sysv_sem.c revision 59828 
1/* $FreeBSD: head/sys/kern/sysv_sem.c 59828 2000-05-01 11:13:41Z peter $ */
2
3/*
4 * Implementation of SVID semaphores
5 *
6 * Author:  Daniel Boulet
7 *
8 * This software is provided ``AS IS'' without any warranties of any kind.
9 */
10
11#include <sys/param.h>
12#include <sys/systm.h>
13#include <sys/sysproto.h>
14#include <sys/kernel.h>
15#include <sys/proc.h>
16#include <sys/sem.h>
17#include <sys/sysent.h>
18
19static void seminit __P((void *));
20SYSINIT(sysv_sem, SI_SUB_SYSV_SEM, SI_ORDER_FIRST, seminit, NULL)
21
22#ifndef _SYS_SYSPROTO_H_
23struct __semctl_args;
24int __semctl __P((struct proc *p, struct __semctl_args *uap));
25struct semget_args;
26int semget __P((struct proc *p, struct semget_args *uap));
27struct semop_args;
28int semop __P((struct proc *p, struct semop_args *uap));
29#endif
30
31static struct sem_undo *semu_alloc __P((struct proc *p));
32static int semundo_adjust __P((struct proc *p, struct sem_undo **supptr,
33		int semid, int semnum, int adjval));
34static void semundo_clear __P((int semid, int semnum));
35
36/* XXX casting to (sy_call_t *) is bogus, as usual. */
37static sy_call_t *semcalls[] = {
38	(sy_call_t *)__semctl, (sy_call_t *)semget,
39	(sy_call_t *)semop
40};
41
42static int	semtot = 0;
43struct semid_ds *sema;		/* semaphore id pool */
44struct sem *sem;		/* semaphore pool */
45static struct sem_undo *semu_list; 	/* list of active undo structures */
46int	*semu;			/* undo structure pool */
47
48void
49seminit(dummy)
50	void *dummy;
51{
52	register int i;
53
54	if (sema == NULL)
55		panic("sema is NULL");
56	if (semu == NULL)
57		panic("semu is NULL");
58
59	for (i = 0; i < seminfo.semmni; i++) {
60		sema[i].sem_base = 0;
61		sema[i].sem_perm.mode = 0;
62	}
63	for (i = 0; i < seminfo.semmnu; i++) {
64		register struct sem_undo *suptr = SEMU(i);
65		suptr->un_proc = NULL;
66	}
67	semu_list = NULL;
68}
69
70/*
71 * Entry point for all SEM calls
72 */
73int
74semsys(p, uap)
75	struct proc *p;
76	/* XXX actually varargs. */
77	struct semsys_args /* {
78		u_int	which;
79		int	a2;
80		int	a3;
81		int	a4;
82		int	a5;
83	} */ *uap;
84{
85
86	if (uap->which >= sizeof(semcalls)/sizeof(semcalls[0]))
87		return (EINVAL);
88	return ((*semcalls[uap->which])(p, &uap->a2));
89}
90
91/*
92 * Allocate a new sem_undo structure for a process
93 * (returns ptr to structure or NULL if no more room)
94 */
95
96static struct sem_undo *
97semu_alloc(p)
98	struct proc *p;
99{
100	register int i;
101	register struct sem_undo *suptr;
102	register struct sem_undo **supptr;
103	int attempt;
104
105	/*
106	 * Try twice to allocate something.
107	 * (we'll purge any empty structures after the first pass so
108	 * two passes are always enough)
109	 */
110
111	for (attempt = 0; attempt < 2; attempt++) {
112		/*
113		 * Look for a free structure.
114		 * Fill it in and return it if we find one.
115		 */
116
117		for (i = 0; i < seminfo.semmnu; i++) {
118			suptr = SEMU(i);
119			if (suptr->un_proc == NULL) {
120				suptr->un_next = semu_list;
121				semu_list = suptr;
122				suptr->un_cnt = 0;
123				suptr->un_proc = p;
124				return(suptr);
125			}
126		}
127
128		/*
129		 * We didn't find a free one, if this is the first attempt
130		 * then try to free some structures.
