[Bug nptl/9804] pthread_exit from main thread: poor semantics, potential tty session lockup.

["kkylheku at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

------- Additional Comments From kkylheku at gmail dot com  2009-01-31 07:01 -------
(In reply to comment #1)
> The tasks of the other threads terminate in ten seconds, but
> the main one must be killed by SIGKILL, and control of the tty
> cannot be wrestled away from it.

This statement is wrong. In fact, the threads other than main do not 
terminate. They also stick around. Somehow, the Ctrl-Z signal prevents their 
termination.

The main thread runs all the way through the do_exit routine in the kernel, 
and makes the final schedule call, turning into a defunct process. (I added 
traces to do_exit).

The Ctrl-Z hang seems to be causing the othread threads to be stuck in the 
kernel function do_signal_stop, according to what is reported 
in /proc/<pid>/wchan.






The repro program is this:

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <pthread.h>

#define NUM_THREADS 5

void *task(void *a)
{
    sleep(10);
    pthread_exit(NULL);
}

int
main(int argc, char *argv[])
{
    pthread_t thr[NUM_THREADS];
    int i;

    for (i = 0; i < NUM_THREADS; i++) {
        if (pthread_create(&thr[i], NULL, task, 0) != 0) {
            fprintf(stderr, "pthread_create failed\n");
            return EXIT_FAILURE;
        }
    }

    pthread_exit(NULL);
}




-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=9804

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