Issue #17664 has been updated by ioquatix (Samuel Williams). @eviljoel thanks for your report. My initial thoughts are: - If you are using Ruby to construct sockets, you should probably use the Ruby methods to accept connections, etc. They will correctly deal with this. At worst, you might be blocking without releasing the GVL. Better to use `rb_io_wait`. - I don't think we will roll back this change but it's not impossible - in theory it should not be externally visible. The reason for non-blocking IO is nuanced and complex, and we might eventually be able to achieve what we want without making all file descriptors non-blocking. - You can set a socket back to blocking if you don't intend for Ruby code to use it directly, but make sure you are handling releasing the GVL. ---------------------------------------- Bug #17664: Behavior of sockets changed in Ruby 3.0 to non-blocking https://bugs.ruby-lang.org/issues/17664#change-101563 * Author: ciconia (Sharon Rosner) * Status: Assigned * Priority: Normal * Assignee: ioquatix (Samuel Williams) * ruby -v: 3.0.0 * Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN ---------------------------------------- I'm not sure this is a bug, but apparently a change was introduced in Ruby 3.0 that makes sockets non-blocking by default. This change was apparently introduced as part of the work on the [FiberScheduler interface](https://github.com/ruby/ruby/blame/78f188524f551c97b1a7a44ae13514729f1a21c7/...). This change of behaviour is not discussed in the Ruby 3.0.0 release notes. This change complicates the implementation of an io_uring-based fiber scheduler, since io_uring SQE's on fd's with `O_NONBLOCK` can return `EAGAIN` just like normal syscalls. Using io_uring with non-blocking fd's defeats the whole purpose of using io_uring in the first place. A workaround I have put in place in the Polyphony [io_uring backend](https://github.com/digital-fabric/polyphony/blob/d3c9cf3ddc1f414387948fa40e5...) is to make sure `O_NONBLOCK` is not set before attempting I/O operations on any fd. -- https://bugs.ruby-lang.org/