[ruby-core:103993] [Ruby master Bug#17827] Monitor is not fiber safe

Issue #17827 has been updated by nagachika (Tomoyuki Chikanaga).

Backport changed from 2.6: DONTNEED, 2.7: DONTNEED, 3.0: REQUIRED to 2.6: DONTNEED, 2.7: DONTNEED, 3.0: DONE

ruby_3_0 f9196de1dee6f5ab8b6fe115070b92775a3500fe merged revision(s) 3a3b19b2bba49e5d6f1cf13764eb6dd701397be9.

----------------------------------------
Bug #17827: Monitor is not fiber safe
https://bugs.ruby-lang.org/issues/17827#change-92130

* Author: ioquatix (Samuel Williams)
* Status: Closed
* Priority: Normal
* Assignee: Eregon (Benoit Daloze)
* Backport: 2.6: DONTNEED, 2.7: DONTNEED, 3.0: DONE
----------------------------------------
According to our discussion here https://github.com/rspec/rspec-support/issues/501 it seems like typical implementation of per-thread reentrant mutex is no longer valid and can lead to some deadlock situation.

```
#!/usr/bin/env ruby

require 'monitor'

def monitor_failure
	m = Monitor.new
	
	f1 = Fiber.new do
		m.synchronize do
			puts "f1 A"
			Fiber.yield
			puts "f1 B"
		end
	end
	
	f2 = Fiber.new do
		m.synchronize do
			puts "f2 A"
			# Fiber.yield
			f1.resume
			puts "f2 B"
		end
	end
	
	f1.resume
	f2.resume
end

monitor_failure
```



-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:[e-mail]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>