1 /*- 2 * Copyright (c) 1980, 1991 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 */ 7 8 #ifndef lint 9 static char sccsid[] = "@(#)tape.c 5.24 (Berkeley) 07/02/92"; 10 #endif /* not lint */ 11 12 #ifdef sunos 13 #include <sys/param.h> 14 #include <stdio.h> 15 #include <ctype.h> 16 #include <sys/stat.h> 17 #include <ufs/fs.h> 18 #else 19 #include <sys/param.h> 20 #include <sys/wait.h> 21 #include <ufs/ffs/fs.h> 22 #endif 23 #include <sys/time.h> 24 #include <ufs/ufs/dinode.h> 25 #include <signal.h> 26 #include <fcntl.h> 27 #include <protocols/dumprestore.h> 28 #include <errno.h> 29 #include <setjmp.h> 30 #ifdef __STDC__ 31 #include <unistd.h> 32 #include <stdlib.h> 33 #include <string.h> 34 #endif 35 #include <sys/socket.h> 36 #include "dump.h" 37 #include "pathnames.h" 38 39 int writesize; /* size of malloc()ed buffer for tape */ 40 long lastspclrec = -1; /* tape block number of last written header */ 41 int trecno = 0; /* next record to write in current block */ 42 extern long blocksperfile; /* number of blocks per output file */ 43 long blocksthisvol; /* number of blocks on current output file */ 44 extern int ntrec; /* blocking factor on tape */ 45 extern int cartridge; 46 extern char *host; 47 char *nexttape; 48 #ifdef RDUMP 49 int rmtopen(), rmtwrite(); 50 void rmtclose(); 51 #endif RDUMP 52 void rollforward(); 53 int atomic(); 54 void doslave(), enslave(), flushtape(), killall(); 55 56 /* 57 * Concurrent dump mods (Caltech) - disk block reading and tape writing 58 * are exported to several slave processes. While one slave writes the 59 * tape, the others read disk blocks; they pass control of the tape in 60 * a ring via signals. The parent process traverses the filesystem and 61 * sends writeheader()'s and lists of daddr's to the slaves via pipes. 62 * The following structure defines the instruction packets sent to slaves. 63 */ 64 struct req { 65 daddr_t dblk; 66 int count; 67 }; 68 int reqsiz; 69 70 #define SLAVES 3 /* 1 slave writing, 1 reading, 1 for slack */ 71 struct slave { 72 int tapea; /* header number at start of this chunk */ 73 int count; /* count to next header (used for TS_TAPE */ 74 /* after EOT) */ 75 int inode; /* inode that we are currently dealing with */ 76 int fd; /* FD for this slave */ 77 int pid; /* PID for this slave */ 78 int sent; /* 1 == we've sent this slave requests */ 79 int firstrec; /* record number of this block */ 80 char (*tblock)[TP_BSIZE]; /* buffer for data blocks */ 81 struct req *req; /* buffer for requests */ 82 } slaves[SLAVES+1]; 83 struct slave *slp; 84 85 char (*nextblock)[TP_BSIZE]; 86 87 int master; /* pid of master, for sending error signals */ 88 int tenths; /* length of tape used per block written */ 89 static int caught; /* have we caught the signal to proceed? */ 90 static int ready; /* have we reached the lock point without having */ 91 /* received the SIGUSR2 signal from the prev slave? */ 92 static jmp_buf jmpbuf; /* where to jump to if we are ready when the */ 93 /* SIGUSR2 arrives from the previous slave */ 94 95 int 96 alloctape() 97 { 98 int pgoff = getpagesize() - 1; 99 char *buf; 100 int i; 101 102 writesize = ntrec * TP_BSIZE; 103 reqsiz = (ntrec + 1) * sizeof(struct req); 104 /* 105 * CDC 92181's and 92185's make 0.8" gaps in 1600-bpi start/stop mode 106 * (see DEC TU80 User's Guide). The shorter gaps of 6250-bpi require 107 * repositioning after stopping, i.e, streaming mode, where the gap is 108 * variable, 0.30" to 0.45". The gap is maximal when the tape stops. 