C++11 Watchdog class, test application doesn't want to exit - c++

Question

I am using an online C++11 compiler, link found here: cpp.sh (C++ Shell).
In my current project, I would like to have a watchdog class, to be able to check somehow the status of a thread or FSM (for example).
After some work (I'm not a C++11 guru), I finally got the code below, that compiles ok.
I also did some basic/trivial tests, but it seems the test program doesn't want to exit.
It says "Program running" and the only way to (force) exit is to hit the "Stop" button... :(
Well, my question : What am I doing wrong?
Any ideas, suggestions you can provide are highly appreciated.
Here is the full code, including my test app:
Watchdog (as MCVE):
#include <thread>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <mutex>
#include <iostream>
using namespace std::chrono;
class Watchdog
{
public:
Watchdog();
~Watchdog();
void Start(unsigned int milliseconds, std::function<void()> callback = 0);
void Stop();
void Pet();
private:
unsigned int m_interval;
std::atomic<bool> m_running;
std::thread m_thread;
std::function<void()> m_callback;
std::mutex m_mutex;
steady_clock::time_point m_lastPetTime;
std::condition_variable m_stopCondition;
void Loop();
};
Watchdog::Watchdog()
{
m_running = false;
}
Watchdog::~Watchdog()
{
Stop();
}
void Watchdog::Start(unsigned int milliseconds, std::function<void()> callback)
{
std::unique_lock<std::mutex> locker(m_mutex);
if(m_running == false)
{
m_lastPetTime = steady_clock::now();
m_interval = milliseconds;
m_callback = callback;
m_running = true;
m_thread = std::thread(&Watchdog::Loop, this);
}
}
void Watchdog::Stop()
{
std::unique_lock<std::mutex> locker(m_mutex);
if(m_running == true)
{
m_running = false;
m_stopCondition.notify_all();
m_thread.join();
}
}
void Watchdog::Pet()
{
std::unique_lock<std::mutex> locker(m_mutex);
m_lastPetTime = steady_clock::now();
m_stopCondition.notify_all();
}
void Watchdog::Loop()
{
std::unique_lock<std::mutex> locker(m_mutex);
while(m_running == true)
{
if(m_stopCondition.wait_for(locker, milliseconds(m_interval)) == std::cv_status::timeout)
{
if(m_callback != nullptr)
m_callback();
}
}
}
int main(int argc, char *argv[])
{
Watchdog wdog;
wdog.Start(3000, [] { std::cout << " WDOG TRIGGERED!!! "; });
for(auto i = 0; i < 10; i++)
{
std::cout << "[+]";
wdog.Pet();
std::this_thread::sleep_for(std::chrono::milliseconds(500));
}
}
-

Answer 1

You're doing a deadlock here.
void Watchdog::Stop()
{
std::unique_lock<std::mutex> locker(m_mutex);
if(m_running == true)
{
m_running = false;
m_stopCondition.notify_all();
m_thread.join();
^ ~~~~~~~~~~~~~~
m_mutex is locked; m_thread cannot continue execution
}
}
Some additional suggestion: use simple if conditions, do not compare with true or false.