Fix deadlock issue that caused by other mutexes locked in CancelCallback

Kaven Yau · Kaven Yau · commit b8f567bbffe6 · 2021-04-15T20:46:41.000+08:00
diff --git a/rclcpp_action/include/rclcpp_action/server.hpp b/rclcpp_action/include/rclcpp_action/server.hpp
@@ -356,16 +356,20 @@ class Server : public ServerBase, public std::enable_shared_from_this<Server<Act
   CancelResponse
   call_handle_cancel_callback(const GoalUUID & uuid) override
   {
-    std::lock_guard<std::mutex> lock(goal_handles_mutex_);
+    std::shared_ptr<ServerGoalHandle<ActionT>> goal_handle;
+    {
+      std::lock_guard<std::mutex> lock(goal_handles_mutex_);
+      auto element = goal_handles_.find(uuid);
+      if (element != goal_handles_.end()) {
+        goal_handle = element->second.lock();
+      }
+    }
+
     CancelResponse resp = CancelResponse::REJECT;
-    auto element = goal_handles_.find(uuid);
-    if (element != goal_handles_.end()) {
-      std::shared_ptr<ServerGoalHandle<ActionT>> goal_handle = element->second.lock();
-      if (goal_handle) {
-        resp = handle_cancel_(goal_handle);
-        if (CancelResponse::ACCEPT == resp) {
-          goal_handle->_cancel_goal();
-        }
+    if (goal_handle) {
+      resp = handle_cancel_(goal_handle);
+      if (CancelResponse::ACCEPT == resp) {
+        goal_handle->_cancel_goal();
       }
     }
     return resp;
