usr/src/test/zfs-tests/cmd/mmapwrite/mmapwrite.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #include <unistd.h>
  28 #include <fcntl.h>
  29 #include <stdio.h>
  30 #include <stdlib.h>
  31 #include <sys/mman.h>
  32 #include <pthread.h>
  33
  34 /*
  35  * --------------------------------------------------------------------
  36  * Bug Id: 5032643
  37  *
  38  * Simply writing to a file and mmaping that file at the same time can
  39  * result in deadlock.  Nothing perverse like writing from the file's
  40  * own mapping is required.
  41  * --------------------------------------------------------------------
  42  */
  43
  44 static void *
  45 mapper(void *fdp)
  46 {
  47         void *addr;
  48         int fd = *(int *)fdp;
  49
  50         if ((addr =
  51             mmap(0, 8192, PROT_READ, MAP_SHARED, fd, 0)) == MAP_FAILED) {
  52                 perror("mmap");
  53                 exit(1);
  54         }
  55         for (;;) {
  56                 if (mmap(addr, 8192, PROT_READ,
  57                     MAP_SHARED|MAP_FIXED, fd, 0) == MAP_FAILED) {
  58                         perror("mmap");
  59                         exit(1);
  60                 }
  61         }
  62         /* NOTREACHED */
  63         return ((void *)1);
  64 }
  65
  66 int
  67 main(int argc, char **argv)
  68 {
  69         int fd;
  70         char buf[BUFSIZ];
  71
  72         if (argc != 2) {
  73                 (void) printf("usage: %s <file name>\n", argv[0]);
  74                 exit(1);
  75         }
  76
  77         if ((fd = open(argv[1], O_RDWR|O_CREAT|O_TRUNC, 0666)) == -1) {
  78                 perror("open");
  79                 exit(1);
  80         }
  81
  82         if (pthread_create(NULL, NULL, mapper, &fd) != 0) {
  83                 perror("pthread_create");
  84                 exit(1);
  85         }
  86         for (;;) {
  87                 if (write(fd, buf, sizeof (buf)) == -1) {
  88                         perror("write");
  89                         exit(1);
  90                 }
  91         }
  92
  93         /* NOTREACHED */
  94         return (0);
  95 }