Added SYSV ipcs.

Obtained from: NetBSD and FreeBSD-1.1.5

1 files changed, 939 insertions, 0 deletions

diff --git a/sys/kern/sysv_sem.c b/sys/kern/sysv_sem.c
new file mode 100644
index 0000000..fb0ff5f
--- /dev/null
+++ b/sys/kern/sysv_sem.c
@@ -0,0 +1,939 @@
+/*	$Id$ */
+
+/*
+ * Implementation of SVID semaphores
+ *
+ * Author:  Daniel Boulet
+ *
+ * This software is provided ``AS IS'' without any warranties of any kind.
+ */
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/proc.h>
+#include <sys/sem.h>
+#include <sys/malloc.h>
+
+static int	semctl(), semget(), semop(), semconfig();
+int	(*semcalls[])() = { semctl, semget, semop, semconfig };
+int	semtot = 0;
+
+static struct proc *semlock_holder = NULL;
+
+int
+seminit()
+{
+	register int i;
+	vm_offset_t whocares1, whocares2;
+
+	if (sema == NULL)
+		panic("sema is NULL");
+	if (semu == NULL)
+		panic("semu is NULL");
+
+	for (i = 0; i < seminfo.semmni; i++) {
+		sema[i].sem_base = 0;
+		sema[i].sem_perm.mode = 0;
+	}
+	for (i = 0; i < seminfo.semmnu; i++) {
+		register struct sem_undo *suptr = SEMU(i);
+		suptr->un_proc = NULL;
+	}
+	semu_list = NULL;
+}
+
+/*
+ * Entry point for all SEM calls
+ */
+
+struct semsys_args {
+	u_int	which;
+};
+
+int
+semsys(p, uap, retval)
+	struct proc *p;
+	struct semsys_args *uap;
+	int *retval;
+{
+
+	while (semlock_holder != NULL && semlock_holder != p)
+		sleep((caddr_t)&semlock_holder, (PZERO - 4));
+
+	if (uap->which >= sizeof(semcalls)/sizeof(semcalls[0]))
+		return (EINVAL);
+	return ((*semcalls[uap->which])(p, &uap[1], retval));
+}
+
+/*
+ * Lock or unlock the entire semaphore facility.
+ *
+ * This will probably eventually evolve into a general purpose semaphore
+ * facility status enquiry mechanism (I don't like the "read /dev/kmem"
+ * approach currently taken by ipcs and the amount of info that we want
+ * to be able to extract for ipcs is probably beyond what the capability
+ * of the getkerninfo facility.
+ *
+ * At the time that the current version of semconfig was written, ipcs is
+ * the only user of the semconfig facility.  It uses it to ensure that the
+ * semaphore facility data structures remain static while it fishes around
+ * in /dev/kmem.
+ */
+
+struct semconfig_args {
+	semconfig_ctl_t	flag;
+};
+
+int
+semconfig(p, uap, retval)
+	struct proc *p;
+	struct semconfig_args *uap;
+	int *retval;
+{
+	int eval = 0;
+
+	switch (uap->flag) {
+	case SEM_CONFIG_FREEZE:
+		semlock_holder = p;
+		break;
+
+	case SEM_CONFIG_THAW:
+		semlock_holder = NULL;
+		wakeup((caddr_t)&semlock_holder);
+		break;
+
+	default:
+		printf("semconfig: unknown flag parameter value (%d) - ignored\n",
+		    uap->flag);
+		eval = EINVAL;
+		break;
+	}
+
+	*retval = 0;
+	return(eval);
+}
+
+/*
+ * Allocate a new sem_undo structure for a process
+ * (returns ptr to structure or NULL if no more room)
+ */
+
+struct sem_undo *
+semu_alloc(p)
+	struct proc *p;
+{
+	register int i;
+	register struct sem_undo *suptr;
+	register struct sem_undo **supptr;
+	int attempt;
+
+	/*
+	 * Try twice to allocate something.
+	 * (we'll purge any empty structures after the first pass so
+	 * two passes are always enough)
+	 */
+
+	for (attempt = 0; attempt < 2; attempt++) {
+		/*
+		 * Look for a free structure.
+		 * Fill it in and return it if we find one.
