Issue #20414 has been reported by ioquatix (Samuel Williams). ---------------------------------------- Bug #20414: `Fiber#raise` should recurse to `resumed_fiber` rather than failing. https://bugs.ruby-lang.org/issues/20414 * Author: ioquatix (Samuel Williams) * Status: Open * Assignee: ioquatix (Samuel Williams) * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- The following program will fail with `FiberError`, and is difficult to properly clean up: ```ruby root_fiber = Fiber.current f1 = Fiber.new do root_fiber.transfer end f2 = Fiber.new do f1.resume end f2.transfer f2.raise("error") # => `raise': attempt to transfer to a resuming fiber (FiberError) ``` This program deliberately set's up a scenario where `f2` is resuming `f1`. Trying to raise an exception on `f2` is impossible, because the only way control flow can return to it, is when `f1` yields or exits. We can avoid this problem, by raising the exception on f1, and we can do this automatically using the following logic: ```c static VALUE fiber_raise(rb_fiber_t *fiber, VALUE exception) { // Add this recursive step: if (fiber->resuming_fiber) { return fiber_raise(fiber->resuming_fiber, exception); } // Existing code ... else if (FIBER_SUSPENDED_P(fiber) && !fiber->yielding) { return fiber_transfer_kw(fiber, -1, &exception, RB_NO_KEYWORDS); } else { return fiber_resume_kw(fiber, -1, &exception, RB_NO_KEYWORDS); } } ``` This makes `Fiber#raise` much more robust and useful for the purpose of stopping fibers, without knowing exactly what they are doing. -- https://bugs.ruby-lang.org/