Allocate two objects simultaneously in multi-threading

Ruby
1

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

2

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.

Elise