+		 */
+
+		for (i = 0; i < seminfo.semmnu; i++) {
+			suptr = SEMU(i);
+			if (suptr->un_proc == NULL) {
+				suptr->un_next = semu_list;
+				semu_list = suptr;
+				suptr->un_cnt = 0;
+				suptr->un_proc = p;
+				return(suptr);
+			}
+		}
+
+		/*
+		 * We didn't find a free one, if this is the first attempt
+		 * then try to free some structures.
+		 */
+
+		if (attempt == 0) {
+			/* All the structures are in use - try to free some */
+			int did_something = 0;
+
+			supptr = &semu_list;
+			while ((suptr = *supptr) != NULL) {
+				if (suptr->un_cnt == 0)  {
+					suptr->un_proc = NULL;
+					*supptr = suptr->un_next;
+					did_something = 1;
+				} else
+					supptr = &(suptr->un_next);
+			}
+
+			/* If we didn't free anything then just give-up */
+			if (!did_something)
+				return(NULL);
+		} else {
+			/*
+			 * The second pass failed even though we freed
+			 * something after the first pass!
+			 * This is IMPOSSIBLE!
+			 */
+			panic("semu_alloc - second attempt failed");
+		}
+	}
+}
+
+/*
+ * Adjust a particular entry for a particular proc
+ */
+
+int
+semundo_adjust(p, supptr, semid, semnum, adjval)
+	register struct proc *p;
+	struct sem_undo **supptr;
+	int semid, semnum;
+	int adjval;
+{
+	register struct sem_undo *suptr;
+	register struct undo *sunptr;
+	int i;
+
+	/* Look for and remember the sem_undo if the caller doesn't provide
+	   it */
+
+	suptr = *supptr;
+	if (suptr == NULL) {
+		for (suptr = semu_list; suptr != NULL;
+		    suptr = suptr->un_next) {
+			if (suptr->un_proc == p) {
+				*supptr = suptr;
+				break;
+			}
+		}
+		if (suptr == NULL) {
+			if (adjval == 0)
+				return(0);
+			suptr = semu_alloc(p);
+			if (suptr == NULL)
+				return(ENOSPC);
+			*supptr = suptr;
+		}
+	}
+
+	/*
+	 * Look for the requested entry and adjust it (delete if adjval becomes
+	 * 0).
+	 */
+	sunptr = &suptr->un_ent[0];
+	for (i = 0; i < suptr->un_cnt; i++, sunptr++) {
+		if (sunptr->un_id != semid || sunptr->un_num != semnum)
+			continue;
+		if (adjval == 0)
+			sunptr->un_adjval = 0;
+		else
+			sunptr->un_adjval += adjval;
+		if (sunptr->un_adjval == 0) {
+			suptr->un_cnt--;
+			if (i < suptr->un_cnt)
+				suptr->un_ent[i] =
+				    suptr->un_ent[suptr->un_cnt];
+		}
+		return(0);
+	}
+
+	/* Didn't find the right entry - create it */
+	if (adjval == 0)
+		return(0);
+	if (suptr->un_cnt != SEMUME) {
+		sunptr = &suptr->un_ent[suptr->un_cnt];
+		suptr->un_cnt++;
+		sunptr->un_adjval = adjval;
+		sunptr->un_id = semid; sunptr->un_num = semnum;
+	} else
+		return(EINVAL);
+	return(0);
+}
+
+void
+semundo_clear(semid, semnum)
+	int semid, semnum;
+{
+	register struct sem_undo *suptr;
+
+	for (suptr = semu_list; suptr != NULL; suptr = suptr->un_next) {
+		register struct undo *sunptr = &suptr->un_ent[0];
+		register int i = 0;
+
+		while (i < suptr->un_cnt) {
+			if (sunptr->un_id == semid) {
+				if (semnum == -1 || sunptr->un_num == semnum) {
+					suptr->un_cnt--;
+					if (i < suptr->un_cnt) {
+						suptr->un_ent[i] =
+						  suptr->un_ent[suptr->un_cnt];
+						continue;
+					}
+				}
+				if (semnum != -1)
+					break;
+			}
+			i++, sunptr++;
+		}
+	}
+}
+
+struct semctl_args {
+	int	semid;
+	int	semnum;
+	int	cmd;
+	union	semun *arg;
+};
+
+int
+semctl(p, uap, retval)
+	struct proc *p;
+	register struct semctl_args *uap;
+	int *retval;
+{
+	int semid = uap->semid;
