second try.  first was applied incorrectly do to incorrect environment
used for patch

remove spls from ilocks and test against nil rather than
using 0 or !.

Reference: /n/atom/patch/applied2013/fssplinilock
Date: Tue Sep  3 19:12:07 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/fs/port/sub.c	Tue Sep  3 19:10:47 2013
+++ /sys/src/fs/port/sub.c	Tue Sep  3 19:10:47 2013
@@ -1086,7 +1086,6 @@
 	User *p;
 	void *a;
 	int i, c;
-	long s;
 
 	if(q == nil)
 		panic("recv null q");
@@ -1095,7 +1094,16 @@
 		c = q->count;
 		if(c > 0) {
 			if(ret == 0){
-				iunlock(q);
+				/* since we consume nothing, wake up next guy */
+				p = q->rhead;
+				if(p != nil) {
+					q->rhead = p->qnext;
+					if(q->rhead == nil)
+						q->rtail = nil;
+					iunlock(q);
+					ready(p);
+				}else
+					iunlock(q);
 				return 0;
 			}
 			i = q->loc;
@@ -1122,10 +1130,8 @@
 		else
 			p->qnext = u;
 		q->rtail = u;
-		s = splhi();
 		u->qnext = 0;
 		u->state = Recving;
-		splx(s);
 		iunlock(q);
 		sched();
 	}
@@ -1136,7 +1142,6 @@
 {
 	User *p;
 	int i, c;
-	long s;
 
 	if(q == 0)
 		panic("send null q %#p", getcallerpc(q));
@@ -1158,10 +1163,10 @@
 			q->args[i] = a;
 			q->count = c+1;
 			p = q->rhead;
-			if(p) {
+			if(p != nil) {
 				q->rhead = p->qnext;
-				if(q->rhead == 0)
-					q->rtail = 0;
+				if(q->rhead == nil)
+					q->rtail = nil;
 				iunlock(q);
 				ready(p);
 			}else
@@ -1176,10 +1181,8 @@
 		else
 			p->qnext = u;
 		q->wtail = u;
-		s = splhi();
 		u->qnext = 0;
 		u->state = Sending;
-		splx(s);
 		iunlock(q);
 		sched();
 	}
--- /sys/src/fs/port/proc.c	Tue Sep  3 19:10:47 2013
+++ /sys/src/fs/port/proc.c	Tue Sep  3 19:10:47 2013
@@ -130,7 +130,7 @@
 void
 ready(User *p)
 {
-	int s;
+	Mpl s;
 
 	if(p->state == Ready){
 		print("ready Ready\n");
@@ -259,7 +259,7 @@
 	 */
 	p = r->p;
 	if(p)
-		print("double sleep pid %d/%#p\n", u->pid, getcallerpc(&r));
+		print("double sleep pid %d/%#p %d\n", u->pid, getcallerpc(&r), p->pid);
 	u->state = Wakeme;
 	r->p = u;
 
@@ -321,13 +321,13 @@
 wakeup(Rendez *r)
 {
 	User *p;
-	int s;
+	Mpl s;
 
 	s = splhi();
 	lock(r);
 	p = r->p;
-	if(p) {
-		r->p = 0;
+	if(p != nil) {
+		r->p = nil;
 		if(p->state != Wakeme)
 			panic("wakeup: not Wakeme");
 		ready(p);