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C++常用锁总结

news 来源：原创 2025/4/19 7:36:13

一、基础互斥锁 `std::mutex`

用途：保护共享资源的基础互斥锁

#include <iostream>
#include <thread>
#include <mutex>std::mutex mtx;
int shared_data = 0;void increment() {mtx.lock();for (int i = 0; i < 100000; ++i) {++shared_data;}mtx.unlock();
}int main() {std::thread t1(increment);std::thread t2(increment);t1.join();t2.join();std::cout << "Final value: " << shared_data << std::endl;// 正确输出 200000
}

编译命令：

g++ -std=c++11 -pthread example.cpp

二、RAII 锁 `std::lock_guard`

用途：自动管理锁的生命周期

#include <mutex>
#include <vector>
#include <thread>std::mutex mtx;
std::vector<int> vec;void add_element(int val) {std::lock_guard<std::mutex> lock(mtx); // 自动加锁/解锁vec.push_back(val);
}int main() {std::thread threads[5];for (int i = 0; i < 5; ++i) {threads[i] = std::thread(add_element, i);}for (auto& t : threads) t.join();std::cout << "Vector size: " << vec.size() << std::endl;// 正确输出 5
}

三、灵活锁 `std::unique_lock`

用途：支持延迟锁定和所有权转移

#include <mutex>
#include <queue>std::mutex mtx;
std::queue<int> data_queue;void data_preparation() {for (int i = 0; i < 10; ++i) {std::unique_lock<std::mutex> lock(mtx);data_queue.push(i);lock.unlock(); // 显式解锁std::this_thread::sleep_for(std::chrono::milliseconds(10));}
}void data_processing() {while (true) {std::unique_lock<std::mutex> lock(mtx);if (!data_queue.empty()) {int data = data_queue.front();data_queue.pop();lock.unlock(); // 提前解锁std::cout << "Processed: " << data << std::endl;} else {lock.unlock();break;}}
}int main() {std::thread t1(data_preparation);std::thread t2(data_processing);t1.join();t2.join();
}

四、递归锁 `std::recursive_mutex`

用途：允许同一线程多次加锁

#include <mutex>
#include <thread>std::recursive_mutex rmtx;void recursive_func(int n) {if (n <= 0) return;rmtx.lock();std::cout << "Locked, n = " << n << std::endl;recursive_func(n - 1);rmtx.unlock();
}int main() {std::thread t(recursive_func, 3);t.join();// 输出 3次加锁信息
}

五、超时锁 `std::timed_mutex`

用途：尝试获取锁时设置超时

#include <mutex>
#include <chrono>
#include <thread>std::timed_mutex tmtx;void timed_job() {auto start = std::chrono::steady_clock::now();if (tmtx.try_lock_for(std::chrono::milliseconds(100))) {std::cout << "Got lock after waiting\n";std::this_thread::sleep_for(std::chrono::milliseconds(200));tmtx.unlock();} else {auto end = std::chrono::steady_clock::now();auto diff = end - start;std::cout << "Timeout after " << std::chrono::duration<double, std::milli>(diff).count()<< "ms\n";}
}int main() {std::thread t1(timed_job);std::thread t2(timed_job);t1.join();t2.join();
}

六、共享锁 `std::shared_mutex` (C++17)

用途：实现读写锁（读者共享，写者互斥）

#include <shared_mutex>
#include <thread>
#include <vector>std::shared_mutex smtx;
std::string data;void reader(int id) {std::shared_lock<std::shared_mutex> lock(smtx);std::cout << "Reader " << id << " sees: " << data << "\n";
}void writer() {std::unique_lock<std::shared_mutex> lock(smtx);data = "New data";std::cout << "Writer updated data\n";
}int main() {std::vector<std::thread> readers;for (int i = 0; i < 5; ++i) {readers.emplace_back(reader, i);}std::thread w(writer);for (auto& r : readers) r.join();w.join();
}

七、条件变量 `std::condition_variable`

用途：线程间条件同步

#include <condition_variable>
#include <queue>std::mutex mtx;
std::queue<int> data_queue;
std::condition_variable cv;void producer() {for (int i = 0; i < 5; ++i) {std::this_thread::sleep_for(std::chrono::seconds(1));{std::lock_guard<std::mutex> lock(mtx);data_queue.push(i);}cv.notify_one();}
}void consumer() {while (true) {std::unique_lock<std::mutex> lock(mtx);cv.wait(lock, []{ return !data_queue.empty(); });int data = data_queue.front();data_queue.pop();std::cout << "Consumed: " << data << std::endl;if (data == 4) break;}
}int main() {std::thread p(producer);std::thread c(consumer);p.join();c.join();
}

关键总结表格

锁类型	特性	适用场景
`std::mutex`	基础互斥锁	简单资源保护
`std::lock_guard`	RAII自动管理	局部作用域自动解锁
`std::unique_lock`	灵活所有权控制	需要手动控制解锁时机
`std::recursive_mutex`	同一线程可重入	递归调用场景
`std::timed_mutex`	支持超时尝试	避免死锁等待
`std::shared_mutex`	读写分离	读多写少场景
`std::condition_variable`	线程间条件同步	生产者-消费者模式