+	int semnum = uap->semnum;
+	int cmd = uap->cmd;
+	union semun *arg = uap->arg;
+	union semun real_arg;
+	struct ucred *cred = p->p_ucred;
+	int i, rval, eval;
+	struct semid_ds sbuf;
+	register struct semid_ds *semaptr;
+
+#ifdef SEM_DEBUG
+	printf("call to semctl(%d, %d, %d, 0x%x)\n", semid, semnum, cmd, arg);
+#endif
+
+	semid = IPCID_TO_IX(semid);
+	if (semid < 0 || semid >= seminfo.semmsl)
+		return(EINVAL);
+
+	semaptr = &sema[semid];
+	if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
+	    semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid))
+		return(EINVAL);
+
+	eval = 0;
+	rval = 0;
+
+	switch (cmd) {
+	case IPC_RMID:
+		if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_M)))
+			return(eval);
+		semaptr->sem_perm.cuid = cred->cr_uid;
+		semaptr->sem_perm.uid = cred->cr_uid;
+		semtot -= semaptr->sem_nsems;
+		for (i = semaptr->sem_base - sem; i < semtot; i++)
+			sem[i] = sem[i + semaptr->sem_nsems];
+		for (i = 0; i < seminfo.semmni; i++) {
+			if ((sema[i].sem_perm.mode & SEM_ALLOC) &&
+			    sema[i].sem_base > semaptr->sem_base)
+				sema[i].sem_base -= semaptr->sem_nsems;
+		}
+		semaptr->sem_perm.mode = 0;
+		semundo_clear(semid, -1);
+		wakeup((caddr_t)semaptr);
+		break;
+
+	case IPC_SET:
+		if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_M)))
+			return(eval);
+		if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
+			return(eval);
+		if ((eval = copyin(real_arg.buf, (caddr_t)&sbuf,
+		    sizeof(sbuf))) != 0)
+			return(eval);
+		semaptr->sem_perm.uid = sbuf.sem_perm.uid;
+		semaptr->sem_perm.gid = sbuf.sem_perm.gid;
+		semaptr->sem_perm.mode = (semaptr->sem_perm.mode & ~0777) |
+		    (sbuf.sem_perm.mode & 0777);
+		semaptr->sem_ctime = time.tv_sec;
+		break;
+
+	case IPC_STAT:
+		if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
+			return(eval);
+		if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
+			return(eval);
+		eval = copyout((caddr_t)semaptr, real_arg.buf,
+		    sizeof(struct semid_ds));
+		break;
+
+	case GETNCNT:
+		if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
+			return(eval);
+		if (semnum < 0 || semnum >= semaptr->sem_nsems)
+			return(EINVAL);
+		rval = semaptr->sem_base[semnum].semncnt;
+		break;
+
+	case GETPID:
+		if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
+			return(eval);
+		if (semnum < 0 || semnum >= semaptr->sem_nsems)
+			return(EINVAL);
+		rval = semaptr->sem_base[semnum].sempid;
+		break;
+
+	case GETVAL:
+		if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
+			return(eval);
+		if (semnum < 0 || semnum >= semaptr->sem_nsems)
+			return(EINVAL);
+		rval = semaptr->sem_base[semnum].semval;
+		break;
+
+	case GETALL:
+		if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
+			return(eval);
+		if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
+			return(eval);
+		for (i = 0; i < semaptr->sem_nsems; i++) {
+			eval = copyout((caddr_t)&semaptr->sem_base[i].semval,
+			    &real_arg.array[i], sizeof(real_arg.array[0]));
+			if (eval != 0)
+				break;
+		}
+		break;
+
+	case GETZCNT:
+		if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
+			return(eval);
+		if (semnum < 0 || semnum >= semaptr->sem_nsems)
+			return(EINVAL);
+		rval = semaptr->sem_base[semnum].semzcnt;
+		break;
+
+	case SETVAL:
+		if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_W)))
