usr/src/cmd/make/lib/vroot/lock.cc

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