1 /* $FreeBSD: src/sys/kern/sysv_sem.c,v 1.69 2004/03/17 09:37:13 cperciva Exp $ */
2 /* $DragonFly: src/sys/kern/sysv_sem.c,v 1.19 2008/01/06 16:55:51 swildner Exp $ */
5 * Implementation of SVID semaphores
7 * Author: Daniel Boulet
9 * This software is provided ``AS IS'' without any warranties of any kind.
12 #include "opt_sysvipc.h"
14 #include <sys/param.h>
15 #include <sys/systm.h>
16 #include <sys/sysproto.h>
17 #include <sys/kernel.h>
20 #include <sys/sysent.h>
21 #include <sys/sysctl.h>
22 #include <sys/malloc.h>
25 static MALLOC_DEFINE(M_SEM, "sem", "SVID compatible semaphores");
27 static void seminit (void *);
29 static struct sem_undo *semu_alloc (struct proc *p);
30 static int semundo_adjust (struct proc *p, struct sem_undo **supptr,
31 int semid, int semnum, int adjval);
32 static void semundo_clear (int semid, int semnum);
34 /* XXX casting to (sy_call_t *) is bogus, as usual. */
35 static sy_call_t *semcalls[] = {
36 (sy_call_t *)sys___semctl, (sy_call_t *)sys_semget,
37 (sy_call_t *)sys_semop
40 static int semtot = 0;
41 static struct semid_ds *sema; /* semaphore id pool */
42 static struct sem *sem; /* semaphore pool */
43 static struct sem_undo *semu_list; /* list of active undo structures */
44 static int *semu; /* undo structure pool */
47 u_short semval; /* semaphore value */
48 pid_t sempid; /* pid of last operation */
49 u_short semncnt; /* # awaiting semval > cval */
50 u_short semzcnt; /* # awaiting semval = 0 */
54 * Undo structure (one per process)
57 struct sem_undo *un_next; /* ptr to next active undo structure */
58 struct proc *un_proc; /* owner of this structure */
59 short un_cnt; /* # of active entries */
61 short un_adjval; /* adjust on exit values */
62 short un_num; /* semaphore # */
63 int un_id; /* semid */
64 } un_ent[1]; /* undo entries */
68 * Configuration parameters
71 #define SEMMNI 10 /* # of semaphore identifiers */
74 #define SEMMNS 60 /* # of semaphores in system */
77 #define SEMUME 10 /* max # of undo entries per process */
80 #define SEMMNU 30 /* # of undo structures in system */
83 /* shouldn't need tuning */
85 #define SEMMAP 30 /* # of entries in semaphore map */
88 #define SEMMSL SEMMNS /* max # of semaphores per id */
91 #define SEMOPM 100 /* max # of operations per semop call */
94 #define SEMVMX 32767 /* semaphore maximum value */
95 #define SEMAEM 16384 /* adjust on exit max value */
98 * Due to the way semaphore memory is allocated, we have to ensure that
99 * SEMUSZ is properly aligned.
