Possible race condition with PathTracer and tbb #571
Description
Running into a segfault with vtk's TestPathTracerMaterials sometimes.
Stack trace
Thread 14 "vtkRenderingRay" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffc6ffb6c0 (LWP 243266)]
FresnelConductorSpectral_create___un_3C_s_5B_unShadingContext_5D__3E_REFCunf_3C_8_3E_REFCunf_3C_8_3E__avx512skx (ctx=0x7fffc6fb45c0, eta=..., k=...) at /home/sankhesh/Projects/ospray/ospray/modules/cpu/render/bsdfs/Fresnel.ih:310
310 self->eta = eta;
(gdb) bt
#0 FresnelConductorSpectral_create___un_3C_s_5B_unShadingContext_5D__3E_REFCunf_3C_8_3E_REFCunf_3C_8_3E__avx512skx (ctx=0x7fffc6fb45c0, eta=..., k=...) at /home/sankhesh/Projects/ospray/ospray/modules/cpu/render/bsdfs/Fresnel.ih:310
#1 Metal_getBSDF___un_3C_s_5B__c_unMaterial_5D__3E_un_3C_s_5B_unShadingContext_5D__3E_REFs_5B__c_vyDifferentialGeometry_5D_REFs_5B__c_vyRay_5D_REFs_5B__c_vyMedium_5D__avx512skx (super=0x5555568304b0, ctx=0x7fffc6fb45c0, dg=..., __anon_parameter_3=..., __anon_parameter_4=...) at Metal.ispc:29
#2 0x00007fffeaaf8c36 in samplePath___REFs_5B__c_vyPathContext_5D_REFs_5B_vyPathState_5D_REFs_5B_vyRay_5D_REFs_5B_vyScreenSample_5D_REFs_5B__c_unFeatureFlagsHandler_5D__avx512skx (pathContext=..., pathState=..., ray=..., sample=..., ffh=...) at PathSampler.ispc:276
#3 0x00007fffeaabad11 in PathTraceIntegrator_Li___un_3C_s_5B__c_unPathTracer_5D__3E_un_3C_s_5B__c_unWorld_5D__3E_REFs_5B__c_vyvec2f_5D_REFs_5B_vyRay_5D_un_3C_s_5B_vyLDSampler_5D__3E_un_3C_s_5B_vyRandomSampler_5D__3E_REFs_5B__c_unFeatureFlagsHandler_5D__avx512skx (self=0x5555568308f0, world=0x555557810560, ldSampler=<optimized out>, randomSampler=<optimized out>, ffh=..., pixel=..., ray=...) at PathTracer.ispc:92
#4 PathTracer_renderPixel___un_3C_s_5B_unPathTracer_5D__3E_un_3C_s_5B_unFrameBuffer_5D__3E_un_3C_s_5B_unCamera_5D__3E_un_3C_s_5B_unWorld_5D__3E_CvyuCvyuCvyuREFs_5B__c_unFeatureFlagsHandler_5D__avx512skx (self=0x5555568308f0, fb=0x555556d73c30, camera=0x5555568470f0, world=0x555557810560, ix=..., iy=..., accumID=..., ffh=...) at PathTracer.ispc:158
#5 0x00007fffeaabb420 in PathTracer_renderTask___un_3C_s_5B_unRenderer_5D__3E_un_3C_s_5B_unFrameBuffer_5D__3E_un_3C_s_5B_unCamera_5D__3E_un_3C_s_5B_unWorld_5D__3E_un_3C_Cunu_3E_REFs_5B__c_unFeatureFlagsHandler_5D__avx512skx (_self=<optimized out>, fb=0x555556d73c30, camera=0x5555568470f0, world=0x555557810560, taskIDs=<optimized out>, ffh=...) at PathTracer.ispc:220
#6 0x00007fffeafcc708 in operator() (__closure=0x7fffc6bf84b0, i=3210) at /home/sankhesh/Projects/ospray/ospray/modules/cpu/ispc_tasksys.cpp:57
#7 0x00007fffeafcd6d8 in tbb::detail::d1::parallel_for_body_wrapper<rkcommon::ISPCLaunch(void**, void*, void*, int, int, int)::<lambda(size_t)>, long unsigned int>::operator()(const tbb::detail::d1::blocked_range<unsigned long> &) const (this=0x7fffde5a2e58, r=...) at /home/sankhesh/Projects/ospray/install/include/oneapi/tbb/parallel_for.h:211
#8 0x00007fffeafcd4cf in tbb::detail::d1::start_for<tbb::detail::d1::blocked_range<long unsigned int>, tbb::detail::d1::parallel_for_body_wrapper<rkcommon::ISPCLaunch(void**, void*, void*, int, int, int)::<lambda(size_t)>, long unsigned int>, const tbb::detail::d1::auto_partitioner>::run_body(tbb::detail::d1::blocked_range<unsigned long> &) (this=0x7fffde5a2e00, r=...)