+			return(eval);
+		if (semnum < 0 || semnum >= semaptr->sem_nsems)
+			return(EINVAL);
+		if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
+			return(eval);
+		semaptr->sem_base[semnum].semval = real_arg.val;
+		semundo_clear(semid, semnum);
+		wakeup((caddr_t)semaptr);
+		break;
+
+	case SETALL:
+		if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_W)))
+			return(eval);
+		if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
+			return(eval);
+		for (i = 0; i < semaptr->sem_nsems; i++) {
+			eval = copyin(&real_arg.array[i],
+			    (caddr_t)&semaptr->sem_base[i].semval,
+			    sizeof(real_arg.array[0]));
+			if (eval != 0)
+				break;
+		}
+		semundo_clear(semid, -1);
+		wakeup((caddr_t)semaptr);
+		break;
+
+	default:
+		return(EINVAL);
+	}
+
+	if (eval == 0)
+		*retval = rval;
+	return(eval);
+}
+
+struct semget_args {
+	key_t	key;
+	int	nsems;
+	int	semflg;
+};
+
+int
+semget(p, uap, retval)
+	struct proc *p;
+	register struct semget_args *uap;
+	int *retval;
+{
+	int semid, eval;
+	int key = uap->key;
+	int nsems = uap->nsems;
+	int semflg = uap->semflg;
+	struct ucred *cred = p->p_ucred;
+
+#ifdef SEM_DEBUG
+	printf("semget(0x%x, %d, 0%o)\n", key, nsems, semflg);
+#endif
+
+	if (key != IPC_PRIVATE) {
+		for (semid = 0; semid < seminfo.semmni; semid++) {
+			if ((sema[semid].sem_perm.mode & SEM_ALLOC) &&
+			    sema[semid].sem_perm.key == key)
+				break;
+		}
+		if (semid < seminfo.semmni) {
+#ifdef SEM_DEBUG
+			printf("found public key\n");
+#endif
+			if ((eval = ipcperm(cred, &sema[semid].sem_perm,
+			    semflg & 0700)))
+				return(eval);
+			if (nsems > 0 && sema[semid].sem_nsems < nsems) {
+#ifdef SEM_DEBUG
+				printf("too small\n");
+#endif
+				return(EINVAL);
+			}
+			if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) {
+#ifdef SEM_DEBUG
+				printf("not exclusive\n");
+#endif
+				return(EEXIST);
+			}
+			goto found;
+		}
+	}
+
+#ifdef SEM_DEBUG
+	printf("need to allocate the semid_ds\n");
+#endif
+	if (key == IPC_PRIVATE || (semflg & IPC_CREAT)) {
+		if (nsems <= 0 || nsems > seminfo.semmsl) {
+#ifdef SEM_DEBUG
+			printf("nsems out of range (0<%d<=%d)\n", nsems,
+			    seminfo.semmsl);
+#endif
+			return(EINVAL);
+		}
+		if (nsems > seminfo.semmns - semtot) {
+#ifdef SEM_DEBUG
+			printf("not enough semaphores left (need %d, got %d)\n",
+			    nsems, seminfo.semmns - semtot);
+#endif
+			return(ENOSPC);
+		}
+		for (semid = 0; semid < seminfo.semmni; semid++) {
+			if ((sema[semid].sem_perm.mode & SEM_ALLOC) == 0)
+				break;
+		}
+		if (semid == seminfo.semmni) {
+#ifdef SEM_DEBUG
+			printf("no more semid_ds's available\n");
+#endif
+			return(ENOSPC);
+		}
+#ifdef SEM_DEBUG
+		printf("semid %d is available\n", semid);
+#endif
+		sema[semid].sem_perm.key = key;
+		sema[semid].sem_perm.cuid = cred->cr_uid;
+		sema[semid].sem_perm.uid = cred->cr_uid;
+		sema[semid].sem_perm.cgid = cred->cr_gid;
+		sema[semid].sem_perm.gid = cred->cr_gid;
+		sema[semid].sem_perm.mode = (semflg & 0777) | SEM_ALLOC;
+		sema[semid].sem_perm.seq =
+		    (sema[semid].sem_perm.seq + 1) & 0x7fff;
+		sema[semid].sem_nsems = nsems;
+		sema[semid].sem_otime = 0;
+		sema[semid].sem_ctime = time.tv_sec;
+		sema[semid].sem_base = &sem[semtot];
+		semtot += nsems;
+		bzero(sema[semid].sem_base,
+		    sizeof(sema[semid].sem_base[0])*nsems);
+#ifdef SEM_DEBUG
