PR #7902 uncovered a pre-existing bug in multi-threaded scheduling,
where we can end up with an un-ordered R-W hazard in the MTask graph,
resulting in non-deterministic runtime behaviour.
This is extremely hard to actually trigger on a small example, so using
ThreadSanitizer to flag it, which can identify the race reliably.
In this patch:
- Add configure and `verilator --get-supported TSAN` to check if the
configured compiler supports ThreadSanitizer
- Add a --tsan option to the test driver.py which builds the test with
thread sanitizer (similar idea to --gdbsim).
- Add a tests.enable_tsan() method to allow turning on TSan in the test
Python file.
- Add a suppressions file that waives TSan errors in the runtime library
- Finally add `t_sched_hybrid_hazard` that demonstrates the data race
triggered after #7902. This is currently expected failing, fix later.
With the suppression, there are 17 vltmt tests failing due races in the
generated code. (Using `driver.py --vltmt --tsan --quiet -j0`)
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