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 5.26 (Berkeley) 01/25/93"; 10 #endif /* not lint */ 11 12 #include <sys/param.h> 13 #include <sys/socket.h> 14 #include <sys/time.h> 15 #include <sys/wait.h> 16 #ifdef sunos 17 #include <sys/vnode.h> 18 19 #include <ufs/fs.h> 20 #include <ufs/inode.h> 21 #else 22 #include <ufs/ffs/fs.h> 23 #include <ufs/ufs/dinode.h> 24 #endif 25 26 #include <protocols/dumprestore.h> 27 28 #include <errno.h> 29 #include <fcntl.h> 30 #include <setjmp.h> 31 #include <signal.h> 32 #include <stdio.h> 33 #ifdef __STDC__ 34 #include <stdlib.h> 35 #include <string.h> 36 #include <unistd.h> 37 #else 38 int write(), read(); 39 #endif 40 41 #include "dump.h" 42 #include "pathnames.h" 43 44 int writesize; /* size of malloc()ed buffer for tape */ 45 long lastspclrec = -1; /* tape block number of last written header */ 46 int trecno = 0; /* next record to write in current block */ 47 extern long blocksperfile; /* number of blocks per output file */ 48 long blocksthisvol; /* number of blocks on current output file */ 49 extern int ntrec; /* blocking factor on tape */ 50 extern int cartridge; 51 extern char *host; 52 char *nexttape; 53 54 static int atomic __P((int (*)(), int, char *, int)); 55 static void doslave __P((int, int)); 56 static void enslave __P((void)); 57 static void flushtape __P((void)); 58 static void killall __P((void)); 59 static void rollforward __P((void)); 60 61 /* 62 * Concurrent dump mods (Caltech) - disk block reading and tape writing 63 * are exported to several slave processes. While one slave writes the 64 * tape, the others read disk blocks; they pass control of the tape in 65 * a ring via signals. The parent process traverses the filesystem and 66 * sends writeheader()'s and lists of daddr's to the slaves via pipes. 67 * The following structure defines the instruction packets sent to slaves. 68 */ 69 struct req { 70 daddr_t dblk; 71 int count; 72 }; 73 int reqsiz; 74 75 #define SLAVES 3 /* 1 slave writing, 1 reading, 1 for slack */ 76 struct slave { 77 int tapea; /* header number at start of this chunk */ 78 int count; /* count to next header (used for TS_TAPE */ 79 /* after EOT) */ 80 int inode; /* inode that we are currently dealing with */ 81 int fd; /* FD for this slave */ 82 int pid; /* PID for this slave */ 83 int sent; /* 1 == we've sent this slave requests */ 84 int firstrec; /* record number of this block */ 85 char (*tblock)[TP_BSIZE]; /* buffer for data blocks */ 86 struct req *req; /* buffer for requests */ 87 } slaves[SLAVES+1]; 88 struct slave *slp; 89 90 char (*nextblock)[TP_BSIZE]; 91 92 int master; /* pid of master, for sending error signals */ 93 int tenths; /* length of tape used per block written */ 94 static int caught; /* have we caught the signal to proceed? */ 95 static int ready; /* have we reached the lock point without having */ 96 /* received the SIGUSR2 signal from the prev slave? */ 97 static jmp_buf jmpbuf; /* where to jump to if we are ready when the */ 98 /* SIGUSR2 arrives from the previous slave */ 99 100 int 101 alloctape() 102 { 103 int pgoff = getpagesize() - 1; 104 char *buf; 105 int i; 106 107 writesize = ntrec * TP_BSIZE; 108 reqsiz = (ntrec + 1) * sizeof(struct req); 109 /* 110 * CDC 92181's and 92185's make 0.8" gaps in 1600-bpi start/stop mode 111 * (see DEC TU80 User's Guide). The shorter gaps of 6250-bpi require 112 * repositioning after stopping, i.e, streaming mode, where the gap is 113 * variable, 0.30" to 0.45". The gap is maximal when the tape stops. 