1  /* Copyright (C) 2002-2023 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"