[ruby-core:123035] [Ruby Bug#20346] FiberScheduler.unblock not called by Thread#join when Thread body contains Ractor.take

Issue #20346 has been updated by jhawthorn (John Hawthorn).

Status changed from Assigned to Closed

This no longer deadlocks. Under the new Ractor API the `take` should be replaced with `value`.

``` ruby
require "async"

class RactorWrapper
  def initialize
    @ractor = Ractor.new do
      Ractor.recv # Ractor doesn't start until explicitly told to
      # Do some calculations
      fib = ->(x) { x < 2 ? 1 : fib.call(x - 1) + fib.call(x - 2) }
      fib.call(20)
    end
  end

  def take_async
    @ractor.send(nil)
    Thread.new { @ractor.value }.value
  end
end

Async do |task|
  10000.times do |i|
    task.async do
      RactorWrapper.new.take_async
      puts i
    end
  end
end
```

I recorded a profile showing that the concurrency is happening properly (warning: this has 10k threads of data) https://share.firefox.dev/4lCxnFK

----------------------------------------
Bug #20346: FiberScheduler.unblock not called by Thread#join when Thread body contains Ractor.take
https://bugs.ruby-lang.org/issues/20346#change-114346

* Author: forthoney (Seong-Heon Jung)
* Status: Closed
* Assignee: ractor
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
When using a `Ractor.take` inside a different thread, `Thread#join` on the thread running `Ractor.take` fails to call `FiberScheduler.unblock`. The below code can replicate this behavior
```ruby
require "async"
class RactorWrapper
  def initialize
    @ractor = Ractor.new do
      Ractor.recv # Ractor doesn't start until explicitly told to
      # Do some calculations
      fib = ->(x) { x < 2 ? 1 : fib.call(x - 1) + fib.call(x - 2) }
      fib.call(20)
    end
  end
  
  def take_async
    @ractor.send(nil)
    Thread.new { @ractor.take }.join.value
  end
end

Async do |task|
  10000.times do |i|
    task.async do
      RactorWrapper.new.take_async
      puts i
    end
  end
end
```
The above code deadlocks, and when we leave a debugging print statement inside of `Async`'s scheduler's `block` and `unblock` method, we can confirm that we only call `Scheduler.block`, and never `Scheduler.unblock`



-- 
https://bugs.ruby-lang.org/
______________________________________________
 ruby-core mailing list -- [e-mail]
 To unsubscribe send an email to [e-mail]
 ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/