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Annotation of coherent/b/etc/init/lock.c, revision 1.1

1.1     ! root        1: /*
        !             2:  *  lock.c
        !             3:  *
        !             4:  *  Provide a locking mechanism for UUCP
        !             5:  */
        !             6: 
        !             7: #include <stdio.h>
        !             8: #include <access.h>
        !             9: #include <sys/stat.h>
        !            10: 
        !            11: char *gen_res_name();
        !            12: 
        !            13: #ifdef UUCP
        !            14: #include "dcp.h"
        !            15: #else
        !            16: #define SPOOLDIR       "/usr/spool/uucp"
        !            17: #define LOCKSIG                9       /* Significant Chars of Lockable Resources.  */
        !            18: #define LOKFLEN                64      /* Max Length of UUCP Lock File Name.        */
        !            19: #endif /* UUCP */
        !            20: 
        !            21: #define LOCKDIR        SPOOLDIR
        !            22: #define        LOCKPRE "LCK.."
        !            23: #define PIDLEN 6       /* Maximum length of string representing a PID.  */
        !            24: 
        !            25: /* There is a special version of DEVMASK for the PE multiport driver
        !            26:  * because of the peculiar way it uses the minor device number.  For
        !            27:  * all other drivers, the lower 5 bits describe the physical port--
        !            28:  * the upper 3 bits give attributes for the port.
        !            29:  */
        !            30: 
        !            31: #define PE_DRIVER 21   /* Major device number for the PE driver.  */
        !            32: #define PE_DEVMASK 0x3f        /* PE driver minor device mask.  */
        !            33: #define DEVMASK 0x1f   /* Minor device mask.  */
        !            34: 
        !            35: 
        !            36: /*
        !            37:  *  lockit(resource)  char *resource;
        !            38:  *
        !            39:  *  Lock the given resource.
        !            40:  *  Returns (-1) if already locked or error in locking.
        !            41:  *          ( 0) if all ok, resource locked.
        !            42:  */
        !            43: 
        !            44: lockit(resource)
        !            45: char *resource;
        !            46: {
        !            47: 
        !            48:        int lockfd;
        !            49:        char lockfn[LOKFLEN];
        !            50:        char pidstring[PIDLEN];
        !            51: 
        !            52:        sprintf(lockfn, "%s/%s%.*s", LOCKDIR, LOCKPRE, LOCKSIG, resource);
        !            53:        if ( (access(lockfn, AEXISTS) == 0) ||
        !            54:             ((lockfd=creat(lockfn, 0644)) == -1) ) {
        !            55: #ifdef UUCP
        !            56:                printmsg(M_DEBUG, "Can't lock: %s", lockfn);
        !            57: #endif /* UUCP */
        !            58:                return( -1 );
        !            59:        }
        !            60: #ifdef UUCP
        !            61:        printmsg(M_DEBUG, "Just created lock: %s", lockfn);
        !            62: #endif /* UUCP */
        !            63:        sprintf(pidstring, "%d", getpid());
        !            64:        if(-1 == write(lockfd, pidstring, strlen(pidstring))){
        !            65:                close(lockfd);
        !            66:                unlink(lockfn);
        !            67:                return(-1);
        !            68:        }
        !            69: 
        !            70:        close(lockfd);
        !            71:        return( 0 );
        !            72: }
        !            73: 
        !            74: /*
        !            75:  *  lockrm(resource)  char *resource;
        !            76:  *
        !            77:  *  Simply remove the lock on the given resource.
        !            78:  *  Returns (-1) if not locked or error in unlocking.
        !            79:  *          ( 0) if all ok, resource lock removed.
        !            80:  *
        !            81:  *
        !            82:  * Open the lock file for read operations to try to read the PID
        !            83:  * stored in the file. If the open fails, abort. If the read fails, 
        !            84:  * abort. If the read PID does not match our PID, abort. We will only
        !            85:  * remove the lock if our PID matches the PID written to the file.