102 #define SEM_ALIGN(bytes) (((bytes) + (sizeof(long) - 1)) & ~(sizeof(long) - 1))
104 /* actual size of an undo structure */
105 #define SEMUSZ SEM_ALIGN(offsetof(struct sem_undo, un_ent[SEMUME]))
108 * Macro to find a particular sem_undo vector
110 #define SEMU(ix) ((struct sem_undo *)(((intptr_t)semu)+ix * seminfo.semusz))
113 * semaphore info struct
115 struct seminfo seminfo = {
116 SEMMAP, /* # of entries in semaphore map */
117 SEMMNI, /* # of semaphore identifiers */
118 SEMMNS, /* # of semaphores in system */
119 SEMMNU, /* # of undo structures in system */
120 SEMMSL, /* max # of semaphores per id */
121 SEMOPM, /* max # of operations per semop call */
122 SEMUME, /* max # of undo entries per process */
123 SEMUSZ, /* size in bytes of undo structure */
124 SEMVMX, /* semaphore maximum value */
125 SEMAEM /* adjust on exit max value */
128 TUNABLE_INT("kern.ipc.semmap", &seminfo.semmap);
129 TUNABLE_INT("kern.ipc.semmni", &seminfo.semmni);
130 TUNABLE_INT("kern.ipc.semmns", &seminfo.semmns);
131 TUNABLE_INT("kern.ipc.semmnu", &seminfo.semmnu);
132 TUNABLE_INT("kern.ipc.semmsl", &seminfo.semmsl);
133 TUNABLE_INT("kern.ipc.semopm", &seminfo.semopm);
134 TUNABLE_INT("kern.ipc.semume", &seminfo.semume);
135 TUNABLE_INT("kern.ipc.semusz", &seminfo.semusz);
136 TUNABLE_INT("kern.ipc.semvmx", &seminfo.semvmx);
137 TUNABLE_INT("kern.ipc.semaem", &seminfo.semaem);
139 SYSCTL_INT(_kern_ipc, OID_AUTO, semmap, CTLFLAG_RW, &seminfo.semmap, 0, "");
140 SYSCTL_INT(_kern_ipc, OID_AUTO, semmni, CTLFLAG_RD, &seminfo.semmni, 0, "");
141 SYSCTL_INT(_kern_ipc, OID_AUTO, semmns, CTLFLAG_RD, &seminfo.semmns, 0, "");
142 SYSCTL_INT(_kern_ipc, OID_AUTO, semmnu, CTLFLAG_RD, &seminfo.semmnu, 0, "");
143 SYSCTL_INT(_kern_ipc, OID_AUTO, semmsl, CTLFLAG_RW, &seminfo.semmsl, 0, "");
144 SYSCTL_INT(_kern_ipc, OID_AUTO, semopm, CTLFLAG_RD, &seminfo.semopm, 0, "");
145 SYSCTL_INT(_kern_ipc, OID_AUTO, semume, CTLFLAG_RD, &seminfo.semume, 0, "");
146 SYSCTL_INT(_kern_ipc, OID_AUTO, semusz, CTLFLAG_RD, &seminfo.semusz, 0, "");
147 SYSCTL_INT(_kern_ipc, OID_AUTO, semvmx, CTLFLAG_RW, &seminfo.semvmx, 0, "");
148 SYSCTL_INT(_kern_ipc, OID_AUTO, semaem, CTLFLAG_RW, &seminfo.semaem, 0, "");
151 RO seminfo.semmap /* SEMMAP unused */
154 RO seminfo.semmnu /* undo entries per system */
156 RO seminfo.semopm /* SEMOPM unused */
158 RO seminfo.semusz /* param - derived from SEMUME for per-proc sizeof */
159 RO seminfo.semvmx /* SEMVMX unused - user param */
160 RO seminfo.semaem /* SEMAEM unused - user param */
168 sem = kmalloc(sizeof(struct sem) * seminfo.semmns, M_SEM, M_WAITOK);
169 sema = kmalloc(sizeof(struct semid_ds) * seminfo.semmni, M_SEM, M_WAITOK);
170 semu = kmalloc(seminfo.semmnu * seminfo.semusz, M_SEM, M_WAITOK);
172 for (i = 0; i < seminfo.semmni; i++) {
173 sema[i].sem_base = 0;
174 sema[i].sem_perm.mode = 0;
176 for (i = 0; i < seminfo.semmnu; i++) {
177 struct sem_undo *suptr = SEMU(i);
178 suptr->un_proc = NULL;
182 SYSINIT(sysv_sem, SI_SUB_SYSV_SEM, SI_ORDER_FIRST, seminit, NULL)
185 * Entry point for all SEM calls
187 * semsys_args(int which, a2, a3, ...) (VARARGS)
190 sys_semsys(struct semsys_args *uap)
192 struct proc *p = curproc;
193 unsigned int which = (unsigned int)uap->which;
195 if (!jail_sysvipc_allowed && p->p_ucred->cr_prison != NULL)
198 if (which >= sizeof(semcalls)/sizeof(semcalls[0]))
200 bcopy(&uap->a2, &uap->which,
201 sizeof(struct semsys_args) - offsetof(struct semsys_args, a2));
202 return ((*semcalls[which])(uap));
206 * Allocate a new sem_undo structure for a process
207 * (returns ptr to structure or NULL if no more room)
210 static struct sem_undo *
211 semu_alloc(struct proc *p)
214 struct sem_undo *suptr;
215 struct sem_undo **supptr;
219 * Try twice to allocate something.
