From 61b6b740bc445a133e0b39a9200193304bd1ddf4 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 25 Feb 2020 22:55:59 +0100
Subject: [PATCH] Fix deadlock, shared_ptr d'tor called from
 ScopedConnectionList d'tor

See https://ardour.org/styleguide.html #10
https://pastebin.com/gJfrNhL2
---
 libs/surfaces/websockets/feedback.cc | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/libs/surfaces/websockets/feedback.cc b/libs/surfaces/websockets/feedback.cc
index f7591fb33d..6e956f8f61 100644
--- a/libs/surfaces/websockets/feedback.cc
+++ b/libs/surfaces/websockets/feedback.cc
@@ -68,8 +68,12 @@ struct PluginBypassObserver {
 
 struct PluginParamValueObserver {
 	void operator() (ArdourFeedback* p, uint32_t strip_n, uint32_t plugin_n,
-	                 uint32_t param_n, boost::shared_ptr<AutomationControl> control)
+	                 uint32_t param_n, boost::weak_ptr<AutomationControl> ctrl)
 	{
+		boost::shared_ptr<AutomationControl> control = ctrl.lock ();
+		if (!control) {
+			return;
+		}
 		p->update_all (Node::strip_plugin_param_value, strip_n, plugin_n, param_n,
 		               ArdourStrips::plugin_param_value (control));
 	}
@@ -221,7 +225,7 @@ ArdourFeedback::observe_strip_plugin_param_values (uint32_t strip_n,
 
 		control->Changed.connect (_signal_connections, MISSING_INVALIDATOR,
 		                          boost::bind<void> (PluginParamValueObserver (), this, strip_n, plugin_n, param_n,
-		                                             control),
+		                                             boost::weak_ptr<AutomationControl>(control)),
 		                          event_loop ());
 	}
 }