From 7253b2be6df6d0d36d370c641cdbc82b8abe41d8 Mon Sep 17 00:00:00 2001
From: Dom <dom@itsallbroken.com>
Date: Mon, 4 Jun 2018 13:44:31 +0100
Subject: [PATCH] MGO-156 Avoid iter.Next deadlock on dead sockets (#182)

---
 session.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/session.go b/session.go
index c951e8e72..9defdab30 100644
--- a/session.go
+++ b/session.go
@@ -4536,7 +4536,13 @@ func (iter *Iter) getMore() {
 	} else {
 		op = &iter.op
 	}
-	if err := socket.Query(op); err != nil {
+	// We unlock the iterator around socket.Query because it will call the
+	// replyFunc if the socket is dead, which would deadlock if the iterator
+	// were still locked.
+	iter.m.Unlock()
+	err = socket.Query(op)
+	iter.m.Lock()
+	if err != nil {
 		iter.docsToReceive--
 		iter.err = err
 	}