Issue #8259 has been updated by Petr Chalupa. I would like to revive this issue again and link it to related efforts to provide complete set of low-level tools for writing concurrent libraries. The aggregating issue of this effort can be found [here](https://bugs.ruby-lang.org/issues/12019). Summary can be found in this document: https://docs.google.com/document/d/1c07qfDArx0bhK9sMr24elaIUdOGudiqBhTIRALEbrYY/edit#. It suggests to use following syntax `attr :name, atomic: true`, which makes the variable `name` volatile but it also generates atomic helpers: `get_and_set_name`, `compare_and_set_name`, `compare_and_exchange_name`, `update_name`. They use referential equality for comparison. ---------------------------------------- Feature #8259: Atomic attributes accessors https://bugs.ruby-lang.org/issues/8259#change-56656 * Author: Yura Sokolov * Status: Open * Priority: Normal * Assignee: ---------------------------------------- Motivated by this gist ((<URL:https://gist.github.com/jstorimer/5298581>)) and atomic gem I propose Class.attr_atomic which will add methods for atomic swap and CAS: ```ruby class MyNode attr_accessor :item attr_atomic :successor def initialize(item, successor) @item = item @successor = successor end end node = MyNode.new(i, other_node) # attr_atomic ensures at least #{attr} reader method exists. May be, it should # be sure it does volatile access. node.successor # #{attr}_cas(old_value, new_value) do CAS: atomic compare and swap if node.successor_cas(other_node, new_node) print "there were no interleaving with other threads" end # #{attr}_swap atomically swaps value and returns old value. # It ensures that no other thread interleaves getting old value and setting # new one by cas (or other primitive if exists, like in Java 8) node.successor_swap(new_node) ``` It will be very simple for MRI cause of GIL, and it will use atomic primitives for other implementations. Note: both (({#{attr}_swap})) and (({#{attr}_cas})) should raise an error if instance variable were not explicitly set before. Example for nonblocking queue: ((<URL:https://gist.github.com/funny-falcon/5370416>)) Something similar should be proposed for Structs. May be override same method as (({Struct.attr_atomic})) Open question for reader: should (({attr_atomic :my_attr})) ensure that #my_attr reader method exists? Should it guarantee that (({#my_attr})) provides 'volatile' access? May be, (({attr_reader :my_attr})) already ought to provide 'volatile' semantic? May be, semantic of (({@my_attr})) should have volatile semantic (i doubt for that)? -- https://bugs.ruby-lang.org/ Unsubscribe: <mailto:ruby-core-request / ruby-lang.org?subject=unsubscribe> <http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>