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 * $FreeBSD$
21 */
22
23 /*
24 * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
25 * Use is subject to license terms.
26 */
27
28 #pragma ident "@(#)mmapwrite.c 1.4 07/05/25 SMI"
29
30 #include <unistd.h>
31 #include <fcntl.h>
32 #include <stdio.h>
33 #include <stdlib.h>
34 #include <sys/mman.h>
35 #include <pthread.h>
36
37 /*
38 * --------------------------------------------------------------------
39 * Bug Id: 5032643
40 *
41 * Simply writing to a file and mmaping that file at the same time can
42 * result in deadlock. Nothing perverse like writing from the file's
43 * own mapping is required.
44 * --------------------------------------------------------------------
45 */
46
47 static void *
mapper(void * fdp)48 mapper(void *fdp)
49 {
50 void *addr;
51 int fd = *(int *)fdp;
52
53 if ((addr =
54 mmap(0, 8192, PROT_READ, MAP_SHARED, fd, 0)) == MAP_FAILED) {
55 perror("mmap");
56 exit(1);
57 }
58 for (;;) {
59 if (mmap(addr, 8192, PROT_READ,
60 MAP_SHARED|MAP_FIXED, fd, 0) == MAP_FAILED) {
61 perror("mmap");
62 exit(1);
63 }
64 }
65 /* NOTREACHED */
66 return ((void *)1);
67 }
68
69 int
main(int argc,char ** argv)70 main(int argc, char **argv)
71 {
72 int fd;
73 char buf[BUFSIZ];
74 pthread_t pt;
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 if (pthread_create(&pt, NULL, mapper, &fd) != 0) {
87 perror("pthread_create");
88 exit(1);
89 }
90 for (;;) {
91 if (write(fd, buf, sizeof (buf)) == -1) {
92 perror("write");
93 exit(1);
94 }
95 }
96
97 /* NOTREACHED */
98 return (0);
99 }
100