[TSAN] Fix PythonEngine data-race-on-vptr. (#56808)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56808
For information about data-race-on-vptr in general, see https://www.internalfb.com/intern/wiki/TSAN/Common_Concurrency_Mistakes/Stopping_a_Thread_in_Destructor/
Engine::~Engine() was previously tasked with stopping the threads. This causes a data race on the object's vptr when PythonEngine is being destructed. This fixes the data race by making ~PythonEngine trigger the thread stopping before going down to the base class's destructor.
Test Plan:
Many tests are affected, but here's one example:
buck test mode/dev-tsan -c fbcode.tsan_strict_mode=true //oculus/research/orcoptics/deep_learning/srg_nn/tests:test_grating_net -- 'test_train (oculus.research.orcoptics.deep_learning.srg_nn.tests.test_grating_net.TestGratingNet)' --run-disabled
Reviewed By: walterddr, albanD
Differential Revision: D27972384
fbshipit-source-id: 8b70fec8d9326497c591a2777b355ea590a85082