        !            86: */
        !            87: 
        !            88: lockrm(resource)
        !            89: char *resource;
        !            90: {
        !            91:        return(locknrm(resource, getpid()));
        !            92: }
        !            93: 
        !            94: 
        !            95: /*
        !            96:  *  locknrm(resource, pid)  char *resource;
        !            97:  *
        !            98:  *  Remove the lock on the given resource, using pid as the process id to
        !            99:  *  look for.
        !           100:  *
        !           101:  *  Returns (-1) if not locked or error in unlocking.
        !           102:  *          ( 0) if all ok, resource lock removed.
        !           103:  *
        !           104:  *  Open the lock file for read operations to try to read the PID
        !           105:  *  stored in the file. If the open fails, abort. If the read fails, 
        !           106:  *  abort. If the read PID does not match our PID, abort. We will only
        !           107:  *  remove the lock if the passed matches the PID written to the file,
        !           108:  *  or if the pid we are passed was 0.
        !           109:  *
        !           110:  */
        !           111: 
        !           112: locknrm(resource, pid)
        !           113:        char *resource;
        !           114:        int pid;
        !           115: {
        !           116:        int lockfd;     /* pointer to file to read */
        !           117:        int chars_read; /* Number of characters read().  */
        !           118: 
        !           119:        char gotpid[PIDLEN + 1];        /* String value of the PID that should be stored
        !           120:                                 * in the lock file pointed to by *lockfp.
        !           121:                                 */
        !           122:        char lockfn[LOKFLEN];
        !           123: 
        !           124:        if ( resource == NULL ) {
        !           125: #ifdef UUCP
        !           126:                plog(M_CALL, "Unlocking NULL resource.");
        !           127: #endif /* UUCP */
        !           128:                return( 0 );
        !           129:        }
        !           130: 
        !           131:        sprintf(lockfn, "%s/%s%.*s", LOCKDIR, LOCKPRE, LOCKSIG, resource);
        !           132: 
        !           133:        /* open the lock file for read, abort on failure */
        !           134:        if(-1 == (lockfd = (open(lockfn, 0)))){
        !           135: #ifdef UUCP
        !           136:                printmsg(M_DEBUG, "Error opening lock file for PID verify");
        !           137:                plog(M_CALL, "Error opening lock file for PID verify");
        !           138: #endif /* UUCP */
        !           139:                close(lockfd);
        !           140:                return(-1);
        !           141:        }
        !           142: 
        !           143:        /* read the contents of the file. Abort if empty */
        !           144:        if ( -1 == (chars_read = read(lockfd, gotpid, PIDLEN))) {
        !           145: #ifdef UUCP
        !           146:                printmsg(M_DEBUG, "Lockrm: Error reading lock file for PID verify");
        !           147:                plog(M_CALL, "Lockrm: Error reading lock file for PID verify");
        !           148: #endif /* UUCP */
        !           149:                close(lockfd);
        !           150:                return(-1);
        !           151:        }
        !           152: 
        !           153:        gotpid[chars_read] = '\0';      /* NUL terminate the string.  */
        !           154:        if ( (0 != pid) && (atoi(gotpid) != pid) ){
        !           155: #ifdef UUCP
        !           156:                printmsg(M_DEBUG, "Lockrm: PID verify failed. PID read was %s.", 
        !           157:                        gotpid);
        !           158:                plog(M_CALL, "Lockrm: PID verify failed. PID read was %s", gotpid);
        !           159: #endif /* UUCP */
        !           160:                close(lockfd);
        !           161:                return(-1);
        !           162:        } else {
        !           163: #ifdef UUCP
        !           164:                printmsg(M_DEBUG, "Lockrm: PID verify successful, removing lock.");
        !           165:                plog(M_CALL, "Lockrm: PID verify successful, removing lock.");
        !           166: #endif /* UUCP */
        !           167: 
        !           168:                if ( unlink(lockfn) < 0 ) {
        !           169: #ifdef UUCP
        !           170:                        printmsg(M_DEBUG, "Lockrm: Error unlocking: %s", lockfn);
        !           171:                        plog(M_CALL, "Lockrm: Error unlocking: %s", lockfn);
        !           172: #endif /* UUCP */
        !           173:                        close(lockfd);
        !           174:                        return( -1 );
        !           175:                }
        !           176: #ifdef UUCP
        !           177:                printmsg(M_DEBUG, "Just unlocked: %s", lockfn);
        !           178: #endif /* UUCP */
        !           179:                close(lockfd);
        !           180:                return( 0 );
        !           181:        }
        !           182: #ifdef UUCP
        !           183:        plog(M_CALL, "Unreachable code in locknrm().");
        !           184: #endif /* UUCP */
        !           185: }
        !           186: 
        !           187: /*
        !           188:  *  lockexist(resource)  char *resource;
        !           189:  *
        !           190:  *  Test for existance of a lock on the given resource.
