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added eqlock(), a interruptable version of qlock. addresses issue #81

--- a/sys/src/9/port/devaudio.c

+++ b/sys/src/9/port/devaudio.c

@@ -204,7 +204,7 @@

 	if(fn == nil)

 		error(Egreg);

-	qlock(ac);

+	eqlock(ac);

 	if(waserror()){

 		qunlock(ac);

 		nexterror();

@@ -260,7 +260,7 @@

 	if(fn == nil)

 		error(Egreg);

-	qlock(ac);

+	eqlock(ac);

 	if(waserror()){

 		qunlock(ac);

 		nexterror();

--- a/sys/src/9/port/devmnt.c

+++ b/sys/src/9/port/devmnt.c

@@ -105,7 +105,7 @@

 	uvlong oo;

 	char buf[128];

-	qlock(&c->umqlock);	/* make sure no one else does this until we've established ourselves */

+	eqlock(&c->umqlock);	/* make sure no one else does this until we've established ourselves */

 	if(waserror()){

 		qunlock(&c->umqlock);

 		nexterror();

--- a/sys/src/9/port/portdat.h

+++ b/sys/src/9/port/portdat.h

@@ -735,6 +735,7 @@

 	int	trace;		/* process being traced? */

 	ulong	qpc;		/* pc calling last blocking qlock */

+	QLock	*eql;		/* interruptable eqlock, protected by rlock */

 	int	setargs;

--- a/sys/src/9/port/portfns.h

+++ b/sys/src/9/port/portfns.h

@@ -98,6 +98,7 @@

 int		eqchantdqid(Chan*, int, int, Qid, int);

 int		eqqid(Qid, Qid);

 void		error(char*);

+void		eqlock(QLock*);

 long		execregs(ulong, ulong, ulong);

 void		exhausted(char*);

 void		exit(int);

--- a/sys/src/9/port/proc.c

+++ b/sys/src/9/port/proc.c

@@ -900,8 +900,6 @@

 postnote(Proc *p, int dolock, char *n, int flag)

 {

 	int s, ret;

-	Rendez *r;

-	Proc *d, **l;

 	if(dolock)

 		qlock(&p->debug);

@@ -921,6 +919,8 @@

 	/* this loop is to avoid lock ordering problems. */

 	for(;;){

+		Rendez *r;

+

 		s = splhi();

 		lock(&p->rlock);

 		r = p->r;

@@ -948,24 +948,59 @@

 	unlock(&p->rlock);

 	splx(s);

-	if(p->state != Rendezvous)

-		return ret;

+Pullout:

+	switch(p->state){

+	case Queueing:

+		/* Try and pull out of a eqlock */

+		lock(&p->rlock);

+		if(p->state == Queueing && p->eql && p->notepending){

+			Proc *d, *l;

+			QLock *q;

-	/* Try and pull out of a rendezvous */

-	lock(p->rgrp);

-	if(p->state == Rendezvous) {

-		p->rendval = ~0;

-		l = &REND(p->rgrp, p->rendtag);

-		for(d = *l; d; d = d->rendhash) {

-			if(d == p) {

-				*l = p->rendhash;

-				break;

+			q = p->eql;

+			if(!canlock(&q->use)){

+				unlock(&p->rlock);

+				sched();

+				goto Pullout;

 			}

-			l = &d->rendhash;

+			for(l = nil, d = q->head; d; l = d, d = d->qnext)

+				if(d == p){

+					if(l)

+						l->qnext = p->qnext;

+					else

+						q->head = p->qnext;

+					if(p->qnext == 0)

+						q->tail = l;

+					p->qnext = 0;

+					p->eql = 0;

+					ready(p);

+					break;

+				}

+			unlock(&q->use);

+			break;

 		}

-		ready(p);

+		unlock(&p->rlock);

+		break;

+	case Rendezvous:

+		/* Try and pull out of a rendezvous */

+		lock(p->rgrp);

+		if(p->state == Rendezvous) {

+			Proc *d, **l;

+

+			p->rendval = ~0;

+			l = &REND(p->rgrp, p->rendtag);

+			for(d = *l; d; d = d->rendhash) {

+				if(d == p) {

+					*l = p->rendhash;

+					break;

+				}

+				l = &d->rendhash;

+			}

+			ready(p);

+		}

+		unlock(p->rgrp);

+		break;

 	}

-	unlock(p->rgrp);

 	return ret;

 }

--- a/sys/src/9/port/qio.c

+++ b/sys/src/9/port/qio.c

@@ -1017,7 +1017,7 @@

 	Block *b, *nb;

 	int n;

-	qlock(&q->rlock);

+	eqlock(&q->rlock);

 	if(waserror()){

 		qunlock(&q->rlock);

 		nexterror();

@@ -1072,7 +1072,7 @@

 	Block *b, *first, **l;

 	int m, n;

-	qlock(&q->rlock);

+	eqlock(&q->rlock);

 	if(waserror()){

 		qunlock(&q->rlock);

 		nexterror();

@@ -1173,7 +1173,7 @@

 	}

 	dowakeup = 0;

-	qlock(&q->wlock);

+	eqlock(&q->wlock);

 	if(waserror()){

 		if(b != nil)

 			freeb(b);

--- a/sys/src/9/port/qlock.c

+++ b/sys/src/9/port/qlock.c

@@ -4,6 +4,8 @@

 #include "dat.h"

 #include "fns.h"

+#include	"../port/error.h"

+

 struct {

 	ulong rlock;

 	ulong rlockq;

@@ -14,6 +16,59 @@

 } rwstats;

 void

+eqlock(QLock *q)

+{

+	Proc *p;

+

+	if(m->ilockdepth != 0)

+		print("eqlock: %#p: ilockdepth %d\n", getcallerpc(&q), m->ilockdepth);

+	if(up != nil && up->nlocks.ref)

+		print("eqlock: %#p: nlocks %lud\n", getcallerpc(&q), up->nlocks.ref);

+

+	if(q->use.key == 0x55555555)

+		panic("eqlock: q %#p, key 5*\n", q);

+

+	lock(&q->use);

+	rwstats.qlock++;

+	if(!q->locked) {

+		q->locked = 1;

+		unlock(&q->use);

+		return;

+	}

+	if(up == 0)

+		panic("eqlock");

+	if(up->notepending){

+		unlock(&q->use);

+		error(Eintr);

+	}

+	rwstats.qlockq++;

+

+	p = q->tail;

+	if(p == 0)

+		q->head = up;

+	else

+		p->qnext = up;

+	q->tail = up;

+

+	up->qnext = 0;

+	up->qpc = getcallerpc(&q);

+	up->state = Queueing;

+

+	lock(&up->rlock);

+	up->eql = q;

+	unlock(&up->rlock);

+

+	unlock(&q->use);

+

+	sched();

+

+	if(up->notepending){

+		up->notepending = 0;

+		error(Eintr);

+	}

+}

+

+void

 qlock(QLock *q)

 {

 	Proc *p;

@@ -73,6 +128,12 @@

 			getcallerpc(&q));

 	p = q->head;

 	if(p){

+		if(p->eql){

+			lock(&p->rlock);

+			if(p->eql == q)

+				p->eql = 0;

+			unlock(&p->rlock);

+		}

 		q->head = p->qnext;

 		if(q->head == 0)

 			q->tail = 0;

-- 

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