std::unique_lock<Mutex>:: lock

锁定（即获取所有权）关联的互斥锁。效果上调用 mutex ( ) - > lock ( ) 。

参数

(无)

返回值

(无)

异常

• 由 mutex ( ) - > lock ( ) 抛出的任何异常。

• 如果没有关联的互斥锁，将抛出 std::system_error ，其错误代码为 std::errc::operation_not_permitted 。

• 如果互斥锁已被此 unique_lock 锁定（换言之， owns_lock() 返回 true ），将抛出 std::system_error 异常，其错误码为 std::errc::resource_deadlock_would_occur 。

示例

#include <chrono>
#include <iostream>
#include <mutex>
#include <thread>
#include <vector>
int main()
{
    int counter = 0;
    std::mutex counter_mutex;
    std::vector<std::thread> threads;
    auto worker_task = [&](int id)
    {
        std::unique_lock<std::mutex> lock(counter_mutex);
        ++counter;
        std::cout << id << ", initial counter: " << counter << '\n';
        lock.unlock();
        // don't hold the lock while we simulate an expensive operation
        std::this_thread::sleep_for(std::chrono::seconds(1));
        lock.lock();
        ++counter;
        std::cout << id << ", final counter: " << counter << '\n';
    };
    for (int i = 0; i < 10; ++i)
        threads.emplace_back(worker_task, i);
    for (auto& thread : threads)
        thread.join();
}

0, initial counter: 1
1, initial counter: 2
2, initial counter: 3
3, initial counter: 4
4, initial counter: 5
5, initial counter: 6
6, initial counter: 7
7, initial counter: 8
8, initial counter: 9
9, initial counter: 10
6, final counter: 11
3, final counter: 12
4, final counter: 13
2, final counter: 14
5, final counter: 15
0, final counter: 16
1, final counter: 17
7, final counter: 18
9, final counter: 19
8, final counter: 20

参见