From 895145cfc963877c5b6494d4d8eb0fd6c6678d38 Mon Sep 17 00:00:00 2001
From: ivanpauno <ivanpauno@ekumenlabs.com>
Date: Wed, 25 Sep 2019 15:52:22 -0300
Subject: [PATCH] Fix hang with timers in MultiThreadedExecutor (#835) (#836)
 (#869)

Signed-off-by: Todd Malsbary <todd.malsbary@intel.com>
---
 rclcpp/src/rclcpp/executors/multi_threaded_executor.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/rclcpp/src/rclcpp/executors/multi_threaded_executor.cpp b/rclcpp/src/rclcpp/executors/multi_threaded_executor.cpp
index 24c5c79b2c..f3c54b843a 100644
--- a/rclcpp/src/rclcpp/executors/multi_threaded_executor.cpp
+++ b/rclcpp/src/rclcpp/executors/multi_threaded_executor.cpp
@@ -83,6 +83,11 @@ MultiThreadedExecutor::run(size_t)
       if (any_exec.timer) {
         // Guard against multiple threads getting the same timer.
         if (scheduled_timers_.count(any_exec.timer) != 0) {
+          // Make sure that any_exec's callback group is reset before
+          // the lock is released.
+          if (any_exec.callback_group) {
+            any_exec.callback_group->can_be_taken_from().store(true);
+          }
           continue;
         }
         scheduled_timers_.insert(any_exec.timer);