From b9356e3d26734a8239fe1efcb92f3f823e7cceb5 Mon Sep 17 00:00:00 2001
From: Doug Fawley <dfawley@google.com>
Date: Thu, 3 Aug 2023 11:03:58 -0700
Subject: [PATCH] client: fix race between connection error and subconn
 shutdown (#6494)

---
 clientconn.go | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/clientconn.go b/clientconn.go
index 8d7bb03a0..9b350254c 100644
--- a/clientconn.go
+++ b/clientconn.go
@@ -1353,12 +1353,14 @@ func (ac *addrConn) resetTransport() {
 
 	if err := ac.tryAllAddrs(acCtx, addrs, connectDeadline); err != nil {
 		ac.cc.resolveNow(resolver.ResolveNowOptions{})
-		// After exhausting all addresses, the addrConn enters
-		// TRANSIENT_FAILURE.
+		ac.mu.Lock()
 		if acCtx.Err() != nil {
+			// addrConn was torn down.
+			ac.mu.Unlock()
 			return
 		}
-		ac.mu.Lock()
+		// After exhausting all addresses, the addrConn enters
+		// TRANSIENT_FAILURE.
 		ac.updateConnectivityState(connectivity.TransientFailure, err)
 
 		// Backoff.