mutex, unique_lock & lock_guard

最新推荐文章于 2025-01-23 09:00:00 发布

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最新推荐文章于 2025-01-23 09:00:00 发布

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本文对比了std::mutex与std::unique_lock的使用，强调std::unique_lock在析构时自动解锁mutex，确保异常安全。同时，介绍了std::unique_lock与std::lock_guard的区别，前者可在运行时决定是否锁定，后者在构造时锁定并在析构时释放。

mutex v.s. unique_lock

The usage of std::mutex and std::unique_lock are similar. They both have lock() and unlock() operations. The difference is that std::unique_lock calls unlock on the mutex in its destructor. The benefit of this is that in case some exception is thrown, you are sure that the mutex will unlock when leaving the scope where the std::unique_lock is defined.

std::mutex mtx;
mtx.lock();
... //protected stuff
mtx.unlock();
... //non-protected stuff
mtx.lock();
... //etc

std::mutex mtx;
std::unique_lock<std::mutex> lck(mtx);
... //protected stuff
lck.unlock();
... //non-protected stuff
lck.lock();
... //etc

unique_lock v.s. lock_guard

The difference between std::unique_lock and std::lock_guard is that you can lock and unlock a std::unique_lock, while std::lock_guard will be locked only once on construction and unlocked on destruction.

void foo() {
	std::mutex mtx;
	std::lock_guard<std::mutex> lg(mtx);
	... //protected stuff
} //mutex is automatically released when lock goes out of scope