From 98cf24c28c7f14f7ea6df78135e55cbf2676f94e Mon Sep 17 00:00:00 2001
From: Ethan Dickson <ethan@coder.com>
Date: Wed, 7 Aug 2024 05:41:14 +0000
Subject: [PATCH] fix: lock adding to tailnet waitgroup to avoid race (and fix
 flake)

---
 tailnet/conn.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tailnet/conn.go b/tailnet/conn.go
index 5f202c0c47b14..4646c2f02cbeb 100644
--- a/tailnet/conn.go
+++ b/tailnet/conn.go
@@ -556,7 +556,6 @@ func (c *Conn) Closed() <-chan struct{} {
 func (c *Conn) Close() error {
 	c.logger.Info(context.Background(), "closing tailnet Conn")
 	c.watchCancel()
-	c.telemetryWg.Wait()
 	c.configMaps.close()
 	c.nodeUpdater.close()
 	c.mutex.Lock()
@@ -567,6 +566,7 @@ func (c *Conn) Close() error {
 	default:
 	}
 	close(c.closed)
+	c.telemetryWg.Wait()
 	c.mutex.Unlock()
 
 	var wg sync.WaitGroup
@@ -783,6 +783,13 @@ func (c *Conn) newTelemetryEvent() *proto.TelemetryEvent {
 }
 
 func (c *Conn) sendTelemetryBackground(e *proto.TelemetryEvent) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	select {
+	case <-c.closed:
+		return
+	default:
+	}
 	c.telemetryWg.Add(1)
 	go func() {
 		defer c.telemetryWg.Done()