109 */ 110 if (blocksperfile == 0) 111 tenths = writesize / density + 112 (cartridge ? 16 : density == 625 ? 5 : 8); 113 /* 114 * Allocate tape buffer contiguous with the array of instruction 115 * packets, so flushtape() can write them together with one write(). 116 * Align tape buffer on page boundary to speed up tape write(). 117 */ 118 for (i = 0; i <= SLAVES; i++) { 119 buf = (char *) 120 malloc((unsigned)(reqsiz + writesize + pgoff + TP_BSIZE)); 121 if (buf == NULL) 122 return(0); 123 slaves[i].tblock = (char (*)[TP_BSIZE]) 124 (((long)&buf[ntrec + 1] + pgoff) &~ pgoff); 125 slaves[i].req = (struct req *)slaves[i].tblock - ntrec - 1; 126 } 127 slp = &slaves[0]; 128 slp->count = 1; 129 slp->tapea = 0; 130 slp->firstrec = 0; 131 nextblock = slp->tblock; 132 return(1); 133 } 134 135 void 136 writerec(dp, isspcl) 137 char *dp; 138 int isspcl; 139 { 140 141 slp->req[trecno].dblk = (daddr_t)0; 142 slp->req[trecno].count = 1; 143 *(union u_spcl *)(*(nextblock)++) = *(union u_spcl *)dp; 144 if (isspcl) 145 lastspclrec = spcl.c_tapea; 146 trecno++; 147 spcl.c_tapea++; 148 if (trecno >= ntrec) 149 flushtape(); 150 } 151 152 void 153 dumpblock(blkno, size) 154 daddr_t blkno; 155 int size; 156 { 157 int avail, tpblks, dblkno; 158 159 dblkno = fsbtodb(sblock, blkno); 160 tpblks = size >> tp_bshift; 161 while ((avail = MIN(tpblks, ntrec - trecno)) > 0) { 162 slp->req[trecno].dblk = dblkno; 163 slp->req[trecno].count = avail; 164 trecno += avail; 165 spcl.c_tapea += avail; 166 if (trecno >= ntrec) 167 flushtape(); 168 dblkno += avail << (tp_bshift - dev_bshift); 169 tpblks -= avail; 170 } 171 } 172 173 int nogripe = 0; 174 175 void 176 tperror() 177 { 178 179 if (pipeout) { 180 msg("write error on %s\n", tape); 181 quit("Cannot recover\n"); 182 /* NOTREACHED */ 183 } 184 msg("write error %d blocks into volume %d\n", blocksthisvol, tapeno); 185 broadcast("DUMP WRITE ERROR!\n"); 186 if (!query("Do you want to restart?")) 187 dumpabort(); 188 msg("Closing this volume. Prepare to restart with new media;\n"); 189 msg("this dump volume will be rewritten.\n"); 190 killall(); 191 nogripe = 1; 192 close_rewind(); 193 Exit(X_REWRITE); 194 } 195 196 void 197 sigpipe() 198 { 199 200 quit("Broken pipe\n"); 201 } 202 203 void 204 flushtape() 205 { 206 int i, blks, got; 207 long lastfirstrec; 208 #ifndef __STDC__ 209 int write(), read(); 210 #endif 211 212 int siz = (char *)nextblock - (char *)slp->req; 213 214 slp->req[trecno].count = 0; /* Sentinel */ 215 216 if (atomic(write, slp->fd, (char *)slp->req, siz) != siz) 217 quit("error writing command pipe: %s\n", strerror(errno)); 218 slp->sent = 1; /* we sent a request, read the response later */ 219 220 lastfirstrec = slp->firstrec; 221 222 if (++slp >= &slaves[SLAVES]) 223 slp = &slaves[0]; 224 225 /* Read results back from next slave */ 226 if (slp->sent) { 227 if (atomic(read, slp->fd, (char *)&got, sizeof got) 228 != sizeof got) { 229 perror(" DUMP: error reading command pipe in master"); 230 dumpabort(); 231 } 232 slp->sent = 0; 233 234 /* Check for end of tape */ 235 if (got < writesize) { 236 msg("End of tape detected\n"); 237 238 /* 239 * Drain the results, don't care what the values were. 240 * If we read them here then trewind won't... 241 */ 242 for (i = 0; i < SLAVES; i++) { 243 if (slaves[i].sent) { 244 if (atomic(read, slaves[i].fd, 245 (char *)&got, sizeof got) 246 != sizeof got) { 247 perror(" DUMP: error reading command pipe in master"); 248 dumpabort(); 249 } 250 slaves[i].sent = 0; 251 } 252 } 253 254 close_rewind(); 255 rollforward(); 256 return; 257 } 258 } 259 260 blks = 0; 261 if (spcl.c_type != TS_END) { 262 for (i = 0; i < spcl.c_count; i++) 263 if (spcl.c_addr[i] != 0) 264 blks++; 265 } 266 slp->count = lastspclrec + blks + 1 - spcl.c_tapea; 267 slp->tapea = spcl.c_tapea; 268 slp->firstrec = lastfirstrec + ntrec; 269 slp->inode = curino; 270 nextblock = slp->tblock; 271 trecno = 0; 272 asize += tenths; 273 blockswritten += ntrec; 274 blocksthisvol += ntrec; 275 if (!pipeout && (blocksperfile ? 