+		printf("sembase = 0x%x, next = 0x%x\n", sema[semid].sem_base,
+		    &sem[semtot]);
+#endif
+	} else {
+#ifdef SEM_DEBUG
+		printf("didn't find it and wasn't asked to create it\n");
+#endif
+		return(ENOENT);
+	}
+
+found:
+	*retval = IXSEQ_TO_IPCID(semid, sema[semid].sem_perm);
+	return(0);
+}
+
+struct semop_args {
+	int	semid;
+	struct	sembuf *sops;
+	int	nsops;
+};
+
+int
+semop(p, uap, retval)
+	struct proc *p;
+	register struct semop_args *uap;
+	int *retval;
+{
+	int semid = uap->semid;
+	int nsops = uap->nsops;
+	struct sembuf sops[MAX_SOPS];
+	register struct semid_ds *semaptr;
+	register struct sembuf *sopptr;
+	register struct sem *semptr;
+	struct sem_undo *suptr = NULL;
+	struct ucred *cred = p->p_ucred;
+	int i, j, eval;
+	int all_ok, do_wakeup, do_undos;
+
+#ifdef SEM_DEBUG
+	printf("call to semop(%d, 0x%x, %d)\n", semid, sops, nsops);
+#endif
+
+	semid = IPCID_TO_IX(semid);	/* Convert back to zero origin */
+
+	if (semid < 0 || semid >= seminfo.semmsl)
+		return(EINVAL);
+
+	semaptr = &sema[semid];
+	if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0)
+		return(EINVAL);
+	if (semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid))
+		return(EINVAL);
+
+	if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_W))) {
+#ifdef SEM_DEBUG
+		printf("eval = %d from ipaccess\n", eval);
+#endif
+		return(eval);
+	}
+
+	if (nsops > MAX_SOPS) {
+#ifdef SEM_DEBUG
+		printf("too many sops (max=%d, nsops=%d)\n", MAX_SOPS, nsops);
+#endif
+		return(E2BIG);
+	}
+
+	if ((eval = copyin(uap->sops, &sops, nsops * sizeof(sops[0]))) != 0) {
+#ifdef SEM_DEBUG
+		printf("eval = %d from copyin(%08x, %08x, %d)\n", eval,
+		    uap->sops, &sops, nsops * sizeof(sops[0]));
+#endif
+		return(eval);
+	}
+
+	/* 
+	 * Loop trying to satisfy the vector of requests.
+	 * If we reach a point where we must wait, any requests already
+	 * performed are rolled back and we go to sleep until some other
+	 * process wakes us up.  At this point, we start all over again.
+	 *
+	 * This ensures that from the perspective of other tasks, a set
+	 * of requests is atomic (never partially satisfied).
+	 */
+	do_undos = 0;
+
+	for (;;) {
+		do_wakeup = 0;
+
+		for (i = 0; i < nsops; i++) {
+			sopptr = &sops[i];
+
+			if (sopptr->sem_num >= semaptr->sem_nsems)
+				return(EFBIG);
+
+			semptr = &semaptr->sem_base[sopptr->sem_num];
+
+#ifdef SEM_DEBUG
+			printf("semop:  semaptr=%x, sem_base=%x, semptr=%x, sem[%d]=%d : op=%d, flag=%s\n",
+			    semaptr, semaptr->sem_base, semptr,
+			    sopptr->sem_num, semptr->semval, sopptr->sem_op,
+			    (sopptr->sem_flg & IPC_NOWAIT) ? "nowait" : "wait");
+#endif
+
+			if (sopptr->sem_op < 0) {
+				if (semptr->semval + sopptr->sem_op < 0) {
+#ifdef SEM_DEBUG
+					printf("semop:  can't do it now\n");
+#endif
+					break;
+				} else {
+					semptr->semval += sopptr->sem_op;
+					if (semptr->semval == 0 &&
+					    semptr->semzcnt > 0)
+						do_wakeup = 1;
+				}
+				if (sopptr->sem_flg & SEM_UNDO)
+					do_undos = 1;
+			} else if (sopptr->sem_op == 0) {
+				if (semptr->semval > 0) {
+#ifdef SEM_DEBUG
+					printf("semop:  not zero now\n");
+#endif
+					break;
+				}
+			} else {
+				if (semptr->semncnt > 0)
+					do_wakeup = 1;
+				semptr->semval += sopptr->sem_op;
+				if (sopptr->sem_flg & SEM_UNDO)
+					do_undos = 1;
+			}
+		}
+
+		/*
+		 * Did we get through the entire vector?
