nptl/tst-sem3.c

   1 /* Copyright (C) 2002, 2003 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <semaphore.h>
  22 #include <stdint.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <unistd.h>
  27 #include <sys/mman.h>
  28 #include <sys/wait.h>
  29
  30
  31 int
  32 main (void)
  33 {
  34   size_t ps = sysconf (_SC_PAGESIZE);
  35   char tmpfname[] = "/tmp/tst-sem3.XXXXXX";
  36   char data[ps];
  37   void *mem;
  38   int fd;
  39   sem_t *s;
  40   pid_t pid;
  41   char *p;
  42
  43   fd = mkstemp (tmpfname);
  44   if (fd == -1)
  45     {
  46       printf ("cannot open temporary file: %m\n");
  47       exit (1);
  48     }
  49
  50   /* Make sure it is always removed.  */
  51   unlink (tmpfname);
  52
  53   /* Create one page of data.  */
  54   memset (data, '\0', ps);
  55
  56   /* Write the data to the file.  */
  57   if (write (fd, data, ps) != (ssize_t) ps)
  58     {
  59       puts ("short write");
  60       exit (1);
  61     }
  62
  63   mem = mmap (NULL, ps, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
  64   if (mem == MAP_FAILED)
  65     {
  66       printf ("mmap failed: %m\n");
  67       exit (1);
  68     }
  69
  70   s = (sem_t *) (((uintptr_t) mem + __alignof (sem_t))
  71                  & ~(__alignof (sem_t) - 1));
  72   p = (char *) (s + 1);
  73
  74   if (sem_init (s, 1, 1) == -1)
  75     {
  76       puts ("init failed");
  77       exit (1);
  78     }
  79
  80   if (TEMP_FAILURE_RETRY (sem_wait (s)) == -1)
  81     {
  82       puts ("1st wait failed");
  83       exit (1);
  84     }
  85
  86   errno = 0;
  87   if (TEMP_FAILURE_RETRY (sem_trywait (s)) != -1)
  88     {
  89       puts ("trywait succeeded");
  90       exit (1);
  91     }
  92   else if (errno != EAGAIN)
  93     {
  94       puts ("trywait didn't return EAGAIN");
  95       exit (1);
  96     }
  97
  98   *p = 0;
  99
 100   puts ("going to fork now");
 101   pid = fork ();
 102   if (pid == -1)
 103     {
 104       puts ("fork failed");
 105       exit (1);
 106     }
 107   else if (pid == 0)
 108     {
 109       /* Play some lock ping-pong.  It's our turn to unlock first.  */
 110       if ((*p)++ != 0)
 111         {
 112           puts ("child: *p != 0");
 113           exit (1);
 114         }
 115
 116       if (sem_post (s) == -1)
 117         {
 118           puts ("child: 1st post failed");
 119           exit (1);
 120         }
 121
 122       puts ("child done");
 123     }
 124   else
 125     {
 126       if (TEMP_FAILURE_RETRY (sem_wait (s)) == -1)
 127         {
 128           printf ("parent: 2nd wait failed: %m\n");
 129           exit (1);
 130         }
 131
 132       if (*p != 1)
 133         {
 134           puts ("*p != 1");
 135           exit (1);
 136         }
 137
 138       puts ("parent done");
 139     }
 140
 141   exit (0);
 142 }