131		 */
132
133		if (attempt == 0) {
134			/* All the structures are in use - try to free some */
135			int did_something = 0;
136
137			supptr = &semu_list;
138			while ((suptr = *supptr) != NULL) {
139				if (suptr->un_cnt == 0)  {
140					suptr->un_proc = NULL;
141					*supptr = suptr->un_next;
142					did_something = 1;
143				} else
144					supptr = &(suptr->un_next);
145			}
146
147			/* If we didn't free anything then just give-up */
148			if (!did_something)
149				return(NULL);
150		} else {
151			/*
152			 * The second pass failed even though we freed
153			 * something after the first pass!
154			 * This is IMPOSSIBLE!
155			 */
156			panic("semu_alloc - second attempt failed");
157		}
158	}
159	return (NULL);
160}
161
162/*
163 * Adjust a particular entry for a particular proc
164 */
165
166static int
167semundo_adjust(p, supptr, semid, semnum, adjval)
168	register struct proc *p;
169	struct sem_undo **supptr;
170	int semid, semnum;
171	int adjval;
172{
173	register struct sem_undo *suptr;
174	register struct undo *sunptr;
175	int i;
176
177	/* Look for and remember the sem_undo if the caller doesn't provide
178	   it */
179
180	suptr = *supptr;
181	if (suptr == NULL) {
182		for (suptr = semu_list; suptr != NULL;
183		    suptr = suptr->un_next) {
184			if (suptr->un_proc == p) {
185				*supptr = suptr;
186				break;
187			}
188		}
189		if (suptr == NULL) {
190			if (adjval == 0)
191				return(0);
192			suptr = semu_alloc(p);
193			if (suptr == NULL)
194				return(ENOSPC);
195			*supptr = suptr;
196		}
197	}
198
199	/*
200	 * Look for the requested entry and adjust it (delete if adjval becomes
201	 * 0).
202	 */
203	sunptr = &suptr->un_ent[0];
204	for (i = 0; i < suptr->un_cnt; i++, sunptr++) {
205		if (sunptr->un_id != semid || sunptr->un_num != semnum)
206			continue;
207		if (adjval == 0)
208			sunptr->un_adjval = 0;
209		else
210			sunptr->un_adjval += adjval;
211		if (sunptr->un_adjval == 0) {
212			suptr->un_cnt--;
213			if (i < suptr->un_cnt)
214				suptr->un_ent[i] =
215				    suptr->un_ent[suptr->un_cnt];
216		}
217		return(0);
218	}
219
220	/* Didn't find the right entry - create it */
221	if (adjval == 0)
222		return(0);
223	if (suptr->un_cnt != seminfo.semume) {
224		sunptr = &suptr->un_ent[suptr->un_cnt];
225		suptr->un_cnt++;
226		sunptr->un_adjval = adjval;
227		sunptr->un_id = semid; sunptr->un_num = semnum;
228	} else
229		return(EINVAL);
230	return(0);
231}
232
233static void
234semundo_clear(semid, semnum)
235	int semid, semnum;
236{
237	register struct sem_undo *suptr;
238
239	for (suptr = semu_list; suptr != NULL; suptr = suptr->un_next) {
240		register struct undo *sunptr = &suptr->un_ent[0];
241		register int i = 0;
242
243		while (i < suptr->un_cnt) {
244			if (sunptr->un_id == semid) {
245				if (semnum == -1 || sunptr->un_num == semnum) {
246					suptr->un_cnt--;
247					if (i < suptr->un_cnt) {
248						suptr->un_ent[i] =
249						  suptr->un_ent[suptr->un_cnt];
250						continue;
251					}
252				}
253				if (semnum != -1)
254					break;
255			}
256			i++, sunptr++;
257		}
258	}
259}
260
261/*
262 * Note that the user-mode half of this passes a union, not a pointer
263 */
264#ifndef _SYS_SYSPROTO_H_
265struct __semctl_args {