276 (blocksthisvol >= blocksperfile) : (asize > tsize))) { 277 close_rewind(); 278 startnewtape(0); 279 } 280 timeest(); 281 } 282 283 void 284 trewind() 285 { 286 int f; 287 int got; 288 289 for (f = 0; f < SLAVES; f++) { 290 /* 291 * Drain the results, but unlike EOT we DO (or should) care 292 * what the return values were, since if we detect EOT after 293 * we think we've written the last blocks to the tape anyway, 294 * we have to replay those blocks with rollforward. 295 * 296 * fixme: punt for now. 297 */ 298 if (slaves[f].sent) { 299 if (atomic(read, slaves[f].fd, (char *)&got, sizeof got) 300 != sizeof got) { 301 perror(" DUMP: error reading command pipe in master"); 302 dumpabort(); 303 } 304 slaves[f].sent = 0; 305 if (got != writesize) { 306 msg("EOT detected in last 2 tape records!\n"); 307 msg("Use a longer tape, decrease the size estimate\n"); 308 quit("or use no size estimate at all.\n"); 309 } 310 } 311 (void) close(slaves[f].fd); 312 } 313 while (wait((int *)NULL) >= 0) /* wait for any signals from slaves */ 314 /* void */; 315 316 if (pipeout) 317 return; 318 319 msg("Closing %s\n", tape); 320 321 #ifdef RDUMP 322 if (host) { 323 rmtclose(); 324 while (rmtopen(tape, 0) < 0) 325 sleep(10); 326 rmtclose(); 327 return; 328 } 329 #endif 330 (void) close(tapefd); 331 while ((f = open(tape, 0)) < 0) 332 sleep (10); 333 (void) close(f); 334 } 335 336 void 337 close_rewind() 338 { 339 trewind(); 340 if (nexttape) 341 return; 342 if (!nogripe) { 343 msg("Change Volumes: Mount volume #%d\n", tapeno+1); 344 broadcast("CHANGE DUMP VOLUMES!\7\7\n"); 345 } 346 while (!query("Is the new volume mounted and ready to go?")) 347 if (query("Do you want to abort?")) { 348 dumpabort(); 349 /*NOTREACHED*/ 350 } 351 } 352 353 void 354 rollforward() 355 { 356 register struct req *p, *q, *prev; 357 register struct slave *tslp; 358 int i, size, savedtapea, got; 359 union u_spcl *ntb, *otb; 360 tslp = &slaves[SLAVES]; 361 ntb = (union u_spcl *)tslp->tblock[1]; 362 363 /* 364 * Each of the N slaves should have requests that need to 365 * be replayed on the next tape. Use the extra slave buffers 366 * (slaves[SLAVES]) to construct request lists to be sent to 367 * each slave in turn. 368 */ 369 for (i = 0; i < SLAVES; i++) { 370 q = &tslp->req[1]; 371 otb = (union u_spcl *)slp->tblock; 372 373 /* 374 * For each request in the current slave, copy it to tslp. 375 */ 376 377 for (p = slp->req; p->count > 0; p += p->count) { 378 *q = *p; 379 if (p->dblk == 0) 380 *ntb++ = *otb++; /* copy the datablock also */ 381 prev = q; 382 q += q->count; 383 } 384 if (prev->dblk != 0) 385 prev->count -= 1; 386 else 387 ntb--; 388 q -= 1; 389 q->count = 0; 390 q = &tslp->req[0]; 391 if (i == 0) { 392 q->dblk = 0; 393 q->count = 1; 394 trecno = 0; 395 nextblock = tslp->tblock; 396 savedtapea = spcl.c_tapea; 397 spcl.c_tapea = slp->tapea; 398 startnewtape(0); 399 spcl.c_tapea = savedtapea; 400 lastspclrec = savedtapea - 1; 401 } 402 size = (char *)ntb - (char *)q; 403 if (atomic(write, slp->fd, (char *)q, size) != size) { 404 perror(" DUMP: error writing command pipe"); 405 dumpabort(); 406 } 407 slp->sent = 1; 408 if (++slp >= &slaves[SLAVES]) 409 slp = &slaves[0]; 410 411 q->count = 1; 412 413 if (prev->dblk != 0) { 414 /* 415 * If the last one was a disk block, make the 416 * first of this one be the last bit of that disk 417 * block... 