test and fix non-blocking chan ops on buffered chans

R=ken
DELTA=68  (19 added, 0 deleted, 49 changed)
OCL=15966
CL=15969

src/runtime/chan.c

@@ -198,12 +198,18 @@ sendchan(Hchan *c, byte *ep, bool *pres)
 	sg = g->param;
 	freesg(c, sg);
 	unlock(&chanlock);
+	if(pres != nil)
+		*pres = true;
 	return;
 
 asynch:
 //prints("\nasend\n");
 	while(c->qcount >= c->dataqsiz) {
-		// (rsc) should check for pres != nil
+		if(pres != nil) {
+			unlock(&chanlock);
+			*pres = false;
+			return;
+		}
 		sg = allocsg(c);
 		g->status = Gwaiting;
 		enqueue(&c->sendq, sg);
@@ -227,6 +233,8 @@ asynch:
 		ready(gp);
 	} else
 		unlock(&chanlock);
+	if(pres != nil)
+		*pres = true;
 }
 
 static void
@@ -277,10 +285,17 @@ chanrecv(Hchan* c, byte *ep, bool* pres)
 	c->elemalg->copy(c->elemsize, ep, sg->elem);
 	freesg(c, sg);
 	unlock(&chanlock);
+	if(pres != nil)
+		*pres = true;
 	return;
 
 asynch:
 	while(c->qcount <= 0) {
+		if(pres != nil) {
+			unlock(&chanlock);
+			*pres = false;
+			return;
+		}
 		sg = allocsg(c);
 		g->status = Gwaiting;
 		enqueue(&c->recvq, sg);
@@ -300,6 +315,8 @@ asynch:
 		ready(gp);
 	} else
 		unlock(&chanlock);
+	if(pres != nil)
+		*pres = true;
 }
 
 // chansend1(hchan *chan any, elem any);

test/chan/nonblock.go

@@ -52,10 +52,11 @@ func main() {
 	var s string;
 	var ok bool;
 
-	c32 := new(chan int32);
-	c64 := new(chan int64);
-	cb := new(chan bool);
-	cs := new(chan string);
+	for buffer := 0; buffer < 2; buffer++ {
+		c32 := new(chan int32, buffer);
+		c64 := new(chan int64, buffer);
+		cb := new(chan bool, buffer);
+		cs := new(chan string, buffer);
 	
 		i32, ok = <-c32;
 		if ok { panic("blocked i32sender") }
@@ -108,5 +109,6 @@ func main() {
 		s, ok = <-cs;
 		if !ok { panic("ssender") }
 		if s != "hello again" { panic("ssender value") }
+	}
 	print("PASS\n")
 }