266	int	semid;
267	int	semnum;
268	int	cmd;
269	union	semun *arg;
270};
271#endif
272
273int
274__semctl(p, uap)
275	struct proc *p;
276	register struct __semctl_args *uap;
277{
278	int semid = uap->semid;
279	int semnum = uap->semnum;
280	int cmd = uap->cmd;
281	union semun *arg = uap->arg;
282	union semun real_arg;
283	struct ucred *cred = p->p_ucred;
284	int i, rval, eval;
285	struct semid_ds sbuf;
286	register struct semid_ds *semaptr;
287
288#ifdef SEM_DEBUG
289	printf("call to semctl(%d, %d, %d, 0x%x)\n", semid, semnum, cmd, arg);
290#endif
291
292	semid = IPCID_TO_IX(semid);
293	if (semid < 0 || semid >= seminfo.semmsl)
294		return(EINVAL);
295
296	semaptr = &sema[semid];
297	if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
298	    semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid))
299		return(EINVAL);
300
301	eval = 0;
302	rval = 0;
303
304	switch (cmd) {
305	case IPC_RMID:
306		if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_M)))
307			return(eval);
308		semaptr->sem_perm.cuid = cred->cr_uid;
309		semaptr->sem_perm.uid = cred->cr_uid;
310		semtot -= semaptr->sem_nsems;
311		for (i = semaptr->sem_base - sem; i < semtot; i++)
312			sem[i] = sem[i + semaptr->sem_nsems];
313		for (i = 0; i < seminfo.semmni; i++) {
314			if ((sema[i].sem_perm.mode & SEM_ALLOC) &&
315			    sema[i].sem_base > semaptr->sem_base)
316				sema[i].sem_base -= semaptr->sem_nsems;
317		}
318		semaptr->sem_perm.mode = 0;
319		semundo_clear(semid, -1);
320		wakeup((caddr_t)semaptr);
321		break;
322
323	case IPC_SET:
324		if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_M)))
325			return(eval);
326		if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
327			return(eval);
328		if ((eval = copyin(real_arg.buf, (caddr_t)&sbuf,
329		    sizeof(sbuf))) != 0)
330			return(eval);
331		semaptr->sem_perm.uid = sbuf.sem_perm.uid;
332		semaptr->sem_perm.gid = sbuf.sem_perm.gid;
333		semaptr->sem_perm.mode = (semaptr->sem_perm.mode & ~0777) |
334		    (sbuf.sem_perm.mode & 0777);
335		semaptr->sem_ctime = time_second;
336		break;
337
338	case IPC_STAT:
339		if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
340			return(eval);
341		if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
342			return(eval);
343		eval = copyout((caddr_t)semaptr, real_arg.buf,
344		    sizeof(struct semid_ds));
345		break;
346
347	case GETNCNT:
348		if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
349			return(eval);
350		if (semnum < 0 || semnum >= semaptr->sem_nsems)
351			return(EINVAL);
352		rval = semaptr->sem_base[semnum].semncnt;
353		break;
354
355	case GETPID:
356		if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
357			return(eval);
358		if (semnum < 0 || semnum >= semaptr->sem_nsems)
359			return(EINVAL);
360		rval = semaptr->sem_base[semnum].sempid;
361		break;
362
363	case GETVAL:
364		if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
365			return(eval);
366		if (semnum < 0 || semnum >= semaptr->sem_nsems)
367			return(EINVAL);
368		rval = semaptr->sem_base[semnum].semval;
369		break;
370
371	case GETALL:
372		if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
373			return(eval);
374		if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
