How to synchronize threads in C++?

Thread synchronization in C++ refers to coordinating thread access to shared resources to prevent data competition and resource destruction. To do this, mutexes can be used to control exclusive access to shared resources, and condition variables can be used to coordinate communication between threads. In actual combat, mutex locks are used to manage task queues, while condition variables are used to wake up threads waiting for new tasks, thereby achieving coordinated execution of multi-threaded applications.

#How to synchronize threads in C++?

Understanding thread synchronization

Thread synchronization refers to coordinating concurrently executing threads to ensure that they access shared resources in an orderly manner. Various synchronization mechanisms are available in C++ to help us achieve this.

Mutex (Mutex)

Mutex is a lock used to control exclusive access to shared resources. Only one thread is allowed to hold the mutex lock at a time, which prevents data races and resource corruption.

Sample code:

#include <thread>
#include <mutex>

int shared_value = 0;

// 创建互斥锁
std::mutex m;

void increment_shared_value() {
  // 获取互斥锁
  m.lock();
  // 临界区：独占访问共享值
  ++shared_value;
  // 释放互斥锁
  m.unlock();
}

Condition Variable

Condition variable is used to coordinate communication between threads . One thread can use a condition variable to wait for a specific condition to be met, while another thread can use notify_one() or notify_all() to wake up the waiting thread.

Sample code:

#include <thread>
#include <condition_variable>

bool condition_met = false;
std::condition_variable cv;
std::mutex m;

void wait_for_condition() {
  // 获取互斥锁
  std::unique_lock<std::mutex> lock(m);
  
  // 等待条件得到满足
  cv.wait(lock, [] { return condition_met; });
  
  // 条件已得到满足，可以继续执行
  // ...
}

Practical case:

Consider a multi-threaded program that assigns multiple tasks to Different threads. In order to coordinate the execution of tasks, we can use mutex locks to prevent multiple threads from accessing the task queue at the same time. Condition variables can be used to wake up threads waiting for new tasks.

Conclusion:

Mutex locks and condition variables are powerful synchronization mechanisms in C++. They allow us to control resource access and communication between threads. By understanding and using these mechanisms, we can write robust multi-threaded applications that take full advantage of the multi-core architecture of modern computers.

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