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freebsd/sys/kern/sysv_sem.c

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/* $Id: sysv_sem.c,v 1.11 1995/12/14 08:31:52 phk Exp $ */
/*
* 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/sysproto.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/sem.h>
#include <sys/sysent.h>
static void seminit __P((void *));
SYSINIT(sysv_sem, SI_SUB_SYSV_SEM, SI_ORDER_FIRST, seminit, NULL)
#ifndef _SYS_SYSPROTO_H_
struct __semctl_args;
int __semctl __P((struct proc *p, struct __semctl_args *uap, int *retval));
struct semget_args;
int semget __P((struct proc *p, struct semget_args *uap, int *retval));
struct semop_args;
int semop __P((struct proc *p, struct semop_args *uap, int *retval));
struct semconfig_args;
int semconfig __P((struct proc *p, struct semconfig_args *uap,
int *retval));
#endif
static struct sem_undo *semu_alloc __P((struct proc *p));
static int semundo_adjust __P((struct proc *p, struct sem_undo **supptr,
int semid, int semnum, int adjval));
static void semundo_clear __P((int semid, int semnum));
static void semexit __P((struct proc *p));
/* XXX casting to (sy_call_t *) is bogus, as usual. */
static sy_call_t *semcalls[] = {
(sy_call_t *)__semctl, (sy_call_t *)semget,
(sy_call_t *)semop, (sy_call_t *)semconfig
};
static int semtot = 0;
struct semid_ds *sema; /* semaphore id pool */
struct sem *sem; /* semaphore pool */
static struct map *semmap; /* semaphore allocation map */
static struct sem_undo *semu_list; /* list of active undo structures */
int *semu; /* undo structure pool */
static struct proc *semlock_holder = NULL;
void
seminit(dummy)
void *dummy;
{
register int i;
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
*/
int
semsys(p, uap, retval)
struct proc *p;
/* XXX actually varargs. */
struct semsys_args /* {
u_int which;
int a2;
int a3;
int a4;
int a5;
} */ *uap;
int *retval;
{
while (semlock_holder != NULL && semlock_holder != p)
(void) tsleep((caddr_t)&semlock_holder, (PZERO - 4), "semsys", 0);
if (uap->which >= sizeof(semcalls)/sizeof(semcalls[0]))
return (EINVAL);
return ((*semcalls[uap->which])(p, &uap->a2, 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.
*/
#ifndef _SYS_SYSPROTO_H_
struct semconfig_args {
semconfig_ctl_t flag;
};
#endif
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)
*/
static 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");
}
}
return (NULL);
}
/*
* Adjust a particular entry for a particular proc
*/
static 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);
}
static 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++;
}
}
}
/*
* Note that the user-mode half of this passes a union, not a pointer
*/
#ifndef _SYS_SYSPROTO_H_
struct __semctl_args {
int semid;
int semnum;
int cmd;
union semun *arg;
};
#endif
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);
}
#ifndef _SYS_SYSPROTO_H_
struct semget_args {
key_t key;
int nsems;
int semflg;
};
#endif
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);
}
#ifndef _SYS_SYSPROTO_H_
struct semop_args {
int semid;
struct sembuf *sops;
int nsops;
};
#endif
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 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.
*/
static void
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
(void) tsleep((caddr_t)&semlock_holder, (PZERO - 4), "semext", 0);
}
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);
}
}
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