simplify threadring slightly; slight speed improvement

R=rsc
DELTA=7  (3 added, 3 deleted, 1 changed)
OCL=32885
CL=32889

test/bench/threadring.go

@@ -39,7 +39,6 @@ import (
 	"flag";
 	"fmt";
 	"os";
-	"time";
 )
 
 var n = flag.Int("n", 1000, "how many passes")
@@ -68,7 +67,5 @@ func main() {
 	}
 	go f(Nthread, out, one);
 	one <- *n;
-	for {
-		time.Sleep(100*1e9);	// wait for ring to run
-	}
+	<-make(chan int);	// hang until ring completes
 }

test/bench/timing.log

@@ -120,3 +120,6 @@ threadring 50000000
 	gccgo -O2 threadring.go	90.33u 459.95s 448.03r
 	gc threadring	33.11u 0.00s 33.14r
 	GOMAXPROCS=4 gc threadring	114.48u 226.65s 371.59r
+	# change wait code to do <-make(chan int) instead of time.Sleep
+	gc threadring	28.41u 0.01s 29.35r
+	GOMAXPROCS=4 gc threadring	112.59u 232.83s 384.72r