114 */ 115 if (blocksperfile == 0) 116 tenths = writesize / density + 117 (cartridge ? 16 : density == 625 ? 5 : 8); 118 /* 119 * Allocate tape buffer contiguous with the array of instruction 120 * packets, so flushtape() can write them together with one write(). 121 * Align tape buffer on page boundary to speed up tape write(). 122 */ 123 for (i = 0; i <= SLAVES; i++) { 124 buf = (char *) 125 malloc((unsigned)(reqsiz + writesize + pgoff + TP_BSIZE)); 126 if (buf == NULL) 127 return(0); 128 slaves[i].tblock = (char (*)[TP_BSIZE]) 129 (((long)&buf[ntrec + 1] + pgoff) &~ pgoff); 130 slaves[i].req = (struct req *)slaves[i].tblock - ntrec - 1; 131 } 132 slp = &slaves[0]; 133 slp->count = 1; 134 slp->tapea = 0; 135 slp->firstrec = 0; 136 nextblock = slp->tblock; 137 return(1); 138 } 139 140 void 141 writerec(dp, isspcl) 142 char *dp; 143 int isspcl; 144 { 145 146 slp->req[trecno].dblk = (daddr_t)0; 147 slp->req[trecno].count = 1; 148 *(union u_spcl *)(*(nextblock)++) = *(union u_spcl *)dp; 149 if (isspcl) 150 lastspclrec = spcl.c_tapea; 151 trecno++; 152 spcl.c_tapea++; 153 if (trecno >= ntrec) 154 flushtape(); 155 } 156 157 void 158 dumpblock(blkno, size) 159 daddr_t blkno; 160 int size; 161 { 162 int avail, tpblks, dblkno; 163 164 dblkno = fsbtodb(sblock, blkno); 165 tpblks = size >> tp_bshift; 166 while ((avail = MIN(tpblks, ntrec - trecno)) > 0) { 167 slp->req[trecno].dblk = dblkno; 168 slp->req[trecno].count = avail; 169 trecno += avail; 170 spcl.c_tapea += avail; 171 if (trecno >= ntrec) 172 flushtape(); 173 dblkno += avail << (tp_bshift - dev_bshift); 174 tpblks -= avail; 175 } 176 } 177 178 int nogripe = 0; 179 180 void 181 tperror(signo) 182 int signo; 183 { 184 185 if (pipeout) { 186 msg("write error on %s\n", tape); 187 quit("Cannot recover\n"); 188 /* NOTREACHED */ 189 } 190 msg("write error %d blocks into volume %d\n", blocksthisvol, tapeno); 191 broadcast("DUMP WRITE ERROR!\n"); 192 if (!query("Do you want to restart?")) 193 dumpabort(0); 194 msg("Closing this volume. Prepare to restart with new media;\n"); 195 msg("this dump volume will be rewritten.\n"); 196 killall(); 197 nogripe = 1; 198 close_rewind(); 199 Exit(X_REWRITE); 200 } 201 202 void 203 sigpipe(signo) 204 int signo; 205 { 206 207 quit("Broken pipe\n"); 208 } 209 210 static void 211 flushtape() 212 { 213 int i, blks, got; 214 long lastfirstrec; 215 216 int siz = (char *)nextblock - (char *)slp->req; 217 218 slp->req[trecno].count = 0; /* Sentinel */ 219 220 if (atomic(write, slp->fd, (char *)slp->req, siz) != siz) 221 quit("error writing command pipe: %s\n", strerror(errno)); 222 slp->sent = 1; /* we sent a request, read the response later */ 223 224 lastfirstrec = slp->firstrec; 225 226 if (++slp >= &slaves[SLAVES]) 227 slp = &slaves[0]; 228 229 /* Read results back from next slave */ 230 if (slp->sent) { 231 if (atomic(read, slp->fd, (char *)&got, sizeof got) 232 != sizeof got) { 233 perror(" DUMP: error reading command pipe in master"); 234 dumpabort(0); 235 } 236 slp->sent = 0; 237 238 /* Check for end of tape */ 239 if (got < writesize) { 240 msg("End of tape detected\n"); 241 242 /* 243 * Drain the results, don't care what the values were. 244 * If we read them here then trewind won't... 245 */ 246 for (i = 0; i < SLAVES; i++) { 247 if (slaves[i].sent) { 248 if (atomic(read, slaves[i].fd, 249 (char *)&got, sizeof got) 250 != sizeof got) { 251 perror(" DUMP: error reading command pipe in master"); 252 dumpabort(0); 253 } 254 slaves[i].sent = 0; 255 } 256 } 257 258 close_rewind(); 259 rollforward(); 260 return; 261 } 262 } 263 264 blks = 0; 265 if (spcl.c_type != TS_END) { 266 for (i = 0; i < spcl.c_count; i++) 267 if (spcl.c_addr[i] != 0) 268 blks++; 269 } 270 slp->count = lastspclrec + blks + 1 - spcl.c_tapea; 271 slp->tapea = spcl.c_tapea; 272 slp->firstrec = lastfirstrec + ntrec; 273 slp->inode = curino; 274 nextblock = slp->tblock; 275 trecno = 0; 276 asize += tenths; 277 blockswritten += ntrec; 278 blocksthisvol += ntrec; 279 if (!pipeout && (blocksperfile ? 