Allow IO#close to interrupt IO operations on fibers using fiber_interrupt hook.

[ioquatix]

Ruby's IO#close can cause IO#read, IO#write, IO#wait, IO#wait_readable and IO#wait_writable to be interrupted with an IOError (stream closed on another thread).

The fiber scheduler did not implement this for io_read, io_write and io_wait hooks. Finally after several years, someone made a bug report - see socketry/async#368 for background. In order to solve this problem for the fiber scheduler, we need to expose the ability for IO#close to interrupt a fiber.

This PR introduces a new internal C function rb_thread_io_blocking_operation which takes an IO instance and a callback. During that callback, if the IO is closed, the callback will be interrupted.

It also introduces a new fiber scheduler method, fiber_interrupt which allows us to interrupt a specific fiber with an error, in this case with an IOError.

https://bugs.ruby-lang.org/issues/21166

[launchable-app]

❌ Tests Failed

✖️no tests failed ✔️61866 tests passed(1 flake)

[luke-gru]

For what it's worth this patch makes sense and LGTM, but I have no experience using the fiber scheduler and this needs another reviewer. But thank you for making the changes I suggested 😄

[Copilot]

Pull Request Overview

This PR introduces a new C function to perform interruptible IO operations in the fiber scheduler, allowing IO#close to interrupt fibers and raise an IOError during blocking operations. Key changes include the implementation of rb_thread_io_blocking_operation with its ensure routine, integration of a new Fiber::Scheduler#fiber_interrupt hook for interrupting fibers, and updated IO buffering and scheduler functions to use the new interruptible operations.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
thread.c	Added new functions for interruptible IO operations and modified return type conversion in IO close.
test/fiber/scheduler.rb	Added exception handling for IO.select and introduced FiberInterrupt and fiber_interrupt functions.
scheduler.c	Added new scheduler methods that wrap IO methods with the new interruptible blocking operation.
io_buffer.c	Updated read/write/pwrite functions to correctly resolve IO instances before performing operations.
internal/thread.h	Declared the new rb_thread_io_blocking_operation function along with updated comments.
include/ruby/fiber/scheduler.h	Updated documentation for the new fiber_interrupt API.
NEWS.md	Documented the addition of Fiber::Scheduler#fiber_interrupt for better developer visibility.

[ioquatix]

Benchmark results:

> make benchmark BENCH_RUBY=/Users/samuel/.rubies/ruby-head/bin/ruby COMPARE_RUBY=/Users/samuel/.rubies/ruby-a6435bef/bin/ruby ITEM=io_close
/Users/samuel/.rubies/ruby-3.4.2/bin/ruby --disable=gems -rrubygems -I./benchmark/lib ./benchmark/benchmark-driver/exe/benchmark-driver \
	            --executables="compare-ruby::/Users/samuel/.rubies/ruby-a6435bef/bin/ruby -I.ext/common --disable-gem" \
	            --executables="built-ruby::/Users/samuel/.rubies/ruby-head/bin/ruby --disable-gem" \
	            --output=markdown --output-compare -v $(find ./benchmark -maxdepth 1 -name 'io_close' -o -name '*io_close*.yml' -o -name '*io_close*.rb' | sort) 
compare-ruby: ruby 3.5.0dev (2025-05-13T08:35:34Z master a6435befa7) +PRISM [arm64-darwin24]
built-ruby: ruby 3.5.0dev (2025-05-17T00:42:12Z master aa0f689bf4) +PRISM [arm64-darwin24]
last_commit=[ruby/net-http] Freeze some constants to improve Ractor compatibility
# Iteration per second (i/s)

|                    |compare-ruby|built-ruby|
|:-------------------|-----------:|---------:|
|io_close_contended  |     117.394|   179.029|
|                    |           -|     1.53x|
|io_close            |     821.862|   900.114|
|                    |           -|     1.10x|