PyCall on thread != main: process will not exit #186
Description
If you use PyCall from only one thread , but that thread is NOT the main thread, the process will not exit when the main thread exits.
This is not the same issue as: "Is PyCall Thread Safe" #96, as we are only using PyCall from one thread:
- PyCall is only called from one thread: "side_thread"
- side_thread exits
- Process still does not exit
Example:
#!/usr/bin/env ruby
def run(do_pycall_import:)
if do_pycall_import
puts "Running with do_pycall_import=true, process will not exit when main thread is done"
else
puts "Running with do_pycall_import=false, process will exit when main thread is done"
end
puts "Main thread ID: #{Thread.current.object_id}\n"
def print_threads
puts
puts "Threads:"
Thread.list.each do |thread|
puts "\tThread ID: #{thread.object_id}, Status: #{thread.status}, Name: #{thread.name}"
end
puts
end
Thread.new do
Thread.current.name = "side_thread"
Thread.current.abort_on_exception = true
# Demonstrate that PyCall has not been used:
raise "Only load pycall in this thread" if defined?(PyCall)
require 'pycall'
if do_pycall_import
puts "side_thread: import sys"
# This will initialize libpython, if this happens, the process wil not exit:
PyCall.import_module('sys')
end
sleep 2
puts "side_thread: exiting"
end
sleep 1
print_threads() #=> Two threads: main and side_thread
sleep 4
print_threads() #=> One thread: main
end
if __FILE__ == $0
run(do_pycall_import: true) #=> Process does NOT exit after printing "End of main thread"
# run(do_pycall_import: false) #=> Process exits after printing "End of main thread"
end
at_exit { puts "at_exit called"}
puts "End of main thread"
Output when do_pycall_import: true
zsh >> ./pycall_hangs_main_thread.rb
Running with do_pycall_import=true, process will not exit when main thread is done
Main thread ID: 60
side_thread: import sys
Threads:
Thread ID: 60, Status: run, Name:
Thread ID: 80, Status: sleep, Name: side_thread
side_thread: exiting
Threads:
Thread ID: 60, Status: run, Name:
End of main thread
at_exit called
#=> control never returns to the shell
Output when do_pycall_import: false
zsh >> ./pycall_hangs_main_thread.rb
Running with do_pycall_import=false, process will exit when main thread is done
Main thread ID: 60
Threads:
Thread ID: 60, Status: run, Name:
Thread ID: 80, Status: sleep, Name: side_thread
side_thread: exiting
Threads:
Thread ID: 60, Status: run, Name:
End of main thread
at_exit called
zsh >> # notice, process exited