Detailed explanation of synchronization primitives in C++ concurrent programming

In C multi-threaded programming, the role of synchronization primitives is to ensure the correctness of multiple threads accessing shared resources. It includes: Mutex (Mutex): protects shared resources and prevents simultaneous access; condition variables (Condition Variable): The thread waits for specific conditions to be met before continuing execution; Atomic operation: ensures that the operation is executed in an uninterruptible manner.

C Detailed explanation of synchronization primitives in concurrent programming

In multi-thread programming, synchronization primitives are crucial , which can ensure the correctness when multiple threads access shared resources. C provides a rich set of synchronization primitives, including mutex locks, condition variables, and atomic operations.

Mutex (Mutex)

Mutex is a synchronization mechanism used to protect shared resources. When a thread acquires a mutex lock, other threads will be blocked until the mutex lock is released. In C, you can use the std::mutex class to implement a mutex lock:

std::mutex mtx;
// ...
{
    // 获取互斥锁
    std::lock_guard<std::mutex> lock(mtx);
    // 临界区
} // 互斥锁在离开作用域时自动释放

Condition Variable

Condition variable Allows a thread to wait for a specific condition to be met before continuing execution. In C, you can use the std::condition_variable class to implement condition variables:

std::condition_variable cv;
// ...
{
    std::unique_lock<std::mutex> lock(mtx);
    // 等待条件满足
    cv.wait(lock);
    // 执行条件满足后要执行的代码
}

Atomic operations

Atomic operations guarantee that an operation can Executed in interrupt mode. In C, you can use the atomic library to perform atomic operations:

std::atomic<int> counter;
// ...
counter++; // 原子地增加 counter 的值

Practical example

Consider a program with a shared counter and a writing thread. The writing thread needs to atomically increment the counter, while the reading thread needs to read the counter protectedly:

std::atomic<int> counter;
std::mutex mtx;

// 写入线程
void write_thread() {
    while (true) {
        // 原子地增加计数器
        counter++;
    }
}

// 读取线程
void read_thread() {
    while (true) {
        // 保护地读取计数器
        std::lock_guard<std::mutex> lock(mtx);
        std::cout << "Counter: " << counter << std::endl;
    }
}

int main() {
    std::thread t1(write_thread);
    std::thread t2(read_thread);
    t1.join();
    t2.join();
    return 0;
}

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