// Signal all threads to start.
start_event_.Set();
// Wait for all threads to finish.
return done_event_.Wait(kLongTime);
}
void SetExpectedThreadCount(int count) { threads_active_ = count; }
int shared_value() {
int shared_value;
locker_.Lock();
shared_value = shared_value_;
locker_.Unlock();
return shared_value;
}
void Loop() {
ASSERT_TRUE(start_event_.Wait(kLongTime));
locker_.Lock();
EXPECT_EQ(0, shared_value_);
int old = shared_value_;
// Use a loop to increase the chance of race. If the `locker_`
// implementation is faulty, it would be improbable that the error slips
// through.
for (int i = 0; i < kOperationsToRun; ++i) {
benchmark::DoNotOptimize(++shared_value_);
}
EXPECT_EQ(old + kOperationsToRun, shared_value_);
shared_value_ = 0;
locker_.Unlock();
if (threads_active_.fetch_sub(1) == 1) {
done_event_.Set();
}
}
private:
static constexpr TimeDelta kLongTime = TimeDelta::Seconds(10);
static constexpr int kOperationsToRun = 1000;
std::atomic<int> threads_active_;
Event start_event_;
Event done_event_;
int shared_value_;
MutexType mutex_;
MutexLocker locker_;
};
template <typename Runner>
void StartThreads(std::vector<std::unique_ptr<Thread>>& threads,
Runner* handler) {
for (int i = 0; i < kNumThreads; ++i) {
std::unique_ptr<Thread> thread(Thread::Create());
thread->Start();
thread->PostTask([handler] { handler->Loop(); });
threads.push_back(std::move(thread));
}
}
TEST(MutexTest, ProtectsSharedResourceWithMutexAndRawMutexLocker) {
std::vector<std::unique_ptr<Thread>> threads;
LockRunner<Mutex, RawMutexLocker<Mutex>> runner;
StartThreads(threads, &runner);
runner.SetExpectedThreadCount(kNumThreads);
EXPECT_TRUE(runner.Run());
EXPECT_EQ(0, runner.shared_value());
}
TEST(MutexTest, ProtectsSharedResourceWithMutexAndRawMutexTryLocker) {
std::vector<std::unique_ptr<Thread>> threads;
LockRunner<Mutex, RawMutexTryLocker> runner;
StartThreads(threads, &runner);
runner.SetExpectedThreadCount(kNumThreads);
EXPECT_TRUE(runner.Run());
EXPECT_EQ(0, runner.shared_value());
}
TEST(MutexTest, ProtectsSharedResourceWithMutexAndMutexLocker) {
std::vector<std::unique_ptr<Thread>> threads;
LockRunner<Mutex, MutexLockLocker<Mutex, MutexLock>> runner;
StartThreads(threads, &runner);
runner.SetExpectedThreadCount(kNumThreads);
EXPECT_TRUE(runner.Run());
EXPECT_EQ(0, runner.shared_value());
}
} // namespace
} // namespace webrtc
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