From f153cf7173dc2b6bac1f856e52d9813b209c3757 Mon Sep 17 00:00:00 2001
From: Todd Malsbary <todd.malsbary@intel.com>
Date: Fri, 30 Aug 2019 10:38:51 -0700
Subject: [PATCH] Fix hang with timers in MultiThreadedExecutor (#835) (#836)

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 cc34d09..e2f878a 100644
--- a/rclcpp/src/rclcpp/executors/multi_threaded_executor.cpp
+++ b/rclcpp/src/rclcpp/executors/multi_threaded_executor.cpp
@@ -86,6 +86,11 @@ 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);