418 */ 419 q->dblk = prev->dblk + 420 prev->count * (TP_BSIZE / DEV_BSIZE); 421 ntb = (union u_spcl *)tslp->tblock; 422 } else { 423 /* 424 * It wasn't a disk block. Copy the data to its 425 * new location in the buffer. 426 */ 427 q->dblk = 0; 428 *((union u_spcl *)tslp->tblock) = *ntb; 429 ntb = (union u_spcl *)tslp->tblock[1]; 430 } 431 } 432 slp->req[0] = *q; 433 nextblock = slp->tblock; 434 if (q->dblk == 0) 435 nextblock++; 436 trecno = 1; 437 438 /* 439 * Clear the first slaves' response. One hopes that it 440 * worked ok, otherwise the tape is much too short! 441 */ 442 if (slp->sent) { 443 if (atomic(read, slp->fd, (char *)&got, sizeof got) 444 != sizeof got) { 445 perror(" DUMP: error reading command pipe in master"); 446 dumpabort(); 447 } 448 slp->sent = 0; 449 450 if (got != writesize) { 451 quit("EOT detected at start of the tape!\n"); 452 } 453 } 454 } 455 456 /* 457 * We implement taking and restoring checkpoints on the tape level. 458 * When each tape is opened, a new process is created by forking; this 459 * saves all of the necessary context in the parent. The child 460 * continues the dump; the parent waits around, saving the context. 461 * If the child returns X_REWRITE, then it had problems writing that tape; 462 * this causes the parent to fork again, duplicating the context, and 463 * everything continues as if nothing had happened. 464 */ 465 void 466 startnewtape(top) 467 int top; 468 { 469 int parentpid; 470 int childpid; 471 int status; 472 int waitpid; 473 char *p; 474 #ifdef sunos 475 void (*interrupt_save)(); 476 char *index(); 477 #else 478 sig_t interrupt_save; 479 #endif 480 481 interrupt_save = signal(SIGINT, SIG_IGN); 482 parentpid = getpid(); 483 484 restore_check_point: 485 (void)signal(SIGINT, interrupt_save); 486 /* 487 * All signals are inherited... 488 */ 489 childpid = fork(); 490 if (childpid < 0) { 491 msg("Context save fork fails in parent %d\n", parentpid); 492 Exit(X_ABORT); 493 } 494 if (childpid != 0) { 495 /* 496 * PARENT: 497 * save the context by waiting 498 * until the child doing all of the work returns. 499 * don't catch the interrupt 500 */ 501 signal(SIGINT, SIG_IGN); 502 #ifdef TDEBUG 503 msg("Tape: %d; parent process: %d child process %d\n", 504 tapeno+1, parentpid, childpid); 505 #endif TDEBUG 506 while ((waitpid = wait(&status)) != childpid) 507 msg("Parent %d waiting for child %d has another child %d return\n", 508 parentpid, childpid, waitpid); 509 if (status & 0xFF) { 510 msg("Child %d returns LOB status %o\n", 511 childpid, status&0xFF); 512 } 513 status = (status >> 8) & 0xFF; 514 #ifdef TDEBUG 515 switch(status) { 516 case X_FINOK: 517 msg("Child %d finishes X_FINOK\n", childpid); 518 break; 519 case X_ABORT: 520 msg("Child %d finishes X_ABORT\n", childpid); 521 break; 522 case X_REWRITE: 523 msg("Child %d finishes X_REWRITE\n", childpid); 524 break; 525 default: 526 msg("Child %d finishes unknown %d\n", 527 childpid, status); 528 break; 529 } 530 #endif TDEBUG 531 switch(status) { 532 case X_FINOK: 533 Exit(X_FINOK); 534 case X_ABORT: 535 Exit(X_ABORT); 536 case X_REWRITE: 537 goto restore_check_point; 538 default: 539 msg("Bad return code from dump: %d\n", status); 540 Exit(X_ABORT); 541 } 542 /*NOTREACHED*/ 543 } else { /* we are the child; just continue */ 544 #ifdef TDEBUG 545 sleep(4); /* allow time for parent's message to get out */ 546 msg("Child on Tape %d has parent %d, my pid = %d\n", 547 tapeno+1, parentpid, getpid()); 548 #endif TDEBUG 549 /* 550 * If we have a name like "/dev/rmt0,/dev/rmt1", 551 * use the name before the comma first, and save 552 * the remaining names for subsequent volumes. 