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Bug #18904
closed
Mutex and Fiber: No live threads left. Deadlock? (fatal)
Bug #18904: Mutex and Fiber: No live threads left. Deadlock? (fatal)
Status:
Rejected
Assignee:
-
Target version:
-
ruby -v:
ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [arm64-darwin21]
Description
Hi,
I was investigating an issue with the climate_control gem and minitest-around and it seems like the bug is coming from 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' 
Updated by dorianmariefr (Dorian Marié) over 3 years ago
Same error happens with Monitor
Updated by jeremyevans0 (Jeremy Evans) over 3 years ago
- 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.
Updated by dorianmariefr (Dorian Marié) over 3 years ago
What would you suggest using instead?
Updated by jeremyevans0 (Jeremy Evans) over 3 years ago
dorianmariefr (Dorian Marié) wrote in #note-3:
What would you suggest using instead?
Stop nesting the calls?:
around do MUTEX.synchronize do # don't call around here end end Actions