+		 */
+		if (i >= nsops)
+			goto done;
+
+		/*
+		 * No ... rollback anything that we've already done
+		 */
+#ifdef SEM_DEBUG
+		printf("semop:  rollback 0 through %d\n", i-1);
+#endif
+		for (j = 0; j < i; j++)
+			semaptr->sem_base[sops[j].sem_num].semval -=
+			    sops[j].sem_op;
+
+		/*
+		 * If the request that we couldn't satisfy has the
+		 * NOWAIT flag set then return with EAGAIN.
+		 */
+		if (sopptr->sem_flg & IPC_NOWAIT)
+			return(EAGAIN);
+
+		if (sopptr->sem_op == 0)
+			semptr->semzcnt++;
+		else
+			semptr->semncnt++;
+
+#ifdef SEM_DEBUG
+		printf("semop:  good night!\n");
+#endif
+		eval = tsleep((caddr_t)semaptr, (PZERO - 4) | PCATCH,
+		    "semwait", 0);
+#ifdef SEM_DEBUG
+		printf("semop:  good morning (eval=%d)!\n", eval);
+#endif
+
+		suptr = NULL;	/* sem_undo may have been reallocated */
+
+		if (eval != 0)
+			return(EINTR);
+#ifdef SEM_DEBUG
+		printf("semop:  good morning!\n");
+#endif
+
+		/*
+		 * Make sure that the semaphore still exists
+		 */
+		if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
+		    semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid)) {
+			/* The man page says to return EIDRM. */
+			/* Unfortunately, BSD doesn't define that code! */
+#ifdef EIDRM
+			return(EIDRM);
+#else
+			return(EINVAL);
+#endif
+		}
+
+		/*
+		 * The semaphore is still alive.  Readjust the count of
+		 * waiting processes.
+		 */
+		if (sopptr->sem_op == 0)
+			semptr->semzcnt--;
+		else
+			semptr->semncnt--;
+	}
+
+done:
+	/*
+	 * Process any SEM_UNDO requests.
+	 */
+	if (do_undos) {
+		for (i = 0; i < nsops; i++) {
+			/*
+			 * We only need to deal with SEM_UNDO's for non-zero
+			 * op's.
+			 */
+			int adjval;
+
+			if ((sops[i].sem_flg & SEM_UNDO) == 0)
+				continue;
+			adjval = sops[i].sem_op;
+			if (adjval == 0)
+				continue;
+			eval = semundo_adjust(p, &suptr, semid,
+			    sops[i].sem_num, -adjval);
+			if (eval == 0)
+				continue;
+
+			/*
+			 * Oh-Oh!  We ran out of either sem_undo's or undo's.
+			 * Rollback the adjustments to this point and then
+			 * rollback the semaphore ups and down so we can return
+			 * with an error with all structures restored.  We
+			 * rollback the undo's in the exact reverse order that
+			 * we applied them.  This guarantees that we won't run
+			 * out of space as we roll things back out.