375			return(eval);
376		for (i = 0; i < semaptr->sem_nsems; i++) {
377			eval = copyout((caddr_t)&semaptr->sem_base[i].semval,
378			    &real_arg.array[i], sizeof(real_arg.array[0]));
379			if (eval != 0)
380				break;
381		}
382		break;
383
384	case GETZCNT:
385		if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
386			return(eval);
387		if (semnum < 0 || semnum >= semaptr->sem_nsems)
388			return(EINVAL);
389		rval = semaptr->sem_base[semnum].semzcnt;
390		break;
391
392	case SETVAL:
393		if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_W)))
394			return(eval);
395		if (semnum < 0 || semnum >= semaptr->sem_nsems)
396			return(EINVAL);
397		if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
398			return(eval);
399		semaptr->sem_base[semnum].semval = real_arg.val;
400		semundo_clear(semid, semnum);
401		wakeup((caddr_t)semaptr);
402		break;
403
404	case SETALL:
405		if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_W)))
406			return(eval);
407		if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
408			return(eval);
409		for (i = 0; i < semaptr->sem_nsems; i++) {
410			eval = copyin(&real_arg.array[i],
411			    (caddr_t)&semaptr->sem_base[i].semval,
412			    sizeof(real_arg.array[0]));
413			if (eval != 0)
414				break;
415		}
416		semundo_clear(semid, -1);
417		wakeup((caddr_t)semaptr);
418		break;
419
420	default:
421		return(EINVAL);
422	}
423
424	if (eval == 0)
425		p->p_retval[0] = rval;
426	return(eval);
427}
428
429#ifndef _SYS_SYSPROTO_H_
430struct semget_args {
431	key_t	key;
432	int	nsems;
433	int	semflg;
434};
435#endif
436
437int
438semget(p, uap)
439	struct proc *p;
440	register struct semget_args *uap;
441{
442	int semid, eval;
443	int key = uap->key;
444	int nsems = uap->nsems;
445	int semflg = uap->semflg;
446	struct ucred *cred = p->p_ucred;
447
448#ifdef SEM_DEBUG
449	printf("semget(0x%x, %d, 0%o)\n", key, nsems, semflg);
450#endif
451
452	if (key != IPC_PRIVATE) {
453		for (semid = 0; semid < seminfo.semmni; semid++) {
454			if ((sema[semid].sem_perm.mode & SEM_ALLOC) &&
455			    sema[semid].sem_perm.key == key)
456				break;
457		}
458		if (semid < seminfo.semmni) {
459#ifdef SEM_DEBUG
460			printf("found public key\n");
461#endif
462			if ((eval = ipcperm(p, &sema[semid].sem_perm,
463			    semflg & 0700)))
464				return(eval);
465			if (nsems > 0 && sema[semid].sem_nsems < nsems) {
466#ifdef SEM_DEBUG
467				printf("too small\n");
468#endif
469				return(EINVAL);
470			}
471			if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) {
472#ifdef SEM_DEBUG
473				printf("not exclusive\n");
474#endif
475				return(EEXIST);
476			}
477			goto found;
478		}
479	}
480
481#ifdef SEM_DEBUG
482	printf("need to allocate the semid_ds\n");
483#endif
484	if (key == IPC_PRIVATE || (semflg & IPC_CREAT)) {
485		if (nsems <= 0 || nsems > seminfo.semmsl) {
486#ifdef SEM_DEBUG
487			printf("nsems out of range (0<%d<=%d)\n", nsems,
488			    seminfo.semmsl);
489#endif
490			return(EINVAL);
491		}
492		if (nsems > seminfo.semmns - semtot) {
493#ifdef SEM_DEBUG
494			printf("not enough semaphores left (need %d, got %d)\n",
495			    nsems, seminfo.semmns - semtot);
496#endif
497			return(ENOSPC);
498		}
499		for (semid = 0; semid < seminfo.semmni; semid++) {