        !           191:  *
        !           192:  *  Returns:  (1)  Resource is locked.
        !           193:  *           (0)  Resource is not locked.
        !           194:  */
        !           195: 
        !           196: lockexist(resource)
        !           197: char   *resource;
        !           198: {
        !           199:        char lockfn[LOKFLEN];
        !           200: 
        !           201:        if ( resource == NULL )
        !           202:                return(0);
        !           203:        sprintf(lockfn, "%s/%s%.*s", LOCKDIR, LOCKPRE, LOCKSIG, resource);
        !           204: 
        !           205:        return (!access(lockfn, AEXISTS));
        !           206: }
        !           207: 
        !           208: 
        !           209: /*
        !           210:  * Attempt to lock a tty device.  Takes the name of the tty itself,
        !           211:  * otherwise behaves like lockit().
        !           212:  */
        !           213: locktty(ttyname)
        !           214: {
        !           215:        char resource[LOKFLEN];
        !           216:        char filename[LOKFLEN];
        !           217: 
        !           218:        sprintf(filename, "/dev/%s", ttyname);
        !           219:        if (NULL == gen_res_name(filename, resource)){
        !           220:                return(-1);
        !           221:        }
        !           222:        return(lockit(resource));
        !           223: 
        !           224: } /* locktty() */
        !           225: 
        !           226: /*
        !           227:  * Unlock a tty device.  Takes the name of the tty itself,
        !           228:  * otherwise behaves like lockrm().
        !           229:  */
        !           230: unlocktty(ttyname)
        !           231:        char *ttyname;
        !           232: {
        !           233:        return(unlockntty(ttyname, getpid()));
        !           234: } /* unlocktty() */
        !           235: 
        !           236: /*
        !           237:  * Unlock a tty device.  Takes the name of the tty itself,
        !           238:  * otherwise behaves like locknrm().
        !           239:  */
        !           240: unlockntty(ttyname, pid)
        !           241:        char *ttyname;
        !           242:        int pid;
        !           243: {
        !           244:        char resource[LOKFLEN];
        !           245:        char filename[LOKFLEN];
        !           246: 
        !           247:        sprintf(filename, "/dev/%s", ttyname);
        !           248:        if (NULL == gen_res_name(filename, resource)){
        !           249: #ifdef UUCP
        !           250:                plog(M_CALL, "Can't generate resource for %s.", ttyname);
        !           251: #endif /* UUCP */
        !           252:                return(-1);
        !           253:        }
        !           254:        return(locknrm(resource, pid));
        !           255: } /* unlockntty() */
        !           256: 
        !           257: /*
        !           258:  * Attempt to lock a tty device.  Takes the name of the tty itself,
        !           259:  * otherwise behaves like lockit().
        !           260:  */
        !           261: lockttyexist(ttyname)
        !           262: {
        !           263:        char resource[LOKFLEN];
        !           264:        char filename[LOKFLEN];
        !           265: 
        !           266:        sprintf(filename, "/dev/%s", ttyname);
        !           267:        if (NULL == gen_res_name(filename, resource)){
        !           268:                return(0);      /* Non-existent tty can not be locked :-) */
        !           269:        }
        !           270: 
        !           271:        return(lockexist(resource));
        !           272: } /* lockttyexist() */
        !           273: 
        !           274: /*
        !           275:  * Generates a resource name for locking, based on the major number
        !           276:  * and the lower 4 bits of the minor number of the tty device.
