zlib and bignum both contain unblocking functions which are
async-signal-safe and do not require spawning additional
We can execute those functions directly in signal handlers
without incurring overhead of extra threads, so provide C-API
users the ability to deal with that. Other C-API users may
have similar need.
This flexible API can supercede existing uses of
rb_thread_call_without_gvl and rb_thread_call_without_gvl2 by
introducing a flags argument to control behavior.
Note: this API is NOT finalized. It needs approval from other
committers. I prefer shorter name than previous
rb_thread_call_without_gvl* functions because my eyes requires
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66712 b2dd03c8-39d4-4d8f-98ff-823fe69b080e