220 * (we'll purge any empty structures after the first pass so
221 * two passes are always enough)
224 for (attempt = 0; attempt < 2; attempt++) {
226 * Look for a free structure.
227 * Fill it in and return it if we find one.
230 for (i = 0; i < seminfo.semmnu; i++) {
232 if (suptr->un_proc == NULL) {
233 suptr->un_next = semu_list;
242 * We didn't find a free one, if this is the first attempt
243 * then try to free some structures.
247 /* All the structures are in use - try to free some */
248 int did_something = 0;
251 while ((suptr = *supptr) != NULL) {
252 if (suptr->un_cnt == 0) {
253 suptr->un_proc = NULL;
254 *supptr = suptr->un_next;
257 supptr = &(suptr->un_next);
260 /* If we didn't free anything then just give-up */
265 * The second pass failed even though we freed
266 * something after the first pass!
267 * This is IMPOSSIBLE!
269 panic("semu_alloc - second attempt failed");
276 * Adjust a particular entry for a particular proc
280 semundo_adjust(struct proc *p, struct sem_undo **supptr, int semid, int semnum,
283 struct sem_undo *suptr;
287 /* Look for and remember the sem_undo if the caller doesn't provide
292 for (suptr = semu_list; suptr != NULL;
293 suptr = suptr->un_next) {
294 if (suptr->un_proc == p) {
302 suptr = semu_alloc(p);
310 * Look for the requested entry and adjust it (delete if adjval becomes
313 sunptr = &suptr->un_ent[0];
314 for (i = 0; i < suptr->un_cnt; i++, sunptr++) {
315 if (sunptr->un_id != semid || sunptr->un_num != semnum)
318 sunptr->un_adjval = 0;
320 sunptr->un_adjval += adjval;
321 if (sunptr->un_adjval == 0) {
323 if (i < suptr->un_cnt)
325 suptr->un_ent[suptr->un_cnt];
330 /* Didn't find the right entry - create it */
333 if (suptr->un_cnt != seminfo.semume) {
334 sunptr = &suptr->un_ent[suptr->un_cnt];
336 sunptr->un_adjval = adjval;
337 sunptr->un_id = semid; sunptr->un_num = semnum;
344 semundo_clear(int semid, int semnum)
346 struct sem_undo *suptr;
348 for (suptr = semu_list; suptr != NULL; suptr = suptr->un_next) {
349 struct undo *sunptr = &suptr->un_ent[0];
352 while (i < suptr->un_cnt) {
353 if (sunptr->un_id == semid) {
354 if (semnum == -1 || sunptr->un_num == semnum) {
356 if (i < suptr->un_cnt) {
358 suptr->un_ent[suptr->un_cnt];
371 * Note that the user-mode half of this passes a union, not a pointer
375 sys___semctl(struct __semctl_args *uap)
377 struct proc *p = curproc;
378 int semid = uap->semid;
379 int semnum = uap->semnum;
381 union semun *arg = uap->arg;
382 union semun real_arg;
383 struct ucred *cred = p->p_ucred;
385 struct semid_ds sbuf;
386 struct semid_ds *semaptr;
389 kprintf("call to semctl(%d, %d, %d, 0x%x)\n", semid, semnum, cmd, arg);
392 if (!jail_sysvipc_allowed && p->p_ucred->cr_prison != NULL)
395 semid = IPCID_TO_IX(semid);
396 if (semid < 0 || semid >= seminfo.semmni)
399 semaptr = &sema[semid];
400 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
401 semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid))
409 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_M)))
411 semaptr->sem_perm.cuid = cred->cr_uid;
412 semaptr->sem_perm.uid = cred->cr_uid;
413 semtot -= semaptr->sem_nsems;
414 for (i = semaptr->sem_base - sem; i < semtot; i++)
415 sem[i] = sem[i + semaptr->sem_nsems];
416 for (i = 0; i < seminfo.semmni; i++) {
417 if ((sema[i].sem_perm.mode & SEM_ALLOC) &&
418 sema[i].sem_base > semaptr->sem_base)
419 sema[i].sem_base -= semaptr->sem_nsems;
421 semaptr->sem_perm.mode = 0;