553 */ 554 tapeno++; /* current tape sequence */ 555 if (nexttape || index(tape, ',')) { 556 if (nexttape && *nexttape) 557 tape = nexttape; 558 if (p = index(tape, ',')) { 559 *p = '\0'; 560 nexttape = p + 1; 561 } else 562 nexttape = NULL; 563 msg("Dumping volume %d on %s\n", tapeno, tape); 564 } 565 #ifdef RDUMP 566 while ((tapefd = (host ? rmtopen(tape, 2) : 567 pipeout ? 1 : open(tape, O_WRONLY|O_CREAT, 0666))) < 0) 568 #else 569 while ((tapefd = (pipeout ? 1 : 570 open(tape, O_WRONLY|O_CREAT, 0666))) < 0) 571 #endif 572 { 573 msg("Cannot open output \"%s\".\n", tape); 574 if (!query("Do you want to retry the open?")) 575 dumpabort(); 576 } 577 578 enslave(); /* Share open tape file descriptor with slaves */ 579 580 asize = 0; 581 blocksthisvol = 0; 582 if (top) 583 newtape++; /* new tape signal */ 584 spcl.c_count = slp->count; 585 /* 586 * measure firstrec in TP_BSIZE units since restore doesn't 587 * know the correct ntrec value... 588 */ 589 spcl.c_firstrec = slp->firstrec; 590 spcl.c_volume++; 591 spcl.c_type = TS_TAPE; 592 spcl.c_flags |= DR_NEWHEADER; 593 writeheader((ino_t)slp->inode); 594 spcl.c_flags &=~ DR_NEWHEADER; 595 if (tapeno > 1) 596 msg("Volume %d begins with blocks from inode %d\n", 597 tapeno, slp->inode); 598 } 599 } 600 601 void 602 dumpabort() 603 { 604 605 if (master != 0 && master != getpid()) 606 /* Signals master to call dumpabort */ 607 (void) kill(master, SIGTERM); 608 else { 609 killall(); 610 msg("The ENTIRE dump is aborted.\n"); 611 } 612 Exit(X_ABORT); 613 } 614 615 void 616 Exit(status) 617 int status; 618 { 619 620 #ifdef TDEBUG 621 msg("pid = %d exits with status %d\n", getpid(), status); 622 #endif TDEBUG 623 (void) exit(status); 624 } 625 626 /* 627 * proceed - handler for SIGUSR2, used to synchronize IO between the slaves. 628 */ 629 void 630 proceed() 631 { 632 633 if (ready) 634 longjmp(jmpbuf, 1); 635 caught++; 636 } 637 638 void 639 enslave() 640 { 641 int cmd[2]; 642 register int i, j; 643 644 master = getpid(); 645 646 signal(SIGTERM, dumpabort); /* Slave sends SIGTERM on dumpabort() */ 647 signal(SIGPIPE, sigpipe); 648 signal(SIGUSR1, tperror); /* Slave sends SIGUSR1 on tape errors */ 649 signal(SIGUSR2, proceed); /* Slave sends SIGUSR2 to next slave */ 650 651 for (i = 0; i < SLAVES; i++) { 652 if (i == slp - &slaves[0]) { 653 caught = 1; 654 } else { 655 caught = 0; 656 } 657 658 if (socketpair(AF_UNIX, SOCK_STREAM, 0, cmd) < 0 || 659 (slaves[i].pid = fork()) < 0) 660 quit("too many slaves, %d (recompile smaller): %s\n", 661 i, strerror(errno)); 662 663 slaves[i].fd = cmd[1]; 664 slaves[i].sent = 0; 665 if (slaves[i].pid == 0) { /* Slave starts up here */ 666 for (j = 0; j <= i; j++) 667 (void) close(slaves[j].fd); 668 signal(SIGINT, SIG_IGN); /* Master handles this */ 669 doslave(cmd[0], i); 670 Exit(X_FINOK); 671 } 672 } 673 674 for (i = 0; i < SLAVES; i++) 675 (void) atomic(write, slaves[i].fd, 676 (char *) &slaves[(i + 1) % SLAVES].pid, 677 sizeof slaves[0].pid); 678 679 master = 0; 680 } 681 682 void 683 killall() 684 { 685 register int i; 686 687 for (i = 0; i < SLAVES; i++) 688 if (slaves[i].pid > 0) 689 (void) kill(slaves[i].pid, SIGKILL); 690 } 691 692 /* 693 * Synchronization - each process has a lockfile, and shares file 694 * descriptors to the following process's lockfile. When our write 695 * completes, we release our lock on the following process's lock- 696 * file, allowing the following process to lock it and proceed. We 697 * get the lock back for the next cycle by swapping descriptors. 