Actor's position can be determined in 3 ways:
1/ as a result of physics simulation
2/ after a script require a relative position change (SetPos, Move)
3/ absolutely set from games mechanics event (teleport) or script
(PositionCell)
In case 1/, RefData::mPosition is updated with the physics simulation result
In case 2/, when RefData::mPosition is updated, physics simulation is informed of the change and update accordingly
In case 3/, when RefData::mPosition is updated, the physics simulation state is reset
In all 3 cases, we don't need to check the RefData::mPosition to get a
correct behaviour.
TSAN reported the following data race:
Read of size 4 at 0x7b50005b75b0 by thread T12 (mutexes: write M656173, write M84859534346343880):
#0 ESM::Position::asVec3() const /build/openmw/openmw/master2/.build/freebsd/TSAN/../../.././components/esm/defs.hpp:55:27 (openmw+0xb809d5)
#1 MWPhysics::Actor::updateWorldPosition() /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwphysics/actor.cpp:131:59 (openmw+0xb809d5)
#2 MWPhysics::Actor::setPosition(osg::Vec3f const&) /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwphysics/actor.cpp:177:5 (openmw+0xb809d5)
#3 MWPhysics::PhysicsTaskScheduler::updateActorsPositions() /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwphysics/mtphysics.cpp:524:28 (openmw+0xb91ac0)
#4 MWPhysics::PhysicsTaskScheduler::afterPostStep() /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwphysics/mtphysics.cpp:614:13 (openmw+0xb915e7)
#5 MWPhysics::PhysicsTaskScheduler::worker()::$_5::operator()() const /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwphysics/mtphysics.cpp:498:45 (openmw+0xb915e7)
#6 void Misc::Barrier::wait<MWPhysics::PhysicsTaskScheduler::worker()::$_5>(MWPhysics::PhysicsTaskScheduler::worker()::$_5&&) /build/openmw/openmw/master2/.build/freebsd/TSAN/../../.././components/misc/barrier.hpp:30:21 (openmw+0xb915e7)
#7 MWPhysics::PhysicsTaskScheduler::worker() /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwphysics/mtphysics.cpp:498:31 (openmw+0xb915e7)
#8 MWPhysics::PhysicsTaskScheduler::PhysicsTaskScheduler(float, btCollisionWorld*, MWRender::DebugDrawer*)::$_0::operator()() const /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwphysics/mtphysics.cpp:162:45 (openmw+0xb92630)
#9 decltype(std::__1::forward<MWPhysics::PhysicsTaskScheduler::PhysicsTaskScheduler(float, btCollisionWorld*, MWRender::DebugDrawer*)::$_0>(fp)()) std::__1::__invoke<MWPhysics::PhysicsTaskScheduler::PhysicsTaskScheduler(float, btCollisionWorld*, MWRender::DebugDrawer*)::$_0>(MWPhysics::PhysicsTaskScheduler::PhysicsTaskScheduler(float, btCollisionWorld*, MWRender::DebugDrawer*)::$_0&&) /usr/include/c++/v1/type_traits:3899:1 (openmw+0xb92630)
#10 void std::__1::__thread_execute<std::__1::unique_ptr<std::__1::__thread_struct, std::__1::default_delete<std::__1::__thread_struct> >, MWPhysics::PhysicsTaskScheduler::PhysicsTaskScheduler(float, btCollisionWorld*, MWRender::DebugDrawer*)::$_0>(std::__1::tuple<std::__1::unique_ptr<std::__1::__thread_struct, std::__1::default_delete<std::__1::__thread_struct> >, MWPhysics::PhysicsTaskScheduler::PhysicsTaskScheduler(float, btCollisionWorld*, MWRender::DebugDrawer*)::$_0>&, std::__1::__tuple_indices<>) /usr/include/c++/v1/thread:280:5 (openmw+0xb92630)
#11 void* std::__1::__thread_proxy<std::__1::tuple<std::__1::unique_ptr<std::__1::__thread_struct, std::__1::default_delete<std::__1::__thread_struct> >, MWPhysics::PhysicsTaskScheduler::PhysicsTaskScheduler(float, btCollisionWorld*, MWRender::DebugDrawer*)::$_0> >(void*) /usr/include/c++/v1/thread:291:5 (openmw+0xb92630)
Previous write of size 8 at 0x7b50005b75b0 by main thread:
#0 memcpy /wrkdirs/usr/ports/devel/llvm-devel/work-default/llvm-project-3f6753efe1990a928ed120bd907940a9fb3e2fc3/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:827:5 (openmw+0x55a057)
#1 MWWorld::RefData::setPosition(ESM::Position const&) /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwworld/refdata.cpp:216:19 (openmw+0xa3de1c)
#2 MWWorld::World::moveObject(MWWorld::Ptr const&, MWWorld::CellStore*, float, float, float, bool) /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwworld/worldimp.cpp:1130:26 (openmw+0xa57300)
#3 MWWorld::World::moveObject(MWWorld::Ptr const&, float, float, float, bool, bool) /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwworld/worldimp.cpp:1253:16 (openmw+0xa580c8)
#4 MWWorld::World::doPhysics(float, unsigned long long, unsigned int, osg::Stats&) /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwworld/worldimp.cpp:1530:17 (openmw+0xa5af8f)
#5 MWWorld::World::updatePhysics(float, bool, unsigned long long, unsigned int, osg::Stats&) /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/mwworld/worldimp.cpp:1862:13 (openmw+0xa61a7c)
#6 OMW::Engine::frame(float) /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/engine.cpp:333:42 (openmw+0xcce9e7)
#7 OMW::Engine::go() /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/engine.cpp:935:14 (openmw+0xcd86ed)
#8 runApplication(int, char**) /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/main.cpp:296:17 (openmw+0xcbffac)
#9 wrapApplication(int (*)(int, char**), int, char**, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../components/debug/debugging.cpp:205:15 (openmw+0x1335442)
#10 main /build/openmw/openmw/master2/.build/freebsd/TSAN/../../../apps/openmw/main.cpp:308:12 (openmw+0xcc008a)
:wqa
The idea is to avoid std::map lookup for each CellRef. Instead generate a
sequence of added and removed RefNums into a vector then order them by RefNum
using a stable sort that preserves relative order of elements with the same
RefNum. RefIDs are stored in a different vector to avoid std::string move ctor
calls when swapping elements while sorting. Reversed iteration over added and
removed RefNums for each unique RefNum is an equivalent to what map-based
algorithm produces. The main benefit from sorting a vector is a data locality
that means less cache misses for each access. Reduces ESMStore::countRecords
perf cycles by 25%.