/*------------------------------------------------------------------------
* ldelete -- delete a lock by releasing its table entry
*------------------------------------------------------------------------
*/
int ldelete (int lockdescriptor)
{
STATWORD ps;
int pid;
int temp,temp1;
struct lentry *lptr;
disable(ps);
if (isbadlock(lockdescriptor) || locks[lockdescriptor].lstate==DELETED || locks[lockdescriptor].lstate==LFREE) {
restore(ps);
return(SYSERR);
}
lptr = &locks[lockdescriptor];
lptr->lstate = DELETED;
lptr->ltype = NONE;
lptr->lreaders= 0;
if (nonempty(lptr->lqhead)) {
while( (pid=getfirst(lptr->lqhead)) != EMPTY)
{
proctab[pid].plockwaitret = DELETED;
proctab[pid].locktype[lockdescriptor] = DELETED;
dequeue(pid);
ready(pid,RESCHNO);
//kprintf("\n\t\t[LDELETE.C: 37] Proc '%s' deleted from waitqueue of Lock %d\n",proctab[pid].pname,lockdescriptor);
}
resched();
}
for(pid=1;pid<NPROC;pid++) {
if(locks[lockdescriptor].lprocs[pid] == READ || locks[lockdescriptor].lprocs[pid] == WRITE)
{
locks[lockdescriptor].lprocs[pid] = DELETED;
}
}
restore(ps);
return(OK);
}
int ldelete(int ldes)
{
STATWORD ps;
struct lentry *lptr;
int pid, lockID;
disable(ps);
lockID = getLockID(ldes);
if( isbadlock(lockID) || (lptr=&locktab[lockID])->lstate == LOCKFREE )
{
restore(ps);
return(SYSERR);
}
//lptr = &locktab[ldes];
lptr->lstate = LOCKFREE;
lptr->locked = 0;
lptr->acquiredby[currpid]=-1;
lptr->lockType = DELETED;
lptr->lprio=-1;
if( nonempty(lptr->lhead) )
{
while( (pid=getlast(lptr->lhead)) != EMPTY )
{
proctab[pid].waitPriority = -1;
proctab[pid].lockID = -1;
proctab[pid].procLockType[lockID] = DELETED;
proctab[pid].pwaitret = DELETED;
ready(pid, RESCHNO);
}
resched();
}
restore(ps);
return(OK);
}
int ldelete (int lockdescriptor)
{
STATWORD ps;
int pid;
struct lentry *lptr;
disable(ps);
if (isbadlock(lockdescriptor%100) || lockarr[lockdescriptor%100].lstate==LFREE) {
restore(ps);
return(SYSERR);
}
lptr = &lockarr[lockdescriptor%100];
lptr->lstate = LFREE;
if (nonempty(lptr->lqhead)) {
while( (pid=getfirst(lptr->lqhead)) != EMPTY)
{
proctab[pid].pwaitret = DELETED;
ready(pid,RESCHNO);
}
resched();
}
restore(ps);
return(OK);
}
int lock(int ldes, int type, int priority) //priority here = process wait priority
{
STATWORD ps;
struct lentry *lptr;
struct pentry *pptr;
int lockNotGivenToRead = 0;
int temp = -1;
int lockID;
disable(ps);
pptr = &proctab[currpid];
lockID = getLockID(ldes);
//kprintf("\n IN lock: %d...lock des..%d", lockID, ldes);
if( isbadlock(lockID) || (lptr=&locktab[lockID])->lstate == LOCKFREE || type == DELETED)
{
restore(ps);
return(SYSERR);
}
if( lptr->locked == 0 )
{
lptr->lstate = LOCKUSED;
lptr->locked = 1; //indicates someone has acquired lockID
lptr->acquiredby[currpid] = 1; //stores the PID of process which has acquired lockID
lptr->lockType = type;
lptr->lprio = pptr->pprio;
pptr->procLockType[lockID] = type; //indicates type of locking (WRITE or READ) for a process
pptr->waitPriority = priority; //sets wait priority of process
pptr->lockID = -1; //process not in wait queue so its lock id is -1;
restore(ps);
return(OK);
}
else if( lptr->locked != 0 )
{
if(lptr->lockType == WRITE)
{
pptr->pstate = PRWAIT;
pptr->lockID = ldes;
pptr->procLockType[lockID] = type; //indicates type of locking (WRITE or READ) for a process
pptr->waitPriority = priority; //sets wait priority of process
pptr->timeInWaiting = ctr1000;
rampUpPriority(lockID, pptr->pprio);
insert(currpid, lptr->lhead, priority);