280 (blocksthisvol >= blocksperfile) : (asize > tsize))) { 281 close_rewind(); 282 startnewtape(0); 283 } 284 timeest(); 285 } 286 287 void 288 trewind() 289 { 290 int f; 291 int got; 292 293 for (f = 0; f < SLAVES; f++) { 294 /* 295 * Drain the results, but unlike EOT we DO (or should) care 296 * what the return values were, since if we detect EOT after 297 * we think we've written the last blocks to the tape anyway, 298 * we have to replay those blocks with rollforward. 299 * 300 * fixme: punt for now. 301 */ 302 if (slaves[f].sent) { 303 if (atomic(read, slaves[f].fd, (char *)&got, sizeof got) 304 != sizeof got) { 305 perror(" DUMP: error reading command pipe in master"); 306 dumpabort(0); 307 } 308 slaves[f].sent = 0; 309 if (got != writesize) { 310 msg("EOT detected in last 2 tape records!\n"); 311 msg("Use a longer tape, decrease the size estimate\n"); 312 quit("or use no size estimate at all.\n"); 313 } 314 } 315 (void) close(slaves[f].fd); 316 } 317 while (wait((int *)NULL) >= 0) /* wait for any signals from slaves */ 318 /* void */; 319 320 if (pipeout) 321 return; 322 323 msg("Closing %s\n", tape); 324 325 #ifdef RDUMP 326 if (host) { 327 rmtclose(); 328 while (rmtopen(tape, 0) < 0) 329 sleep(10); 330 rmtclose(); 331 return; 332 } 333 #endif 334 (void) close(tapefd); 335 while ((f = open(tape, 0)) < 0) 336 sleep (10); 337 (void) close(f); 338 } 339 340 void 341 close_rewind() 342 { 343 trewind(); 344 if (nexttape) 345 return; 346 if (!nogripe) { 347 msg("Change Volumes: Mount volume #%d\n", tapeno+1); 348 broadcast("CHANGE DUMP VOLUMES!\7\7\n"); 349 } 350 while (!query("Is the new volume mounted and ready to go?")) 351 if (query("Do you want to abort?")) { 352 dumpabort(0); 353 /*NOTREACHED*/ 354 } 355 } 356 357 void 358 rollforward() 359 { 360 register struct req *p, *q, *prev; 361 register struct slave *tslp; 362 int i, size, savedtapea, got; 363 union u_spcl *ntb, *otb; 364 tslp = &slaves[SLAVES]; 365 ntb = (union u_spcl *)tslp->tblock[1]; 366 367 /* 368 * Each of the N slaves should have requests that need to 369 * be replayed on the next tape. Use the extra slave buffers 370 * (slaves[SLAVES]) to construct request lists to be sent to 371 * each slave in turn. 372 */ 373 for (i = 0; i < SLAVES; i++) { 374 q = &tslp->req[1]; 375 otb = (union u_spcl *)slp->tblock; 376 377 /* 378 * For each request in the current slave, copy it to tslp. 379 */ 380 381 for (p = slp->req; p->count > 0; p += p->count) { 382 *q = *p; 383 if (p->dblk == 0) 384 *ntb++ = *otb++; /* copy the datablock also */ 385 prev = q; 386 q += q->count; 387 } 388 if (prev->dblk != 0) 389 prev->count -= 1; 390 else 391 ntb--; 392 q -= 1; 393 q->count = 0; 394 q = &tslp->req[0]; 395 if (i == 0) { 396 q->dblk = 0; 397 q->count = 1; 398 trecno = 0; 399 nextblock = tslp->tblock; 400 savedtapea = spcl.c_tapea; 401 spcl.c_tapea = slp->tapea; 402 startnewtape(0); 403 spcl.c_tapea = savedtapea; 404 lastspclrec = savedtapea - 1; 405 } 406 size = (char *)ntb - (char *)q; 407 if (atomic(write, slp->fd, (char *)q, size) != size) { 408 perror(" DUMP: error writing command pipe"); 409 dumpabort(0); 410 } 411 slp->sent = 1; 412 if (++slp >= &slaves[SLAVES]) 413 slp = &slaves[0]; 414 415 q->count = 1; 416 417 if (prev->dblk != 0) { 418 /* 419 * If the last one was a disk block, make the 420 * first of this one be the last bit of that disk 421 * block... 