[ruby-core:102115] [Ruby master Bug#17543] Ractor isolation broken by `self` in shareable proc

Issue #17543 has been updated by Eregon (Benoit Daloze).


marcandre (Marc-Andre Lafortune) wrote in #note-4:
> Note that they are *not* treated the same way. `Ractor.new{}` forbids any reference to outside variables, while `make_shareable(proc)` allows it as long as the values are themselves shareable.

Yes, Ractor.new{} seems special, but actually it seems like the Ractor.make_shareable() semantics would be more useful, that way some frozen data could be passed directly in the new Ractor.

> I agree that is the most obvious, but that makes `Ractor.make_shareable(-> { puts "hello" })` fail, which is far from being useful.

In my view, `Ractor.make_shareable` should deeply freeze/share some object graph rooted by some initial object.
So I think it should freeze captures and self for a Proc.
If it's needed to e.g. `Ractor.make_shareable(self); o = Ractor.make_shareable(Object.new); Ractor.make_shareable(-> { p o; ... })`, it feels so redundant.
I think `Ractor.make_shareable` should always succeed, except if it sees a truly unshareable object (e.g., a Mutex).

----------------------------------------
Bug #17543: Ractor isolation broken by `self` in shareable proc
https://bugs.ruby-lang.org/issues/17543#change-89971

* Author: marcandre (Marc-Andre Lafortune)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* ruby -v: 3.0.0p0
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
Discussing with @MaxLap we realized that the `self` in a shareable proc is not properly isolated:

```
class Foo
  attr_accessor :x

  def pr
    Ractor.make_shareable(Proc.new { self })
  end
end

f = Foo.new
f.x = [1, 2, 3]
Ractor.new(f.pr) { |pr| pr.call.x << :oops }
p f.x # => [1, 2, 3, :oops]
```

If the `self` refers to a shareable object then it's fine, but for non-shareable objects it has to be reset to `nil` or to a global shareable object that would have an instructive `inspect`.

```ruby
Ractor::DETACHED_SELF = Object.new
def << Ractor::DETACHED_SELF
  def inspect
    '<#detached self>'
  end
  alias to_s inspect
end
Ractor::DETACHED_SELF.freeze
```




-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:[e-mail]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>