From: samuel@...
Date: 2021-07-18T17:37:32+00:00
Subject: [ruby-core:104638] [Ruby master Bug#17666] Thread#join hangs when Fiber.set_scheduler is set

Issue #17666 has been updated by ioquatix (Samuel Williams).


@nagachika thanks so much for your effort here. I have a local test case which can easily fail without this fix, so I'll try your PR to confirm it fixes the issue.

----------------------------------------
Bug #17666: Thread#join hangs when Fiber.set_scheduler is set
https://bugs.ruby-lang.org/issues/17666#change-92940

* Author: arjunmdas (arjun das)
* Status: Closed
* Priority: Normal
* ruby -v: ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin19]
* Backport: 2.7: DONTNEED, 3.0: REQUIRED
----------------------------------------

``` ruby
class MockScheduler
  def block(blocker, timeout = nil)
    byebug
  end

  def close
    byebug
  end

  def fiber(&block)
    byebug
    Fiber.new(blocking: false, &block).tap(&:resume)
  end

  def io_wait(io, events, timeout)
    byebug
  end

  def kernel_sleep(duration=nil)
    byebug
    Fiber.yield
  end

  def process_wait(pid, flags)
    byebug
  end

  def unblock(blocker, fiber)
    byebug
  end
end
  
Fiber.set_scheduler(MockScheduler.new)

t1 = Thread.new do
       p 'before'
       sleep 1
       p 'after'
     end

t1.join
```

Code hangs at this point.




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