lib/vroot/lock.cc

10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe/*
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * CDDL HEADER START
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe *
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * The contents of this file are subject to the terms of the
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * Common Development and Distribution License (the "License").
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * You may not use this file except in compliance with the License.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe *
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * or http://www.opensolaris.org/os/licensing.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * See the License for the specific language governing permissions
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * and limitations under the License.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe *
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * When distributing Covered Code, include this CDDL HEADER in each
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * If applicable, add the following below this CDDL HEADER, with the
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * fields enclosed by brackets "[]" replaced with your own identifying
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * information: Portions Copyright [yyyy] [name of copyright owner]
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe *
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * CDDL HEADER END
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe */
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe/*
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * Use is subject to license terms.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe */
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <stdio.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <stdlib.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <string.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <sys/errno.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <sys/param.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <sys/stat.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <sys/types.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <unistd.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <vroot/vroot.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <signal.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <errno.h>          /* errno */
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#include <libintl.h>
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Loweextern  char        *sys_errlist[];
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Loweextern  int     sys_nerr;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowestatic  void        file_lock_error(char *msg, char *file, char *str, int arg1, int arg2);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#define BLOCK_INTERUPTS sigfillset(&newset) ; \
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    sigprocmask(SIG_SETMASK, &newset, &oldset)
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe#define UNBLOCK_INTERUPTS \
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    sigprocmask(SIG_SETMASK, &oldset, &newset)
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe/*
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * This code stolen from the NSE library and changed to not depend
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * upon any NSE routines or header files.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe *
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * Simple file locking.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * Create a symlink to a file.  The "test and set" will be
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * atomic as creating the symlink provides both functions.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe *
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * The timeout value specifies how long to wait for stale locks
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * to disappear.  If the lock is more than 'timeout' seconds old
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * then it is ok to blow it away.  This part has a small window
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * of vunerability as the operations of testing the time,
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * removing the lock and creating a new one are not atomic.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * It would be possible for two processes to both decide to blow
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * away the lock and then have process A remove the lock and establish
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * its own, and then then have process B remove the lock which accidentily
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * removes A's lock rather than the stale one.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe *
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * A further complication is with the NFS.  If the file in question is
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * being served by an NFS server, then its time is set by that server.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * We can not use the time on the client machine to check for a stale
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * lock.  Therefore, a temp file on the server is created to get
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * the servers current time.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe *
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * Returns an error message.  NULL return means the lock was obtained.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe *
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * 12/6/91 Added the parameter "file_locked".  Before this parameter
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * was added, the calling procedure would have to wait for file_lock()
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * to return before it sets the flag. If the user interrupted "make"
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * between the time the lock was acquired and the time file_lock()
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * returns, make wouldn't know that the file has been locked, and therefore
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * it wouldn' remove the lock. Setting the flag right after locking the file
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * makes this window much smaller.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe */
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Loweint
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowefile_lock(char *name, char *lockname, int *file_locked, int timeout)
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe{
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    int     counter = 0;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    static char msg[MAXPATHLEN+1];
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    int     printed_warning = 0;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    int     r;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    struct stat statb;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    sigset_t newset;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    sigset_t oldset;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    *file_locked = 0;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    if (timeout <= 0) {
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        timeout = 120;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    }
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    for (;;) {
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        BLOCK_INTERUPTS;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        r = symlink(name, lockname);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        if (r == 0) {
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            *file_locked = 1;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            UNBLOCK_INTERUPTS;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            return 0; /* success */
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        }
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        UNBLOCK_INTERUPTS;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        if (errno != EEXIST) {
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            file_lock_error(msg, name, (char *)"symlink(%s, %s)",
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                (int) name, (int) lockname);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            fprintf(stderr, "%s", msg);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            return errno;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        }
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        counter = 0;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        for (;;) {
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            sleep(1);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            r = lstat(lockname, &statb);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            if (r == -1) {
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                /*
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                 * The lock must have just gone away - try
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                 * again.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                 */
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                break;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            }
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            if ((counter > 5) && (!printed_warning)) {
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                /* Print waiting message after 5 secs */
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                (void) getcwd(msg, MAXPATHLEN);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                fprintf(stderr,
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                    gettext("file_lock: file %s is already locked.\n"),
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                    name);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                fprintf(stderr,
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                    gettext("file_lock: will periodically check the lockfile %s for two minutes.\n"),
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                    lockname);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                fprintf(stderr,
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                    gettext("Current working directory %s\n"),
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                    msg);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                printed_warning = 1;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            }
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            if (++counter > timeout ) {
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                /*
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                 * Waited enough - return an error..
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                 */
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe                return EEXIST;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe            }
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        }
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    }
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    /* NOTREACHED */
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe}
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe/*
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe * Format a message telling why the lock could not be created.
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe */
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowestatic  void
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowefile_lock_error(char *msg, char *file, char *str, int arg1, int arg2)
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe{
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    int     len;
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    sprintf(msg, gettext("Could not lock file `%s'; "), file);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    len = strlen(msg);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    sprintf(&msg[len], str, arg1, arg2);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    strcat(msg, gettext(" failed - "));
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    if (errno < sys_nerr) {
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        strcat(msg, strerror(errno));
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    } else {
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        len = strlen(msg);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe        sprintf(&msg[len], "errno %d", errno);
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe    }
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe}
10d63b7db37a83b39c7f511cf9426c9d03ea0760Richard Lowe