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.
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";
}
Output:
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.
Live Demo on coliru
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:
Missing #include <mutex> added
Initialization of std::atomic<bool> exitThread = false; changed to
std::atomic<bool> exitThread(false);
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++.)
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.
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
$
Compiled and started:
$ 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.
$
Note:
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.
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.