422 semundo_clear(semid, -1);
423 wakeup((caddr_t)semaptr);
427 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_M)))
429 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
431 if ((eval = copyin(real_arg.buf, (caddr_t)&sbuf,
434 semaptr->sem_perm.uid = sbuf.sem_perm.uid;
435 semaptr->sem_perm.gid = sbuf.sem_perm.gid;
436 semaptr->sem_perm.mode = (semaptr->sem_perm.mode & ~0777) |
437 (sbuf.sem_perm.mode & 0777);
438 semaptr->sem_ctime = time_second;
442 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
444 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
446 eval = copyout((caddr_t)semaptr, real_arg.buf,
447 sizeof(struct semid_ds));
451 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
453 if (semnum < 0 || semnum >= semaptr->sem_nsems)
455 rval = semaptr->sem_base[semnum].semncnt;
459 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
461 if (semnum < 0 || semnum >= semaptr->sem_nsems)
463 rval = semaptr->sem_base[semnum].sempid;
467 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
469 if (semnum < 0 || semnum >= semaptr->sem_nsems)
471 rval = semaptr->sem_base[semnum].semval;
475 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
477 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
479 for (i = 0; i < semaptr->sem_nsems; i++) {
480 eval = copyout((caddr_t)&semaptr->sem_base[i].semval,
481 &real_arg.array[i], sizeof(real_arg.array[0]));
488 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_R)))
490 if (semnum < 0 || semnum >= semaptr->sem_nsems)
492 rval = semaptr->sem_base[semnum].semzcnt;
496 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_W)))
498 if (semnum < 0 || semnum >= semaptr->sem_nsems)
500 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
502 semaptr->sem_base[semnum].semval = real_arg.val;
503 semundo_clear(semid, semnum);
504 wakeup((caddr_t)semaptr);
508 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_W)))
510 if ((eval = copyin(arg, &real_arg, sizeof(real_arg))) != 0)
512 for (i = 0; i < semaptr->sem_nsems; i++) {
513 eval = copyin(&real_arg.array[i],
514 (caddr_t)&semaptr->sem_base[i].semval,
515 sizeof(real_arg.array[0]));
519 semundo_clear(semid, -1);
520 wakeup((caddr_t)semaptr);
528 uap->sysmsg_result = rval;
533 sys_semget(struct semget_args *uap)
535 struct proc *p = curproc;
538 int nsems = uap->nsems;
539 int semflg = uap->semflg;
540 struct ucred *cred = p->p_ucred;
543 kprintf("semget(0x%x, %d, 0%o)\n", key, nsems, semflg);
546 if (!jail_sysvipc_allowed && p->p_ucred->cr_prison != NULL)
549 if (key != IPC_PRIVATE) {
550 for (semid = 0; semid < seminfo.semmni; semid++) {
551 if ((sema[semid].sem_perm.mode & SEM_ALLOC) &&
552 sema[semid].sem_perm.key == key)
555 if (semid < seminfo.semmni) {
557 kprintf("found public key\n");
559 if ((eval = ipcperm(p, &sema[semid].sem_perm,
562 if (nsems > 0 && sema[semid].sem_nsems < nsems) {
564 kprintf("too small\n");
568 if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) {
570 kprintf("not exclusive\n");
579 kprintf("need to allocate the semid_ds\n");
581 if (key == IPC_PRIVATE || (semflg & IPC_CREAT)) {
582 if (nsems <= 0 || nsems > seminfo.semmsl) {
584 kprintf("nsems out of range (0<%d<=%d)\n", nsems,
589 if (nsems > seminfo.semmns - semtot) {
591 kprintf("not enough semaphores left (need %d, got %d)\n",
592 nsems, seminfo.semmns - semtot);
596 for (semid = 0; semid < seminfo.semmni; semid++) {
597 if ((sema[semid].sem_perm.mode & SEM_ALLOC) == 0)
600 if (semid == seminfo.semmni) {
