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 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25
26 #include <avo/intl.h> /* for NOCATGETS */
27 #include <stdio.h>
28 #include <stdlib.h>
29 #include <string.h>
30 #include <sys/errno.h>
31 #include <sys/param.h>
32 #include <sys/stat.h>
33 #include <sys/types.h>
34 #include <unistd.h>
35 #include <vroot/vroot.h>
36 #include <mksdmsi18n/mksdmsi18n.h>
37 #include <signal.h>
38 #include <errno.h> /* errno */
39
40 extern char *sys_errlist[];
41 extern int sys_nerr;
42
43 static void file_lock_error(char *msg, char *file, char *str, int arg1, int arg2);
44
45 #define BLOCK_INTERUPTS sigfillset(&newset) ; \
46 sigprocmask(SIG_SETMASK, &newset, &oldset)
47
48 #define UNBLOCK_INTERUPTS \
49 sigprocmask(SIG_SETMASK, &oldset, &newset)
50
51 /*
52 * This code stolen from the NSE library and changed to not depend
53 * upon any NSE routines or header files.
54 *
55 * Simple file locking.
56 * Create a symlink to a file. The "test and set" will be
57 * atomic as creating the symlink provides both functions.
58 *
59 * The timeout value specifies how long to wait for stale locks
60 * to disappear. If the lock is more than 'timeout' seconds old
61 * then it is ok to blow it away. This part has a small window
62 * of vunerability as the operations of testing the time,
63 * removing the lock and creating a new one are not atomic.
64 * It would be possible for two processes to both decide to blow
65 * away the lock and then have process A remove the lock and establish
66 * its own, and then then have process B remove the lock which accidentily
67 * removes A's lock rather than the stale one.
68 *
69 * A further complication is with the NFS. If the file in question is
70 * being served by an NFS server, then its time is set by that server.
71 * We can not use the time on the client machine to check for a stale
72 * lock. Therefore, a temp file on the server is created to get
73 * the servers current time.
74 *
75 * Returns an error message. NULL return means the lock was obtained.
76 *
77 * 12/6/91 Added the parameter "file_locked". Before this parameter
78 * was added, the calling procedure would have to wait for file_lock()
79 * to return before it sets the flag. If the user interrupted "make"
80 * between the time the lock was acquired and the time file_lock()
81 * returns, make wouldn't know that the file has been locked, and therefore
82 * it wouldn' remove the lock. Setting the flag right after locking the file
83 * makes this window much smaller.
84 */
85
86 int
87 file_lock(char *name, char *lockname, int *file_locked, int timeout)
88 {
89 int counter = 0;
90 static char msg[MAXPATHLEN+1];
91 int printed_warning = 0;
92 int r;
93 struct stat statb;
94 sigset_t newset;
95 sigset_t oldset;
96
97 *file_locked = 0;
98 if (timeout <= 0) {
99 timeout = 120;
100 }
101 for (;;) {
102 BLOCK_INTERUPTS;
103 r = symlink(name, lockname);
104 if (r == 0) {
105 *file_locked = 1;
106 UNBLOCK_INTERUPTS;
107 return 0; /* success */
108 }
109 UNBLOCK_INTERUPTS;
110
111 if (errno != EEXIST) {
112 file_lock_error(msg, name, (char *)NOCATGETS("symlink(%s, %s)"),
113 (int) name, (int) lockname);
114 fprintf(stderr, "%s", msg);
115 return errno;
116 }
117
118 counter = 0;
119 for (;;) {
120 sleep(1);
121 r = lstat(lockname, &statb);
122 if (r == -1) {
123 /*
124 * The lock must have just gone away - try
125 * again.
126 */
127 break;
128 }
129
130 if ((counter > 5) && (!printed_warning)) {
131 /* Print waiting message after 5 secs */
132 (void) getcwd(msg, MAXPATHLEN);
133 fprintf(stderr,
134 catgets(libmksdmsi18n_catd, 1, 162, "file_lock: file %s is already locked.\n"),
135 name);
136 fprintf(stderr,
137 catgets(libmksdmsi18n_catd, 1, 163, "file_lock: will periodically check the lockfile %s for two minutes.\n"),
138 lockname);
139 fprintf(stderr,
140 catgets(libmksdmsi18n_catd, 1, 144, "Current working directory %s\n"),
141 msg);
142
143 printed_warning = 1;
144 }
145
146 if (++counter > timeout ) {
147 /*
148 * Waited enough - return an error..
149 */
150 return EEXIST;
151 }
152 }
153 }
154 /* NOTREACHED */
155 }
156
157 /*
158 * Format a message telling why the lock could not be created.
159 */
160 static void
161 file_lock_error(char *msg, char *file, char *str, int arg1, int arg2)
162 {
163 int len;
164
165 sprintf(msg, catgets(libmksdmsi18n_catd, 1, 145, "Could not lock file `%s'; "), file);
166 len = strlen(msg);
167 sprintf(&msg[len], str, arg1, arg2);
168 strcat(msg, catgets(libmksdmsi18n_catd, 1, 146, " failed - "));
169 if (errno < sys_nerr) {
170 strcat(msg, strerror(errno));
171 } else {
172 len = strlen(msg);
173 sprintf(&msg[len], NOCATGETS("errno %d"), errno);
174 }
175 }
176