        !           277:  *
        !           278:  * Builds the name in buff as two "." separated decimal numbers.
        !           279:  * Returns NULL on failure, buff on success.
        !           280:  */
        !           281: char *
        !           282: gen_res_name(path, buff)
        !           283:        char *path;
        !           284:        char *buff;
        !           285: {
        !           286:        struct stat sbuf;
        !           287:        int status;
        !           288:        
        !           289:        if (0 != (status = stat(path, &sbuf))) {
        !           290:                /* Can't stat the file.  */
        !           291:                return (NULL);
        !           292:        }
        !           293: 
        !           294:        if (PE_DRIVER == major(sbuf.st_rdev)) {
        !           295:                sprintf(buff, "%d.%d", major(sbuf.st_rdev),
        !           296:                                       PE_DEVMASK & minor(sbuf.st_rdev));
        !           297:        } else {
        !           298:                sprintf(buff, "%d.%d", major(sbuf.st_rdev),
        !           299:                                       DEVMASK & minor(sbuf.st_rdev));
        !           300:        }
        !           301: 
        !           302:        return(buff);
        !           303: } /* gen_res_name */
        !           304: 
        !           305: #ifdef TEST
        !           306: #include <stdio.h>
        !           307: 
        !           308: #define LOCKSIG 9      /* Significant Chars of Lockable Resources.  */
        !           309: 
        !           310: main(argc, argv)
        !           311:        int argc;
        !           312:        char *argv[];
        !           313: {
        !           314:        char buffer[LOCKSIG + 1];
        !           315:        char path[LOKFLEN];
        !           316: 
        !           317:        if (argc != 2) {
        !           318:                fprintf(stderr, "Usage: %s ttyname\n", argv[0]);
        !           319:                exit(1);
        !           320:        }
        !           321: 
        !           322:        sprintf(path, "/dev/%s", argv[1]);
        !           323: 
        !           324:        if (NULL == gen_res_name(path, buffer)) {
        !           325:                fprintf(stderr, "%s: Can't stat %s.\n", argv[0], argv[1]);
        !           326:                exit(1);
        !           327:        }
        !           328: 
        !           329:        printf("Resource to lock: %s\n", buffer);
        !           330: 
        !           331:        if (-1 == locktty(argv[1])) {
        !           332:                fprintf(stderr, "%s: Can't lock %s.\n", argv[0], argv[1]);
        !           333:                exit(1);
        !           334:        }
        !           335: 
        !           336:        printf("I think I've locked %s.\n", argv[1]);
        !           337: 
        !           338:        if (lockttyexist(argv[1])) {
        !           339:                printf("Yep, %s is locked.\n", argv[1]);
        !           340:        } else {
        !           341:                fprintf(stderr, "%s: Failed to lock %s.\n", argv[0], argv[1]);
        !           342:                exit(1);
        !           343:        }
        !           344: 
        !           345: 
        !           346:        sprintf(path, "cat /usr/spool/uucp/LCK..%s", buffer);
        !           347:        printf("Contents of lock file: ");
        !           348:        fflush(stdout);
        !           349:        system(path);
        !           350:        printf("\n");
        !           351: 
        !           352:        if (-1 == unlocktty(argv[1])) {
        !           353:                fprintf(stderr, "%s: Problem removing lock on %s.\n", argv[0], argv[1]);
        !           354:                exit(1);
        !           355:        }
        !           356: 
        !           357:        printf("I think I've unlocked %s.\n", argv[1]);
        !           358: 
        !           359:        if (lockttyexist(argv[1])) {
        !           360:                fprintf(stderr, "%s: Failed to unlock %s.\n", argv[0], argv[1]);
        !           361:                exit(1);
        !           362:        } else {
        !           363:                printf("Successfully unlocked %s.\n", argv[1]);
        !           364:        }
        !           365: 
        !           366:        
        !           367:        exit(0);
        !           368: }
        !           369: #endif /* TEST */

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