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.
When configured with --enable-partial-static (default on), only the
availability of static libraries were checked. Some platform only
package dynamic libs. If the static library is not found, fall back on
trying the dynamic one.
Add jemalloc as an alternative malloc implementation for the Verilator
binary. When both tcmalloc and jemalloc are available, jemalloc is
preferred due to its better performance on RTLMeter.
The new --enable-jemalloc flag (default=check) mirrors the existing
--enable-tcmalloc behavior: auto-detected at configure time, supports
both static and dynamic linking, and is disabled when --enable-dev-asan
is active.
Lately ccache was mostly missing when using clang. Add '-Xclang
-fno-pch-timestamp' as recommended in the ccache manual. This indeed
fixes the caching.
Geza Lore
Wilson Snyder
Matthew Ballance
Yangyu Chen
Geza Lore
Nathan Graybeal