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Date: Sun, 23 Apr 2000 14:09:40 -0400 (EDT)
From: Daniel Eischen <eischen@vigrid.com>
Message-Id: <200004231809.OAA29230@pcnet1.pcnet.com>
To: Alexander@Leidinger.net, current@FreeBSD.ORG
Subject: Re: pthread_cond_broadcast() not delivered
Sender: owner-freebsd-current@FreeBSD.ORG
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Alexander Leidinger wrote:
> Hi,
> 
> (14) netchild@ttyp2% uname -a
> FreeBSD Magelan.Leidinger.net 5.0-CURRENT FreeBSD 5.0-CURRENT #14: Fri Apr 21 17:28:37 CEST 2000     root@:/big/usr/src/sys/compile/WORK  i386
> 
> I've an application which uses pthread_cond_{wait,broadcast}() and
> the debug output gives me the impression that the broadcast did not get
> delivered anymore.
> 
> I run this program only occasionally, but with 4-current (last year) it
> worked, and I haven't changed anything mutex-/cond-related in it since
> then.
> 
> I've attached a short test-prog (1.7k) which shows the same behavior,
> compile it with "cc -D_THREAD_SAFE -pthread test.c" and run "./a.out".

If you want it to work correctly, you have to make the second thread
release the mutex.  Look at it more closely:

    void *
    second_thread(void *arg)
    {
      /* syncronize */
      fprintf(stderr, "Second: lock.\n");
      pthread_mutex_lock(main_mutex);

      fprintf(stderr, "Second: broadcast.\n");
      pthread_cond_broadcast(main_cond);

      fprintf(stderr, "Second: unlock.\n");
      pthread_mutex_lock(main_mutex);
      ^^^^^^^^^^^^^^^^^^

      fprintf(stderr, "Second: sleep.\n");
      sleep(10);

      fprintf(stderr, "Second: exit.\n");
      pthread_exit(0);
    }

-- 
Dan Eischen


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