Bug #19853: Segfault when calling `system` from a non-blocking fiber

• Status: Closed
• Assignee: ioquatix (Samuel Williams)
• Target version: -
• ruby -v: ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-darwin22]
• Backport: 3.0: DONTNEED, 3.1: REQUIRED, 3.2: DONE

[rmosolgo (Robert Mosolgo)]

Hi! I'm trying to improve my Ruby library to support transfer-based fibers (https://github.com/rmosolgo/graphql-ruby/pull/4322). To test parallel I/O, I'm using system("sleep #{duration}"), but this causes a segfault sometimes. I'd love to find a way to keep developing this feature but I'm not sure where to go next.

I have attached a script which replicates the bug and I have attached the full segfault error dump. I encountered this error by running:

ruby fiber_bug.rb 2>out.txt

Does that help debug? Please let me know if I can provide anything else that'd be helpful.

[ioquatix (Samuel Williams)]

• Assignee set to ioquatix (Samuel Williams)

Thanks, I'll take a look.

[ioquatix (Samuel Williams)]

I could reproduce the error with the native backends, but not the pure Ruby backend. That means it's a bug with io-event gem. I'll probably move the issue there once I have time to investigate fully.

> IO_EVENT_SELECTOR=Select ./test.rb
Starting...
{"data"=>{"v1"=>0.5, "v2"=>0.5}}
Ended
[:duration, 0.603101918]

Using a native selector fails with a segfault.

[ioquatix (Samuel Williams)]

https://github.com/ruby/ruby/pull/8315 fixes the segfault and turns it into a TypeError.

[ioquatix (Samuel Williams)]

• Status changed from Open to Closed
• Backport changed from 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN to 3.0: DONTNEED, 3.1: REQUIRED, 3.2: REQUIRED

Merged in https://github.com/ruby/ruby/commit/901b6d9c5025a30b3d7a5ed0a2c00baf9cfb061d

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 3.0: DONTNEED, 3.1: REQUIRED, 3.2: REQUIRED to 3.0: DONTNEED, 3.1: REQUIRED, 3.2: DONE

ruby_3_2 9cd28caa7cc3b0d987db7c1231fe101fb3b27399 merged revision(s) 901b6d9c5025a30b3d7a5ed0a2c00baf9cfb061d.