+			 */
+			for (j = i - 1; j >= 0; j--) {
+				if ((sops[j].sem_flg & SEM_UNDO) == 0)
+					continue;
+				adjval = sops[j].sem_op;
+				if (adjval == 0)
+					continue;
+				if (semundo_adjust(p, &suptr, semid,
+				    sops[j].sem_num, adjval) != 0)
+					panic("semop - can't undo undos");
+			}
+
+			for (j = 0; j < nsops; j++)
+				semaptr->sem_base[sops[j].sem_num].semval -=
+				    sops[j].sem_op;
+
+#ifdef SEM_DEBUG
+			printf("eval = %d from semundo_adjust\n", eval);
+#endif
+			return(eval);
+		} /* loop through the sops */
+	} /* if (do_undos) */
+
+	/* We're definitely done - set the sempid's */
+	for (i = 0; i < nsops; i++) {
+		sopptr = &sops[i];
+		semptr = &semaptr->sem_base[sopptr->sem_num];
+		semptr->sempid = p->p_pid;
+	}
+
+	/* Do a wakeup if any semaphore was up'd. */
+	if (do_wakeup) {
+#ifdef SEM_DEBUG
+		printf("semop:  doing wakeup\n");
+#ifdef SEM_WAKEUP
+		sem_wakeup((caddr_t)semaptr);
+#else
+		wakeup((caddr_t)semaptr);
+#endif
+		printf("semop:  back from wakeup\n");
+#else
+		wakeup((caddr_t)semaptr);
+#endif
+	}
+#ifdef SEM_DEBUG
+	printf("semop:  done\n");
+#endif
+	*retval = 0;
+	return(0);
+}
+
+/*
+ * Go through the undo structures for this process and apply the adjustments to
+ * semaphores.
+ */
+semexit(p)
+	struct proc *p;
+{
+	register struct sem_undo *suptr;
+	register struct sem_undo **supptr;
+	int did_something;
+
+	/*
+	 * If somebody else is holding the global semaphore facility lock
+	 * then sleep until it is released.
+	 */
+	while (semlock_holder != NULL && semlock_holder != p) {
+#ifdef SEM_DEBUG
+		printf("semaphore facility locked - sleeping ...\n");
+#endif
+		sleep((caddr_t)&semlock_holder, (PZERO - 4));
+	}
+
+	did_something = 0;
+
+	/*
+	 * Go through the chain of undo vectors looking for one
+	 * associated with this process.
+	 */
+
+	for (supptr = &semu_list; (suptr = *supptr) != NULL;
+	    supptr = &suptr->un_next) {
+		if (suptr->un_proc == p)
+			break;
+	}
+
+	if (suptr == NULL)
+		goto unlock;
+
+#ifdef SEM_DEBUG
+	printf("proc @%08x has undo structure with %d entries\n", p,
+	    suptr->un_cnt);
+#endif
+
+	/*
+	 * If there are any active undo elements then process them.
+	 */
+	if (suptr->un_cnt > 0) {
+		int ix;
+
+		for (ix = 0; ix < suptr->un_cnt; ix++) {
+			int semid = suptr->un_ent[ix].un_id;
+			int semnum = suptr->un_ent[ix].un_num;
+			int adjval = suptr->un_ent[ix].un_adjval;
+			struct semid_ds *semaptr;
+
+			semaptr = &sema[semid];
+			if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0)
+				panic("semexit - semid not allocated");
+			if (semnum >= semaptr->sem_nsems)
+				panic("semexit - semnum out of range");
+
+#ifdef SEM_DEBUG
+			printf("semexit:  %08x id=%d num=%d(adj=%d) ; sem=%d\n",
+			    suptr->un_proc, suptr->un_ent[ix].un_id,
+			    suptr->un_ent[ix].un_num,
+			    suptr->un_ent[ix].un_adjval,
+			    semaptr->sem_base[semnum].semval);
+#endif
+
+			if (adjval < 0) {
+				if (semaptr->sem_base[semnum].semval < -adjval)
+					semaptr->sem_base[semnum].semval = 0;
+				else
+					semaptr->sem_base[semnum].semval +=
+					    adjval;
+			} else
+				semaptr->sem_base[semnum].semval += adjval;
+
+#ifdef SEM_WAKEUP
+			sem_wakeup((caddr_t)semaptr);
+#else
+			wakeup((caddr_t)semaptr);
+#endif
+#ifdef SEM_DEBUG
+			printf("semexit:  back from wakeup\n");
+#endif
+		}
+	}
+
+	/*
+	 * Deallocate the undo vector.
+	 */
+#ifdef SEM_DEBUG
+	printf("removing vector\n");
+#endif
+	suptr->un_proc = NULL;
+	*supptr = suptr->un_next;
+
+unlock:
+	/*
+	 * If the exiting process is holding the global semaphore facility
+	 * lock then release it.
+	 */
+	if (semlock_holder == p) {
+		semlock_holder = NULL;
+		wakeup((caddr_t)&semlock_holder);
+	}
+}