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