From dcd425a165802880321ea23a439c1854495c1159 Mon Sep 17 00:00:00 2001
From: "Anthony J. Thibault" <tony@highfidelity.io>
Date: Tue, 4 Oct 2016 10:56:44 -0700
Subject: [PATCH] Add an entityTree lock around the
 AvatarHoldAction::lateAvatarUpdate calls

---
 interface/src/avatar/MyAvatar.cpp | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/interface/src/avatar/MyAvatar.cpp b/interface/src/avatar/MyAvatar.cpp
index 20c4f41568..19346e51db 100644
--- a/interface/src/avatar/MyAvatar.cpp
+++ b/interface/src/avatar/MyAvatar.cpp
@@ -2280,8 +2280,18 @@ void MyAvatar::removeHoldAction(AvatarActionHold* holdAction) {
 }
 
 void MyAvatar::updateHoldActions(const AnimPose& prePhysicsPose, const AnimPose& postUpdatePose) {
-    std::lock_guard<std::mutex> guard(_holdActionsMutex);
-    for (auto& holdAction : _holdActions) {
-        holdAction->lateAvatarUpdate(prePhysicsPose, postUpdatePose);
+    EntityTreeRenderer* entityTreeRenderer = qApp->getEntities();
+    EntityTreePointer entityTree = entityTreeRenderer ? entityTreeRenderer->getTree() : nullptr;
+    if (entityTree) {
+        // to prevent actions from adding or removing themselves from the _holdActions vector
+        // while we are iterating, we need to enter a critical section.
+        std::lock_guard<std::mutex> guard(_holdActionsMutex);
+
+        // lateAvatarUpdate will modify entity position & orientation, so we need an entity write lock
+        entityTree->withWriteLock([&] {
+            for (auto& holdAction : _holdActions) {
+                holdAction->lateAvatarUpdate(prePhysicsPose, postUpdatePose);
+            }
+        });
     }
 }