/usr/ is in ruby-atomic 1.1.16-2build5.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/ruby/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.3.0/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.3.0/atomic_reference.so
/usr/lib/ruby/
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/atomic/
/usr/lib/ruby/vendor_ruby/atomic/concurrent_update_error.rb
/usr/lib/ruby/vendor_ruby/atomic/numeric_cas_wrapper.rb
/usr/lib/ruby/vendor_ruby/atomic/fallback.rb
/usr/lib/ruby/vendor_ruby/atomic/ruby.rb
/usr/lib/ruby/vendor_ruby/atomic/jruby.rb
/usr/lib/ruby/vendor_ruby/atomic/rbx.rb
/usr/lib/ruby/vendor_ruby/atomic/delegated_update.rb
/usr/lib/ruby/vendor_ruby/atomic/direct_update.rb
/usr/lib/ruby/vendor_ruby/atomic.rb
/usr/share/
/usr/share/rubygems-integration/
/usr/share/rubygems-integration/2.3.0/
/usr/share/rubygems-integration/2.3.0/specifications/
/usr/share/rubygems-integration/2.3.0/specifications/atomic-1.1.16.gemspec
/usr/share/doc/
/usr/share/doc/ruby-atomic/
/usr/share/doc/ruby-atomic/examples/
/usr/share/doc/ruby-atomic/examples/atomic_example.rb
/usr/share/doc/ruby-atomic/examples/bench_atomic_1.rb
/usr/share/doc/ruby-atomic/examples/graph_atomic_bench.rb
/usr/share/doc/ruby-atomic/examples/bench_atomic.rb
/usr/share/doc/ruby-atomic/copyright
/usr/share/doc/ruby-atomic/changelog.Debian.gz
/usr/share/doc/ruby-atomic/README.md