From 3d43f73a882ddcad9a79424a8f0b35d016db90bf Mon Sep 17 00:00:00 2001
From: "Anthony J. Thibault" <tony@highfidelity.io>
Date: Thu, 31 Mar 2016 17:57:20 -0700
Subject: [PATCH] Application: don't call Model::simulate on network thread.

This can cause a crash.

On startup the Application::processOctreeStats method on the network thread will call into entities entity->isReadyToComputeShape() (without a tree lock) and trigger Model::simulate.  Model is NOT thread safe.  This was leading to a single model to be initialized on two threads simultaneously.

This might be somewhat rare, I only caught it because I was running a debug build.
---
 interface/src/Application.cpp | 36 +++++++++++++++++++----------------
 interface/src/Application.h   |  2 ++
 2 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/interface/src/Application.cpp b/interface/src/Application.cpp
index ffc9b0333c..bd1a44fc76 100644
--- a/interface/src/Application.cpp
+++ b/interface/src/Application.cpp
@@ -3215,6 +3215,25 @@ void Application::update(float deltaTime) {
 
     updateLOD();
 
+    if (!_physicsEnabled && _processOctreeStatsCounter > 0) {
+
+        // process octree stats packets are sent in between full sends of a scene.
+        // We keep physics disabled until we've recieved a full scene and everything near the avatar in that
+        // scene is ready to compute its collision shape.
+
+        if (nearbyEntitiesAreReadyForPhysics()) {
+            _physicsEnabled = true;
+            getMyAvatar()->updateMotionBehaviorFromMenu();
+        } else {
+            auto characterController = getMyAvatar()->getCharacterController();
+            if (characterController) {
+                // if we have a character controller, disable it here so the avatar doesn't get stuck due to
+                // a non-loading collision hull.
+                characterController->setEnabled(false);
+            }
+        }
+    }
+
     {
         PerformanceTimer perfTimer("devices");
         DeviceTracker::updateAll();
@@ -4260,22 +4279,7 @@ int Application::processOctreeStats(ReceivedMessage& message, SharedNodePointer
         });
     });
 
-    if (!_physicsEnabled) {
-        if (nearbyEntitiesAreReadyForPhysics()) {
-            // These stats packets are sent in between full sends of a scene.
-            // We keep physics disabled until we've recieved a full scene and everything near the avatar in that
-            // scene is ready to compute its collision shape.
-            _physicsEnabled = true;
-            getMyAvatar()->updateMotionBehaviorFromMenu();
-        } else {
-            auto characterController = getMyAvatar()->getCharacterController();
-            if (characterController) {
-                // if we have a character controller, disable it here so the avatar doesn't get stuck due to
-                // a non-loading collision hull.
-                characterController->setEnabled(false);
-            }
-        }
-    }
+    _processOctreeStatsCounter++;
 
     return statsMessageLength;
 }
diff --git a/interface/src/Application.h b/interface/src/Application.h
index 31c865ad90..2512bc7918 100644
--- a/interface/src/Application.h
+++ b/interface/src/Application.h
@@ -515,6 +515,8 @@ private:
 
     std::map<void*, std::function<void()>> _preRenderLambdas;
     std::mutex _preRenderLambdasLock;
+
+    std::atomic<uint32_t> _processOctreeStatsCounter { 0 };
 };
 
 #endif // hifi_Application_h