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.
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.
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.
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
21 #include <semaphore.h>
34 size_t ps = sysconf (_SC_PAGESIZE);
35 char tmpfname[] = "/tmp/tst-sem3.XXXXXX";
43 fd = mkstemp (tmpfname);
46 printf ("cannot open temporary file: %m\n");
50 /* Make sure it is always removed. */
53 /* Create one page of data. */
54 memset (data, '\0', ps);
56 /* Write the data to the file. */
57 if (write (fd, data, ps) != (ssize_t) ps)
63 mem = mmap (NULL, ps, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
64 if (mem == MAP_FAILED)
66 printf ("mmap failed: %m\n");
70 s = (sem_t *) (((uintptr_t) mem + __alignof (sem_t))
71 & ~(__alignof (sem_t) - 1));
74 if (sem_init (s, 1, 1) == -1)
80 if (TEMP_FAILURE_RETRY (sem_wait (s)) == -1)
82 puts ("1st wait failed");
87 if (TEMP_FAILURE_RETRY (sem_trywait (s)) != -1)
89 puts ("trywait succeeded");
92 else if (errno != EAGAIN)
94 puts ("trywait didn't return EAGAIN");
100 puts ("going to fork now");
104 puts ("fork failed");
109 /* Play some lock ping-pong. It's our turn to unlock first. */
112 puts ("child: *p != 0");
116 if (sem_post (s) == -1)
118 puts ("child: 1st post failed");
126 if (TEMP_FAILURE_RETRY (sem_wait (s)) == -1)
128 printf ("parent: 2nd wait failed: %m\n");
138 puts ("parent done");