500			if ((sema[semid].sem_perm.mode & SEM_ALLOC) == 0)
501				break;
502		}
503		if (semid == seminfo.semmni) {
504#ifdef SEM_DEBUG
505			printf("no more semid_ds's available\n");
506#endif
507			return(ENOSPC);
508		}
509#ifdef SEM_DEBUG
510		printf("semid %d is available\n", semid);
511#endif
512		sema[semid].sem_perm.key = key;
513		sema[semid].sem_perm.cuid = cred->cr_uid;
514		sema[semid].sem_perm.uid = cred->cr_uid;
515		sema[semid].sem_perm.cgid = cred->cr_gid;
516		sema[semid].sem_perm.gid = cred->cr_gid;
517		sema[semid].sem_perm.mode = (semflg & 0777) | SEM_ALLOC;
518		sema[semid].sem_perm.seq =
519		    (sema[semid].sem_perm.seq + 1) & 0x7fff;
520		sema[semid].sem_nsems = nsems;
521		sema[semid].sem_otime = 0;
522		sema[semid].sem_ctime = time_second;
523		sema[semid].sem_base = &sem[semtot];
524		semtot += nsems;
525		bzero(sema[semid].sem_base,
526		    sizeof(sema[semid].sem_base[0])*nsems);
527#ifdef SEM_DEBUG
528		printf("sembase = 0x%x, next = 0x%x\n", sema[semid].sem_base,
529		    &sem[semtot]);
530#endif
531	} else {
532#ifdef SEM_DEBUG
533		printf("didn't find it and wasn't asked to create it\n");
534#endif
535		return(ENOENT);
536	}
537
538found:
539	p->p_retval[0] = IXSEQ_TO_IPCID(semid, sema[semid].sem_perm);
540	return(0);
541}
542
543#ifndef _SYS_SYSPROTO_H_
544struct semop_args {
545	int	semid;
546	struct	sembuf *sops;
547	int	nsops;
548};
549#endif
550
551int
552semop(p, uap)
553	struct proc *p;
554	register struct semop_args *uap;
555{
556	int semid = uap->semid;
557	int nsops = uap->nsops;
558	struct sembuf sops[MAX_SOPS];
559	register struct semid_ds *semaptr;
560	register struct sembuf *sopptr;
561	register struct sem *semptr;
562	struct sem_undo *suptr = NULL;
563	int i, j, eval;
564	int do_wakeup, do_undos;
565
566#ifdef SEM_DEBUG
567	printf("call to semop(%d, 0x%x, %d)\n", semid, sops, nsops);
568#endif
569
570	semid = IPCID_TO_IX(semid);	/* Convert back to zero origin */
571
572	if (semid < 0 || semid >= seminfo.semmsl)
573		return(EINVAL);
574
575	semaptr = &sema[semid];
576	if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0)
577		return(EINVAL);
578	if (semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid))
579		return(EINVAL);
580
581	if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_W))) {
582#ifdef SEM_DEBUG
583		printf("eval = %d from ipaccess\n", eval);
584#endif
585		return(eval);
586	}
587
588	if (nsops > MAX_SOPS) {
589#ifdef SEM_DEBUG
590		printf("too many sops (max=%d, nsops=%d)\n", MAX_SOPS, nsops);
591#endif
592		return(E2BIG);
593	}
594
595	if ((eval = copyin(uap->sops, &sops, nsops * sizeof(sops[0]))) != 0) {
596#ifdef SEM_DEBUG
597		printf("eval = %d from copyin(%08x, %08x, %d)\n", eval,
598		    uap->sops, &sops, nsops * sizeof(sops[0]));
599#endif
600		return(eval);
601	}
602
603	/*
604	 * Loop trying to satisfy the vector of requests.
605	 * If we reach a point where we must wait, any requests already
606	 * performed are rolled back and we go to sleep until some other
607	 * process wakes us up.  At this point, we start all over again.
608	 *
609	 * This ensures that from the perspective of other tasks, a set
610	 * of requests is atomic (never partially satisfied).
