Turns out the test was working by accident: we need to ensure
TSan instrumentation is not called from the fork() hook, otherwise the
tool will deadlock. Previously it worked because alloc_free_blocks() got
inlined into __tsan_test_only_on_fork(), but it cannot always be the
case.
Adding __attribute__((disable_sanitizer_instrumentation)) will prevent
TSan from instrumenting alloc_free_blocks().
Reviewed By: dvyukov
Differential Revision: https://reviews.llvm.org/D120050
Add a fork test that models what happens on Mac
where fork calls malloc/free inside of our atfork
callbacks.
Reviewed By: vitalybuka, yln
Differential Revision: https://reviews.llvm.org/D114250
