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 https://opensource.org/licenses/CDDL-1.0.
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 #include <errno.h>
35 #include <err.h>
36 
37 /*
38  * --------------------------------------------------------------------
39  * Bug Issue Id: #7512
40  * The bug time sequence:
41  * 1. context #1, zfs_write assign a txg "n".
42  * 2. In the same process, context #2, mmap page fault (which means the mm_sem
43  *    is hold) occurred, zfs_dirty_inode open a txg failed, and wait previous
44  *    txg "n" completed.
45  * 3. context #1 call zfs_uiomove to write, however page fault is occurred in
46  *    zfs_uiomove, which means it needs mm_sem, but mm_sem is hold by
47  *    context #2, so it stuck and can't complete, then txg "n" will not
48  *    complete.
49  *
50  * So context #1 and context #2 trap into the "dead lock".
51  * --------------------------------------------------------------------
52  */
53 
54 #define	NORMAL_WRITE_TH_NUM	2
55 #define	MAX_WRITE_BYTES	262144000
56 
57 static void *
58 normal_writer(void *filename)
59 {
60 	char *file_path = filename;
61 	int fd = -1;
62 	ssize_t write_num = 0;
63 	int page_size = getpagesize();
64 
65 	fd = open(file_path, O_RDWR | O_CREAT, 0777);
66 	if (fd == -1) {
67 		err(1, "failed to open %s", file_path);
68 	}
69 
70 	char buf = 'z';
71 	off_t bytes_written = 0;
72 
73 	while (bytes_written < MAX_WRITE_BYTES) {
74 		write_num = write(fd, &buf, 1);
75 		if (write_num == 0) {
76 			err(1, "write failed!");
77 			break;
78 		}
79 		if ((bytes_written = lseek(fd, page_size, SEEK_CUR)) == -1) {
80 			err(1, "lseek failed on %s: %s", file_path,
81 			    strerror(errno));
82 			break;
83 		}
84 	}
85 
86 	if (close(fd) != 0)
87 		err(1, "failed to close file");
88 
89 	return (NULL);
90 }
91 
92 static void *
93 map_writer(void *filename)
94 {
95 	int fd = -1;
96 	int ret = 0;
97 	char *buf = NULL;
98 	int page_size = getpagesize();
99 	char *file_path = filename;
100 
101 	while (1) {
102 		fd = open(file_path, O_RDWR);
103 		if (fd == -1) {
104 			if (errno == ENOENT) {
105 				fd = open(file_path, O_RDWR | O_CREAT, 0777);
106 				if (fd == -1) {
107 					err(1, "open file failed");
108 				}
109 				ret = ftruncate(fd, page_size);
110 				if (ret == -1) {
111 					err(1, "truncate file failed");
112 				}
113 			} else {
114 				err(1, "open file failed");
115 			}
116 		}
117 
118 		if ((buf = mmap(NULL, page_size, PROT_READ | PROT_WRITE,
119 		    MAP_SHARED, fd, 0)) == MAP_FAILED) {
120 			err(1, "map file failed");
121 		}
122 
123 		if (fd != -1)
124 			close(fd);
125 
126 		char s[10] = {0, };
127 		memcpy(buf, s, 10);
128 		ret = munmap(buf, page_size);
129 		if (ret != 0) {
130 			err(1, "unmap file failed");
131 		}
132 	}
133 }
134 
135 int
136 main(int argc, char **argv)
137 {
138 	pthread_t map_write_tid;
139 	pthread_t normal_write_tid[NORMAL_WRITE_TH_NUM];
140 	int i = 0;
141 
142 	if (argc != 3) {
143 		(void) printf("usage: %s <normal write file name> "
144 		    "<map write file name>\n", argv[0]);
145 		exit(1);
146 	}
147 
148 	for (i = 0; i < NORMAL_WRITE_TH_NUM; i++) {
149 		if (pthread_create(&normal_write_tid[i], NULL, normal_writer,
150 		    argv[1])) {
151 			err(1, "pthread_create normal_writer failed.");
152 		}
153 	}
154 
155 	if (pthread_create(&map_write_tid, NULL, map_writer, argv[2])) {
156 		err(1, "pthread_create map_writer failed.");
157 	}
158 
159 	pthread_join(map_write_tid, NULL);
160 	return (0);
161 }
162