//pptr->pwaitret = OK;
resched();
restore(ps);
return(OK);
}
else if(lptr->lockType == READ )
{
if( type == READ )
{
//check if incoming process is reader and has wait priority larger than any waiting writer process wait priority
temp = lptr->lhead;
while( q[temp].qnext != lptr->ltail )
{
if( (proctab[q[temp].qnext].procLockType[lockID] == WRITE) && (priority < proctab[q[temp].qnext].waitPriority) )
{
lockNotGivenToRead = 1; //1 value indicates the lock should not be given because a writer with larger wait prio than this read is waiting
}
temp = q[temp].qnext;
}
if(lockNotGivenToRead == 1)
{
pptr->pstate = PRWAIT;
pptr->lockID = ldes;
pptr->procLockType[lockID] = type; //indicates type of locking (WRITE or READ) for a process
pptr->waitPriority = priority; //sets wait priority of process
rampUpPriority(lockID, pptr->pprio);
pptr->timeInWaiting = ctr1000;
insert(currpid, lptr->lhead, priority);
//pptr->pwaitret = OK;
resched();
restore(ps);
return(OK);
}
else if(lockNotGivenToRead != 1) //READER can be given lockID as no writer with wait prio greater than currpid wait prio is there
{
if( lptr->lprio < pptr->pprio )
{
lptr->lprio = pptr->pprio;
}
lptr->acquiredby[currpid] = 1;
pptr->procLockType[lockID] = type; //indicates type of locking (WRITE or READ) for a process
pptr->waitPriority = priority;
pptr->lockID = -1;
restore(ps);
return(OK);
}
}
else if( type == WRITE )
{
pptr->pstate = PRWAIT;
pptr->lockID = ldes;
pptr->procLockType[lockID] = type; //indicates type of locking (WRITE or READ) for a process
pptr->waitPriority = priority; //sets wait priority of process
rampUpPriority(lockID, pptr->pprio);
pptr->timeInWaiting = ctr1000;
insert(currpid, lptr->lhead, priority);
//pptr->pwaitret = OK;
resched();
restore(ps);
return(OK);
}
}
}
restore(ps);
return(OK);
}
/*------------------------------------------------------------------------
* lock -- make current process wait on a lock
*------------------------------------------------------------------------
*/
int lock(int ldes1, int type, int priority)
{
STATWORD ps;
struct lentry *lptr;
struct pentry *pptr;
/* disable interupts */
disable(ps);
int lockid = getIndexForLockDescriptor(ldes1);
/* check for a bad lock, free lock or invalid type */
if (isbadlock(lockid) || (lptr= &locks[lockid])->lstate==LFREE
|| (type != READ && type != WRITE)) {
/* restore interupts */
restore(ps);
return SYSERR;
}
/* if this lock is acquired and being requested by a reader */
if (lptr->llocked != UNLOCKED && type == READ) {
/* if the lock is held by a reader and if the
* request priority is equal to or greater than the
* highest priority writer on the queue, then this
* process is allowed to continue */
if (lptr->llocked == LOCKED_READ &&
priority >= lastkey(lptr->lwqtail)) {
/* bump the number of readers */
lptr->lnreaders++;
/* set this processes locker flag to TRUE */
lptr->llockers[currpid] = TRUE;
/* restore interupts */
return OK;
}
/* otherwise, since its priority is lower, it should
* go on the reader queue */
insert(currpid, lptr->lrqhead, priority);
/* get the current process */
(pptr = &proctab[currpid])->pstate = PRWAIT;
/* update this locks max wait prio based on this new waiter */
updateMaxWaitPrio(pptr, lptr);
/* update the pentry for waiting */
updateProcessForWaiting(pptr, ldes1);
/* reschedule since this process is now blocked */
/* a context switch should happen here */
resched();
/* the number of readers and locker flag will be set when
* releaselock(...) is called in releaseall.c */