698 */ 699 void 700 doslave(cmd, slave_number) 701 register int cmd; 702 int slave_number; 703 { 704 register int nread; 705 int nextslave, size, wrote, eot_count; 706 #ifndef __STDC__ 707 int read(); 708 #endif 709 710 /* 711 * Need our own seek pointer. 712 */ 713 (void) close(diskfd); 714 if ((diskfd = open(disk, O_RDONLY)) < 0) 715 quit("slave couldn't reopen disk: %s\n", strerror(errno)); 716 717 /* 718 * Need the pid of the next slave in the loop... 719 */ 720 if ((nread = atomic(read, cmd, (char *)&nextslave, sizeof nextslave)) 721 != sizeof nextslave) { 722 quit("master/slave protocol botched - didn't get pid of next slave.\n"); 723 } 724 725 /* 726 * Get list of blocks to dump, read the blocks into tape buffer 727 */ 728 while ((nread = atomic(read, cmd, (char *)slp->req, reqsiz)) == reqsiz) { 729 register struct req *p = slp->req; 730 731 for (trecno = 0; trecno < ntrec; 732 trecno += p->count, p += p->count) { 733 if (p->dblk) { 734 bread(p->dblk, slp->tblock[trecno], 735 p->count * TP_BSIZE); 736 } else { 737 if (p->count != 1 || atomic(read, cmd, 738 (char *)slp->tblock[trecno], 739 TP_BSIZE) != TP_BSIZE) 740 quit("master/slave protocol botched.\n"); 741 } 742 } 743 if (setjmp(jmpbuf) == 0) { 744 ready = 1; 745 if (!caught) 746 (void) pause(); 747 } 748 ready = 0; 749 caught = 0; 750 751 /* Try to write the data... */ 752 eot_count = 0; 753 size = 0; 754 755 while (eot_count < 10 && size < writesize) { 756 #ifdef RDUMP 757 if (host) 758 wrote = rmtwrite(slp->tblock[0]+size, 759 writesize-size); 760 else 761 #endif 762 wrote = write(tapefd, slp->tblock[0]+size, 763 writesize-size); 764 #ifdef WRITEDEBUG 765 printf("slave %d wrote %d\n", slave_number, wrote); 766 #endif 767 if (wrote < 0) 768 break; 769 if (wrote == 0) 770 eot_count++; 771 size += wrote; 772 } 773 774 #ifdef WRITEDEBUG 775 if (size != writesize) 776 printf("slave %d only wrote %d out of %d bytes and gave up.\n", 777 slave_number, size, writesize); 778 #endif 779 780 if (eot_count > 0) 781 size = 0; 782 783 /* 784 * fixme: Pyramids running OSx return ENOSPC 785 * at EOT on 1/2 inch drives. 786 */ 787 if (size < 0) { 788 (void) kill(master, SIGUSR1); 789 for (;;) 790 (void) sigpause(0); 791 } else { 792 /* 793 * pass size of write back to master 794 * (for EOT handling) 795 */ 796 (void) atomic(write, cmd, (char *)&size, sizeof size); 797 } 798 799 /* 800 * If partial write, don't want next slave to go. 801 * Also jolts him awake. 802 */ 803 (void) kill(nextslave, SIGUSR2); 804 } 805 if (nread != 0) 806 quit("error reading command pipe: %s\n", strerror(errno)); 807 } 808 809 /* 810 * Since a read from a pipe may not return all we asked for, 811 * or a write may not write all we ask if we get a signal, 812 * loop until the count is satisfied (or error). 813 */ 814 int 815 atomic(func, fd, buf, count) 816 int (*func)(), fd, count; 817 char *buf; 818 { 819 int got, need = count; 820 821 while ((got = (*func)(fd, buf, need)) > 0 && (need -= got) > 0) 822 buf += got; 823 return (got < 0 ? got : count - need); 824 } 825