C/C ++:中断到达时如何退出sleep()? [英] C/C++: How to exit sleep() when an interrupt arrives?
问题描述
我正在寻找一种方法，可在用户中断到达时退出睡眠状态-重要的是退出睡眠，而不是这样做:中断睡眠，进行ISR处理并返回睡眠状态-是我正在寻找解决方案的地方.
I'm looking for a way to exit sleep when an user interrupt arrives - its important to exit sleep rather than do this: interrupt sleep , do ISR processing, and go back to sleep - which is what I'm finding solutions for.
我正在C ++中寻找类似的东西-C中的等效项甚至更好:
I'm looking for something like this in C++ - an equivalent in C is even better:
void * timer_thread(void*dummy)
{
while(1)
{
// Check if some callbacks are to be given
// when all are given, Determine x duration to sleep
try
{
sleep(x);
}
except(/* the except block should hit ONLY when an interrupt arrives,
that too only when sleep() is executed. It's OK to delay
interrupt until the sleep is beginning execution */)
{
//Do something else
}
}
到达的中断通常会告诉您应该减少睡眠，以使计时器线程更早地进行回调.但是不管用例如何，我只需要在中断到达时以某种方式退出睡眠状态.我只是找不到有关如何执行此操作的信息.
The arriving interrupt will mostly tell that the sleep should be reduced for the timer thread to give callbacks earlier. But irrespective of the usecase, I just need the sleep to be exited in some way when interrupt arrives. I just couldn't find info on how to do this.
PS:如果在没有睡眠的情况下发生中断，则可以放弃/取消中断
PS: It's ok to discard/NOP the interrupts if it occurs when sleep wasn't happening
这是在Windows 10(C/C ++)上的Cygwin gcc v9.3.0上-不需要代码可移植，因此任何特定于平台的解决方案也可以.使用Eclipse进行处理(最新日期为2020年4月).
This is on Cygwin gcc v9.3.0 on Windows 10 (C/C++) - Don't need the code to be portable, so any platform specific solution is ok as well. Working on this using Eclipse (latest - dated 04/2020)..
如果还有其他类似的解决方案(不使用sleep()和中断)，欢迎您听听.我只是在寻找一种不涉及轮询的方法.
If there's some other solution which is similar to this working (which doesn't use sleep() and interrupts), would be welcome to hear it. I'm just looking for a way which doesn't involve polling.
推荐答案
To wait for a certain time or on a certain event, I would use a combination of std::mutex and std::condition_variable and specifically std::condition_variable::wait_for() to await either time-out or a signaled change of something.
用于演示的最小示例程序:
A minimal sample program for demonstration:
#include <atomic>
#include <condition_variable>
#include <iostream>
#include <mutex>
#include <thread>
#include <chrono>
using namespace std::chrono_literals;
// a thread-shared flag to signal exit
std::atomic<bool> exitThread = false;
// a mutex to sync. inter-thread communication
std::mutex mtxAlert;
// a condition variable to signal changed data
std::condition_variable sigAlert;
// the data of inter-thread communication
bool alert = false;
void timerThread()
{
// the timeout for timer thread
auto timeout = 100ms;
// runtime loop
while (!exitThread) {
// lock mutex (preparation to wait in cond. var.)
std::unique_lock<std::mutex> lock(mtxAlert);
// unlock mutex and wait for timeout or signaled alert
sigAlert.wait_for(lock, timeout, []() { return alert || exitThread; });
// mutex is locked again
// check why wait_for() exited
if (exitThread) {
std::cout << "Timer thread exiting...\n";
return;
} else if (alert) {
std::cout << "Timer was interrupted due to alert.\n";
alert = false;
} else {
std::cout << "Timer achieved time-out.\n";
}
}
}
int main()
{
std::thread threadWait(&timerThread);
// wait a bit
std::cout << "main(): Waiting 300ms...\n";
std::this_thread::sleep_for(300ms);
// sim. interrupt
std::cout << "main(): Sim. interrupt.\n";
{ std::lock_guard<std::mutex> lock(mtxAlert);
alert = true;
}
sigAlert.notify_all();
// wait a bit
std::cout << "main(): Waiting 50 ms...\n";
std::this_thread::sleep_for(50ms);
// sim. interrupt
std::cout << "main(): Sim. interrupt.\n";
{ std::lock_guard<std::mutex> lock(mtxAlert);
alert = true;
}
sigAlert.notify_all();
// wait a bit
std::cout << "main(): Waiting 50 ms...\n";
std::this_thread::sleep_for(50ms);
// exiting application
exitThread = true;
sigAlert.notify_all();
threadWait.join();
// done
std::cout << "Done.\n";
}
输出:
main(): Waiting 300ms...
Timer achieved time-out.
Timer achieved time-out.
main(): Sim. interrupt.
main(): Waiting 50 ms...
