Simple Detached pThread does not cancel! (cout blocks and interleaves even if mutexed)

Posted by Gabriel on Stack Overflow See other posts from Stack Overflow or by Gabriel
Published on 2010-03-13T23:50:12Z Indexed on 2010/03/13 23:55 UTC
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I have a hard problem here, which I can not solve and do not find the right answer on the net:

I have created a detached thread with a clean up routing, the problem is that on my Imac and Ubuntu 9.1 (Dual Core). I am not able to correctly cancel the detached thread in the fallowing code:

#include <iostream>
#include <pthread.h>
#include <sched.h>
#include <signal.h>

#include <time.h>

pthread_mutex_t mutex_t;

using namespace std;

static void cleanup(void *arg){
    pthread_mutex_lock(&mutex_t);
    cout << " doing clean up"<<endl;
    pthread_mutex_unlock(&mutex_t);
}


static void *thread(void *aArgument)
{

    pthread_setcancelstate(PTHREAD_CANCEL_ENABLE,NULL);
    pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED,NULL);

    pthread_cleanup_push(&cleanup,NULL);
    int n=0;
    while(1){
        pthread_testcancel();
        sched_yield();
        n++;

        pthread_mutex_lock(&mutex_t);
        cout << " Thread 2: "<< n<<endl;
        pthread_mutex_unlock(&mutex_t);

    }
    pthread_cleanup_pop(0);

    return NULL;
}


int main()
{

    pthread_t thread_id;

    pthread_attr_t attr;
    pthread_attr_init(&attr);
    pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_DETACHED);

    int error;

    if (pthread_mutex_init(&mutex_t,NULL) != 0) return 1;

    if (pthread_create(&thread_id, &attr, &(thread) , NULL) != 0) return 1;

    pthread_mutex_lock(&mutex_t);
    cout << "waiting 1s for thread...\n" <<endl;
    pthread_mutex_unlock(&mutex_t);

    int n =0;

    while(n<1E3){
        pthread_testcancel();
        sched_yield();
        n++;

        pthread_mutex_lock(&mutex_t);
        cout << " Thread 1: "<< n<<endl;
        pthread_mutex_unlock(&mutex_t);
    }

    pthread_mutex_lock(&mutex_t);
    cout << "canceling thread...\n" <<endl;
    pthread_mutex_unlock(&mutex_t);

    if (pthread_cancel(thread_id) == 0)
    {
        //This doesn't wait for the thread to exit
        pthread_mutex_lock(&mutex_t);
        cout << "detaching thread...\n"<<endl;
        pthread_mutex_unlock(&mutex_t);

        pthread_detach(thread_id);

        while (pthread_kill(thread_id,0)==0)
        {
                sched_yield();
        }

        pthread_mutex_lock(&mutex_t);
        cout << "thread is canceled";
        pthread_mutex_unlock(&mutex_t);

    }

    pthread_mutex_lock(&mutex_t);
    cout << "exit"<<endl;
    pthread_mutex_unlock(&mutex_t);

    return 0;
}

When I replace the Cout with printf() i workes to the end "exit" , but with the cout (even locked) the executable hangs after outputting "detaching thread...

It would be very cool to know from a Pro, what the problem here is?. Why does this not work even when cout is locked by a mutex!?

Thanks a lot for your support!!

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