Add io_close hook to TestScheduler#171
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…eration_wait rb_funcall(scheduler, :blocking_operation_wait, 1, blocking_operation) can cause a fiber switch if the scheduler calls rb_fiber_scheduler_block. When the fiber is suspended, the C frame of rb_fiber_scheduler_blocking_operation_wait is no longer active. In optimised builds (-O3 --enable-shared), blocking_operation may be held only in a machine register not saved/scanned by the conservative GC, allowing it to be collected. get_blocking_operation() at line 1104 then reads freed/reused memory, crashing with rb_unexpected_object_type. Confirmed by reproducing the crash using: ./configure --enable-shared --disable-install-doc --enable-yjit cppflags=-DENABLE_PATH_CHECK=0 RB_GC_GUARD(blocking_operation) after rb_funcall forces the compiler to keep the VALUE on the stack (volatile read), ensuring the GC always finds it. See: socketry/io-event#170 socketry/io-event#171 Co-authored-by: Cursor <cursoragent@cursor.com>
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…eration_wait rb_funcall(scheduler, :blocking_operation_wait, 1, blocking_operation) can cause a fiber switch if the scheduler calls rb_fiber_scheduler_block. When the fiber is suspended, blocking_operation may only be in a machine register not scanned by the conservative GC, allowing collection. Confirmed by reproducing the crash (segfault in get_blocking_operation) with: ./configure --enable-shared --disable-install-doc --enable-yjit RB_GC_GUARD forces the VALUE onto the stack ensuring the GC always finds it. See: socketry/io-event#171 Co-authored-by: Cursor <cursoragent@cursor.com>
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…eration_wait rb_funcall(scheduler, :blocking_operation_wait, 1, blocking_operation) can cause a fiber switch if the scheduler calls rb_fiber_scheduler_block. When the fiber is suspended, blocking_operation may only be in a machine register not scanned by the conservative GC, allowing collection. Confirmed by reproducing the crash (segfault in get_blocking_operation) with: ./configure --enable-shared --disable-install-doc --enable-yjit RB_GC_GUARD forces the VALUE onto the stack ensuring the GC always finds it. See: socketry/io-event#171 Co-authored-by: Cursor <cursoragent@cursor.com>
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…eration_wait rb_funcall(scheduler, :blocking_operation_wait, 1, blocking_operation) can cause a fiber switch if the scheduler calls rb_fiber_scheduler_block. When the fiber is suspended, blocking_operation may only be in a machine register not scanned by the conservative GC, allowing collection. Confirmed by reproducing the crash (segfault in get_blocking_operation) with: ./configure --enable-shared --disable-install-doc --enable-yjit RB_GC_GUARD forces the VALUE onto the stack ensuring the GC always finds it. See: socketry/io-event#171 Co-authored-by: Cursor <cursoragent@cursor.com>
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…eration_wait rb_funcall(scheduler, :blocking_operation_wait, 1, blocking_operation) can cause a fiber switch if the scheduler calls rb_fiber_scheduler_block. When the fiber is suspended, blocking_operation may not be reachable via the conservative GC scan of the suspended fiber's C stack. rb_gc_register_address pins blocking_operation in the global GC root list, which is always walked regardless of fiber state. The address is kept registered through the last implicit use of the VALUE — including all accesses via the raw C pointer derived from it — so that a compacting GC cannot move the object and leave dangling. Confirmed by reproducing the crash in io-event CI: ./configure --enable-shared --disable-install-doc --enable-yjit See: socketry/io-event#171 ruby#16908 Co-authored-by: Cursor <cursoragent@cursor.com>
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…eration_wait rb_funcall(scheduler, :blocking_operation_wait, 1, blocking_operation) can cause a fiber switch if the scheduler calls rb_fiber_scheduler_block. When the fiber is suspended, blocking_operation may not be reachable via the conservative GC scan of the suspended fiber's C stack. rb_gc_register_address pins blocking_operation in the global GC root list, which is always walked regardless of fiber state. The address is kept registered through the last implicit use of the VALUE — including all accesses via the raw C pointer derived from it — so that a compacting GC cannot move the object and leave dangling. Confirmed by reproducing the crash in io-event CI: ./configure --enable-shared --disable-install-doc --enable-yjit See: socketry/io-event#171 ruby#16908 Co-authored-by: Cursor <cursoragent@cursor.com>
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…eration_wait Use rb_gc_register_address to pin blocking_operation as a precise GC root during rb_funcall. The scheduler's blocking_operation_wait may cause a fiber switch via rb_fiber_scheduler_block, which suspends the calling fiber. The conservative GC does not find the VALUE on the suspended fiber's C stack (possibly due to it being in a machine register not captured in the saved context), so the object can be collected or moved without updating the local VALUE. rb_gc_register_address ensures the object is a precise root that is always found and properly handled by both the regular and compacting GC. rb_gc_unregister_address is called after the last use of the raw pointer (which is derived from blocking_operation) to avoid a dangling registered address. Confirmed by io-event CI which reliably crashes without this fix and passes with it: socketry/io-event#171 Co-authored-by: Cursor <cursoragent@cursor.com>
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When a TestScheduler is active, IO#close was previously falling back to rb_nogvl and blocking_operation_wait. Adding the io_close scheduler hook routes the close through the selector (when supported) or closes the descriptor synchronously via Fiber.blocking, avoiding an unnecessary trip through the worker pool. Handles both legacy IO objects and raw Integer file descriptors (Ruby 4.0+ passes the raw fd to the hook). Co-authored-by: Cursor <cursoragent@cursor.com>
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Ruby's fiber-scheduler `io_close` hook (Ruby 4.0+, see `rb_fiber_scheduler_io_close` in CRuby) is invoked with a raw integer file descriptor — never an `IO` object. Earlier Rubies don't invoke the hook at all. Only `URing` implements `io_close` (async close via the ring); other selectors let Ruby use its default `IO#close` path. Both `Debug::Selector` and `TestScheduler` now define a small `Forwarders` module whose methods are mixed into their singleton class only when the wrapped selector actually implements the corresponding method. This preserves async close when wrapping `URing` and keeps `respond_to?` reflecting the real backend. Drops the dead `IO`-object branch from `uring.c`, the `Forwarders` doc, and the test — Ruby's contract is integer-only. Co-authored-by: Cursor <cursoragent@cursor.com>
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When a
TestScheduleris active andIO#closeis invoked from inside a scheduled fiber, Ruby looks for anio_closescheduler hook. Until now the test scheduler did not define one, so Ruby fell back torb_nogvlandblocking_operation_wait— routing every close through the worker pool unnecessarily.This PR adds the hook:
io_close(e.g. URing), delegate to it.Fiber.blocking { ... }, which suppresses scheduler hooks for the duration of the close.Handles both legacy
IOobjects and rawIntegerfile descriptors — Ruby 4.0+ passes the raw fd to the hook.The change is one method, fourteen lines.