602 kprintf("no more semid_ds's available\n");
607 kprintf("semid %d is available\n", semid);
609 sema[semid].sem_perm.key = key;
610 sema[semid].sem_perm.cuid = cred->cr_uid;
611 sema[semid].sem_perm.uid = cred->cr_uid;
612 sema[semid].sem_perm.cgid = cred->cr_gid;
613 sema[semid].sem_perm.gid = cred->cr_gid;
614 sema[semid].sem_perm.mode = (semflg & 0777) | SEM_ALLOC;
615 sema[semid].sem_perm.seq =
616 (sema[semid].sem_perm.seq + 1) & 0x7fff;
617 sema[semid].sem_nsems = nsems;
618 sema[semid].sem_otime = 0;
619 sema[semid].sem_ctime = time_second;
620 sema[semid].sem_base = &sem[semtot];
622 bzero(sema[semid].sem_base,
623 sizeof(sema[semid].sem_base[0])*nsems);
625 kprintf("sembase = 0x%x, next = 0x%x\n", sema[semid].sem_base,
630 kprintf("didn't find it and wasn't asked to create it\n");
636 uap->sysmsg_result = IXSEQ_TO_IPCID(semid, sema[semid].sem_perm);
641 sys_semop(struct semop_args *uap)
643 struct proc *p = curproc;
644 int semid = uap->semid;
645 u_int nsops = uap->nsops;
646 struct sembuf sops[MAX_SOPS];
647 struct semid_ds *semaptr;
648 struct sembuf *sopptr;
650 struct sem_undo *suptr = NULL;
652 int do_wakeup, do_undos;
655 kprintf("call to semop(%d, 0x%x, %u)\n", semid, sops, nsops);
658 if (!jail_sysvipc_allowed && p->p_ucred->cr_prison != NULL)
661 semid = IPCID_TO_IX(semid); /* Convert back to zero origin */
663 if (semid < 0 || semid >= seminfo.semmni)
666 semaptr = &sema[semid];
667 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0)
669 if (semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid))
672 if ((eval = ipcperm(p, &semaptr->sem_perm, IPC_W))) {
674 kprintf("eval = %d from ipaccess\n", eval);
679 if (nsops > MAX_SOPS) {
681 kprintf("too many sops (max=%d, nsops=%u)\n", MAX_SOPS, nsops);
686 if ((eval = copyin(uap->sops, &sops, nsops * sizeof(sops[0]))) != 0) {
688 kprintf("eval = %d from copyin(%08x, %08x, %u)\n", eval,
689 uap->sops, &sops, nsops * sizeof(sops[0]));
695 * Loop trying to satisfy the vector of requests.
696 * If we reach a point where we must wait, any requests already
697 * performed are rolled back and we go to sleep until some other
698 * process wakes us up. At this point, we start all over again.
700 * This ensures that from the perspective of other tasks, a set
701 * of requests is atomic (never partially satisfied).
708 for (i = 0; i < nsops; i++) {
711 if (sopptr->sem_num >= semaptr->sem_nsems)
714 semptr = &semaptr->sem_base[sopptr->sem_num];
717 kprintf("semop: semaptr=%x, sem_base=%x, semptr=%x, sem[%d]=%d : op=%d, flag=%s\n",
718 semaptr, semaptr->sem_base, semptr,
719 sopptr->sem_num, semptr->semval, sopptr->sem_op,
720 (sopptr->sem_flg & IPC_NOWAIT) ? "nowait" : "wait");
723 if (sopptr->sem_op < 0) {
724 if (semptr->semval + sopptr->sem_op < 0) {
726 kprintf("semop: can't do it now\n");
730 semptr->semval += sopptr->sem_op;
731 if (semptr->semval == 0 &&
735 if (sopptr->sem_flg & SEM_UNDO)
737 } else if (sopptr->sem_op == 0) {
738 if (semptr->semval > 0) {
740 kprintf("semop: not zero now\n");
745 if (semptr->semncnt > 0)
747 semptr->semval += sopptr->sem_op;
748 if (sopptr->sem_flg & SEM_UNDO)
754 * Did we get through the entire vector?
760 * No ... rollback anything that we've already done
763 kprintf("semop: rollback 0 through %d\n", i-1);
765 for (j = 0; j < i; j++)
766 semaptr->sem_base[sops[j].sem_num].semval -=
770 * If the request that we couldn't satisfy has the
771 * NOWAIT flag set then return with EAGAIN.
