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In multi-threaded programming, using a mutex lock (mutex) can prevent multiple threads from accessing shared data at the same time, thereby avoiding data competition and inconsistency. The main functions include: 1. Protection of shared data; 2. Thread synchronization. In C++, mutex objects can be created and used through std::mutex. Shared data can only be accessed after acquiring the lock, and other threads can acquire the lock only after the lock is released.
The role of mutex in C++ multi-thread programming
In multi-thread programming, when multiple threads access shared data at the same time , may lead to data races and inconsistencies. To prevent this, a mutex can be used to ensure that shared data is only accessed by one thread at the same time.
What is mutex
Mutex is a synchronization primitive that allows threads to have mutually exclusive access to shared resources. After a thread acquires the mutex lock, other threads cannot acquire the lock until the thread releases the lock.
The role of mutex
In multi-threaded programming, mutex mainly has the following functions:
How to use mutex
In C++, you can use std::mutex
to create and use mutex objects:
// 创建一个 mutex 对象 std::mutex m; // 获取 mutex 的锁 m.lock(); // 访问共享数据或执行操作 // 释放 mutex 的锁 m.unlock();
Practical case
The following is a practical case of using mutex to protect shared data:
#include <iostream> #include <thread> #include <mutex> std::mutex m; int shared_data = 0; void increment_shared_data() { m.lock(); shared_data++; m.unlock(); } int main() { std::thread t1(increment_shared_data); std::thread t2(increment_shared_data); t1.join(); t2.join(); std::cout << "Final value of shared_data: " << shared_data << std::endl; return 0; }
In this case, two threads execute at the same time increment_shared_data()
function to perform increment operation on shared_data
. Since a mutex is used in the increment_shared_data()
function to protect shared data, it is guaranteed that two threads will not access shared_data
at the same time, thereby avoiding data competition.
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