From: eregontp@... Date: 2021-02-01T19:27:05+00:00 Subject: [ruby-core:102371] [Ruby master Feature#17592] Ractor should allowing reading shareable class instance variables Issue #17592 has been updated by Eregon (Benoit Daloze). To be more precise, and looking at the source, currently there is no synchronization for module ivars, only a check that only the main Ractor can access them: https://github.com/ruby/ruby/blob/5803ac1c734568837d2010bd38f122ba24cbae2b/variable.c#L906-L913 The fast path for the "ivar set" bytecode already doesn't handle T_MODULE/T_CLASS: https://github.com/ruby/ruby/blob/5803ac1c734568837d2010bd38f122ba24cbae2b/vm_insnhelper.c#L1250-L1253 And it ends up here which has the Module-specific logic: https://github.com/ruby/ruby/blob/5803ac1c734568837d2010bd38f122ba24cbae2b/variable.c#L1480-L1484 Other state like constants and methods already have synchronization, e.g., https://github.com/ruby/ruby/blob/5803ac1c734568837d2010bd38f122ba24cbae2b/variable.c#L3621-L3625 ---------------------------------------- Feature #17592: Ractor should allowing reading shareable class instance variables https://bugs.ruby-lang.org/issues/17592#change-90231 * Author: marcandre (Marc-Andre Lafortune) * Status: Open * Priority: Normal * Assignee: ko1 (Koichi Sasada) ---------------------------------------- It would be very helpful if Ractor was allowing reading class instance variables from non-main Ractor. Currently is raises an IsolationError: ```ruby module Foo singleton_class.attr_accessor :config Foo.config = {example: 42}.freeze end Ractor.new { p Foo.config } # => IsolationError ``` This limitation makes it challenging to have an efficient way to store general configs, i.e. global data that mutated a few times when resources get loaded but it immutable afterwards, and needs to be read all the time. Currently the only way to do this is to use a constant and use `remove_const` + `const_set` (which can not be made atomic easily). I think that allowing reading only may be the best solution to avoid any race condition, e.g. two different Ractors that call `@counter += 1`. The only 3 scenarios I see here are: 0) declare the constant hack the official way to store config-style data 1) allow reading of instance variables for shareable objects (as long as the data is shareable) 2) allow read-write I prefer 1) -- https://bugs.ruby-lang.org/ Unsubscribe: