sysv_sem.c revision 1.6
1 /* 2 * Implementation of SVID semaphores 3 * 4 * Author: Daniel Boulet 5 * 6 * This software is provided ``AS IS'' without any warranties of any kind. 7 * 8 * $Id: sysv_sem.c,v 1.6 1994/02/13 11:31:16 mycroft Exp $ 9 */ 10 11 #include <sys/param.h> 12 #include <sys/systm.h> 13 #include <sys/kernel.h> 14 #include <sys/proc.h> 15 #include <sys/sem.h> 16 #include <sys/malloc.h> 17 18 static int semctl(), semget(), semop(), semconfig(); 19 int (*semcalls[])() = { semctl, semget, semop, semconfig }; 20 int semtot = 0; 21 22 static struct proc *semlock_holder = NULL; 23 24 int 25 seminit() 26 { 27 register int i; 28 vm_offset_t whocares1, whocares2; 29 30 if (sema == NULL) 31 panic("sema is NULL"); 32 if (semu == NULL) 33 panic("semu is NULL"); 34 35 for (i = 0; i < seminfo.semmni; i++) { 36 sema[i].sem_base = 0; 37 sema[i].sem_perm.mode = 0; 38 } 39 for (i = 0; i < seminfo.semmnu; i++) { 40 register struct sem_undo *suptr = SEMU(i); 41 suptr->un_proc = NULL; 42 } 43 semu_list = NULL; 44 } 45 46 /* 47 * Entry point for all SEM calls 48 */ 49 50 struct semsys_args { 51 u_int which; 52 }; 53 54 int 55 semsys(p, uap, retval) 56 struct proc *p; 57 struct semsys_args *uap; 58 int *retval; 59 { 60 61 while (semlock_holder != NULL && semlock_holder != p) 62 sleep((caddr_t)&semlock_holder, (PZERO - 4)); 63 64 if (uap->which >= sizeof(semcalls)/sizeof(semcalls[0])) 65 return (EINVAL); 66 return ((*semcalls[uap->which])(p, &uap[1], retval)); 67 } 68 69 /* 70 * Lock or unlock the entire semaphore facility. 71 * 72 * This will probably eventually evolve into a general purpose semaphore 73 * facility status enquiry mechanism (I don't like the "read /dev/kmem" 74 * approach currently taken by ipcs and the amount of info that we want 75 * to be able to extract for ipcs is probably beyond what the capability 76 * of the getkerninfo facility. 77 * 78 * At the time that the current version of semconfig was written, ipcs is 79 * the only user of the semconfig facility. It uses it to ensure that the 80 * semaphore facility data structures remain static while it fishes around 81 * in /dev/kmem. 82 */ 83 84 struct semconfig_args { 85 semconfig_ctl_t flag; 86 }; 87 88 int 89 semconfig(p, uap, retval) 90 struct proc *p; 91 struct semconfig_args *uap; 92 int *retval; 93 { 94 int eval = 0; 95 96 switch (uap->flag) { 97 case SEM_CONFIG_FREEZE: 98 semlock_holder = p; 99 break; 100 101 case SEM_CONFIG_THAW: 102 semlock_holder = NULL; 103 wakeup((caddr_t)&semlock_holder); 104 break; 105 106 default: 107 printf("semconfig: unknown flag parameter value (%d) - ignored\n", 108 uap->flag); 109 eval = EINVAL; 110 break; 111 } 112 113 *retval = 0; 114 return(eval); 115 } 116 117 /* 118 * Allocate a new sem_undo structure for a process 119 * (returns ptr to structure or NULL if no more room) 120 */ 121 122 struct sem_undo * 123 semu_alloc(p) 124 struct proc *p; 125 { 126 register int i; 127 register struct sem_undo *suptr; 128 register struct sem_undo **supptr; 129 int attempt; 130 131 /* 132 * Try twice to allocate something. 133 * (we'll purge any empty structures after the first pass so 134 * two passes are always enough) 135 */ 136 137 for (attempt = 0; attempt < 2; attempt++) { 138 /* 139 * Look for a free structure. 