rspec-core: --bisect deadlocks when reporting results

–bisect deadlocks when reporting results

david@davids:~/git/puppet-resource_api$ bundle exec rspec --seed 40589 --bisect=verbose --pattern spec/\*\*\{,/\*/\*\*\}/\*_spec.rb  --exclude-pattern 'spec/{fixtures/**/*.rb,fixtures/modules/*/**/*.rb}' 
Bisect started using options: "--seed 40589 --pattern spec/**{,/*/**}/*_spec.rb --exclude-pattern spec/{fixtures/**/*.rb,fixtures/modules/*/**/*.rb}" and bisect runner: :fork
Running suite to find failures...^C

Bisect aborted!

The most minimal reproduction command discovered so far is:
  (Not yet enough information to provide any repro command)


Bisect aborted!

The most minimal reproduction command discovered so far is:
  (Not yet enough information to provide any repro command)

david@davids:~/git/puppet-resource_api$

at the point of ctrl+c, the process has been already sitting a lot longer than the test suite would run.

stracing the processes shows the following situation:

david@davids:~$ strace -s 10000 -p 6090 -p 6096
strace: Process 6090 attached
strace: Process 6096 attached
[pid  6090] wait4(6096,  <unfinished ...>
[pid  6096] ppoll([{fd=10, events=POLLOUT}], 1, NULL, NULL, 8^Cstrace: Process 6090 detached
strace: Process 6096 detached
 <detached ...>

david@davids:~$ 

where pid 6090 is the --bisect process and pid 6096 is the child rspec process. From other traces I’ve been running, I understand that the ppoll is waiting on an IO event after/while writing the results to fd 10. Meanwhile the main process is hanging in waitpid at https://github.com/rspec/rspec-core/blob/2800fe118fa2efeb87b7bdc7888476373debf6ca/lib/rspec/core/bisect/fork_runner.rb#L95

A common reason why this might not show up in testing is if the result report in the tests is smaller than the underlying OS’s buffer size. In that case the runner process exits after writing to the buffer and the parent continues happily reading from the buffer. In my case the testsuite results are ~93kB and the processes deadlock.

Your environment

• Ruby version: ruby 2.5.5p157 (2019-03-15 revision 67260) [x86_64-linux-gnu]
• rspec-core version: 3.8.0

Steps to reproduce

• checkout https://github.com/DavidS/puppet-resource_api/tree/rspec-core-repro
• bundle install the gems according to the Gemfile.lock
• the following command hangs:

david@davids:~/git/puppet-resource_api$ bundle exec rspec --bisect=verbose --seed 40589 --pattern 'spec/**{,/*/**}/*_spec.rb' --exclude-pattern 'spec/{fixtures/**/*.rb,fixtures/modules/*/**/*.rb}'
Bisect started using options: "--seed 40589 --pattern spec/**{,/*/**}/*_spec.rb --exclude-pattern spec/{fixtures/**/*.rb,fixtures/modules/*/**/*.rb}" and bisect runner: :fork
Running suite to find failures...

while this creates results:

david@davids:~/git/puppet-resource_api$ bundle exec rspec --bisect=verbose --require shell --seed 40589 --pattern 'spec/**{,/*/**}/*_spec.rb' --exclude-pattern 'spec/{fixtures/**/*.rb,fixtures/modules/*/**/*.rb}'
Bisect started using options: "--require shell --seed 40589 --pattern spec/**{,/*/**}/*_spec.rb --exclude-pattern spec/{fixtures/**/*.rb,fixtures/modules/*/**/*.rb}" and bisect runner: :shell
Running suite to find failures... (2 minutes 48.2 seconds)
 - Failing examples (1):
    - ./spec/puppet/resource_api_spec.rb[1:16:2:1]
 - Non-failing examples (1398):
    - ./spec/acceptance/array_spec.rb[1:1:1]
[...]