fix: shutdown deadlock of pipe when its ring is full (#108)

pipe.go

@@ -217,6 +217,11 @@ func (p *pipe) _background() {
 	}
 	go func() {
 		exit(p._backgroundWrite())
+		for atomic.LoadInt32(&p.waits) != 0 {
+			if _, _, ch := p.queue.NextWriteCmd(); ch == nil {
+				runtime.Gosched()
+			}
+		}
 		close(wait)
 	}()
 	{
@@ -228,7 +233,6 @@ func (p *pipe) _background() {
 			atomic.AddInt32(&p.waits, -1)
 		}()
 	}
-	<-wait
 
 	p.nsubs.Close()
 	p.psubs.Close()
@@ -253,7 +257,6 @@ func (p *pipe) _background() {
 		p.onInvalidations(nil)
 	}
 	for atomic.LoadInt32(&p.waits) != 0 {
-		p.queue.NextWriteCmd()
 		if ones[0], multi, ch, cond = p.queue.NextResultCh(); ch != nil {
 			if multi == nil {
 				multi = ones
@@ -269,6 +272,7 @@ func (p *pipe) _background() {
 			runtime.Gosched()
 		}
 	}
+	<-wait
 	atomic.StoreInt32(&p.state, 4)
 }
 

pipe_test.go

@@ -2445,6 +2445,33 @@ func TestExitOnWriteMultiError(t *testing.T) {
 	}
 }
 
+func TestExitOnRingFullAndConnError(t *testing.T) {
+	p, mock, _, closeConn := setup(t, ClientOption{
+		RingScaleEachConn: 1,
+	})
+	p.background()
+
+	// fill the ring
+	for i := 0; i < len(p.queue.(*ring).store); i++ {
+		go func() {
+			if err := p.Do(context.Background(), cmds.NewCompleted([]string{"GET", "a"})).Error(); err != io.EOF && !strings.HasPrefix(err.Error(), "io:") {
+				t.Errorf("unexpected result, expected io err, got %v", err)
+			}
+		}()
+	}
+	// let writer loop over the ring
+	for i := 0; i < len(p.queue.(*ring).store); i++ {
+		mock.Expect("GET", "a")
+	}
+
+	time.Sleep(time.Second) // make sure the writer is waiting for the next write
+	closeConn()
+
+	if err := p.Do(context.Background(), cmds.NewCompleted([]string{"GET", "a"})).Error(); err != io.EOF && !strings.HasPrefix(err.Error(), "io:") {
+		t.Errorf("unexpected result, expected io err, got %v", err)
+	}
+}
+
 func TestExitAllGoroutineOnWriteError(t *testing.T) {
 	conn, mock, _, closeConn := setup(t, ClientOption{})