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`)
Change default debug build to use -O0 instead of -Og as the latter is
still not great debugging experience. Use -Og -gz, plus the new -ggdb1,
which together significantly cut down debug info size, to save CI cache
space, while still enabling -gdbbt tests to work.
Cache key isolation: Include the build flavour (ccwarn/asan/gcov) in the
build ccache key, so the coverage (gcov), asan, and RTLMeter
(ccwarn-off) configurations no longer share and thrash the single
'<runs-on>-<cc>' bucket, nor warm-start from each other's (near-useless)
caches.
Prune stale entries instead of a fixed size cap: After building/testing,
evict ccache entries this run did not touch (--evict-older-than, based
on the run's own duration). This bounds the saved cache to the current
working set, so CCACHE_MAXSIZE and CCACHE_LIMIT_MULTIPLE are no longer
needed and are removed (ccache falls back to its 5G default ceiling, but
is realistically much smaller).
ccache configuration:
- Drop CCACHE_COMPRESS (already the default in ccache 4.x).
- Add CCACHE_COMPILERCHECK=content, so a changed compiler mtime on a rebuilt
ephemeral runner image does not invalidate the whole restored cache.
- Hoist all ccache-related variables (CACHE_BASE_KEY, CCACHE_*, CXX) to the
workflow-level env.
Remove dead ccache scaffolding:
- reusable-lint-py: the job never compiles or caches; drop its ccache env.
- reusable-rtlmeter-run: remove the disabled persistent-cache step and its
storage variables; keep CCACHE_DISABLE=1, since caching must stay off to
keep RTLMeter timings representative.
Store test job ccache as artifacts for reuse
Yilou Wang
Igor Zaworski
Marco Bartoli
Jeffrey Song
Nick Brereton
Geza Lore
Yogish Sekhar
Wilson Snyder
Artur Bieniek
Kornel Uriasz
Adam Kostrzewski
github action
Jaeuk Lee
Patrick Creighton
Jakub Michalski
Matthew Ballance
dependabot[bot]