-lthr vs. -pthread

From: Cyrille Lefevre (clefevre-lists_at_9online.fr)
Date: 06/20/04

  • Next message: David Xu: "Re: -lthr vs. -pthread" 
    To: <current@freebsd.org>
Date: Sun, 20 Jun 2004 04:14:53 +0200

    Hi,

    I'm currently working on enhancements to ps w/ "Garance A Drosehn".
    I've just added some thread related stuffs and to see them, I'm
    using the following program :

    #define _REENTRANT
    #include <pthread.h>

    #define NUM_THREADS 5
    #define SLEEP_TIME 10

    void *sleeping(void *);
    pthread_t tid[NUM_THREADS];

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

            for (i = 0; i < NUM_THREADS; i++)
                    pthread_create(&tid[i], NULL, sleeping, (void *)SLEEP_TIME);
            for (i = 0; i < NUM_THREADS; i++)
                    pthread_join(tid[i], NULL);
            printf("main() reporting that all %d threads have terminated\n", i);
            return (0);
    }

    void *
    sleeping(void *arg)
    {
            int sleep_time = (int)arg;
            printf("thread %d sleeping %d seconds ...\n", thr_self(), sleep_time);
            sleep(sleep_time);
            printf("\nthread %d awakening\n", thr_self());
            return (NULL);
    }

    then, I compile this one in 2 way :

    # cc -o thread thread.c -lthr
    and
    # cc -pthread -o pthread thread.c

    here is some of the "new ps" outputs :

    "lwp" is the thread id and "nlwp" the the number of threads.
    -q switch in posix mode (aka SystemV) and -C select processes
    by name (a la pgrep).

    # ./thread& sleep 1; ps -H -O lwp,nlwp -qC thread
    (thread, using -H)
      PID LWP NLWP TTY TIME COMMAND
    85146 100005 6 ttyp0 00:00:00 thread
    85146 100004 6 ttyp0 00:00:00 thread
    85146 100003 6 ttyp0 00:00:00 thread
    85146 100002 6 ttyp0 00:00:00 thread
    85146 100001 6 ttyp0 00:00:00 thread
    85146 85146 6 ttyp0 00:00:00 thread
    # ./pthread& sleep 1; ps -H -O lwp,nlwp -qC thread
    (pthread, using -H)
      PID LWP NLWP TTY TIME COMMAND
    96689 100002 2 ttyp0 00:00:00 pthread
    96689 96689 2 ttyp0 00:00:00 pthread

    is it normal that -pthread only forks only 1 thread where
    -lthr forks 5 of them ?

    # ./thread& sleep 1; ps -O lwp,nlwp -qC thread
    (thread ot pthread, not using -H)
      PID LWP NLWP TTY TIME COMMAND
    73718 100005 6 ttyp0 00:00:00 thread

    is it normal that the selected process is the last forked thread and
    not the thread owner (father) ?

    PS : using -lc_r, there is no thread at all, but I suppose this is an
    expected behaviour.

    CC -current and -hackers

    Cyrille Lefevre. 

    -- 
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