611	 */
612	do_undos = 0;
613
614	for (;;) {
615		do_wakeup = 0;
616
617		for (i = 0; i < nsops; i++) {
618			sopptr = &sops[i];
619
620			if (sopptr->sem_num >= semaptr->sem_nsems)
621				return(EFBIG);
622
623			semptr = &semaptr->sem_base[sopptr->sem_num];
624
625#ifdef SEM_DEBUG
626			printf("semop:  semaptr=%x, sem_base=%x, semptr=%x, sem[%d]=%d : op=%d, flag=%s\n",
627			    semaptr, semaptr->sem_base, semptr,
628			    sopptr->sem_num, semptr->semval, sopptr->sem_op,
629			    (sopptr->sem_flg & IPC_NOWAIT) ? "nowait" : "wait");
630#endif
631
632			if (sopptr->sem_op < 0) {
633				if (semptr->semval + sopptr->sem_op < 0) {
634#ifdef SEM_DEBUG
635					printf("semop:  can't do it now\n");
636#endif
637					break;
638				} else {
639					semptr->semval += sopptr->sem_op;
640					if (semptr->semval == 0 &&
641					    semptr->semzcnt > 0)
642						do_wakeup = 1;
643				}
644				if (sopptr->sem_flg & SEM_UNDO)
645					do_undos = 1;
646			} else if (sopptr->sem_op == 0) {
647				if (semptr->semval > 0) {
648#ifdef SEM_DEBUG
649					printf("semop:  not zero now\n");
650#endif
651					break;
652				}
653			} else {
654				if (semptr->semncnt > 0)
655					do_wakeup = 1;
656				semptr->semval += sopptr->sem_op;
657				if (sopptr->sem_flg & SEM_UNDO)
658					do_undos = 1;
659			}
660		}
661
662		/*
663		 * Did we get through the entire vector?
664		 */
665		if (i >= nsops)
666			goto done;
667
668		/*
669		 * No ... rollback anything that we've already done
670		 */
671#ifdef SEM_DEBUG
672		printf("semop:  rollback 0 through %d\n", i-1);
673#endif
674		for (j = 0; j < i; j++)
675			semaptr->sem_base[sops[j].sem_num].semval -=
676			    sops[j].sem_op;
677
678		/*
679		 * If the request that we couldn't satisfy has the
680		 * NOWAIT flag set then return with EAGAIN.
681		 */
682		if (sopptr->sem_flg & IPC_NOWAIT)
683			return(EAGAIN);
684
685		if (sopptr->sem_op == 0)
686			semptr->semzcnt++;
687		else
688			semptr->semncnt++;
689
690#ifdef SEM_DEBUG
691		printf("semop:  good night!\n");
692#endif
693		eval = tsleep((caddr_t)semaptr, (PZERO - 4) | PCATCH,
694		    "semwait", 0);
695#ifdef SEM_DEBUG
696		printf("semop:  good morning (eval=%d)!\n", eval);
697#endif
698
699		suptr = NULL;	/* sem_undo may have been reallocated */
700
701		if (eval != 0)
702			return(EINTR);
703#ifdef SEM_DEBUG
704		printf("semop:  good morning!\n");
705#endif
706
707		/*
708		 * Make sure that the semaphore still exists
709		 */
710		if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
711		    semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid)) {
712			/* The man page says to return EIDRM. */
713			/* Unfortunately, BSD doesn't define that code! */
714#ifdef EIDRM
715			return(EIDRM);
716#else
717			return(EINVAL);
718#endif
719		}
720
721		/*
722		 * The semaphore is still alive.  Readjust the count of
723		 * waiting processes.
724		 */
725		if (sopptr->sem_op == 0)
726			semptr->semzcnt--;
727		else
728			semptr->semncnt--;
729	}
730
731done:
732	/*
733	 * Process any SEM_UNDO requests.
734	 */
735	if (do_undos) {
736		for (i = 0; i < nsops; i++) {
737			/*
738			 * We only need to deal with SEM_UNDO's for non-zero
739			 * op's.
740			 */
741			int adjval;
742
743			if ((sops[i].sem_flg & SEM_UNDO) == 0)
744				continue;
745			adjval = sops[i].sem_op;
746			if (adjval == 0)
747				continue;
748			eval = semundo_adjust(p, &suptr, semid,
749			    sops[i].sem_num, -adjval);
750			if (eval == 0)
751				continue;
752
753			/*
754			 * Oh-Oh!  We ran out of either sem_undo's or undo's.
755			 * Rollback the adjustments to this point and then
756			 * rollback the semaphore ups and down so we can return
757			 * with an error with all structures restored.  We
758			 * rollback the undo's in the exact reverse order that
759			 * we applied them.  This guarantees that we won't run
760			 * out of space as we roll things back out.
