Attempt to unlock a mutex which is not locked in Async::Task, version 2.32.0

[emiltin]

Hi,
I recently upgraded to the latest async, which involved replacing io-event and async-io with io-endpoint and io-stream.
I got it working, but I recently saw this on a Github Action test:

Attempt to unlock a mutex which is not locked in task: #<Async::Task:0x0000000000002b98
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/task.rb:97:in `backtrace' (running)>
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/promise.rb:83:in `synchronize'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/promise.rb:83:in `wait'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/task.rb:258:in `wait'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/rsmp-0.37.0/lib/rsmp/task.rb:58:in `wait'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/rsmp-0.37.0/lib/rsmp/supervisor.rb:206:in `accept_connection'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/rsmp-0.37.0/lib/rsmp/supervisor.rb:107:in `handle_connection'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/rsmp-0.37.0/lib/rsmp/supervisor.rb:73:in `block (2 levels) in run'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/io-endpoint-0.15.2/lib/io/endpoint/wrapper.rb:216:in `block (2 levels) in accept'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/task.rb:207:in `block in run'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/task.rb:452:in `block in schedule'

The supervisor.rb file mentioned is from the'rsmp' gem repo: https://github.com/rsmp-nordic/rsmp/blob/main/lib/rsmp/supervisor.rb#L206

The test failure happened in the 'rsmp_validator' repo: https://github.com/rsmp-nordic/rsmp_validator/actions/runs/17960473877/job/51082450222#step:6:41

[ioquatix]

Thanks I will investigate.

[ioquatix]

Are you able to link me to the failed action?

Also, what version of Ruby are you using?

[emiltin]

Are you able to link me to the failed action?

Sorry, that was actually what i wanted to link to above, but it seems i pasted the wrong link. Updated above, and it's also here:
https://github.com/rsmp-nordic/rsmp_validator/actions/runs/17960473877/job/51082450222#step:6:41

Also, what version of Ruby are you using?

/opt/hostedtoolcache/Ruby/3.3.6/x64/bin/ruby --version
ruby 3.3.6 (2024-11-05 revision 75015d4c1f) [x86_64-linux]

[ioquatix]

Thanks, I'll review it.

[emiltin]

Here's a recent case, also using async 2.32.0, but on Ruby 3.3.6:
https://github.com/rsmp-nordic/rsmp_validator/actions/runs/18923666346/job/54025857466#step:6:45

    2025-10-29T22:30:14.346Z  -      -                    -                    -     Attempt to unlock a mutex which is not locked in task: #<Async::Task:0x0000000000001720 /mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/task.rb:97:in `backtrace' (running)>
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/promise.rb:83:in `synchronize'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/promise.rb:83:in `wait'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/task.rb:258:in `wait'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/rsmp-0.37.0/lib/rsmp/task.rb:58:in `wait'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/rsmp-0.37.0/lib/rsmp/supervisor.rb:206:in `accept_connection'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/rsmp-0.37.0/lib/rsmp/supervisor.rb:107:in `handle_connection'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/rsmp-0.37.0/lib/rsmp/supervisor.rb:73:in `block (2 levels) in run'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/io-endpoint-0.15.2/lib/io/endpoint/wrapper.rb:216:in `block (2 levels) in accept'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/task.rb:207:in `block in run'
/mnt/sdb1/rsmp/actions-runner/_work/rsmp_validator/rsmp_validator/vendor/bundle/ruby/3.3.0/gems/async-2.32.0/lib/async/task.rb:452:in `block in schedule'

I'll let you know if I see this on recent Ruby 3.4.7.

[paddor]

I have the same problem with 2.34.0. It doesn't happen on Ruby 3.4.2.

Example backtrace on Ruby 3.3.5 (with $DEBUG = $VERBOSE = true):