at /home/sankhesh/Projects/ospray/install/include/oneapi/tbb/parallel_for.h:122
#9 0x00007fffeafcd2cd in tbb::detail::d1::dynamic_grainsize_mode<tbb::detail::d1::adaptive_mode<tbb::detail::d1::auto_partition_type> >::work_balance<tbb::detail::d1::start_for<tbb::detail::d1::blocked_range<long unsigned int>, tbb::detail::d1::parallel_for_body_wrapper<rkcommon::ISPCLaunch(void**, void*, void*, int, int, int)::<lambda(size_t)>, long unsigned int>, const tbb::detail::d1::auto_partitioner>, tbb::detail::d1::blocked_range<long unsigned int> >(tbb::detail::d1::start_for<tbb::detail::d1::blocked_range<long unsigned int>, tbb::detail::d1::parallel_for_body_wrapper<rkcommon::ISPCLaunch(void**, void*, void*, int, int, int)::<lambda(size_t)>, long unsigned int>, const tbb::detail::d1::auto_partitioner> &, tbb::detail::d1::blocked_range<unsigned long> &, tbb::detail::d1::execution_data &) (this=0x7fffde5a2e78, start=..., range=...,
ed=...) at /home/sankhesh/Projects/ospray/install/include/oneapi/tbb/partitioner.h:450
#10 0x00007fffeafcd001 in tbb::detail::d1::partition_type_base<tbb::detail::d1::auto_partition_type>::execute<tbb::detail::d1::start_for<tbb::detail::d1::blocked_range<long unsigned int>, tbb::detail::d1::parallel_for_body_wrapper<rkcommon::ISPCLaunch(void**, void*, void*, int, int, int)::<lambda(size_t)>, long unsigned int>, const tbb::detail::d1::auto_partitioner>, tbb::detail::d1::blocked_range<long unsigned int> >(tbb::detail::d1::start_for<tbb::detail::d1::blocked_range<long unsigned int>, tbb::detail::d1::parallel_for_body_wrapper<rkcommon::ISPCLaunch(void**, void*, void*, int, int, int)::<lambda(size_t)>, long unsigned int>, const tbb::detail::d1::auto_partitioner> &, tbb::detail::d1::blocked_range<unsigned long> &, tbb::detail::d1::execution_data &) (this=0x7fffde5a2e78, start=..., range=..., ed=...)
at /home/sankhesh/Projects/ospray/install/include/oneapi/tbb/partitioner.h:289
#11 0x00007fffeafcce1c in tbb::detail::d1::start_for<tbb::detail::d1::blocked_range<long unsigned int>, tbb::detail::d1::parallel_for_body_wrapper<rkcommon::ISPCLaunch(void**, void*, void*, int, int, int)::<lambda(size_t)>, long unsigned int>, const tbb::detail::d1::auto_partitioner>::execute(tbb::detail::d1::execution_data &) (this=0x7fffde5a2e00, ed=...)
at /home/sankhesh/Projects/ospray/install/include/oneapi/tbb/parallel_for.h:175
#12 0x00007fffec63b15e in tbb::detail::r1::task_dispatcher::local_wait_for_all<false, tbb::detail::r1::outermost_worker_waiter> (this=0x7fffde30cf00, t=0x7fffde5a2e00, waiter=...) at /localdisk/ci/runner007/intel-innersource/001/_work/libraries.threading.infrastructure.onetbb-ci/libraries.threading.infrastructure.onetbb-ci/onetbb_source_code/src/tbb/task_dispatcher.h:322
#13 0x00007fffec61bd4b in tbb::detail::r1::task_dispatcher::local_wait_for_all<tbb::detail::r1::outermost_worker_waiter> (this=0x5555568304b0, t=<optimized out>, waiter=...) at /localdisk/ci/runner007/intel-innersource/001/_work/libraries.threading.infrastructure.onetbb-ci/libraries.threading.infrastructure.onetbb-ci/onetbb_source_code/src/tbb/task_dispatcher.h:458
#14 tbb::detail::r1::arena::process (this=0x5555568304b0, tls=...) at /localdisk/ci/runner007/intel-innersource/001/_work/libraries.threading.infrastructure.onetbb-ci/libraries.threading.infrastructure.onetbb-ci/onetbb_source_code/src/tbb/arena.cpp:137
#15 0x00007fffec61b446 in tbb::detail::r1::market::process (this=0x5555568304b0, j=...) at /localdisk/ci/runner007/intel-innersource/001/_work/libraries.threading.infrastructure.onetbb-ci/libraries.threading.infrastructure.onetbb-ci/onetbb_source_code/src/tbb/market.cpp:599
#16 0x00007fffec6207dc in tbb::detail::r1::rml::private_worker::run (this=0x5555568304b0) at /localdisk/ci/runner007/intel-innersource/001/_work/libraries.threading.infrastructure.onetbb-ci/libraries.threading.infrastructure.onetbb-ci/onetbb_source_code/src/tbb/private_server.cpp:271
#17 0x00007fffec620766 in tbb::detail::r1::rml::private_worker::thread_routine (arg=0x5555568304b0) at /localdisk/ci/runner007/intel-innersource/001/_work/libraries.threading.infrastructure.onetbb-ci/libraries.threading.infrastructure.onetbb-ci/onetbb_source_code/src/tbb/private_server.cpp:221
#18 0x00007ffff7c8c9eb in ?? () from /usr/lib/libc.so.6
#19 0x00007ffff7d10dfc in ?? () from /usr/lib/libc.so.6