代码同时从两个不同线程获取相同的互斥量。我知道应该发生死锁。为什么没有发生?为什么它不会发生死锁?
#include <iostream>
#include <thread>
#include <queue>
#include <mutex>
#include <condition_variable>
template <typename T>
class SafeQueue
{
public:
T pop()
{
std::unique_lock<std::mutex> mlock(mutex_);
std::cout << "lock pop()" << std::endl;
while (queue_.empty())
{
cond_.wait(mlock);
std::cout << "lock pop awake. Items: " << queue_.size() << std::endl;
}
auto item = queue_.front();
queue_.pop();
std::cout << "returning from pop" << std::endl;
return item;
}
void push(const T& item)
{
std::unique_lock<std::mutex> mlock(mutex_);
std::cout << "lock push()" << std::endl;
queue_.push(item);
mlock.unlock();
cond_.notify_one();
}
private:
std::queue<T> queue_;
mutable std::mutex mutex_;
std::condition_variable cond_;
};
SafeQueue<int> queue;
void pop()
{
std::cout << "popping..." << std::endl;
std::cout << "popped: " << queue.pop() << std::endl;
}
int main()
{
std::thread consumerThread(pop);
std::this_thread::sleep_for(std::chrono::seconds(3));
std::cout << "main thread will push" << std::endl;
queue.push(2);
std::cout << "pushed" << std::endl;
consumerThread.join();
std::cout << "end" << std::endl << std::endl;
}
我的输出是:
啪......
锁pop()方法
主线程将推动
锁推()
推
锁弹出清醒。项目:1
从弹出
弹出返回:2
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