||   0.0s     info: Async::Debug: Async::Debug [ec=0x1928] [pid=199650] [2025-11-05 21:38:48 +0100]
||                | Live debugger binding to #<Async::HTTP::Endpoint http://0.0.0.0:3500/ {}>...
|| Exception `Async::TimeoutError' at /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:191 - execution expired
|| Exception `ThreadError' at /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/promise.rb:83 - Attempt to unlock a mutex which is not locked
|| Exception `Async::Stop' at /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:191 - Task was stopped
|| Exception `ThreadError' at /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/promise.rb:83 - Attempt to unlock a mutex which is not locked
||   0.4s     warn: Async::Task [oid=0x193c] [ec=0x1950] [pid=199650] [2025-11-05 21:38:49 +0100]
||                | Task may have ended with unhandled exception.
||                |   ThreadError: Attempt to unlock a mutex which is not locked
||                |   → /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/promise.rb:83 in `synchronize'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/promise.rb:83 in `wait'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/task.rb:258 in `wait'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:298 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:311 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:180 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-http-0.91.0/lib/async/http/server.rb:69 in `block in run'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/task.rb:207 in `block in run'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/task.rb:452 in `block in schedule'
||                |   Caused by Async::Stop: Task was stopped
||                |   → /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:191 in `transfer'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:191 in `transfer'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:281 in `kernel_sleep'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/promise.rb:89 in `sleep'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/promise.rb:89 in `wait'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/promise.rb:89 in `block in wait'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/promise.rb:83 in `synchronize'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/promise.rb:83 in `wait'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/task.rb:258 in `wait'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:298 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:311 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:180 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-http-0.91.0/lib/async/http/server.rb:69 in `block in run'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/task.rb:207 in `block in run'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/task.rb:452 in `block in schedule'
||                |   Caused by Async::Stop::Cause: Stopping task!
||                |   → /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/task.rb:285 in `stop'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/node.rb:293 in `block in stop_children'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:298 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:311 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:180 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/node.rb:292 in `stop_children'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/task.rb:431 in `stopped!'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/task.rb:444 in `stop!'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/task.rb:326 in `stop'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:516 in `block in stop'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:298 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:311 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/list.rb:180 in `each'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:515 in `stop'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:484 in `run_once'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:568 in `block in run'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:528 in `block in run_loop'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:525 in `handle_interrupt'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:525 in `run_loop'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/async/scheduler.rb:567 in `run'
||                |     /home/user/.gem/ruby/3.3.5/gems/async-2.34.0/lib/kernel/sync.rb:36 in `Sync'
||                |     /home/user/dev/mylib/spec/spec_helper.rb:70 in `block (2 levels) in <top (required)>'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/example.rb:457 in `instance_exec'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/example.rb:457 in `instance_exec'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/hooks.rb:390 in `execute_with'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/hooks.rb:628 in `block (2 levels) in run_around_example_hooks_for'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/example.rb:352 in `call'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/hooks.rb:629 in `run_around_example_hooks_for'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/hooks.rb:486 in `run'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/example.rb:468 in `with_around_example_hooks'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/example.rb:511 in `with_around_and_singleton_context_hooks'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/example.rb:259 in `run'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/example_group.rb:653 in `block in run_examples'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/example_group.rb:649 in `map'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/example_group.rb:649 in `run_examples'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/example_group.rb:614 in `run'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/runner.rb:121 in `block (3 levels) in run_specs'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/runner.rb:121 in `map'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/runner.rb:121 in `block (2 levels) in run_specs'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/configuration.rb:2097 in `with_suite_hooks'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/runner.rb:116 in `block in run_specs'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/reporter.rb:74 in `report'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/runner.rb:115 in `run_specs'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/runner.rb:89 in `run'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/runner.rb:71 in `run'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/lib/rspec/core/runner.rb:45 in `invoke'
||                |     /home/user/.gem/ruby/3.3.5/gems/rspec-core-3.13.5/exe/rspec:4 in `<top (required)>'
||                |     /home/user/.gem/ruby/3.3.5/bin/rspec:25 in `load'
||                |     /home/user/.gem/ruby/3.3.5/bin/rspec:25 in `<top (required)>'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/cli/exec.rb:59 in `load'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/cli/exec.rb:59 in `kernel_load'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/cli/exec.rb:23 in `run'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/cli.rb:452 in `exec'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/vendor/thor/lib/thor/command.rb:28 in `run'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/vendor/thor/lib/thor/invocation.rb:127 in `invoke_command'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/vendor/thor/lib/thor.rb:538 in `dispatch'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/cli.rb:35 in `dispatch'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/vendor/thor/lib/thor/base.rb:584 in `start'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/cli.rb:29 in `start'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/exe/bundle:28 in `block in <top (required)>'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/lib/bundler/friendly_errors.rb:117 in `with_friendly_errors'
||                |     /home/user/.gem/ruby/3.3.5/gems/bundler-2.6.2/exe/bundle:20 in `<top (required)>'
||                |     /home/user/.gem/ruby/3.3.5/bin/bundle:25 in `load'
||                |     /home/user/.gem/ruby/3.3.5/bin/bundle:25 in `<main>'