linuxthreads/Examples/ex13.c

   1 /* Test for Pthreads/mutexes.
   2    Copyright (C) 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Kurt Garloff <garloff@suse.de>, 2000.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public License as
   8    published by the Free Software Foundation; either version 2.1 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <errno.h>
  22 #include <pthread.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <unistd.h>
  27
  28 static void *thread_start (void *ptr) __attribute__ ((__noreturn__));
  29
  30
  31 struct thr_ctrl
  32 {
  33   pthread_mutex_t mutex;
  34   pthread_cond_t cond;
  35   int retval;
  36 };
  37
  38 static void
  39 dump_mut (pthread_mutex_t * mut)
  40 {
  41   size_t i;
  42   for (i = 0; i < sizeof (*mut); i++)
  43     printf (" %02x", *((unsigned char *) mut + i));
  44   printf ("\n");
  45 };
  46
  47 /* Helper, the opposite of pthread_cond_wait (cond, mut).  */
  48 static void
  49 pthr_cond_signal_mutex (pthread_cond_t * cond, pthread_mutex_t * mut)
  50 {
  51   int err;
  52   err = pthread_mutex_lock (mut);
  53   if (err)
  54     printf ("mutex_lock  : %s\n", strerror (err));
  55   err = pthread_cond_signal (cond);
  56   if (err)
  57     printf ("cond_signal : %s\n", strerror (err));
  58   err = pthread_mutex_unlock (mut);
  59   if (err)
  60     printf ("mutex_unlock: %s\n", strerror (err));
  61 }
  62
  63 static void *
  64 thread_start (void *ptr)
  65 {
  66   struct thr_ctrl *tc = ptr;
  67   /* Do initialization.  */
  68   /* ... */
  69   /* Signal that we are ready.  */
  70   pthr_cond_signal_mutex (&tc->cond, &tc->mutex);
  71   sleep (2);
  72   pthr_cond_signal_mutex (&tc->cond, &tc->mutex);
  73   tc->retval = 0;
  74   pthread_exit (&tc->retval);
  75 }
  76
  77 int
  78 main (void)
  79 {
  80   struct thr_ctrl threadctrl;
  81   pthread_t thread;
  82   int err;
  83   void *res = &threadctrl.retval;
  84   pthread_mutexattr_t mutattr;
  85   pthread_mutexattr_init (&mutattr);
  86   pthread_mutex_init (&threadctrl.mutex, &mutattr);
  87   pthread_cond_init (&threadctrl.cond, NULL);
  88   err = pthread_mutex_lock (&threadctrl.mutex);
  89   if (err)
  90     printf ("mutex_lock : %s\n", strerror (err));
  91   dump_mut (&threadctrl.mutex);
  92   pthread_create (&thread, NULL, thread_start, &threadctrl);
  93   /* Wait until it's ready.  */
  94   err = pthread_cond_wait (&threadctrl.cond, &threadctrl.mutex);
  95   if (err)
  96     printf ("cond_wait  : %s\n", strerror (err));
  97   /* Now, we should have acquired the mutex again!  */
  98   dump_mut (&threadctrl.mutex);
  99   sleep (1);
 100   dump_mut (&threadctrl.mutex);
 101   err = pthread_cond_wait (&threadctrl.cond, &threadctrl.mutex);
 102   if (err)
 103     {
 104       printf ("cond_wait  : %s\n", strerror (err));
 105       printf ("ERROR\n");
 106       abort ();
 107     };
 108   dump_mut (&threadctrl.mutex);
 109   pthread_join (thread, &res);
 110   printf ("OK\n");
 111   return 0;
 112 }