Issue #9751 has been updated by Usaku NAKAMURA.

Backport changed from 2.0.0: REQUIRED, 2.1: DONE to 2.0.0: DONE, 2.1: DONE

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Bug #9751: Process.wait does not work correctly in a thread
https://bugs.ruby-lang.org/issues/9751#change-47404

* Author: Sam Saffron
* Status: Closed
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
* ruby -v: 1.9, 2.0, 2.1, 2.2
* Backport: 2.0.0: DONE, 2.1: DONE
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The following code fails under Ruby 1.9+, used to work on 1.8 with green threads

```
def test
  if pid = fork
    puts "child pid is #{pid} waiting ..."
    begin
      Process.wait(pid)
      puts "child exited"
    rescue => e
      p e
    end
  else
    sleep 3
    puts "exiting child"
    exit 0
  end
end
 
# this works as expected
test
 
puts "testing in thread"
 
# this will hang
Thread.new do
  test
end.join
```

Additionally on SIGINT I am seeing a zombie + [BUG] pthread_mutex_lock: Invalid argument (EINVAL)



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