xref: /netbsd-src/sys/kern/sysv_sem.c (revision ae1bfcddc410612bc8c58b807e1830becb69a24c)
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