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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/errno.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <vroot/vroot.h>
#include <signal.h>
#include <errno.h> /* errno */
#include <libintl.h>
static void file_lock_error(char *msg, char *file, const char *str,
char *arg1, char * arg2);
#define BLOCK_INTERUPTS sigfillset(&newset) ; \
sigprocmask(SIG_SETMASK, &newset, &oldset)
#define UNBLOCK_INTERUPTS \
sigprocmask(SIG_SETMASK, &oldset, &newset)
/*
* This code stolen from the NSE library and changed to not depend
* upon any NSE routines or header files.
*
* Simple file locking.
* Create a symlink to a file. The "test and set" will be
* atomic as creating the symlink provides both functions.
*
* The timeout value specifies how long to wait for stale locks
* to disappear. If the lock is more than 'timeout' seconds old
* then it is ok to blow it away. This part has a small window
* of vunerability as the operations of testing the time,
* removing the lock and creating a new one are not atomic.
* It would be possible for two processes to both decide to blow
* away the lock and then have process A remove the lock and establish
* its own, and then then have process B remove the lock which accidentily
* removes A's lock rather than the stale one.
*
* A further complication is with the NFS. If the file in question is
* being served by an NFS server, then its time is set by that server.
* We can not use the time on the client machine to check for a stale
* lock. Therefore, a temp file on the server is created to get
* the servers current time.
*
* Returns an error message. NULL return means the lock was obtained.
*
* 12/6/91 Added the parameter "file_locked". Before this parameter
* was added, the calling procedure would have to wait for file_lock()
* to return before it sets the flag. If the user interrupted "make"
* between the time the lock was acquired and the time file_lock()
* returns, make wouldn't know that the file has been locked, and therefore
* it wouldn' remove the lock. Setting the flag right after locking the file
* makes this window much smaller.
*/
int
file_lock(char *name, char *lockname, int *file_locked, int timeout)
{
int counter = 0;
static char msg[MAXPATHLEN+1];
int printed_warning = 0;
int r;
struct stat statb;
sigset_t newset;
sigset_t oldset;
*file_locked = 0;
if (timeout <= 0) {
timeout = 120;
}
for (;;) {
BLOCK_INTERUPTS;
r = symlink(name, lockname);
if (r == 0) {
*file_locked = 1;
UNBLOCK_INTERUPTS;
return 0; /* success */
}
UNBLOCK_INTERUPTS;
if (errno != EEXIST) {
file_lock_error(msg, name, "symlink(%s, %s)",
name, lockname);
fprintf(stderr, "%s", msg);
return errno;
}
counter = 0;
for (;;) {
sleep(1);
r = lstat(lockname, &statb);
if (r == -1) {
/*
* The lock must have just gone away - try
* again.
*/
break;
}
if ((counter > 5) && (!printed_warning)) {
/* Print waiting message after 5 secs */
(void) getcwd(msg, MAXPATHLEN);
fprintf(stderr, gettext(
"file_lock: file %s is already locked.\n"),
name);
fprintf(stderr, gettext(
"file_lock: will periodically check the "
"lockfile %s for two minutes.\n"),
lockname);
fprintf(stderr, gettext(
"Current working directory %s\n"), msg);
printed_warning = 1;
}
if (++counter > timeout ) {
/*
* Waited enough - return an error..
*/
return EEXIST;
}
}
}
/* NOTREACHED */
}
/*
* Format a message telling why the lock could not be created.
*/
static void
file_lock_error(char *msg, char *file, const char *str, char *arg1, char *arg2)
{
int len, err;
char *ptr;
sprintf(msg, gettext("Could not lock file `%s'; "), file);
len = strlen(msg);
sprintf(&msg[len], str, arg1, arg2);
strcat(msg, gettext(" failed - "));
err = errno;
errno = 0;
ptr = strerror(err);
if (errno != EINVAL) {
strcat(msg, ptr);
} else {
len = strlen(msg);
sprintf(&msg[len], "errno %d", err);
}
}
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