1 files changed, 49 insertions, 18 deletions
diff --git a/src/runtime/pprof/pprof_test.go b/src/runtime/pprof/pprof_test.go
index 1a44ab7ad7..322579cdc4 100644
--- a/src/runtime/pprof/pprof_test.go
+++ b/src/runtime/pprof/pprof_test.go
@@ -794,7 +794,7 @@ func use(x [8 << 18]byte) {}
 func TestBlockProfile(t *testing.T) {
 	type TestCase struct {
 		name string
-		f    func()
+		f    func(*testing.T)
 		stk  []string
 		re   string
 	}
@@ -903,7 +903,7 @@ func TestBlockProfile(t *testing.T) {
 	runtime.SetBlockProfileRate(1)
 	defer runtime.SetBlockProfileRate(0)
 	for _, test := range tests {
-		test.f()
+		test.f(t)
 	}
 
 	t.Run("debug=1", func(t *testing.T) {
@@ -979,42 +979,73 @@ func containsStack(got [][]string, want []string) bool {
 	return false
 }
 
-const blockDelay = 10 * time.Millisecond
+// awaitBlockedGoroutine spins on runtime.Gosched until a runtime stack dump
+// shows a goroutine in the given state with a stack frame in
+// runtime/pprof.<fName>.
+func awaitBlockedGoroutine(t *testing.T, state, fName string) {
+	re := fmt.Sprintf(`(?m)^goroutine \d+ \[%s\]:\n(?:.+\n\t.+\n)*runtime/pprof\.%s`, regexp.QuoteMeta(state), fName)
+	r := regexp.MustCompile(re)
 
-func blockChanRecv() {
+	if deadline, ok := t.Deadline(); ok {
+		if d := time.Until(deadline); d > 1*time.Second {
+			timer := time.AfterFunc(d-1*time.Second, func() {
+				debug.SetTraceback("all")
+				panic(fmt.Sprintf("timed out waiting for %#q", re))
+			})
+			defer timer.Stop()
+		}
+	}
+
+	buf := make([]byte, 64<<10)
+	for {
+		runtime.Gosched()
+		n := runtime.Stack(buf, true)
+		if n == len(buf) {
+			// Buffer wasn't large enough for a full goroutine dump.
+			// Resize it and try again.
+			buf = make([]byte, 2*len(buf))
+			continue
+		}
+		if r.Match(buf[:n]) {
+			return
+		}
+	}
+}
+
+func blockChanRecv(t *testing.T) {
 	c := make(chan bool)
 	go func() {
-		time.Sleep(blockDelay)
+		awaitBlockedGoroutine(t, "chan receive", "blockChanRecv")
 		c <- true
 	}()
 	<-c
 }
 
-func blockChanSend() {
+func blockChanSend(t *testing.T) {
 	c := make(chan bool)
 	go func() {
-		time.Sleep(blockDelay)
+		awaitBlockedGoroutine(t, "chan send", "blockChanSend")
 		<-c
 	}()
 	c <- true
 }
 
-func blockChanClose() {
+func blockChanClose(t *testing.T) {
 	c := make(chan bool)
 	go func() {
-		time.Sleep(blockDelay)
+		awaitBlockedGoroutine(t, "chan receive", "blockChanClose")
 		close(c)
 	}()
 	<-c
 }
 
-func blockSelectRecvAsync() {
+func blockSelectRecvAsync(t *testing.T) {
 	const numTries = 3
 	c := make(chan bool, 1)
 	c2 := make(chan bool, 1)
 	go func() {
 		for i := 0; i < numTries; i++ {
-			time.Sleep(blockDelay)
+			awaitBlockedGoroutine(t, "select", "blockSelectRecvAsync")
 			c <- true
 		}
 	}()
@@ -1026,11 +1057,11 @@ func blockSelectRecvAsync() {
 	}
 }
 
-func blockSelectSendSync() {
+func blockSelectSendSync(t *testing.T) {
 	c := make(chan bool)
 	c2 := make(chan bool)
 	go func() {
-		time.Sleep(blockDelay)
+		awaitBlockedGoroutine(t, "select", "blockSelectSendSync")
 		<-c
 	}()
 	select {
@@ -1039,11 +1070,11 @@ func blockSelectSendSync() {
 	}
 }
 
-func blockMutex() {
+func blockMutex(t *testing.T) {
 	var mu sync.Mutex
 	mu.Lock()
 	go func() {
-		time.Sleep(blockDelay)
+		awaitBlockedGoroutine(t, "semacquire", "blockMutex")
 		mu.Unlock()
 	}()
 	// Note: Unlock releases mu before recording the mutex event,
@@ -1053,12 +1084,12 @@ func blockMutex() {
 	mu.Lock()
 }
 
-func blockCond() {
+func blockCond(t *testing.T) {
 	var mu sync.Mutex
 	c := sync.NewCond(&mu)
 	mu.Lock()
 	go func() {
-		time.Sleep(blockDelay)
+		awaitBlockedGoroutine(t, "sync.Cond.Wait", "blockCond")
 		mu.Lock()
 		c.Signal()
 		mu.Unlock()
@@ -1144,7 +1175,7 @@ func TestMutexProfile(t *testing.T) {
 		t.Fatalf("need MutexProfileRate 0, got %d", old)
 	}
 
-	blockMutex()
+	blockMutex(t)
 
 	t.Run("debug=1", func(t *testing.T) {
 		var w bytes.Buffer