From 8364a2472c3bbc4f89be719b0535615c6fd1c428 Mon Sep 17 00:00:00 2001
From: Sandro Scherer <sandro.scherer@siemens.com>
Date: Tue, 8 Oct 2024 09:03:29 +0200
Subject: [PATCH] Fix potential deadlock in set_callback

Signed-off-by: Sandro Scherer <sand.scherer@gmail.com>
---
 src/async_client.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/async_client.cpp b/src/async_client.cpp
index 3bcb15be..41632d22 100644
--- a/src/async_client.cpp
+++ b/src/async_client.cpp
@@ -315,9 +315,10 @@ void async_client::remove_token(token* tok)
 
 void async_client::set_callback(callback& cb)
 {
-    guard g(lock_);
-    userCallback_ = &cb;
-
+    {
+        guard g(lock_);
+        userCallback_ = &cb;
+    }
     int rc = MQTTAsync_setConnected(cli_, this, &async_client::on_connected);
 
     if (rc == MQTTASYNC_SUCCESS) {
@@ -330,6 +331,7 @@ void async_client::set_callback(callback& cb)
         MQTTAsync_setConnected(cli_, nullptr, nullptr);
 
     if (rc != MQTTASYNC_SUCCESS) {
+        guard g(lock_);
         userCallback_ = nullptr;
         throw exception(rc);
     }