875
Subj : pthreads - cancellation
To   : comp.programming.threads
From : plinius
Date : Sat Aug 20 2005 07:33 pm

 Hi,
I have a difficult problem:

I'm using pthreads with a communication-librarie.
This librarie has blocking Recv's.
When a "cummunicator" (you can see it as a radio-frequency) changes, I
have to repost the Recv,
because soon after it changed, the old one becomes invalid.
The Recv function is of the following form: Recv(int number, comm
communicator).
Hence I can't let the thread know it should be restarted with a
dummy-message,
because every possible value for "number" is valid.
So I can't initiate the thread-restart from "within" the thread which
should be restarted...
I've red here
http://groups.google.be/group/comp.programming.threads/browse_frm/thread/10721b0bac88e1d0/7007305bfbeea1bf?hl=nl#7007305bfbeea1bf
that you can't just kill the thread. Allso it seems that cancellation
is really tricky (and not allways possible, and never advisable).

Is it possible to stop a thread from another one?
Suppose I have the following case: A,B,C are blocked by a recv.
The communicator of B changes. D wants to kill and restart thread B so
that it's healthy again.

How should I do that?
Has anyone experience with something like that?
Can someone give me a code sample?

Please note, I don't want B to become inactive, but I want it killed.
Not that it matters (I think), but I'm using
http://sources.redhat.com/pthreads-win32/
If something's not clear, please ask it...
Any input is greatly appreciated.
________________________
int main(int argc, char* argv[])
{
pthread_t thread[4];
int status;
pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_JOINABLE);
pthread_create(&thread[0],&attr,A,NULL);
pthread_create(&thread[1],&attr,B,NULL);
pthread_create(&thread[2],&attr,C,NULL);
pthread_create(&thread[3],&attr,D,NULL);
pthread_join(thread[0],(void**)&status);
pthread_join(thread[1],(void**)&status);
pthread_join(thread[2],(void**)&status);
pthread_join(thread[3],(void**)&status);
pthread_attr_destroy(&attr);
pthread_exit(NULL);
}

.

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