From b18c8c8e78172abebb82491700a0b5f9f40c1d66 Mon Sep 17 00:00:00 2001
From: Justin Clark-Casey (justincc)
Date: Thu, 17 May 2012 23:59:43 +0100
Subject: Don't eagerly clear frame collision events when physics actors
 subscribe and unsubscribe from collisions, in order to avoid a race
 condition.

Since this is done directly from ScenePresence, it can lead to a race condition with the simulator loop.
There's no real point doing it anyway since the clear will be done very shortly afterwards by the simulate loop and either there are no events (for a new avatar) or events don't matter (for a departing avatar).
This matches existing behaviour in OdePrim
---
 OpenSim/Region/Physics/OdePlugin/ODECharacter.cs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

(limited to 'OpenSim/Region/Physics/OdePlugin/ODECharacter.cs')

diff --git a/OpenSim/Region/Physics/OdePlugin/ODECharacter.cs b/OpenSim/Region/Physics/OdePlugin/ODECharacter.cs
index 8397eb4..1b1c44a 100644
--- a/OpenSim/Region/Physics/OdePlugin/ODECharacter.cs
+++ b/OpenSim/Region/Physics/OdePlugin/ODECharacter.cs
@@ -1261,14 +1261,20 @@ namespace OpenSim.Region.Physics.OdePlugin
         {
             m_requestedUpdateFrequency = ms;
             m_eventsubscription = ms;
-            CollisionEventsThisFrame.Clear();
+
+            // Don't clear collision event reporting here.  This is called directly from scene code and so can lead
+            // to a race condition with the simulate loop
+
             _parent_scene.AddCollisionEventReporting(this);
         }
 
         public override void UnSubscribeEvents()
         {
             CollisionEventsThisFrame.Clear();
-            _parent_scene.RemoveCollisionEventReporting(this);
+
+            // Don't clear collision event reporting here.  This is called directly from scene code and so can lead
+            // to a race condition with the simulate loop
+            
             m_requestedUpdateFrequency = 0;
             m_eventsubscription = 0;
         }
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