Timer was interrupted due to alert.
main(): Sim. interrupt.
main(): Waiting 50 ms...
Timer was interrupted due to alert.
Timer thread exiting...
Done.
OP根据评论声称此示例无法在 cygwin 上正确编译. .我已经站在一边，可以确认一些我已解决的小问题:
OP claimed per comment that this sample didn't compile properly on cygwin. I tried on my side and can confirm some minor issues which I fixed:
-
添加了
#include <mutex>缺少
std::atomic<bool> exitThread = false;的初始化已更改为
std::atomic<bool> exitThread(false);
当我用g++以及g++ -std=c++14进行编译时，我得到了这个. (看来-std=c++14是我的g++的默认设置.)
I got this when I compiled with g++ as well as with g++ -std=c++14. (It seems that -std=c++14 is the default of my g++.)
当我使用g++ -std=c++17时，我没有任何抱怨.我坚信这与 copy-elision ，其中g++适用于-std=c++17，但不适用于先前版本.
When I use g++ -std=c++17 instead I don't get any complaint. I strongly believe that has something to do with copy-elision which g++ applies with -std=c++17 but not prior.
但是，这是我的示例会话，其中在Windows 10便携式计算机上的 cygwin64 > :
However, this is my sample session with the slightly reviewed code on my Windows 10 laptop in cygwin64:
$ g++ --version
g++ (GCC) 7.4.0
$
$ cat >testCondVar.cc <<'EOF'
> #include <atomic>
> #include <condition_variable>
> #include <iostream>
> #include <mutex>
> #include <thread>
> #include <chrono>
> using namespace std::chrono_literals;
>
> // a thread-shared flag to signal exit
> std::atomic<bool> exitThread(false);
>
> // a mutex to sync. inter-thread communication
> std::mutex mtxAlert;
> // a condition variable to signal changed data
> std::condition_variable sigAlert;
> // the data of inter-thread communication
> bool alert = false;
>
> void timerThread()
> {
> // the timeout for timer thread
> auto timeout = 100ms;
> // runtime loop
> while (!exitThread) {
> // lock mutex (preparation to wait in cond. var.)
> std::unique_lock<std::mutex> lock(mtxAlert);
> // unlock mutex and wait for timeout or signaled alert
> sigAlert.wait_for(lock, timeout, []() { return alert || exitThread; });
> // mutex is locked again
> // check why wait_for() exited
> if (exitThread) {
> std::cout << "Timer thread exiting...\n";
> return;
> } else if (alert) {
> std::cout << "Timer was interrupted due to alert.\n";
> alert = false;
> } else {
> std::cout << "Timer achieved time-out.\n";
> }
> }
> }
>
> int main()
> {
> std::thread threadWait(&timerThread);
> // wait a bit
> std::cout << "main(): Waiting 300ms...\n";
> std::this_thread::sleep_for(300ms);
> // sim. interrupt
> std::cout << "main(): Sim. interrupt.\n";
> { std::lock_guard<std::mutex> lock(mtxAlert);
> alert = true;
> }
> sigAlert.notify_all();
> // wait a bit
> std::cout << "main(): Waiting 50 ms...\n";
> std::this_thread::sleep_for(50ms);
> // sim. interrupt
> std::cout << "main(): Sim. interrupt.\n";
> { std::lock_guard<std::mutex> lock(mtxAlert);
> alert = true;
> }
> sigAlert.notify_all();
> // wait a bit
> std::cout << "main(): Waiting 50 ms...\n";
> std::this_thread::sleep_for(50ms);
> // exiting application
> exitThread = true;
> sigAlert.notify_all();
> threadWait.join();
> // done
> std::cout << "Done.\n";
> }
> EOF
$
已编译并启动:
$ g++ -std=c++14 -o testCondVar testCondVar.cc
$ ./testCondVar
main(): Waiting 300ms...
Timer achieved time-out.
Timer achieved time-out.
main(): Sim. interrupt.
main(): Waiting 50 ms...
Timer was interrupted due to alert.
main(): Sim. interrupt.
main(): Waiting 50 ms...
Timer was interrupted due to alert.
Timer thread exiting...
Done.
$
注意:
此示例至少需要C ++ 14的唯一原因是使用了 std :: chrono_literals 可启用例如300ms.
The only reason that at minimum C++14 is required for this sample is the usage of the std::chrono_literals which enables the usage of e.g. 300ms.
如果没有std::chrono_literals，可以将其写为std::chrono::milliseconds(300)(这显然不太方便).分别替换所有std::chrono_literals，我也可以使用-std=c++11编译并运行示例.
Without std::chrono_literals, this could be written as std::chrono::milliseconds(300) (which is admittedly less convenient). Replacing all std::chrono_literals respectively, I was able to compile and run the sample with -std=c++11 as well.
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