"make -j32 check TESTS=-j32" occasionally fails on rubygems/specification
This only happens occasionally, maybe 1 out of 10 times during "make check",
so it's probably a bug somewhere with GC.
I'll try to reproduce without parallel tests (could take a while).
It seems to reproduce more easily on slower machine.
I initially thought it was a bug in cachelined, but I can also reproduce it with plain trunk.
block in _resort!': undefined methodname' for nil:NilClass (NoMethodError)
Some worker was crashed. It seems ruby interpreter's bug
or, a bug of test/unit/parallel.rb. try again without -j