Locking and synchronization mechanism of C++ functions in concurrent programming?

C Function locks and synchronization mechanisms in concurrent programming are used to manage concurrent access to data in a multi-threaded environment and prevent data competition. The main mechanisms include: Mutex (Mutex): a low-level synchronization primitive that ensures that only one thread accesses the critical section at a time. Condition Variable: Allows threads to wait for conditions to be met and provides inter-thread communication. Atomic operation: Single instruction operation, ensuring single-threaded update of variables or data to prevent conflicts.

C Function lock and synchronization mechanism in concurrent programming

When performing concurrent programming in a multi-threaded environment, manage data Concurrent access is critical. C provides several mechanisms to implement function locking and synchronization, which help prevent data races and other thread-safety issues.

Mutex (Mutex)

A mutex is a low-level synchronization primitive that allows only one thread to access a critical section (shared data or resource). Before entering the critical section, the thread must acquire the mutex and release it after exiting the critical section.

std::mutex mu;
void critical_section() {
  // 获得互斥量
  std::lock_guard<std::mutex> lock(mu);

  // 临界区代码...

  // 释放互斥量（自动释放）
}

Condition Variable

Condition variable allows a thread to wait for a certain condition to be met. A thread can wait on a condition variable until another thread sends a signal.

std::condition_variable cv;
std::mutex mu;

void waiting_thread() {
  // 获得互斥量
  std::unique_lock<std::mutex> lock(mu);

  // 在条件变量上等待
  cv.wait(lock);

  // 条件满足（可选），进行后续操作...

  // 释放互斥量
}

void signalling_thread() {
  // 获得互斥量
  std::lock_guard<std::mutex> lock(mu);

  // 条件得到满足，发送信号
  cv.notify_one();

  // 释放互斥量（自动释放）
}

Atomic operation

Atomic operation is a single instruction that cannot be interrupted by other threads during execution. This can be used to ensure single-threaded updates of variables or data.

std::atomic_flag busy_flag = ATOMIC_FLAG_INIT;

void set_busy_flag() {
  // 原子方式地设置 busy_flag
  busy_flag.test_and_set(std::memory_order_release);
}

bool is_busy() {
  // 原子方式地获取 busy_flag 的值
  return busy_flag.test(std::memory_order_acquire);
}

Practical case

Consider a multi-threaded application in which threads need to access shared counter variables. To prevent data races, we use a mutex to synchronize access to the counter.

std::mutex mu;
int counter = 0;

void increment_counter() {
  // 获得互斥量
  std::lock_guard<std::mutex> lock(mu);

  // 增加计数器
  ++counter;
}

By using these synchronization mechanisms, we can ensure safe and efficient access and sharing of data in a multi-threaded environment.

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