Question

我无法理解conditional_variable wait_for。

示例程序：

#include <iostream>
#include <string>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <chrono>

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

using namespace std;

void worker_thread()
{
    std::unique_lock<std::mutex> lk(m);

    for (int i=0; i<3; i++) {
      auto remaining = chrono::milliseconds::max();

      std::cout << "Going to sleep for " << remaining.count() << endl;
      bool r = cv.wait_for(lk, remaining, [] () { return ready;});
      std::cout << "Wakey wakey " << r << endl;
    }

    std::cout << "Thread finished" << endl;
}

int main()
{
    std::thread worker(worker_thread);
    worker.join();
}

我希望这个程序能做什么：

永远进入睡眠状态，因为我从未将ready设为真，也未设为cv.notify_one()

它实际上做了什么：

Going to sleep for 9223372036854775807
Wakey wakey 0
Going to sleep for 9223372036854775807
Wakey wakey 0
Going to sleep for 9223372036854775807
Wakey wakey 0
Thread finished

这是因为“虚假的觉醒”吗？但我使用了文档中所述的重载(2)：This overload may be used to ignore spurious awakenings.

在此处执行代码：https://repl.it/repls/EnchantedFatalUnderstanding

conditional_variable“虚假”觉醒

0 个答案: