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 #if !defined(linux)
41 extern char *sys_errlist[];
42 extern int sys_nerr;
43 #endif
44
45 static void file_lock_error(char *msg, char *file, char *str, int arg1, int arg2);
46
47 #define BLOCK_INTERUPTS sigfillset(&newset) ; \
48 sigprocmask(SIG_SETMASK, &newset, &oldset)
49
50 #define UNBLOCK_INTERUPTS \
51 sigprocmask(SIG_SETMASK, &oldset, &newset)
52
53 /*
54 * This code stolen from the NSE library and changed to not depend
55 * upon any NSE routines or header files.
56 *
57 * Simple file locking.
58 * Create a symlink to a file. The "test and set" will be
59 * atomic as creating the symlink provides both functions.
60 *
61 * The timeout value specifies how long to wait for stale locks
62 * to disappear. If the lock is more than 'timeout' seconds old
63 * then it is ok to blow it away. This part has a small window
64 * of vunerability as the operations of testing the time,
65 * removing the lock and creating a new one are not atomic.
66 * It would be possible for two processes to both decide to blow
67 * away the lock and then have process A remove the lock and establish
68 * its own, and then then have process B remove the lock which accidentily
69 * removes A's lock rather than the stale one.
70 *
71 * A further complication is with the NFS. If the file in question is
72 * being served by an NFS server, then its time is set by that server.
73 * We can not use the time on the client machine to check for a stale
74 * lock. Therefore, a temp file on the server is created to get
75 * the servers current time.
76 *
77 * Returns an error message. NULL return means the lock was obtained.
78 *
79 * 12/6/91 Added the parameter "file_locked". Before this parameter
80 * was added, the calling procedure would have to wait for file_lock()
81 * to return before it sets the flag. If the user interrupted "make"
82 * between the time the lock was acquired and the time file_lock()
83 * returns, make wouldn't know that the file has been locked, and therefore
84 * it wouldn' remove the lock. Setting the flag right after locking the file
85 * makes this window much smaller.
86 */
87
88 int
89 file_lock(char *name, char *lockname, int *file_locked, int timeout)
90 {
91 int counter = 0;
92 static char msg[MAXPATHLEN+1];
93 int printed_warning = 0;
94 int r;
95 struct stat statb;
96 sigset_t newset;
97 sigset_t oldset;
98
99 *file_locked = 0;
100 if (timeout <= 0) {
101 timeout = 120;
102 }
103 for (;;) {
104 BLOCK_INTERUPTS;
105 r = symlink(name, lockname);
106 if (r == 0) {
107 *file_locked = 1;
108 UNBLOCK_INTERUPTS;
109 return 0; /* success */
110 }
111 UNBLOCK_INTERUPTS;
112
113 if (errno != EEXIST) {
114 file_lock_error(msg, name, NOCATGETS("symlink(%s, %s)"),
115 (int) name, (int) lockname);
116 fprintf(stderr, "%s", msg);
117 return errno;
118 }
119
120 counter = 0;
121 for (;;) {
122 sleep(1);
123 r = lstat(lockname, &statb);
124 if (r == -1) {
125 /*
126 * The lock must have just gone away - try
127 * again.
128 */
129 break;
130 }
131
132 if ((counter > 5) && (!printed_warning)) {
133 /* Print waiting message after 5 secs */
134 #if defined(SUN5_0) || defined(HP_UX) || defined(linux)
135 (void) getcwd(msg, MAXPATHLEN);
136 #else
137 (void) getwd(msg);
138 #endif
139 fprintf(stderr,
140 catgets(libmksdmsi18n_catd, 1, 162, "file_lock: file %s is already locked.\n"),
141 name);
142 fprintf(stderr,
143 catgets(libmksdmsi18n_catd, 1, 163, "file_lock: will periodically check the lockfile %s for two minutes.\n"),
144 lockname);
145 fprintf(stderr,
146 catgets(libmksdmsi18n_catd, 1, 144, "Current working directory %s\n"),
147 msg);
148
149 printed_warning = 1;
150 }
151
152 if (++counter > timeout ) {
153 /*
154 * Waited enough - return an error..
155 */
156 return EEXIST;
157 }
158 }
159 }
160 /* NOTREACHED */
161 }
162
163 /*
164 * Format a message telling why the lock could not be created.
165 */
166 static void
167 file_lock_error(char *msg, char *file, char *str, int arg1, int arg2)
168 {
169 int len;
170
171 sprintf(msg, catgets(libmksdmsi18n_catd, 1, 145, "Could not lock file `%s'; "), file);
172 len = strlen(msg);
173 sprintf(&msg[len], str, arg1, arg2);
174 strcat(msg, catgets(libmksdmsi18n_catd, 1, 146, " failed - "));
175 #if !defined(linux)
176 if (errno < sys_nerr) {
177 #ifdef SUN4_x
178 strcat(msg, sys_errlist[errno]);
179 #endif
180 #ifdef SUN5_0
181 strcat(msg, strerror(errno));
182 #endif
183 } else {
184 len = strlen(msg);
185 sprintf(&msg[len], NOCATGETS("errno %d"), errno);
186 }
187 #else
188 strcat(msg, strerror(errno));
189 #endif
190 }
191