140 * Fill it in and return it if we find one. 141 */ 142 143 for (i = 0; i < seminfo.semmnu; i++) { 144 suptr = SEMU(i); 145 if (suptr->un_proc == NULL) { 146 suptr->un_next = semu_list; 147 semu_list = suptr; 148 suptr->un_cnt = 0; 149 suptr->un_proc = p; 150 return(suptr); 151 } 152 } 153 154 /* 155 * We didn't find a free one, if this is the first attempt 156 * then try to free some structures. 157 */ 158 159 if (attempt == 0) { 160 /* All the structures are in use - try to free some */ 161 int did_something = 0; 162 163 supptr = &semu_list; 164 while ((suptr = *supptr) != NULL) { 165 if (suptr->un_cnt == 0) { 166 suptr->un_proc = NULL; 167 *supptr = suptr->un_next; 168 did_something = 1; 169 } else 170 supptr = &(suptr->un_next); 171 } 172 173 /* If we didn't free anything then just give-up */ 174 if (!did_something) 175 return(NULL); 176 } else { 177 /* 178 * The second pass failed even though we freed 179 * something after the first pass! 180 * This is IMPOSSIBLE! 181 */ 182 panic("semu_alloc - second attempt failed"); 183 } 184 } 185 } 186 187 /* 188 * Adjust a particular entry for a particular proc 189 */ 190 191 int 192 semundo_adjust(p, supptr, semid, semnum, adjval) 193 register struct proc *p; 194 struct sem_undo **supptr; 195 int semid, semnum; 196 int adjval; 197 { 198 register struct sem_undo *suptr; 199 register struct undo *sunptr; 200 int i; 201 202 /* Look for and remember the sem_undo if the caller doesn't provide 203 it */ 204 205 suptr = *supptr; 206 if (suptr == NULL) { 207 for (suptr = semu_list; suptr != NULL; 208 suptr = suptr->un_next) { 209 if (suptr->un_proc == p) { 210 *supptr = suptr; 211 break; 212 } 213 } 214 if (suptr == NULL) { 215 if (adjval == 0) 216 return(0); 217 suptr = semu_alloc(p); 218 if (suptr == NULL) 219 return(ENOSPC); 220 *supptr = suptr; 221 } 222 } 223 224 /* 225 * Look for the requested entry and adjust it (delete if adjval becomes 226 * 0). 227 */ 228 sunptr = &suptr->un_ent[0]; 229 for (i = 0; i < suptr->un_cnt; i++, sunptr++) { 230 if (sunptr->un_id != semid || sunptr->un_num != semnum) 231 continue; 232 if (adjval == 0) 233 sunptr->un_adjval = 0; 234 else 235 sunptr->un_adjval += adjval; 236 if (sunptr->un_adjval == 0) { 237 suptr->un_cnt--; 238 if (i < suptr->un_cnt) 239 suptr->un_ent[i] = 240 suptr->un_ent[suptr->un_cnt]; 241 } 242 return(0); 243 } 244 245 /* Didn't find the right entry - create it */ 246 if (adjval == 0) 247 return(0); 248 if (suptr->un_cnt != SEMUME) { 249 sunptr = &suptr->un_ent[suptr->un_cnt]; 250 suptr->un_cnt++; 251 sunptr->un_adjval = adjval; 252 sunptr->un_id = semid; sunptr->un_num = semnum; 253 } else 254 return(EINVAL); 255 return(0); 256 } 257 258 void 259 semundo_clear(semid, semnum) 260 int semid, semnum; 261 { 262 register struct sem_undo *suptr; 263 264 for (suptr = semu_list; suptr != NULL; suptr = suptr->un_next) { 265 register struct undo *sunptr = &suptr->un_ent[0]; 266 register int i = 0; 267 268 while (i < suptr->un_cnt) { 269 if (sunptr->un_id == semid) { 270 if (semnum == -1 || sunptr->un_num == semnum) { 271 suptr->un_cnt--; 272 if (i < suptr->un_cnt) { 273 suptr->un_ent[i] = 274 suptr->un_ent[suptr->un_cnt]; 275 continue; 276 } 277 } 278 if (semnum != -1) 279 break; 280 } 281 i++, sunptr++; 282 } 283 } 284 } 285 286 struct semctl_args { 287 int semid; 288 int semnum; 289 int cmd; 290 union semun *arg; 291 }; 292 293 int 294 semctl(p, uap, retval) 295 struct proc *p; 296 register struct semctl_args *uap; 297 int *retval; 