p_thread: exit from multiple threads - c++

Question

I created two threads in my program. I wanted to terminate thread_1 inside thread_2 function and vice versa based on flag. I tried exit() and pthread_exit(Thread_id) but it does not work. I wanted to cancel the thread execution by calling pthread_cancel but the problem is that I cannot pass the thread id before pthread_create. Any suggestions ??

Answer 1

You can see how pthread_cancel works in the manpage.
However, since you mention C++, why not use the language features? Signaling one or many other threads can be done with condition-variables.
See it Live On Coliru
If you don't have C++11, you can use Boost Threads.
#include <thread>
#include <condition_variable>
#include <iostream>
using namespace std;
struct workers
{
mutex mx;
condition_variable cv;
bool canceled;
workers() : canceled(false) {}
void thread1()
{
cout << __PRETTY_FUNCTION__ << " start\n";
this_thread::sleep_for(chrono::seconds(2));
{
unique_lock<mutex> lk(mx);
cout << __PRETTY_FUNCTION__ << " signaling cancel\n";
canceled = true;
cv.notify_all();
}
this_thread::sleep_for(chrono::seconds(2));
cout << __PRETTY_FUNCTION__ << " done\n";
}
void thread2()
{
cout << __PRETTY_FUNCTION__ << " start\n";
for(;;)
{
// do some work
unique_lock<mutex> lk(mx);
if (cv.wait_for(lk, chrono::milliseconds(10), [this] { return canceled; }))
break;
}
cout << __PRETTY_FUNCTION__ << " done\n";
}
};
int main()
{
workers demo;
std::thread t1(&workers::thread1, ref(demo));
std::thread t2(&workers::thread2, ref(demo));
t1.join();
t2.join();
}
Output:
void workers::thread1() start
void workers::thread2() start
void workers::thread1() signaling cancel
void workers::thread2() done
void workers::thread1() done
Update The C++03 version with boost is Live On Coliru now too. I've added timestamps for fun:
thread1:21 2014-Mar-26 00:01:40.074269 start
thread2:37 2014-Mar-26 00:01:40.074275 start
thread1:26 2014-Mar-26 00:01:42.074873 signaling cancel
thread2:47 2014-Mar-26 00:01:42.074991 done
thread1:32 2014-Mar-26 00:01:44.075062 done