[ruby-core:37133] Re: [Ruby 1.9-Feature#4328][Open] export rb_thread_call_with_gvl()

SASADA Koichi <[e-mail]> wrote:
> Hi,
> 
> (2011/06/14 14:56), Eric Wong wrote:
> > I think the assumptions and requirements for calling this function are
> > reasonable (and best of all, well-documented).  The API isn't difficult
> > to me and the documentation is clear as to what is safe and what is not.
> > 
> > Threading APIs can always be tricky, but I think the C API for GVL is
> > a good one.
> 
> I think a requirement "caller should be a Ruby thread" is difficult.
> 
> For example, external library calls registered callback in other native
> threads (not ruby threads).  If C extension programmer does not know
> such specification of external library, (s)he would make and register a
> callback function using this API.  Finally, the Ruby code run on non
> Ruby code.  I'm afraid of such situation.
> 
> To avoid this situation, one solution is checking "the thread is really
> Ruby thread or not" when rb_thread_call_with_gvl() is called.  This
> check was already introduced into this API.

Yup, I like this check.  Most C libraries I've used with do not start
threads internally, so I don't think it's a big problem.  I always
review code to all libraries I use so I don't hit surprises like this,
though many programmers do not.

> Other solution is making the non-ruby thread to ruby thread.  I feel
> necessity of such API, however, I need more consideration to implement it.

This would be interesting, I look forward to it.

> To limit to usage of rb_thread_call_with_gvl() as "only blocking
> function", former (current) solution is enough.

Yes, I strongly believe rb_thread_call_with_gvl() is useful for many
general cases already.

> >> BTW, the naming "_with_gvl" is reasonable for native English speakers?
> > 
> > Yes.
> 
> Thank you.  We keep this name.
> 
> Please discuss with me about naming of another "_with_gvl".
> In gc.c, there are other "_with_gvl" functions.
> 
> - negative_size_allocation_error_with_gvl
> - gc_with_gvl
> 
> The functions are callback of rb_thread_call_with_gvl().
> 
> The meaning of "with_gvl" in rb_thread_call_with_gvl() is "acquire GVL
> and call passed function".  However, above two functions use then name
> "*_with_gvl" in different meaning (run in GVL acquired situation, only).

I agree, "*_with_gvl" having two meanings is confusing.

> Do you have good naming idea for them?

Not sure, maybe "*_in_gvl"?

Or "ingvl_*" as prefix since io.c already uses "maygvl_" and "nogvl_" as
prefixes.

Maybe we should avoid "gvl" in the name completely for these two
functions.  Most Ruby functions need GVL anyways and they don't have
"gvl" in the name.

-- 
Eric Wong