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 #pragma ident "@(#)mmapwrite.c 1.4 07/05/25 SMI"
28
29 #include <unistd.h>
30 #include <fcntl.h>
31 #include <stdio.h>
32 #include <stdlib.h>
33 #include <sys/mman.h>
34 #include <pthread.h>
35
36 /*
37 * --------------------------------------------------------------------
38 * Bug Id: 5032643
39 *
40 * Simply writing to a file and mmaping that file at the same time can
41 * result in deadlock. Nothing perverse like writing from the file's
42 * own mapping is required.
43 * --------------------------------------------------------------------
44 */
45
46 static void *
mapper(void * fdp)47 mapper(void *fdp)
48 {
49 void *addr;
50 int fd = *(int *)fdp;
51
52 if ((addr =
53 mmap(0, 8192, PROT_READ, MAP_SHARED, fd, 0)) == MAP_FAILED) {
54 perror("mmap");
55 exit(1);
56 }
57 for (;;) {
58 if (mmap(addr, 8192, PROT_READ,
59 MAP_SHARED|MAP_FIXED, fd, 0) == MAP_FAILED) {
60 perror("mmap");
61 exit(1);
62 }
63 }
64 /* NOTREACHED */
65 return ((void *)1);
66 }
67
68 int
main(int argc,char ** argv)69 main(int argc, char **argv)
70 {
71 int fd;
72 char buf[BUFSIZ];
73 pthread_t pt;
74
75 if (argc != 2) {
76 (void) printf("usage: %s <file name>\n", argv[0]);
77 exit(1);
78 }
79
80 if ((fd = open(argv[1], O_RDWR|O_CREAT|O_TRUNC, 0666)) == -1) {
81 perror("open");
82 exit(1);
83 }
84
85 if (pthread_create(&pt, NULL, mapper, &fd) != 0) {
86 perror("pthread_create");
87 exit(1);
88 }
89 for (;;) {
90 if (write(fd, buf, sizeof (buf)) == -1) {
91 perror("write");
92 exit(1);
93 }
94 }
95
96 /* NOTREACHED */
97 return (0);
98 }
99