422 */ 423 q->dblk = prev->dblk + 424 prev->count * (TP_BSIZE / DEV_BSIZE); 425 ntb = (union u_spcl *)tslp->tblock; 426 } else { 427 /* 428 * It wasn't a disk block. Copy the data to its 429 * new location in the buffer. 430 */ 431 q->dblk = 0; 432 *((union u_spcl *)tslp->tblock) = *ntb; 433 ntb = (union u_spcl *)tslp->tblock[1]; 434 } 435 } 436 slp->req[0] = *q; 437 nextblock = slp->tblock; 438 if (q->dblk == 0) 439 nextblock++; 440 trecno = 1; 441 442 /* 443 * Clear the first slaves' response. One hopes that it 444 * worked ok, otherwise the tape is much too short! 445 */ 446 if (slp->sent) { 447 if (atomic(read, slp->fd, (char *)&got, sizeof got) 448 != sizeof got) { 449 perror(" DUMP: error reading command pipe in master"); 450 dumpabort(0); 451 } 452 slp->sent = 0; 453 454 if (got != writesize) { 455 quit("EOT detected at start of the tape!\n"); 456 } 457 } 458 } 459 460 /* 461 * We implement taking and restoring checkpoints on the tape level. 462 * When each tape is opened, a new process is created by forking; this 463 * saves all of the necessary context in the parent. The child 464 * continues the dump; the parent waits around, saving the context. 465 * If the child returns X_REWRITE, then it had problems writing that tape; 466 * this causes the parent to fork again, duplicating the context, and 467 * everything continues as if nothing had happened. 468 */ 469 void 470 startnewtape(top) 471 int top; 472 { 473 int parentpid; 474 int childpid; 475 int status; 476 int waitpid; 477 char *p; 478 #ifdef sunos 479 void (*interrupt_save)(); 480 #else 481 sig_t interrupt_save; 482 #endif 483 484 interrupt_save = signal(SIGINT, SIG_IGN); 485 parentpid = getpid(); 486 487 restore_check_point: 488 (void)signal(SIGINT, interrupt_save); 489 /* 490 * All signals are inherited... 491 */ 492 childpid = fork(); 493 if (childpid < 0) { 494 msg("Context save fork fails in parent %d\n", parentpid); 495 Exit(X_ABORT); 496 } 497 if (childpid != 0) { 498 /* 499 * PARENT: 500 * save the context by waiting 501 * until the child doing all of the work returns. 502 * don't catch the interrupt 503 */ 504 signal(SIGINT, SIG_IGN); 505 #ifdef TDEBUG 506 msg("Tape: %d; parent process: %d child process %d\n", 507 tapeno+1, parentpid, childpid); 508 #endif /* TDEBUG */ 509 while ((waitpid = wait(&status)) != childpid) 510 msg("Parent %d waiting for child %d has another child %d return\n", 511 parentpid, childpid, waitpid); 512 if (status & 0xFF) { 513 msg("Child %d returns LOB status %o\n", 514 childpid, status&0xFF); 515 } 516 status = (status >> 8) & 0xFF; 517 #ifdef TDEBUG 518 switch(status) { 519 case X_FINOK: 520 msg("Child %d finishes X_FINOK\n", childpid); 521 break; 522 case X_ABORT: 523 msg("Child %d finishes X_ABORT\n", childpid); 524 break; 525 case X_REWRITE: 526 msg("Child %d finishes X_REWRITE\n", childpid); 527 break; 528 default: 529 msg("Child %d finishes unknown %d\n", 530 childpid, status); 531 break; 532 } 533 #endif /* TDEBUG */ 534 switch(status) { 535 case X_FINOK: 536 Exit(X_FINOK); 537 case X_ABORT: 538 Exit(X_ABORT); 539 case X_REWRITE: 540 goto restore_check_point; 541 default: 542 msg("Bad return code from dump: %d\n", status); 543 Exit(X_ABORT); 544 } 545 /*NOTREACHED*/ 546 } else { /* we are the child; just continue */ 547 #ifdef TDEBUG 548 sleep(4); /* allow time for parent's message to get out */ 549 msg("Child on Tape %d has parent %d, my pid = %d\n", 550 tapeno+1, parentpid, getpid()); 551 #endif /* TDEBUG */ 552 /* 553 * If we have a name like "/dev/rmt0,/dev/rmt1", 554 * use the name before the comma first, and save 555 * the remaining names for subsequent volumes. 