tests/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 <string.h>
  32 #include <sys/mman.h>
  33 #include <pthread.h>
  34
  35 /*
  36  * --------------------------------------------------------------------
  37  * Bug Id: 5032643
  38  *
  39  * Simply writing to a file and mmaping that file at the same time can
  40  * result in deadlock.  Nothing perverse like writing from the file's
  41  * own mapping is required.
  42  * --------------------------------------------------------------------
  43  */
  44
  45 static void *
  46 mapper(void *fdp)
  47 {
  48         void *addr;
  49         int fd = *(int *)fdp;
  50
  51         if ((addr =
  52             mmap(0, 8192, PROT_READ, MAP_SHARED, fd, 0)) == MAP_FAILED) {
  53                 perror("mmap");
  54                 exit(1);
  55         }
  56         for (;;) {
  57                 if (mmap(addr, 8192, PROT_READ,
  58                     MAP_SHARED|MAP_FIXED, fd, 0) == MAP_FAILED) {
  59                         perror("mmap");
  60                         exit(1);
  61                 }
  62         }
  63         /* NOTREACHED */
  64         return ((void *)1);
  65 }
  66
  67 int
  68 main(int argc, char **argv)
  69 {
  70         int fd;
  71         char buf[1024];
  72         pthread_t tid;
  73
  74         memset(buf, 'a', sizeof (buf));
  75
  76         if (argc != 2) {
  77                 (void) printf("usage: %s <file name>\n", argv[0]);
  78                 exit(1);
  79         }
  80
  81         if ((fd = open(argv[1], O_RDWR|O_CREAT|O_TRUNC, 0666)) == -1) {
  82                 perror("open");
  83                 exit(1);
  84         }
  85
  86         (void) pthread_setconcurrency(2);
  87         if (pthread_create(&tid, NULL, mapper, &fd) != 0) {
  88                 perror("pthread_create");
  89                 close(fd);
  90                 exit(1);
  91         }
  92         for (;;) {
  93                 if (write(fd, buf, sizeof (buf)) == -1) {
  94                         perror("write");
  95                         close(fd);
  96                         exit(1);
  97                 }
  98         }
  99
 100         close(fd);
 101
 102         /* NOTREACHED */
 103         return (0);
 104 }