How to stop a thread that runs active always?

[kahlenberg]

Hi,
I have trouble with the following code. I want to create a thread that runs always. I want to stop it only when a variable changes from true to false. When I terminate the programm (Ctrl+C) main thread exits but second thread continues to run until I press again Ctrl+C.

#include <csignal>
#include <unistd.h>
#include <iostream>
#include <mutex>
#include <thread>
#include <atomic>
std::atomic_bool run(true);

void waitForSignals(sigset_t& signalSet);
void registerSignals(sigset_t& signalSet);
void signalHandler(int sig);

int main(int argc, char **argv) {

    auto f1 = [&](){
        while(run.load(std::memory_order_acquire))
		{
            std::this_thread::sleep_for(std::chrono::milliseconds(500));
            std::cout << "TH ID " << std::this_thread::get_id() << " run: " << run.load() << std::endl;
        }
    };


    std::thread th1(f1);

    sigset_t signalSet;
    registerSignals(signalSet);
    waitForSignals(signalSet);
    std::cout << "\n\nExiting...\n\n" << std::endl;
	
    if(th1.joinable()) {
		
        th1.join();
    }

exit(0);
}

void signalHandler(int sig) { 
    run.store(false, std::memory_order_release); 
    std::cout << "signal run: " << run << std::endl;
}

void registerSignals(sigset_t& signalSet) {
    signal(SIGTERM, signalHandler);
    signal(SIGINT, signalHandler);

    sigemptyset(&signalSet);
    sigaddset(&signalSet, SIGINT);
    sigaddset(&signalSet, SIGTERM);
}
void waitForSignals(sigset_t& signalSet) {
    int exitSignal;
    sigwait(&signalSet, &exitSignal);
}

[markyrocks]

idk, i can't even get the example you have posted here to compile. From what i've gathered im not entirely sure that ctr + c has anything to do with the signal library. Also what you have posted seems ridiculously complicated for just trying to manage a thread. This is what i got to work.... Idk. Good luck.

#include <Windows.h>
#include <csignal>
#include <iostream>
#include <thread>
#include <atomic>
std::atomic_bool run(true);
using namespace std;
bool WINAPI CtrlHandler(DWORD fdwCtrlType)
{
    switch (fdwCtrlType)
    {
        // Handle the CTRL-C signal. 
    case CTRL_C_EVENT:
        run = false;
        return TRUE;
    }
    return false;
}

int main() {
    SetConsoleCtrlHandler(PHANDLER_ROUTINE(CtrlHandler), TRUE);
    auto f1 = []() {
        while (run)
        {
            std::this_thread::sleep_for(std::chrono::milliseconds(500));
            std::cout << "TH ID " << std::this_thread::get_id() << " run: " << run.load() << std::endl;
        }
    };
    
    std::thread th1(f1);
  
    while(run){}
    cout << "exiting...";
    if (th1.joinable()) {

        th1.join();
    }

}

[kahlenberg]

Ok, I found the solution.
I am using Linux and trying to run it on Linux.
So, I don't know the exact problem but I should not do anything in signal handler. I should just wait for a signal. After that I can flip the flags. Here is the working example:

#include <csignal>
#include <unistd.h>
#include <iostream>
#include <mutex>
#include <thread>
#include <atomic>
std::atomic_bool run(true);

void waitForSignals(sigset_t& signalSet);
void registerSignals(sigset_t& signalSet);
void signalHandler(int sig);

int main(int argc, char **argv) {

    auto f1 = [&](){
        while(run.load(std::memory_order_acquire))
		{
            std::this_thread::sleep_for(std::chrono::milliseconds(500));
            std::cout << "TH ID " << std::this_thread::get_id() << " run: " << run.load() << std::endl;
        }
    };


    std::thread th1(f1);

    sigset_t signalSet;
    registerSignals(signalSet);
    waitForSignals(signalSet);

    run.store(false, std::memory_order_release); 

    std::cout << "\n\nExiting...\n\n" << std::endl;
	
    if(th1.joinable()) {
		
        th1.join();
    }

exit(0);
}

void signalHandler(int sig) { 

}

void registerSignals(sigset_t& signalSet) {
    signal(SIGTERM, signalHandler);
    signal(SIGINT, signalHandler);

    sigemptyset(&signalSet);
    sigaddset(&signalSet, SIGINT);
    sigaddset(&signalSet, SIGTERM);
}
void waitForSignals(sigset_t& signalSet) {
    int exitSignal;
    sigwait(&signalSet, &exitSignal);
}