773 if (sopptr->sem_flg & IPC_NOWAIT)
776 if (sopptr->sem_op == 0)
782 kprintf("semop: good night!\n");
784 eval = tsleep((caddr_t)semaptr, PCATCH, "semwait", 0);
786 kprintf("semop: good morning (eval=%d)!\n", eval);
789 suptr = NULL; /* sem_undo may have been reallocated */
791 /* return code is checked below, after sem[nz]cnt-- */
794 * Make sure that the semaphore still exists
796 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
797 semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid))
801 * The semaphore is still alive. Readjust the count of
804 if (sopptr->sem_op == 0)
810 * Is it really morning, or was our sleep interrupted?
811 * (Delayed check of tsleep() return code because we
812 * need to decrement sem[nz]cnt either way.)
817 kprintf("semop: good morning!\n");
823 * Process any SEM_UNDO requests.
826 for (i = 0; i < nsops; i++) {
828 * We only need to deal with SEM_UNDO's for non-zero
833 if ((sops[i].sem_flg & SEM_UNDO) == 0)
835 adjval = sops[i].sem_op;
838 eval = semundo_adjust(p, &suptr, semid,
839 sops[i].sem_num, -adjval);
844 * Oh-Oh! We ran out of either sem_undo's or undo's.
845 * Rollback the adjustments to this point and then
846 * rollback the semaphore ups and down so we can return
847 * with an error with all structures restored. We
848 * rollback the undo's in the exact reverse order that
849 * we applied them. This guarantees that we won't run
850 * out of space as we roll things back out.
852 for (j = i - 1; j >= 0; j--) {
853 if ((sops[j].sem_flg & SEM_UNDO) == 0)
855 adjval = sops[j].sem_op;
858 if (semundo_adjust(p, &suptr, semid,
859 sops[j].sem_num, adjval) != 0)
860 panic("semop - can't undo undos");
863 for (j = 0; j < nsops; j++)
864 semaptr->sem_base[sops[j].sem_num].semval -=
868 kprintf("eval = %d from semundo_adjust\n", eval);
871 } /* loop through the sops */
872 } /* if (do_undos) */
874 /* We're definitely done - set the sempid's */
875 for (i = 0; i < nsops; i++) {
877 semptr = &semaptr->sem_base[sopptr->sem_num];
878 semptr->sempid = p->p_pid;
881 /* Do a wakeup if any semaphore was up'd. */
884 kprintf("semop: doing wakeup\n");
886 wakeup((caddr_t)semaptr);
888 kprintf("semop: back from wakeup\n");
892 kprintf("semop: done\n");
894 uap->sysmsg_result = 0;
899 * Go through the undo structures for this process and apply the adjustments to
903 semexit(struct proc *p)
905 struct sem_undo *suptr;
906 struct sem_undo **supptr;
912 * Go through the chain of undo vectors looking for one
913 * associated with this process.
916 for (supptr = &semu_list; (suptr = *supptr) != NULL;
917 supptr = &suptr->un_next) {
918 if (suptr->un_proc == p)
926 kprintf("proc @%08x has undo structure with %d entries\n", p,
931 * If there are any active undo elements then process them.
933 if (suptr->un_cnt > 0) {
936 for (ix = 0; ix < suptr->un_cnt; ix++) {
937 int semid = suptr->un_ent[ix].un_id;
938 int semnum = suptr->un_ent[ix].un_num;
939 int adjval = suptr->un_ent[ix].un_adjval;
940 struct semid_ds *semaptr;
942 semaptr = &sema[semid];
943 if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0)
944 panic("semexit - semid not allocated");
945 if (semnum >= semaptr->sem_nsems)
946 panic("semexit - semnum out of range");
949 kprintf("semexit: %08x id=%d num=%d(adj=%d) ; sem=%d\n",
950 suptr->un_proc, suptr->un_ent[ix].un_id,
951 suptr->un_ent[ix].un_num,
952 suptr->un_ent[ix].un_adjval,
953 semaptr->sem_base[semnum].semval);
957 if (semaptr->sem_base[semnum].semval < -adjval)
958 semaptr->sem_base[semnum].semval = 0;
960 semaptr->sem_base[semnum].semval +=
963 semaptr->sem_base[semnum].semval += adjval;
965 wakeup((caddr_t)semaptr);
967 kprintf("semexit: back from wakeup\n");
973 * Deallocate the undo vector.
976 kprintf("removing vector\n");
978 suptr->un_proc = NULL;
979 *supptr = suptr->un_next;