MongoDB | 2612132

Info

Using mongo::Mutex instead of raw std::mutex appears to inhibit TSAN's ability to detect lock order inversions. We should either fix the issue or only run TSAN on --enable-diagnostic-latches=off variants. Reproducer attached in 'steps to reproduce'.

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Steps to Reproduce

Add a unittest like this that contains a simple lock-order-inversion: +TEST(GeorgeTest, LockOrderInversion) { +#ifndef MONGO_CONFIG_USE_RAW_LATCHES +std::cout << "YYYY Using mongo::Mutex" << std::endl; +#else +std::cout << "YYYY Using raw std::mutex" << std::endl; +#endif + LOGV2(24148, "XXXX IN George Test"); + auto m1 = MONGO_MAKE_LATCH("m1"); + auto m2 = MONGO_MAKE_LATCH("m2"); + stdx::thread t1([&] { + stdx::lock_guard lg(m1); + LOGV2(24148, "XXXX Got m1 t1"); + stdx::lock_guard lg2(m2); + LOGV2(24148, "XXXX Got m2 t1"); + + }); + + t1.join(); + stdx::thread t2([&] { + stdx::lock_guard lg(m2); + LOGV2(24148, "XXXX Got m2 t2"); + stdx::lock_guard lg2(m1); + LOGV2(24148, "XXXX Got m1 t2"); + + }); + t2.join(); + +} + Then, create two TSAN compile configurations, one with and one without diagnostic latches: ./buildscripts/scons.py --dbg=on --opt=on --use-libunwind=off --link-model=dynamic --variables-files=./etc/scons/mongodbtoolchain_stable_clang.vars --ninja ICECC=icecc CCACHE=ccache --sanitize=thread --allocator=system --use-diagnostic-latches=on NINJA_PREFIX=tsan-latches and ./buildscripts/scons.py --dbg=on --opt=on --use-libunwind=off --link-model=dynamic --variables-files=./etc/scons/mongodbtoolchain_stable_clang.vars --ninja ICECC=icecc CCACHE=ccache --sanitize=thread --allocator=system NINJA_PREFIX=tsan Then, run the test under each configuration. On my VWS, with the no-diagnostic-latches variant/raw std::mutex, TSAN determinsitically identifies the data race and aborts the program. With the mongo::Mutex/diagnostic-latches, running the test multiple times produces only success outputs and TSAN does not report any issues.