From: "jeremyevans0 (Jeremy Evans)" <noreply@...>
Date: 2022-07-08T17:20:44+00:00
Subject: [ruby-core:109169] [Ruby master Bug#18904] Mutex and Fiber: No live threads left. Deadlock? (fatal)

Issue #18904 has been updated by jeremyevans0 (Jeremy Evans).

Status changed from Open to Rejected

This isn't a bug.  `Mutex` is not designed to be reentrant, so that will always fail in recursive use. `Monitor` is only reentrant in the same fiber, and you are using a separate fiber, so that should fail as well in this case.  The `Monitor` case works in Ruby <3.0, before `Mutex`/`Monitor` were made fiber aware.  However, this behavior change is not a regression, it was explicitly designed this way.

----------------------------------------
Bug #18904: Mutex and Fiber: No live threads left. Deadlock? (fatal)
https://bugs.ruby-lang.org/issues/18904#change-98310

* Author: dorianmariefr (Dorian Mari��)
* Status: Rejected
* Priority: Normal
* ruby -v: ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [arm64-darwin21]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Hi,

I was investigating an issue with the climate_control gem and minitest-around and it seems like the bug is coming from Ruby:

```ruby
def around(&block)
  Fiber.new do |context, resume|
    context.instance_exec(resume, &block)
  end.resume
end

MUTEX = Mutex.new

around do
  MUTEX.synchronize do
    around do
      MUTEX.synchronize do
      end
    end
  end
end
```

```
test.rb:12:in `synchronize': No live threads left. Deadlock? (fatal)
1 threads, 1 sleeps current:0x0000000126804080 main thread:0x0000000126804080
* #<Thread:0x00000001043b8d50 sleep_forever>
   rb_thread_t:0x0000000126804080 native:0x0000000104330580 int:0
   
	from test.rb:12:in `block (3 levels) in <main>'
	from test.rb:3:in `instance_exec'
	from test.rb:3:in `block in around'
```



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