761			 */
762			for (j = i - 1; j >= 0; j--) {
763				if ((sops[j].sem_flg & SEM_UNDO) == 0)
764					continue;
765				adjval = sops[j].sem_op;
766				if (adjval == 0)
767					continue;
768				if (semundo_adjust(p, &suptr, semid,
769				    sops[j].sem_num, adjval) != 0)
770					panic("semop - can't undo undos");
771			}
772
773			for (j = 0; j < nsops; j++)
774				semaptr->sem_base[sops[j].sem_num].semval -=
775				    sops[j].sem_op;
776
777#ifdef SEM_DEBUG
778			printf("eval = %d from semundo_adjust\n", eval);
779#endif
780			return(eval);
781		} /* loop through the sops */
782	} /* if (do_undos) */
783
784	/* We're definitely done - set the sempid's */
785	for (i = 0; i < nsops; i++) {
786		sopptr = &sops[i];
787		semptr = &semaptr->sem_base[sopptr->sem_num];
788		semptr->sempid = p->p_pid;
789	}
790
791	/* Do a wakeup if any semaphore was up'd. */
792	if (do_wakeup) {
793#ifdef SEM_DEBUG
794		printf("semop:  doing wakeup\n");
795#endif
796		wakeup((caddr_t)semaptr);
797#ifdef SEM_DEBUG
798		printf("semop:  back from wakeup\n");
799#endif
800	}
801#ifdef SEM_DEBUG
802	printf("semop:  done\n");
803#endif
804	p->p_retval[0] = 0;
805	return(0);
806}
807
808/*
809 * Go through the undo structures for this process and apply the adjustments to
810 * semaphores.
811 */
812void
813semexit(p)
814	struct proc *p;
815{
816	register struct sem_undo *suptr;
817	register struct sem_undo **supptr;
818	int did_something;
819
820	did_something = 0;
821
822	/*
823	 * Go through the chain of undo vectors looking for one
824	 * associated with this process.
825	 */
826
827	for (supptr = &semu_list; (suptr = *supptr) != NULL;
828	    supptr = &suptr->un_next) {
829		if (suptr->un_proc == p)
830			break;
831	}
832
833	if (suptr == NULL)
834		return;
835
836#ifdef SEM_DEBUG
837	printf("proc @%08x has undo structure with %d entries\n", p,
838	    suptr->un_cnt);
839#endif
840
841	/*
842	 * If there are any active undo elements then process them.
843	 */
844	if (suptr->un_cnt > 0) {
845		int ix;
846
847		for (ix = 0; ix < suptr->un_cnt; ix++) {
848			int semid = suptr->un_ent[ix].un_id;
849			int semnum = suptr->un_ent[ix].un_num;
850			int adjval = suptr->un_ent[ix].un_adjval;
851			struct semid_ds *semaptr;
852
853			semaptr = &sema[semid];
854			if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0)
855				panic("semexit - semid not allocated");
856			if (semnum >= semaptr->sem_nsems)
857				panic("semexit - semnum out of range");
858
859#ifdef SEM_DEBUG
860			printf("semexit:  %08x id=%d num=%d(adj=%d) ; sem=%d\n",
861			    suptr->un_proc, suptr->un_ent[ix].un_id,
862			    suptr->un_ent[ix].un_num,
863			    suptr->un_ent[ix].un_adjval,
864			    semaptr->sem_base[semnum].semval);
865#endif
866
867			if (adjval < 0) {
868				if (semaptr->sem_base[semnum].semval < -adjval)
869					semaptr->sem_base[semnum].semval = 0;
870				else
871					semaptr->sem_base[semnum].semval +=
872					    adjval;
873			} else
874				semaptr->sem_base[semnum].semval += adjval;
875
876			wakeup((caddr_t)semaptr);
877#ifdef SEM_DEBUG
878			printf("semexit:  back from wakeup\n");
879#endif
880		}
881	}
882
883	/*
884	 * Deallocate the undo vector.
885	 */
886#ifdef SEM_DEBUG
887	printf("removing vector\n");
888#endif
889	suptr->un_proc = NULL;
890	*supptr = suptr->un_next;
891}
892