556 */ 557 tapeno++; /* current tape sequence */ 558 if (nexttape || index(tape, ',')) { 559 if (nexttape && *nexttape) 560 tape = nexttape; 561 if (p = index(tape, ',')) { 562 *p = '\0'; 563 nexttape = p + 1; 564 } else 565 nexttape = NULL; 566 msg("Dumping volume %d on %s\n", tapeno, tape); 567 } 568 #ifdef RDUMP 569 while ((tapefd = (host ? rmtopen(tape, 2) : 570 pipeout ? 1 : open(tape, O_WRONLY|O_CREAT, 0666))) < 0) 571 #else 572 while ((tapefd = (pipeout ? 1 : 573 open(tape, O_WRONLY|O_CREAT, 0666))) < 0) 574 #endif 575 { 576 msg("Cannot open output \"%s\".\n", tape); 577 if (!query("Do you want to retry the open?")) 578 dumpabort(0); 579 } 580 581 enslave(); /* Share open tape file descriptor with slaves */ 582 583 asize = 0; 584 blocksthisvol = 0; 585 if (top) 586 newtape++; /* new tape signal */ 587 spcl.c_count = slp->count; 588 /* 589 * measure firstrec in TP_BSIZE units since restore doesn't 590 * know the correct ntrec value... 591 */ 592 spcl.c_firstrec = slp->firstrec; 593 spcl.c_volume++; 594 spcl.c_type = TS_TAPE; 595 spcl.c_flags |= DR_NEWHEADER; 596 writeheader((ino_t)slp->inode); 597 spcl.c_flags &=~ DR_NEWHEADER; 598 if (tapeno > 1) 599 msg("Volume %d begins with blocks from inode %d\n", 600 tapeno, slp->inode); 601 } 602 } 603 604 void 605 dumpabort(signo) 606 int signo; 607 { 608 609 if (master != 0 && master != getpid()) 610 /* Signals master to call dumpabort */ 611 (void) kill(master, SIGTERM); 612 else { 613 killall(); 614 msg("The ENTIRE dump is aborted.\n"); 615 } 616 Exit(X_ABORT); 617 } 618 619 __dead void 620 Exit(status) 621 int status; 622 { 623 624 #ifdef TDEBUG 625 msg("pid = %d exits with status %d\n", getpid(), status); 626 #endif /* TDEBUG */ 627 exit(status); 628 } 629 630 /* 631 * proceed - handler for SIGUSR2, used to synchronize IO between the slaves. 632 */ 633 void 634 proceed(signo) 635 int signo; 636 { 637 638 if (ready) 639 longjmp(jmpbuf, 1); 640 caught++; 641 } 642 643 void 644 enslave() 645 { 646 int cmd[2]; 647 register int i, j; 648 649 master = getpid(); 650 651 signal(SIGTERM, dumpabort); /* Slave sends SIGTERM on dumpabort() */ 652 signal(SIGPIPE, sigpipe); 653 signal(SIGUSR1, tperror); /* Slave sends SIGUSR1 on tape errors */ 654 signal(SIGUSR2, proceed); /* Slave sends SIGUSR2 to next slave */ 655 656 for (i = 0; i < SLAVES; i++) { 657 if (i == slp - &slaves[0]) { 658 caught = 1; 659 } else { 660 caught = 0; 661 } 662 663 if (socketpair(AF_UNIX, SOCK_STREAM, 0, cmd) < 0 || 664 (slaves[i].pid = fork()) < 0) 665 quit("too many slaves, %d (recompile smaller): %s\n", 666 i, strerror(errno)); 667 668 slaves[i].fd = cmd[1]; 669 slaves[i].sent = 0; 670 if (slaves[i].pid == 0) { /* Slave starts up here */ 671 for (j = 0; j <= i; j++) 672 (void) close(slaves[j].fd); 673 signal(SIGINT, SIG_IGN); /* Master handles this */ 674 doslave(cmd[0], i); 675 Exit(X_FINOK); 676 } 677 } 678 679 for (i = 0; i < SLAVES; i++) 680 (void) atomic(write, slaves[i].fd, 681 (char *) &slaves[(i + 1) % SLAVES].pid, 682 sizeof slaves[0].pid); 683 684 master = 0; 685 } 686 687 void 688 killall() 689 { 690 register int i; 691 692 for (i = 0; i < SLAVES; i++) 693 if (slaves[i].pid > 0) 694 (void) kill(slaves[i].pid, SIGKILL); 695 } 696 697 /* 698 * Synchronization - each process has a lockfile, and shares file 699 * descriptors to the following process's lockfile. When our write 700 * completes, we release our lock on the following process's lock- 701 * file, allowing the following process to lock it and proceed. We 702 * get the lock back for the next cycle by swapping descriptors. 