/* restore interupts */
restore(ps);
/* return the wait return value */
return pptr->pwaitret;
/* else if this lock is ackquired by a writer */
} else if (lptr->llocked != UNLOCKED && type == WRITE) {
/* this process must go on the queue because writing locks
* are exclusive */
insert(currpid, lptr->lwqhead, priority);
/* get the current process */
(pptr = &proctab[currpid])->pstate = PRWAIT;
/* update the pentry for waiting */
updateProcessForWaiting(pptr, ldes1);
/* update this locks max wait prio based on this new waiter */
updateMaxWaitPrio(pptr, lptr);
/* reschedule since this process is now blocked */
/* a context switch should happen here */
resched();
/* when we get here, this writer has the lock now, so: */
/* set this processes locker flag to TRUE */
lptr->llockers[currpid] = TRUE;
/* restore interupts */
restore(ps);
return pptr->pwaitret;
}
/* otherwise, the lock is free, so acquire it and set
* the flag and number of readers accordingly */
if (type == READ) {
lptr->llocked = LOCKED_READ;
lptr->lnreaders = 1;
} else {
lptr->llocked = LOCKED_WRITE;
lptr->lnreaders = 0;
}
/* set this processes locker flag to TRUE */
lptr->llockers[currpid] = TRUE;
/* restore interupts */
restore(ps);
return OK;
}
SYSCALL kill(int pid)
{
STATWORD ps;
struct pentry *pptr; /* points to proc. table for pid*/
int dev, i, callResched, lockID;
callResched = RESCHNO;
disable(ps);
if (isbadpid(pid) || (pptr= &proctab[pid])->pstate==PRFREE) {
restore(ps);
return(SYSERR);
}
if (--numproc == 0)
xdone();
dev = pptr->pdevs[0];
if (! isbaddev(dev) )
close(dev);
dev = pptr->pdevs[1];
if (! isbaddev(dev) )
close(dev);
dev = pptr->ppagedev;
if (! isbaddev(dev) )
close(dev);
for( i=0; i<NLOCKS; i++)
{
if( locktab[i].acquiredby[pid] == 1) //this process has acquired some lock and holding it, so release it and resched
{
//kprintf("\n Kill is holding lock %s", proctab[pid].pname);
callResched = RESCHYES;
relLock(pid, i, 0);
}
}
send(pptr->pnxtkin, pid);
freestk(pptr->pbase, pptr->pstklen);
switch (pptr->pstate) {
case PRCURR: pptr->pstate = PRFREE; /* suicide */
resched();
case PRWAIT: semaph[pptr->psem].semcnt++;
//if this proc is in wait queue of any lock i, remove it ... a proc can be in waiting q of any one lock only
/* for( i=0; i<NLOCKS; i++)
{
if( (proctab[pid].procLockType[i]!=DELETED) && (locktab[i].acquiredby[pid]!=1) )
{
kprintf("Killed Process %d waiting on lock %d", pid, i);
locktab[j].effectOfPriorityInheritance = 1;
rampUpPriority(j, proctab[i].pprio);
}
} */
lockID = getLockID(pptr->lockID);
if( !isbadlock(lockID) || locktab[lockID].lstate != LOCKFREE )
{
//dequeue(pid);
//kprintf("\nKill proc getting called in PRWAIT, releasing wait lock %d..%d", lockID, pid);
proctab[pid].pprio = -1;
proctab[pid].mainPrio = -1;
relLock(pid, lockID, 1);
//dequeue(pid);
}
case PRREADY: dequeue(pid);
pptr->pstate = PRFREE;
break;
case PRSLEEP:
case PRTRECV: unsleep(pid);
/* fall through */
default: pptr->pstate = PRFREE;
}
if(callResched)
{
//kprintf("\n About to call resched");
//indicates that this proc was holding lock and is deleted
//in between so now it should release lock and call resched
resched();
}
restore(ps);
return(OK);
}
int release(int ldes1, int pid)
{
register struct sentry *sptr;
struct pentry *pptr;
STATWORD ps;
//unsigned long ctime;
int tail,prev,ldes,ver;
#ifdef DEBUGF
kprintf("\nInside release\n");
#endif
disable (ps);
ldes=GET_LOCK(ldes1);
ver=GET_VER(ldes1);
#ifdef DEBUGF
