sysdeps/pthread/tst-sem3.c

   1 /* Copyright (C) 2002-2024 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <semaphore.h>
  20 #include <stdint.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <sys/mman.h>
  26 #include <sys/wait.h>
  27
  28
  29 int
  30 do_test (void)
  31 {
  32   size_t ps = sysconf (_SC_PAGESIZE);
  33   char tmpfname[] = "/tmp/tst-sem3.XXXXXX";
  34   char data[ps];
  35   void *mem;
  36   int fd;
  37   sem_t *s;
  38   pid_t pid;
  39   char *p;
  40
  41   fd = mkstemp (tmpfname);
  42   if (fd == -1)
  43     {
  44       printf ("cannot open temporary file: %m\n");
  45       return 1;
  46     }
  47
  48   /* Make sure it is always removed.  */
  49   unlink (tmpfname);
  50
  51   /* Create one page of data.  */
  52   memset (data, '\0', ps);
  53
  54   /* Write the data to the file.  */
  55   if (write (fd, data, ps) != (ssize_t) ps)
  56     {
  57       puts ("short write");
  58       return 1;
  59     }
  60
  61   mem = mmap (NULL, ps, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
  62   if (mem == MAP_FAILED)
  63     {
  64       printf ("mmap failed: %m\n");
  65       return 1;
  66     }
  67
  68   s = (sem_t *) (((uintptr_t) mem + __alignof (sem_t))
  69                  & ~(__alignof (sem_t) - 1));
  70   p = (char *) (s + 1);
  71
  72   if (sem_init (s, 1, 1) == -1)
  73     {
  74       puts ("init failed");
  75       return 1;
  76     }
  77
  78   if (TEMP_FAILURE_RETRY (sem_wait (s)) == -1)
  79     {
  80       puts ("1st wait failed");
  81       return 1;
  82     }
  83
  84   errno = 0;
  85   if (TEMP_FAILURE_RETRY (sem_trywait (s)) != -1)
  86     {
  87       puts ("trywait succeeded");
  88       return 1;
  89     }
  90   else if (errno != EAGAIN)
  91     {
  92       puts ("trywait didn't return EAGAIN");
  93       return 1;
  94     }
  95
  96   *p = 0;
  97
  98   puts ("going to fork now");
  99   pid = fork ();
 100   if (pid == -1)
 101     {
 102       puts ("fork failed");
 103       return 1;
 104     }
 105   else if (pid == 0)
 106     {
 107       /* Play some lock ping-pong.  It's our turn to unlock first.  */
 108       if ((*p)++ != 0)
 109         {
 110           puts ("child: *p != 0");
 111           return 1;
 112         }
 113
 114       if (sem_post (s) == -1)
 115         {
 116           puts ("child: 1st post failed");
 117           return 1;
 118         }
 119
 120       puts ("child done");
 121     }
 122   else
 123     {
 124       if (TEMP_FAILURE_RETRY (sem_wait (s)) == -1)
 125         {
 126           printf ("parent: 2nd wait failed: %m\n");
 127           return 1;
 128         }
 129
 130       if (*p != 1)
 131         {
 132           puts ("*p != 1");
 133           return 1;
 134         }
 135
 136       puts ("parent done");
 137     }
 138
 139   return 0;
 140 }
 141
 142 #define TEST_FUNCTION do_test ()
 143 #include "../test-skeleton.c"