netstack: make listening tcp socket close state setting and cleanup atomic.

Otherwise the socket saving logic might find workers still running for closed
sockets unexpectedly.

PiperOrigin-RevId: 210018905
Change-Id: I443a04d355613f5f9983252cc6863bff6e0eda3a

pkg/tcpip/transport/tcp/accept.go

@@ -363,11 +363,6 @@ func (e *endpoint) protocolListenLoop(rcvWnd seqnum.Size) *tcpip.Error {
 		e.mu.Lock()
 		e.state = stateClosed
 
-		// Notify waiters that the endpoint is shutdown.
-		e.mu.Unlock()
-		e.waiterQueue.Notify(waiter.EventIn | waiter.EventOut)
-		e.mu.Lock()
-
 		// Do cleanup if needed.
 		e.completeWorkerLocked()
 
@@ -375,6 +370,9 @@ func (e *endpoint) protocolListenLoop(rcvWnd seqnum.Size) *tcpip.Error {
 			close(e.drainDone)
 		}
 		e.mu.Unlock()
+
+		// Notify waiters that the endpoint is shutdown.
+		e.waiterQueue.Notify(waiter.EventIn | waiter.EventOut)
 	}()
 
 	e.mu.Lock()