298 { 299 int semid = uap->semid; 300 int semnum = uap->semnum; 301 int cmd = uap->cmd; 302 union semun *arg = uap->arg; 303 union semun real_arg; 304 struct ucred *cred = p->p_ucred; 305 int i, rval, eval; 306 struct semid_ds sbuf; 307 register struct semid_ds *semaptr; 308 309 #ifdef SEM_DEBUG 310 printf("call to semctl(%d, %d, %d, 0x%x)\n", semid, semnum, cmd, arg); 311 #endif 312 313 semid = IPCID_TO_IX(semid); 314 if (semid < 0 || semid >= seminfo.semmsl) 315 return(EINVAL); 316 317 semaptr = &sema[semid]; 318 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 || 319 semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid)) 320 return(EINVAL); 321 322 eval = 0; 323 rval = 0; 324 325 switch (cmd) { 326 case IPC_RMID: 327 if (cred->cr_uid != 0 && 328 semaptr->sem_perm.cuid != cred->cr_uid && 329 semaptr->sem_perm.uid != cred->cr_uid) 330 return(EPERM); 331 semaptr->sem_perm.cuid = cred->cr_uid; 332 semaptr->sem_perm.uid = cred->cr_uid; 333 semtot -= semaptr->sem_nsems; 334 for (i = semaptr->sem_base - sem; i < semtot; i++) 335 sem[i] = sem[i + semaptr->sem_nsems]; 336 for (i = 0; i < seminfo.semmni; i++) { 337 if ((sema[i].sem_perm.mode & SEM_ALLOC) && 338 sema[i].sem_base > semaptr->sem_base) 339 sema[i].sem_base -= semaptr->sem_nsems; 340 } 341 semaptr->sem_perm.mode = 0; 342 semundo_clear(semid, -1); 343 wakeup((caddr_t)semaptr); 344 break; 345 346 case IPC_SET: 347 if (cred->cr_uid != 0 && 348 semaptr->sem_perm.cuid != cred->cr_uid && 349 semaptr->sem_perm.uid != cred->cr_uid) 350 return(EPERM); 351 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 352 return(eval); 353 if ((eval = copyin(real_arg.buf, (caddr_t)&sbuf, 354 sizeof(sbuf))) != 0) 355 return(eval); 356 semaptr->sem_perm.uid = sbuf.sem_perm.uid; 357 semaptr->sem_perm.gid = sbuf.sem_perm.gid; 358 semaptr->sem_perm.mode = (semaptr->sem_perm.mode & ~0777) | 359 (sbuf.sem_perm.mode & 0777); 360 semaptr->sem_ctime = time.tv_sec; 361 break; 362 363 case IPC_STAT: 364 if ((eval = ipcaccess(&semaptr->sem_perm, IPC_R, cred))) 365 return(eval); 366 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 367 return(eval); 368 eval = copyout((caddr_t)semaptr, real_arg.buf, 369 sizeof(struct semid_ds)); 370 break; 371 372 case GETNCNT: 373 if ((eval = ipcaccess(&semaptr->sem_perm, IPC_R, cred))) 374 return(eval); 375 if (semnum < 0 || semnum >= semaptr->sem_nsems) 376 return(EINVAL); 377 rval = semaptr->sem_base[semnum].semncnt; 378 break; 379 380 case GETPID: 381 if ((eval = ipcaccess(&semaptr->sem_perm, IPC_R, cred))) 382 return(eval); 383 if (semnum < 0 || semnum >= semaptr->sem_nsems) 384 return(EINVAL); 385 rval = semaptr->sem_base[semnum].sempid; 386 break; 387 388 case GETVAL: 389 if ((eval = ipcaccess(&semaptr->sem_perm, IPC_R, cred))) 390 return(eval); 391 if (semnum < 0 || semnum >= semaptr->sem_nsems) 392 return(EINVAL); 393 rval = semaptr->sem_base[semnum].semval; 394 break; 395 396 case GETALL: 397 if ((eval = ipcaccess(&semaptr->sem_perm, IPC_R, cred))) 398 return(eval); 399 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 400 return(eval); 401 for (i = 0; i < semaptr->sem_nsems; i++) { 402 eval = copyout((caddr_t)&semaptr->sem_base[i].semval, 403 &real_arg.array[i], sizeof(real_arg.array[0])); 404 if (eval != 0) 405 break; 406 } 407 break; 408 409 case GETZCNT: 410 if ((eval = ipcaccess(&semaptr->sem_perm, IPC_R, cred))) 411 return(eval); 