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Date: Sun, 23 Apr 2000 17:58:45 +0200 (CEST)
From: Alexander Leidinger <Alexander@Leidinger.net>
Subject: pthread_cond_broadcast() not delivered
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--0-1804289383-956505532=:1425
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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".
It should print something like:
---snip---
First: thread started, waiting for pthread_cond_broadcast().
Second: lock.
Second: broadcast.
Second: unlock.
Second: sleep.
First: got broadcast.
First: join.
Second: exit.
---snip---

but it prints:
---snip---
First: thread started, waiting for pthread_cond_broadcast().
Second: lock.
Second: broadcast.
Second: unlock.
Second: sleep.
Second: exit.
---snip---

and waits forever (in state "poll").

Bye,
Alexander.

-- 
            Secret hacker rule #11: hackers read manuals.

http://www.Leidinger.net                  Alexander+Home @ Leidinger.net
  GPG fingerprint = 7423 F3E6 3A7E B334 A9CC  B10A 1F5F 130A A638 6E7E

--0-1804289383-956505532=:1425
Content-Type: TEXT/plain; CHARSET=US-ASCII
Content-Disposition: attachment; filename="test.c"

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

pthread_mutex_t *main_mutex;
pthread_cond_t  *main_cond;

void *
second_thread(void *arg);

int
main(void)
{
  pthread_t *thread;
  int thread_error, ret;

  setvbuf(stdout, NULL, _IONBF, BUFSIZ);
  setvbuf(stderr, NULL, _IONBF, BUFSIZ);

  /* mutex */
  main_mutex = (pthread_mutex_t *)malloc(sizeof(pthread_mutex_t));
  if(main_mutex == NULL)
  {
    return -1;
  }

  do {
    ret = pthread_mutex_init(main_mutex, NULL);
  } while(ret == EAGAIN);
  if(ret != 0) return -1;

  /* cond */
  main_cond = (pthread_cond_t *)malloc(sizeof(pthread_cond_t));
  if(main_cond == NULL)
  {
    return -1;
  }

  do {
      ret = pthread_cond_init(main_cond, NULL);
  } while(ret == EAGAIN);
  if(ret != 0) return -1;

  /* lock mutex */
  pthread_mutex_lock(main_mutex);

  /* thread */
  thread = (pthread_t *)malloc(sizeof(pthread_t));
  if(thread == NULL) pthread_exit(0); /* error, not enough memory */
  /* create pthread */
  do{
    thread_error = pthread_create(thread, NULL, &second_thread, NULL);
  } while(thread_error == EAGAIN);


  fprintf(stderr, "First: thread started, waiting for pthread_cond_broadcast().\n");

  /* syncronize */
  pthread_cond_wait(main_cond, main_mutex);

  fprintf(stderr, "First: got broadcast.\n");
  sleep(2);

  fprintf(stderr, "First: join.\n");
  pthread_join(*thread, NULL);

  exit(0);
}

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);
}

--0-1804289383-956505532=:1425--


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