From: SASADA Koichi <ko1@...>
Date: 2011-06-23T16:56:54+09:00
Subject: Re: Ruby embed called from a pthread

Hi,

(2011/06/23 16:37), Luiz Angelo Daros de Luca wrote:
> Currently, my initialization (ruby_init, RUBY_INIT_STACK,...) run
> inside the main thread and all following calls works with no problem.
> However, when the first non-main thread GC, it segfalts. Is it allowed
> to call ruby from a child thread?

No.

Ruby's GC marks machine stack of (registered) all threads.  However,
(maybe) your child thread is not registered.

Now, there are no way to register the other thread.


> I debugged and what I think that I noticed is that GC scans from
> current thread stack to the machine "stack end". For the main thread,
> this is OK. However, when it is a child thread, between the child
> stack and the main stack, there is some unallocated memory, which
> segfalts on access. Something like this:
> 
> [child_stack_start...child_stack_end] unallocated
> [main_stack_start...main_stack_end]
> 
> If I disable GC, it runs flawless. Is it a possible solution to
> disable GC when running a method inside a pthread and reenable it when
> main thread calls a method? Would it miss (not free) some objects
> inside pthread stack?
> 
> One good solution would be some workarround in order to allow calls
> and GC from any thread as the one I proposed. Is it possible?
>
> Another great solution would be to allow all ruby stuck exclusively
> inside a pthread. This way, I could isolate ruby in a dedicated
> pthread with a dedicated stack. All other threads would use ruby
> though this thread. However, my current knowledge tells me that ruby
> must live inside the main thread (it depends on the main thread stack
> end address). Am I right? Is something like running ruby from a single
> pthread possible?
> 
> The best solution would be to allow ruby initialization inside any
> pthread and ruby calls from any pthread. I guess ruby is too far away
> from this one ;-)
> 
> I was hoping that 1.9.x would help me in any way as it uses pthreads
> for ruby threads but I noticed no difference.
> 
> I really searched hard to find a solution before getting to the list
> but nothing helped. Maybe ruby_bind_stack patch could help but I don't
> think it would get upstream too soon.

One simple solution is making Ruby thread and communicate with queue or
something thread-safe data structure.

I think you can run Ruby interpreter in non-main thread.  However, only
one interpreter.

-- 
// SASADA Koichi at atdot dot net