From b58244ac26f3fa970863c2fc713de3368cba3e7f Mon Sep 17 00:00:00 2001
From: fredzio <chardon.frederic@gmail.com>
Date: Fri, 26 Mar 2021 23:45:56 +0100
Subject: [PATCH] Guard the Bullet drawing method with a read lock on the
 btCollisionWorld. It closes a race on the collision shapes coordinates.

---
 apps/openmw/mwphysics/mtphysics.cpp     | 10 +++++++++-
 apps/openmw/mwphysics/mtphysics.hpp     |  9 ++++++++-
 apps/openmw/mwphysics/physicssystem.cpp |  4 ++--
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/apps/openmw/mwphysics/mtphysics.cpp b/apps/openmw/mwphysics/mtphysics.cpp
index 209c5aa653..4be8b2396f 100644
--- a/apps/openmw/mwphysics/mtphysics.cpp
+++ b/apps/openmw/mwphysics/mtphysics.cpp
@@ -9,6 +9,7 @@
 #include "components/settings/settings.hpp"
 #include "../mwmechanics/actorutil.hpp"
 #include "../mwmechanics/movement.hpp"
+#include "../mwrender/bulletdebugdraw.hpp"
 #include "../mwworld/class.hpp"
 #include "../mwworld/player.hpp"
 
@@ -137,11 +138,12 @@ namespace
 
 namespace MWPhysics
 {
-    PhysicsTaskScheduler::PhysicsTaskScheduler(float physicsDt, btCollisionWorld *collisionWorld)
+    PhysicsTaskScheduler::PhysicsTaskScheduler(float physicsDt, btCollisionWorld *collisionWorld, MWRender::DebugDrawer* debugDrawer)
           : mDefaultPhysicsDt(physicsDt)
           , mPhysicsDt(physicsDt)
           , mTimeAccum(0.f)
           , mCollisionWorld(collisionWorld)
+          , mDebugDrawer(debugDrawer)
           , mNumJobs(0)
           , mRemainingSteps(0)
           , mLOSCacheExpiry(Settings::Manager::getInt("lineofsight keep inactive cache", "Physics"))
@@ -626,4 +628,10 @@ namespace MWPhysics
         mTimeBegin = mTimer->tick();
         mFrameNumber = frameNumber;
     }
+
+    void PhysicsTaskScheduler::debugDraw()
+    {
+        std::shared_lock lock(mCollisionWorldMutex);
+        mDebugDrawer->step();
+    }
 }
diff --git a/apps/openmw/mwphysics/mtphysics.hpp b/apps/openmw/mwphysics/mtphysics.hpp
index 22cab3241d..6d2c392c09 100644
--- a/apps/openmw/mwphysics/mtphysics.hpp
+++ b/apps/openmw/mwphysics/mtphysics.hpp
@@ -20,12 +20,17 @@ namespace Misc
     class Barrier;
 }
 
+namespace MWRender
+{
+    class DebugDrawer;
+}
+
 namespace MWPhysics
 {
     class PhysicsTaskScheduler
     {
         public:
-            PhysicsTaskScheduler(float physicsDt, btCollisionWorld* collisionWorld);
+            PhysicsTaskScheduler(float physicsDt, btCollisionWorld* collisionWorld, MWRender::DebugDrawer* debugDrawer);
             ~PhysicsTaskScheduler();
 
             /// @brief move actors taking into account desired movements and collisions
@@ -49,6 +54,7 @@ namespace MWPhysics
             void removeCollisionObject(btCollisionObject* collisionObject);
             void updateSingleAabb(std::weak_ptr<PtrHolder> ptr, bool immediate=false);
             bool getLineOfSight(const std::weak_ptr<Actor>& actor1, const std::weak_ptr<Actor>& actor2);
+            void debugDraw();
 
         private:
             void syncComputation();
@@ -68,6 +74,7 @@ namespace MWPhysics
             float mPhysicsDt;
             float mTimeAccum;
             btCollisionWorld* mCollisionWorld;
+            MWRender::DebugDrawer* mDebugDrawer;
             std::vector<LOSRequest> mLOSCache;
             std::set<std::weak_ptr<PtrHolder>, std::owner_less<std::weak_ptr<PtrHolder>>> mUpdateAabb;
 
diff --git a/apps/openmw/mwphysics/physicssystem.cpp b/apps/openmw/mwphysics/physicssystem.cpp
index f93ffe76d8..ac8dd92f86 100644
--- a/apps/openmw/mwphysics/physicssystem.cpp
+++ b/apps/openmw/mwphysics/physicssystem.cpp
@@ -97,8 +97,8 @@ namespace MWPhysics
             }
         }
 
-        mTaskScheduler = std::make_unique<PhysicsTaskScheduler>(mPhysicsDt, mCollisionWorld.get());
         mDebugDrawer = std::make_unique<MWRender::DebugDrawer>(mParentNode, mCollisionWorld.get(), mDebugDrawEnabled);
+        mTaskScheduler = std::make_unique<PhysicsTaskScheduler>(mPhysicsDt, mCollisionWorld.get(), mDebugDrawer.get());
     }
 
     PhysicsSystem::~PhysicsSystem()
@@ -827,7 +827,7 @@ namespace MWPhysics
     void PhysicsSystem::debugDraw()
     {
         if (mDebugDrawEnabled)
-            mDebugDrawer->step();
+            mTaskScheduler->debugDraw();
     }
 
     bool PhysicsSystem::isActorStandingOn(const MWWorld::Ptr &actor, const MWWorld::ConstPtr &object) const