412 if (semnum < 0 || semnum >= semaptr->sem_nsems) 413 return(EINVAL); 414 rval = semaptr->sem_base[semnum].semzcnt; 415 break; 416 417 case SETVAL: 418 if ((eval = ipcaccess(&semaptr->sem_perm, IPC_W, cred))) 419 return(eval); 420 if (semnum < 0 || semnum >= semaptr->sem_nsems) 421 return(EINVAL); 422 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 423 return(eval); 424 semaptr->sem_base[semnum].semval = real_arg.val; 425 semundo_clear(semid, semnum); 426 wakeup((caddr_t)semaptr); 427 break; 428 429 case SETALL: 430 if ((eval = ipcaccess(&semaptr->sem_perm, IPC_W, cred))) 431 return(eval); 432 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0) 433 return(eval); 434 for (i = 0; i < semaptr->sem_nsems; i++) { 435 eval = copyin(&real_arg.array[i], 436 (caddr_t)&semaptr->sem_base[i].semval, 437 sizeof(real_arg.array[0])); 438 if (eval != 0) 439 break; 440 } 441 semundo_clear(semid, -1); 442 wakeup((caddr_t)semaptr); 443 break; 444 445 default: 446 return(EINVAL); 447 } 448 449 if (eval == 0) 450 *retval = rval; 451 return(eval); 452 } 453 454 struct semget_args { 455 key_t key; 456 int nsems; 457 int semflg; 458 }; 459 460 int 461 semget(p, uap, retval) 462 struct proc *p; 463 register struct semget_args *uap; 464 int *retval; 465 { 466 int semid, eval; 467 int key = uap->key; 468 int nsems = uap->nsems; 469 int semflg = uap->semflg; 470 struct ucred *cred = p->p_ucred; 471 472 #ifdef SEM_DEBUG 473 printf("semget(0x%x, %d, 0%o)\n", key, nsems, semflg); 474 #endif 475 476 if (key != IPC_PRIVATE) { 477 for (semid = 0; semid < seminfo.semmni; semid++) { 478 if ((sema[semid].sem_perm.mode & SEM_ALLOC) && 479 sema[semid].sem_perm.key == key) 480 break; 481 } 482 if (semid < seminfo.semmni) { 483 #ifdef SEM_DEBUG 484 printf("found public key\n"); 485 #endif 486 if ((eval = ipcaccess(&sema[semid].sem_perm, 487 semflg & 0700, cred))) 488 return(eval); 489 if (nsems > 0 && sema[semid].sem_nsems < nsems) { 490 #ifdef SEM_DEBUG 491 printf("too small\n"); 492 #endif 493 return(EINVAL); 494 } 495 if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) { 496 #ifdef SEM_DEBUG 497 printf("not exclusive\n"); 498 #endif 499 return(EEXIST); 500 } 501 goto found; 502 } 503 } 504 505 #ifdef SEM_DEBUG 506 printf("need to allocate the semid_ds\n"); 507 #endif 508 if (key == IPC_PRIVATE || (semflg & IPC_CREAT)) { 509 if (nsems <= 0 || nsems > seminfo.semmsl) { 510 #ifdef SEM_DEBUG 511 printf("nsems out of range (0<%d<=%d)\n", nsems, 512 seminfo.semmsl); 513 #endif 514 return(EINVAL); 515 } 516 if (nsems > seminfo.semmns - semtot) { 517 #ifdef SEM_DEBUG 518 printf("not enough semaphores left (need %d, got %d)\n", 519 nsems, seminfo.semmns - semtot); 520 #endif 521 return(ENOSPC); 522 } 523 for (semid = 0; semid < seminfo.semmni; semid++) { 524 if ((sema[semid].sem_perm.mode & SEM_ALLOC) == 0) 525 break; 526 } 527 if (semid == seminfo.semmni) { 528 #ifdef SEM_DEBUG 529 printf("no more semid_ds's available\n"); 530 #endif 531 return(ENOSPC); 532 } 533 #ifdef SEM_DEBUG 534 printf("semid %d is available\n", semid); 535 #endif 536 sema[semid].sem_perm.key = key; 537 sema[semid].sem_perm.cuid = cred->cr_uid; 538 sema[semid].sem_perm.uid = cred->cr_uid; 539 sema[semid].sem_perm.cgid = cred->cr_gid; 540 sema[semid].sem_perm.gid = cred->cr_gid; 541 sema[semid].sem_perm.mode = (semflg & 0777) | SEM_ALLOC; 542 sema[semid].sem_perm.seq = 543 (sema[semid].sem_perm.seq + 1) & 0x7fff; 544 sema[semid].sem_nsems = nsems; 545 sema[semid].sem_otime = 0; 546 sema[semid].sem_ctime = time.tv_sec; 547 sema[semid].sem_base = &sem[semtot]; 548 semtot += nsems; 549 bzero(sema[semid].sem_base, 550 sizeof(sema[semid].sem_base[0])*nsems); 551 #ifdef SEM_DEBUG 552 printf("sembase = 0x%x, next = 0x%x\n", sema[semid].sem_base, 553 &sem[semtot]); 554 #endif 555 } else { 556 #ifdef SEM_DEBUG 557 printf("didn't find it and wasn't asked to create it\n"); 558 #endif 559 return(ENOENT); 560 } 561 562 found: 563 *retval = IXSEQ_TO_IPCID(semid, sema[semid].sem_perm); 564 return(0); 565 } 566 567 struct semop_args { 568 int semid; 569 struct sembuf *sops; 570 int nsops; 571 }; 572 573 int 574 semop(p, uap, retval) 575 struct proc *p; 576 register struct semop_args *uap; 577 int *retval; 578 { 579 int semid = uap->semid; 580 int nsops = uap->nsops; 581 struct sembuf sops[MAX_SOPS]; 582 register struct semid_ds *semaptr; 583 register struct sembuf *sopptr; 584 register struct sem *semptr; 585 struct sem_undo *suptr = NULL; 586 struct ucred *cred = p->p_ucred; 587 int i, j, eval; 588 int all_ok, do_wakeup, do_undos; 589 590 #ifdef SEM_DEBUG 591 printf("call to semop(%d, 0x%x, %d)\n", semid, sops, nsops); 592 #endif 593 594 semid = IPCID_TO_IX(semid); /* Convert back to zero origin */ 595 596 if (semid < 0 || semid >= seminfo.semmsl) 597 return(EINVAL); 598 599 semaptr = &sema[semid]; 600 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0) 601 return(EINVAL); 602 if (semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid)) 603 return(EINVAL); 604 605 if ((eval = ipcaccess(&semaptr->sem_perm, IPC_W, cred))) { 606 #ifdef SEM_DEBUG 607 printf("eval = %d from ipaccess\n", eval); 608 #endif 609 return(eval); 610 } 611 612 if (nsops > MAX_SOPS) { 613 #ifdef SEM_DEBUG 614 printf("too many sops (max=%d, nsops=%d)\n", MAX_SOPS, nsops); 615 #endif 616 return(E2BIG); 617 } 618 619 if ((eval = copyin(uap->sops, &sops, nsops * sizeof(sops[0]))) != 0) { 620 #ifdef SEM_DEBUG 621 printf("eval = %d from copyin(%08x, %08x, %d)\n", eval, 622 uap->sops, &sops, nsops * sizeof(sops[0])); 623 #endif 624 return(eval); 625 } 626 627 /* 628 * Loop trying to satisfy the vector of requests. 629 * If we reach a point where we must wait, any requests already 630 * performed are rolled back and we go to sleep until some other 631 * process wakes us up. At this point, we start all over again. 632 * 633 * This ensures that from the perspective of other tasks, a set 634 * of requests is atomic (never partially satisfied). 635 */ 636 do_undos = 0; 637 638 for (;;) { 639 do_wakeup = 0; 640 641 for (i = 0; i < nsops; i++) { 642 sopptr = &sops[i]; 643 644 if (sopptr->sem_num >= semaptr->sem_nsems) 645 return(EFBIG); 646 647 semptr = &semaptr->sem_base[sopptr->sem_num]; 648 649 #ifdef SEM_DEBUG 650 printf("semop: semaptr=%x, sem_base=%x, semptr=%x, sem[%d]=%d : op=%d, flag=%s\n", 651 semaptr, semaptr->sem_base, semptr, 652 sopptr->sem_num, semptr->semval, sopptr->sem_op, 653 (sopptr->sem_flg & IPC_NOWAIT) ? "nowait" : "wait"); 654 #endif 655 656 if (sopptr->sem_op < 0) { 657 if (semptr->semval + sopptr->sem_op < 0) { 658 #ifdef SEM_DEBUG 659 printf("semop: can't do it now\n"); 660 #endif 661 break; 662 } else { 663 semptr->semval += sopptr->sem_op; 664 if (semptr->semval == 0 && 665 semptr->semzcnt > 0) 666 do_wakeup = 1; 667 } 668 if (sopptr->sem_flg & SEM_UNDO) 669 do_undos = 1; 670 } else if (sopptr->sem_op == 0) { 671 if (semptr->semval > 0) { 672 #ifdef SEM_DEBUG 673 printf("semop: not zero now\n"); 674 #endif 675 break; 676 } 677 } else { 678 if (semptr->semncnt > 0) 679 do_wakeup = 1; 680 semptr->semval += sopptr->sem_op; 681 if (sopptr->sem_flg & SEM_UNDO) 682 do_undos = 1; 683 } 684 } 685 686 /* 687 * Did we get through the entire vector? 