给定以下代码:
#include <chrono>
#include <ctime>
#include <functional>
#include <iostream>
#include <thread>
#include <utility>
#include <QFuture>
#include <QMutex>
#include <QWaitCondition>
#include <QtConcurrent>
class Async
{
public:
Async() = default;
Async(const Async&) = delete;
Async(Async&&) = delete;
~Async() = default; //{ m_mutex.unlock(); }
Async& operator=(const Async&) = delete;
Async& operator=(Async&&) = delete;
template<typename t_result>
QFuture<bool> operator()(
std::function<t_result()>&& p_function,
std::chrono::milliseconds p_timeout,
t_result* p_result)
{
QtConcurrent::run([this, p_function, p_result]() {
*p_result = p_function();
std::cout << time(nullptr) << " waking" << std::endl;
m_cond.wakeAll();
});
return QtConcurrent::run([this, p_timeout]() {
std::cout << time(nullptr) << " starting to wait for "
<< p_timeout.count() << " ms" << std::endl;
m_mutex.lock();
bool wait =
m_cond.wait(&m_mutex,
static_cast<unsigned
long>(p_timeout.count()));
std::cout << time(nullptr)
<< ", finished waiting = "
<< (wait ? "T" : "F")
<< std::endl;
if (wait) {
return false;
}
return true;
});
}
private:
QMutex m_mutex;
QWaitCondition m_cond;
};
int main()
{
Async async;
char letter = 'z';
std::function<char()> f1 = []() -> char {
std::this_thread::sleep_for(std::chrono::seconds(4));
return 'a';
};
std::cout << "1: " << time(nullptr) << std::endl;
QFuture<bool> result =
async(std::move(f1), std::chrono::milliseconds(3999),
&letter);
std::cout << "2: " << time(nullptr) << std::endl;
std::this_thread::sleep_for(std::chrono::seconds(8));
std::cout << "3: " << time(nullptr) << std::endl;
if (result.result()) {
std::cout << "timeout, letter = " << letter;
} else {
std::cout << "NO timeout, letter = " << letter;
}
std::cout << std::endl;
return 0;
}
最后... 8),当我运行它时,所有的cout
打印出预期的内容,但我得到一个QMutex: destroying locked mutex
在执行结束时。由于我收到消息 finished waiting
,m_cond.wait
被执行,因此(我认为)m_mutex
将被解锁。但似乎并非如此。
如果我使用 ~Async() { m_mutex.unlock();
,我没有收到消息,但我认为不应该这样做。
谁能解释一下为什么互斥量没有被释放?
非常感谢!
最佳答案
当可运行的等待条件变量使用独占互斥锁时,它会在等待结束(超时或未超时)时持有互斥锁上的锁。
这意味着你必须显式解锁互斥量
bool wait = m_cond.wait(&m_mutex,static_cast<unsigned long>(p_timeout.count()));
m_mutex.unlock();
if (wait) {
return false;
}
return true;
关于c++ - QMutex:销毁锁定的互斥体,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/54778058/