kprintf("\nLDES:%04x, VER:%d, LOCK:%d\n",ldes1,ver,ldes);
#endif
if (isbadlock(ldes) || (sptr= &semaph[ldes])->sstate==SFREE) {
#ifdef DEBUGF
kprintf("\npid %d has found an error, ldes=%d, sptr->sstate= %d\n",pid,ldes,sptr->sstate);
#endif
restore(ps);
return(SYSERR);
}
if (ver!=sptr->lversion)
{
#ifdef DEBUGF
kprintf("\nVersion error\n");
#endif
restore(ps);
return(SYSERR);
}
if (fpidinlock(pid,ldes)==0)
{
restore(ps);
return(SYSERR);
}
#ifdef DEBUGF
kprintf("\nPast error check sptr->semcnt:%d\n",sptr->semcnt);
#endif
proctab[pid].lnosheld--;
if ((sptr->semcnt++) < 0)
{
#ifdef DEBUGD
kprintf("\nInside if,sptr->lstate:%d, sptr->nordu:%d \n",sptr->lstate,sptr->nordu);
#endif
if ( ((sptr->lstate==READ) && (--sptr->nordu==0)) || (sptr->lstate==WRITE))
{
#ifdef DEBUGC
kprintf("\nInside second if sptr->hprd:%d sptr->hpwrt:%d\n",sptr->hprd,sptr->hpwrt);
#endif
if (sptr->hprd>sptr->hpwrt)
{
//release all readers with hprd
#ifdef DEBUGC
kprintf("\nReleasing readers\n");
#endif
tail=sptr->sqtail;
prev=q[tail].qprev;
while (q[prev].qkey==sptr->hprd)
{
pptr=&proctab[prev];
if (pptr->lstate==READ)
{
dequeue(prev);
ready(prev,RESCHNO);
lreschedyes=1;
}
prev=q[prev].qprev;
}
sptr->hprd=hpp(ldes,READ);
//resched();
restore(ps);
return (OK);
}
if (sptr->hpwrt>sptr->hprd)
{
#ifdef DEBUGD
kprintf("\nReleasing writer\n");
#endif
//release hpwrt
tail=sptr->sqtail;
prev=q[tail].qprev;
while (q[prev].qkey==sptr->hpwrt)
{
pptr=&proctab[prev];
if (pptr->lstate==WRITE)
{
dequeue(prev);
sptr->hpwrt=hpp(ldes,WRITE);
#ifdef DEBUGD
kprintf("\nReleasing writer pid%d for lock %d, new hpwrt= %d\n",prev,ldes,sptr->hpwrt);
#endif
ready(prev,RESCHNO);
lreschedyes=1;
restore(ps);
return (OK);
}
prev=q[prev].qprev;
}
}
if (sptr->hprd==sptr->hpwrt)
{
if (sptr->wtime-sptr->rtime>1000)
{
#ifdef DEBUGC
kprintf("\nReleasing readers priority equal\n");
#endif
//release all readers with hprd
tail=sptr->sqtail;
prev=q[tail].qprev;
while (q[prev].qkey==sptr->hprd)
{
pptr=&proctab[prev];
if (pptr->lstate==READ)
{
dequeue(prev);
ready(prev,RESCHNO);
lreschedyes=1;
}
prev=q[prev].qprev;
}
sptr->hprd=hpp(ldes,READ);
//resched();
restore(ps);
return (OK);
}
else
{
//release hpwrt
tail=sptr->sqtail;
prev=q[tail].qprev;
while (q[prev].qkey==sptr->hprd)
{
pptr=&proctab[prev];
if (pptr->lstate==WRITE)
{
dequeue(prev);
sptr->hpwrt=hpp(ldes,WRITE);
ready(prev,RESCHNO);
lreschedyes=1;
restore(ps);
return (OK);
}
prev=q[prev].qprev;
}
}
}
}
}
restore(ps);
return OK;
}
int release(int numlocks,int ldes1)
{
struct lentry *lptr;
struct pentry *pptr;
int i;
pptr=&proctab[currpid];
if (pptr->deleted[ldes1]==1) //check if the locks has been deleted
{
pptr->deleted[ldes1]==0;
pptr->pwaitret=OK;
//continue;
return (SYSERR);
}
//if bad lock
if(isbadlock(ldes1) || (lptr=&lockarr[ldes1])->lstate==LFREE ||pptr->pwaitret==DELETED)
{ pptr->pwaitret=OK;
return (SYSERR);
}
if (pptr->pinh != 0)
{
pptr->pinh=0;
//chprio(currpid,pptr->prioh);
}
if (lptr->lstate==READ)
{
lptr->holder[currpid]=-1;
pptr->lockdesc[ldes1]=-1;
if (lptr->r_count>0) //if more readers present in the waiting queue
{
lptr->r_count--;
if (lptr->r_count ==0 && !isEmpty(lptr->lhead))
{
}
else
return OK;
}
}
else //change the holder of the process and of the locks
{
lptr->holder[currpid]=-1;
pptr->lockdesc[ldes1]=-1;
}
pptr->pinh=0; //check for the inverted priority
for(i=0;i<50;i++)
{
if (pptr->lockdesc[i]==1)
{
changePriority(i,getlast((&lockarr[i])->ltail));
}
}
pop_3(lptr->lhead,lptr->ltail,ldes1);
//continue;
return OK;
}