688 */ 689 if (i >= nsops) 690 goto done; 691 692 /* 693 * No ... rollback anything that we've already done 694 */ 695 #ifdef SEM_DEBUG 696 printf("semop: rollback 0 through %d\n", i-1); 697 #endif 698 for (j = 0; j < i; j++) 699 semaptr->sem_base[sops[j].sem_num].semval -= 700 sops[j].sem_op; 701 702 /* 703 * If the request that we couldn't satisfy has the 704 * NOWAIT flag set then return with EAGAIN. 705 */ 706 if (sopptr->sem_flg & IPC_NOWAIT) 707 return(EAGAIN); 708 709 if (sopptr->sem_op == 0) 710 semptr->semzcnt++; 711 else 712 semptr->semncnt++; 713 714 #ifdef SEM_DEBUG 715 printf("semop: good night!\n"); 716 #endif 717 eval = tsleep((caddr_t)semaptr, (PZERO - 4) | PCATCH, 718 "semwait", 0); 719 #ifdef SEM_DEBUG 720 printf("semop: good morning (eval=%d)!\n", eval); 721 #endif 722 723 suptr = NULL; /* sem_undo may have been reallocated */ 724 725 if (eval != 0) 726 return(EINTR); 727 #ifdef SEM_DEBUG 728 printf("semop: good morning!\n"); 729 #endif 730 731 /* 732 * Make sure that the semaphore still exists 733 */ 734 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 || 735 semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid)) { 736 /* The man page says to return EIDRM. */ 737 /* Unfortunately, BSD doesn't define that code! */ 738 #ifdef EIDRM 739 return(EIDRM); 740 #else 741 return(EINVAL); 742 #endif 743 } 744 745 /* 746 * The semaphore is still alive. Readjust the count of 747 * waiting processes. 748 */ 749 if (sopptr->sem_op == 0) 750 semptr->semzcnt--; 751 else 752 semptr->semncnt--; 753 } 754 755 done: 756 /* 757 * Process any SEM_UNDO requests. 758 */ 759 if (do_undos) { 760 for (i = 0; i < nsops; i++) { 761 /* 762 * We only need to deal with SEM_UNDO's for non-zero 763 * op's. 764 */ 765 int adjval; 766 767 if ((sops[i].sem_flg & SEM_UNDO) == 0) 768 continue; 769 adjval = sops[i].sem_op; 770 if (adjval == 0) 771 continue; 772 eval = semundo_adjust(p, &suptr, semid, 773 sops[i].sem_num, -adjval); 774 if (eval == 0) 775 continue; 776 777 /* 778 * Oh-Oh! We ran out of either sem_undo's or undo's. 779 * Rollback the adjustments to this point and then 780 * rollback the semaphore ups and down so we can return 781 * with an error with all structures restored. We 782 * rollback the undo's in the exact reverse order that 783 * we applied them. This guarantees that we won't run 784 * out of space as we roll things back out. 785 */ 786 for (j = i - 1; j >= 0; j--) { 787 if ((sops[j].sem_flg & SEM_UNDO) == 0) 788 continue; 789 adjval = sops[j].sem_op; 790 if (adjval == 0) 791 continue; 792 if (semundo_adjust(p, &suptr, semid, 793 sops[j].sem_num, adjval) != 0) 794 panic("semop - can't undo undos"); 795 } 796 797 for (j = 0; j < nsops; j++) 798 semaptr->sem_base[sops[j].sem_num].semval -= 799 sops[j].sem_op; 800 801 #ifdef SEM_DEBUG 802 printf("eval = %d from semundo_adjust\n", eval); 803 #endif 804 return(eval); 805 } /* loop through the sops */ 806 } /* if (do_undos) */ 807 808 /* We're definitely done - set the sempid's */ 809 for (i = 0; i < nsops; i++) { 810 sopptr = &sops[i]; 811 semptr = &semaptr->sem_base[sopptr->sem_num]; 812 semptr->sempid = p->p_pid; 813 } 814 815 /* Do a wakeup if any semaphore was up'd. */ 816 if (do_wakeup) { 817 #ifdef SEM_DEBUG 818 printf("semop: doing wakeup\n"); 819 #ifdef SEM_WAKEUP 820 sem_wakeup((caddr_t)semaptr); 821 #else 822 wakeup((caddr_t)semaptr); 823 #endif 824 printf("semop: back from wakeup\n"); 825 #else 826 wakeup((caddr_t)semaptr); 827 #endif 828 } 829 #ifdef SEM_DEBUG 830 printf("semop: done\n"); 831 #endif 832 *retval = 0; 833 return(0); 834 } 835 836 /* 837 * Go through the undo structures for this process and apply the adjustments to 838 * semaphores. 839 */ 840 semexit(p) 841 struct proc *p; 842 { 843 register struct sem_undo *suptr; 844 register struct sem_undo **supptr; 845 int did_something; 846 847 /* 848 * If somebody else is holding the global semaphore facility lock 849 * then sleep until it is released. 850 */ 851 while (semlock_holder != NULL && semlock_holder != p) { 852 #ifdef SEM_DEBUG 853 printf("semaphore facility locked - sleeping ...\n"); 854 #endif 855 sleep((caddr_t)&semlock_holder, (PZERO - 4)); 856 } 857 858 did_something = 0; 859 860 /* 861 * Go through the chain of undo vectors looking for one 862 * associated with this process. 863 */ 864 865 for (supptr = &semu_list; (suptr = *supptr) != NULL; 866 supptr = &suptr->un_next) { 867 if (suptr->un_proc == p) 868 break; 869 } 870 871 if (suptr == NULL) 872 goto unlock; 873 874 #ifdef SEM_DEBUG 875 printf("proc @%08x has undo structure with %d entries\n", p, 876 suptr->un_cnt); 877 #endif 878 879 /* 880 * If there are any active undo elements then process them. 881 */ 882 if (suptr->un_cnt > 0) { 883 int ix; 884 885 for (ix = 0; ix < suptr->un_cnt; ix++) { 886 int semid = suptr->un_ent[ix].un_id; 887 int semnum = suptr->un_ent[ix].un_num; 888 int adjval = suptr->un_ent[ix].un_adjval; 889 struct semid_ds *semaptr; 890 891 semaptr = &sema[semid]; 892 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0) 893 panic("semexit - semid not allocated"); 894 if (semnum >= semaptr->sem_nsems) 895 panic("semexit - semnum out of range"); 896 897 #ifdef SEM_DEBUG 898 printf("semexit: %08x id=%d num=%d(adj=%d) ; sem=%d\n", 899 suptr->un_proc, suptr->un_ent[ix].un_id, 900 suptr->un_ent[ix].un_num, 901 suptr->un_ent[ix].un_adjval, 902 semaptr->sem_base[semnum].semval); 903 #endif 904 905 if (adjval < 0) { 906 if (semaptr->sem_base[semnum].semval < -adjval) 907 semaptr->sem_base[semnum].semval = 0; 908 else 909 semaptr->sem_base[semnum].semval += 910 adjval; 911 } else 912 semaptr->sem_base[semnum].semval += adjval; 913 914 #ifdef SEM_WAKEUP 915 sem_wakeup((caddr_t)semaptr); 916 #else 917 wakeup((caddr_t)semaptr); 918 #endif 919 #ifdef SEM_DEBUG 920 printf("semexit: back from wakeup\n"); 921 #endif 922 } 923 } 924 925 /* 926 * Deallocate the undo vector. 927 */ 928 #ifdef SEM_DEBUG 929 printf("removing vector\n"); 930 #endif 931 suptr->un_proc = NULL; 932 *supptr = suptr->un_next; 933 934 unlock: 935 /* 936 * If the exiting process is holding the global semaphore facility 937 * lock then release it. 938 */ 939 if (semlock_holder == p) { 940 semlock_holder = NULL; 941 wakeup((caddr_t)&semlock_holder); 942 } 943 } 944
Indexes created Mon Sep 22 05:09:51 GMT 2025