703 */ 704 static void 705 doslave(cmd, slave_number) 706 register int cmd; 707 int slave_number; 708 { 709 register int nread; 710 int nextslave, size, wrote, eot_count; 711 712 /* 713 * Need our own seek pointer. 714 */ 715 (void) close(diskfd); 716 if ((diskfd = open(disk, O_RDONLY)) < 0) 717 quit("slave couldn't reopen disk: %s\n", strerror(errno)); 718 719 /* 720 * Need the pid of the next slave in the loop... 721 */ 722 if ((nread = atomic(read, cmd, (char *)&nextslave, sizeof nextslave)) 723 != sizeof nextslave) { 724 quit("master/slave protocol botched - didn't get pid of next slave.\n"); 725 } 726 727 /* 728 * Get list of blocks to dump, read the blocks into tape buffer 729 */ 730 while ((nread = atomic(read, cmd, (char *)slp->req, reqsiz)) == reqsiz) { 731 register struct req *p = slp->req; 732 733 for (trecno = 0; trecno < ntrec; 734 trecno += p->count, p += p->count) { 735 if (p->dblk) { 736 bread(p->dblk, slp->tblock[trecno], 737 p->count * TP_BSIZE); 738 } else { 739 if (p->count != 1 || atomic(read, cmd, 740 (char *)slp->tblock[trecno], 741 TP_BSIZE) != TP_BSIZE) 742 quit("master/slave protocol botched.\n"); 743 } 744 } 745 if (setjmp(jmpbuf) == 0) { 746 ready = 1; 747 if (!caught) 748 (void) pause(); 749 } 750 ready = 0; 751 caught = 0; 752 753 /* Try to write the data... */ 754 eot_count = 0; 755 size = 0; 756 757 while (eot_count < 10 && size < writesize) { 758 #ifdef RDUMP 759 if (host) 760 wrote = rmtwrite(slp->tblock[0]+size, 761 writesize-size); 762 else 763 #endif 764 wrote = write(tapefd, slp->tblock[0]+size, 765 writesize-size); 766 #ifdef WRITEDEBUG 767 printf("slave %d wrote %d\n", slave_number, wrote); 768 #endif 769 if (wrote < 0) 770 break; 771 if (wrote == 0) 772 eot_count++; 773 size += wrote; 774 } 775 776 #ifdef WRITEDEBUG 777 if (size != writesize) 778 printf("slave %d only wrote %d out of %d bytes and gave up.\n", 779 slave_number, size, writesize); 780 #endif 781 782 if (eot_count > 0) 783 size = 0; 784 785 /* 786 * fixme: Pyramids running OSx return ENOSPC 787 * at EOT on 1/2 inch drives. 788 */ 789 if (size < 0) { 790 (void) kill(master, SIGUSR1); 791 for (;;) 792 (void) sigpause(0); 793 } else { 794 /* 795 * pass size of write back to master 796 * (for EOT handling) 797 */ 798 (void) atomic(write, cmd, (char *)&size, sizeof size); 799 } 800 801 /* 802 * If partial write, don't want next slave to go. 803 * Also jolts him awake. 804 */ 805 (void) kill(nextslave, SIGUSR2); 806 } 807 if (nread != 0) 808 quit("error reading command pipe: %s\n", strerror(errno)); 809 } 810 811 /* 812 * Since a read from a pipe may not return all we asked for, 813 * or a write may not write all we ask if we get a signal, 814 * loop until the count is satisfied (or error). 815 */ 816 static int 817 atomic(func, fd, buf, count) 818 int (*func)(), fd; 819 char *buf; 820 int count; 821 { 822 int got, need = count; 823 824 while ((got = (*func)(fd, buf, need)) > 0 && (need -= got) > 0) 825 buf += got; 826 return (got < 0 ? got : count - need); 827 } 828