evil deadlock that wasn't.

important to always reread your code.

net/swarm/conn.go

@@ -102,8 +102,8 @@ func (s *Swarm) connSetup(c conn.Conn) (conn.Conn, error) {
 	// add to conns
 	s.connsLock.Lock()
 
-	mc, ok := s.conns[c.RemotePeer().Key()]
-	if !ok {
+	mc, found := s.conns[c.RemotePeer().Key()]
+	if !found {
 		// multiconn doesn't exist, make a new one.
 		conns := []conn.Conn{c}
 		mc, err := conn.NewMultiConn(s.Context(), s.local, c.RemotePeer(), conns)
@@ -116,6 +116,8 @@ func (s *Swarm) connSetup(c conn.Conn) (conn.Conn, error) {
 		s.conns[c.RemotePeer().Key()] = mc
 		s.connsLock.Unlock()
 
+		// kick off reader goroutine
+		go s.fanInSingle(mc)
 		log.Debug("added new multiconn: %s", mc)
 	} else {
 		s.connsLock.Unlock() // unlock before adding new conn
@@ -125,9 +127,6 @@ func (s *Swarm) connSetup(c conn.Conn) (conn.Conn, error) {
 	}
 
 	log.Debug("multiconn added new conn %s", c)
-
-	// kick off reader goroutine
-	go s.fanInSingle(c)
 	return c, nil
 }
 

net/swarm/simul_test.go

@@ -61,8 +61,11 @@ func TestSimultOpenMany(t *testing.T) {
 }
 
 func TestSimultOpenFewStress(t *testing.T) {
+	// t.Skip("skipping for another test")
 
-	for i := 0; i < 100; i++ {
+	num := 10
+	// num := 100
+	for i := 0; i < num; i++ {
 		addrs := []string{
 			fmt.Sprintf("/ip4/127.0.0.1/tcp/%d", 1900+i),
 			fmt.Sprintf("/ip4/127.0.0.1/tcp/%d", 2900+i),

net/swarm/swarm_test.go

@@ -141,6 +141,7 @@ func SubtestSwarm(t *testing.T, addrs []string, MsgNum int) {
 
 		got := map[u.Key]int{}
 		for k := 0; k < (MsgNum * len(*peers)); k++ {
+			log.Debug("%s waiting for pong (%d)", s1.local, k)
 			msg := <-s1.Incoming
 			if string(msg.Data()) != "pong" {
 				t.Error("unexpected conn output", msg.Data)
@@ -180,6 +181,7 @@ func TestSwarm(t *testing.T) {
 		"/ip4/127.0.0.1/tcp/1238",
 	}
 
+	// msgs := 1000
 	msgs := 100
 	SubtestSwarm(t, addrs, msgs)
 }