Programming

Main function creates Thread0 and Thread1 by using pthread_create systemcall.

In Thread0() {
we are calling pthread_exit(0) ;
}

and in Thread1() {
status= pthread_join(tid[0],NULL);
sprintf(ebuf,"timer6: can't join with thread0, status: %d",status);
Assert(status==0,ebuf);
}

My doubt is Will pthread_join throws errors(can't join with thread0) because Thread0 terminated and again trying to join with Thread1 right??
Please let me know..


Below problem happens sometimes,but not reproducible everytime.

Failure message:
==============
timer6: can't join with thread0, status: 3


I have a doubt,that through pthread_exit(0); will Thread0 terminates?? If Thread0 terminates then why to call pthread_join function again??
Please clarify..

Am not able to get the answer..Please help me in understanding it.


Thanks in Advance,
Mansa

I think this error

Code:

Failure message:
==============
timer6: can't join with thread0, status: 3

occurs whenever thread0 dies first, or can say scheduled first.

Run the code again, and make the thread1 to wait. U will always get this error message.

Thanks for your reply and clarification that problem is reproducible everytime..


I have a doubt,that if we call pthread_exit(0); then Thread0 terminates definately right?? If Thread0 terminates then in Thread1() why to call pthread_join function again??What's the use of calling pthread_join() in Thread1().Could you please clarify??


Pthread_join()-waits for the termination of target thread(here Thread0).
But in our case,thread0 terminated right.

Thanks,
Mansa

the pthread_join call suspends the calling thread until a join is complete. When the join is done, the caller receives the joined thread’s termination status as the return from pthread_join. The pthread_join function (somewhat equivalent to the wait function for processes(fork)).

Mansa, I suspect the "join" in pthread_join() is confusing you.

In POSIX threads terminology a join is actually a wait i.e. the calling thread (in your case thread 1) blocks until the specified thread has exited (in your case thread 0). It is equivalant to Win32's NTWaitForSingleObject()/WaitForSingleObject() or the old OS/2 DosWaitThread().

Not all threads can be joined. If you specified a detached thead at creation time, such a thread cannot be joined. Also any thread can call pthread_join() on any other thread but the exiting thread can only be joined once.