Bug #22497: Reading a frozen Set held by another Ractor's class crashes

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN

[himura467 (Akito Shitara)]

S = Set[].freeze
Ractor.new { S }.join

-e:1: [BUG] rb_objspace_reachable_objects_from_local: set is owned by another Ractor

Class variables and instance variables of classes crash the same way. Ruby 4.0.7 doesn't crash.

Cause

A Ractor that doesn't own the class checks whether S is shareable by traversing it. Since git|f0439cdfa7 (GH-19145), the children of a T_DATA without declarative marking are enumerated with rb_objspace_reachable_objects_from_local(), which rejects an object owned by another Ractor. The commit before it doesn't crash.

Question

I'm still looking for a good fix. Here is what I've tried so far.

Restoring the enumeration from before f0439cdfa7 for foreign objects (the VM-locked rb_objspace_reachable_objects_from()) fixes the crash, but passes that function an object its comment doesn't allow ("obj may be owned by another Ractor (a shareable)").

I also tried having the owner check shareability when assigning instead, but it doesn't seem to be enough: lib/tmpdir.rb freezes Dir::Tmpname::RANDOM after assigning it, which breaks Tempfile in non-main Ractors.

[himura467 (Akito Shitara)]

• Description updated (diff)

[himura467 (Akito Shitara)]

Duplicate of #22419. Please close this.

[Earlopain (Earlopain _)]

• Is duplicate of Bug #22419: [BUG] "rb_objspace_reachable_objects_from_local: set is owned by another Ractor" when a non-main Ractor reads a class instance variable since f0439cdfa7 added

[Earlopain (Earlopain _)]

• Status changed from Open to Closed