142 lines
2.9 KiB
C
142 lines
2.9 KiB
C
/* Copyright (C) 2002, 2003 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <semaphore.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/mman.h>
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#include <sys/wait.h>
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int
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main (void)
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{
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size_t ps = sysconf (_SC_PAGESIZE);
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char tmpfname[] = "/tmp/tst-sem3.XXXXXX";
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char data[ps];
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void *mem;
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int fd;
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sem_t *s;
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pid_t pid;
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char *p;
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fd = mkstemp (tmpfname);
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if (fd == -1)
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{
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printf ("cannot open temporary file: %m\n");
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exit (1);
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}
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/* Make sure it is always removed. */
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unlink (tmpfname);
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/* Create one page of data. */
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memset (data, '\0', ps);
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/* Write the data to the file. */
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if (write (fd, data, ps) != (ssize_t) ps)
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{
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puts ("short write");
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exit (1);
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}
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mem = mmap (NULL, ps, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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if (mem == MAP_FAILED)
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{
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printf ("mmap failed: %m\n");
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exit (1);
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}
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s = (sem_t *) (((uintptr_t) mem + __alignof (sem_t))
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& ~(__alignof (sem_t) - 1));
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p = (char *) (s + 1);
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if (sem_init (s, 1, 1) == -1)
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{
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puts ("init failed");
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exit (1);
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}
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if (TEMP_FAILURE_RETRY (sem_wait (s)) == -1)
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{
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puts ("1st wait failed");
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exit (1);
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}
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errno = 0;
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if (TEMP_FAILURE_RETRY (sem_trywait (s)) != -1)
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{
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puts ("trywait succeeded");
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exit (1);
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}
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else if (errno != EAGAIN)
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{
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puts ("trywait didn't return EAGAIN");
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exit (1);
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}
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*p = 0;
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puts ("going to fork now");
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pid = fork ();
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if (pid == -1)
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{
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puts ("fork failed");
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exit (1);
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}
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else if (pid == 0)
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{
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/* Play some lock ping-pong. It's our turn to unlock first. */
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if ((*p)++ != 0)
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{
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puts ("child: *p != 0");
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exit (1);
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}
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if (sem_post (s) == -1)
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{
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puts ("child: 1st post failed");
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exit (1);
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}
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puts ("child done");
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}
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else
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{
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if (TEMP_FAILURE_RETRY (sem_wait (s)) == -1)
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{
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printf ("parent: 2nd wait failed: %m\n");
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exit (1);
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}
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if (*p != 1)
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{
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puts ("*p != 1");
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exit (1);
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}
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puts ("parent done");
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}
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exit (0);
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}
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