Imported Upstream version 1.3upstream/1.3

1 files changed, 48 insertions, 18 deletions

diff --git a/src/pkg/runtime/proc_test.go b/src/pkg/runtime/proc_test.go
index dd70ed97d..5be355195 100644
--- a/src/pkg/runtime/proc_test.go
+++ b/src/pkg/runtime/proc_test.go
@@ -244,6 +244,49 @@ func TestPreemptionGC(t *testing.T) {
 	atomic.StoreUint32(&stop, 1)
 }
 
+func TestGCFairness(t *testing.T) {
+	output := executeTest(t, testGCFairnessSource, nil)
+	want := "OK\n"
+	if output != want {
+		t.Fatalf("want %s, got %s\n", want, output)
+	}
+}
+
+const testGCFairnessSource = `
+package main
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"time"
+)
+
+func main() {
+	runtime.GOMAXPROCS(1)
+	f, err := os.Open("/dev/null")
+	if os.IsNotExist(err) {
+		// This test tests what it is intended to test only if writes are fast.
+		// If there is no /dev/null, we just don't execute the test.
+		fmt.Println("OK")
+		return
+	}
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	for i := 0; i < 2; i++ {
+		go func() {
+			for {
+				f.Write([]byte("."))
+			}
+		}()
+	}
+	time.Sleep(10 * time.Millisecond)
+	fmt.Println("OK")
+}
+`
+
 func stackGrowthRecursive(i int) {
 	var pad [128]uint64
 	if i != 0 && pad[0] == 0 {
@@ -327,24 +370,11 @@ func TestSchedLocalQueueSteal(t *testing.T) {
 }
 
 func benchmarkStackGrowth(b *testing.B, rec int) {
-	const CallsPerSched = 1000
-	procs := runtime.GOMAXPROCS(-1)
-	N := int32(b.N / CallsPerSched)
-	c := make(chan bool, procs)
-	for p := 0; p < procs; p++ {
-		go func() {
-			for atomic.AddInt32(&N, -1) >= 0 {
-				runtime.Gosched()
-				for g := 0; g < CallsPerSched; g++ {
-					stackGrowthRecursive(rec)
-				}
-			}
-			c <- true
-		}()
-	}
-	for p := 0; p < procs; p++ {
-		<-c
-	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			stackGrowthRecursive(rec)
+		}
+	})
 }
 
 func BenchmarkStackGrowth(b *testing.B) {