From: elise huard <huard.elise@...>
Date: 2011-04-29T16:27:08+09:00
Subject: Re: Allocate two objects simultaneously in multi-threading

Hi Vince,

good point, but at the moment this is not an issue, thanks to the
Global Interpreter Lock: only one Ruby thread is ever executed at the
same time.  While this is not a great situation, it will at least make
sure that such a problem will never occur.
http://en.wikipedia.org/wiki/Global_Interpreter_Lock

Elise

On Tue, Apr 26, 2011 at 7:48 AM, dot c. <dot.cyclone@gmail.com> wrote:
> I'm studying Ruby 1.9.2 source code. Some issues about simultaneity.
>
> Object.new will call following funtion to allocate space from heap:
> static VALUE  rb_class_allocate_instance(VALUE klass)
> {
>    NEWOBJ(obj, struct RObject);
>    OBJSETUP(obj, klass, T_OBJECT);
>    return (VALUE)obj;
> }
>
> #define NEWOBJ(obj,type) type *obj = (type*)rb_newobj()
>
> VALUE
> rb_newobj(void)
> {
>    if (during_gc) {
>  dont_gc = 1;
>  during_gc = 0;
>  rb_bug("object allocation during garbage collection phase");
>    }
>
>    return rb_newobj_from_heap(objspace);
> }
>
> static VALUE
> rb_newobj_from_heap(rb_objspace_t *objspace)
> {
>    VALUE obj;
>
>    if ((ruby_gc_stress && !ruby_disable_gc_stress) || !freelist) {
>  if (!heaps_increment(objspace) && !garbage_collect(objspace)) {
>      during_gc = 0;
>      rb_memerror();
>  }
>    }
>
>    obj = (VALUE)freelist;
>    freelist = freelist->as.free.next;
>
>    MEMZERO((void*)obj, RVALUE, 1);
>
>    return obj;
> }
>
>
>
> I doesn’t see any code(in rb_newobj_from_heap), which is to make sure
> only one thread can call the function rb_newobj at the same time in
> multi-threading.
> The issue found in many other places. It seems that there can be only
> one thread in Ruby. But class Thread can create another thread.
>
> x = Thread.new {
> for a in 1..999
>  Object.new
> end
> }
> for b in 1..999
>  Object.new
> End
>
> Please tell me if some other mechanism solve the simultaneity issue.
> Thanks Vince
>
> --
> Posted via http://www.ruby-forum.com/.
>