Bug #16186: Calling Net::HTTP from within an #inspect implementation hang when invoked from p

• Status: Closed
• Assignee: kosaki (Motohiro KOSAKI)
• Target version: -
• ruby -v: ruby 2.7.0dev (2019-09-27T18:22:21Z trunk d53cf85474) [x86_64-linux]
• Backport: 2.7: REQUIRED, 3.0: DONTNEED
• Tags: core, patch

[byteit101 (Patrick Plenefisch)]

Using this script:

require 'net/http'
class Victim
	def inspect
		puts "before"
		Net::HTTP.get('example.com', '/index.html') # this hangs. I haven't tried other network libraries
		puts "After"
		return "success"
	end
end
puts Victim.new.inspect # for some reason this doesn't hang
puts "now we hang"
p Victim.new  # but this implicit invocation of inspect does hang. Independent of ordering, and works on JRuby
puts "It worked!"

Expected:

$ rvm use jruby
$ ruby bug.rb
before
After
success
now we hang
before
After
success
It worked!
$

Actual:

$ rvm use ruby-head 
$ ruby bug.rb
before
After
success
now we hang
before
^C^C^Z
[1]  + 13423 suspended  ruby bug.rb
$ kill %1
$ (time passes)
Traceback (most recent call last):
	11: from bug.rb:12:in `<main>'
	10: from bug.rb:12:in `p'
	 9: from bug.rb:5:in `inspect'
	 8: from /home/byteit101/.rvm/rubies/ruby-head/lib/ruby/2.7.0/net/http.rb:458:in `get'
	 7: from /home/byteit101/.rvm/rubies/ruby-head/lib/ruby/2.7.0/net/http.rb:476:in `get_response'
	 6: from /home/byteit101/.rvm/rubies/ruby-head/lib/ruby/2.7.0/net/http.rb:919:in `start'
	 5: from /home/byteit101/.rvm/rubies/ruby-head/lib/ruby/2.7.0/net/http.rb:930:in `do_start'
	 4: from /home/byteit101/.rvm/rubies/ruby-head/lib/ruby/2.7.0/net/http.rb:945:in `connect'
	 3: from /home/byteit101/.rvm/rubies/ruby-head/lib/ruby/2.7.0/timeout.rb:105:in `timeout'
	 2: from /home/byteit101/.rvm/rubies/ruby-head/lib/ruby/2.7.0/timeout.rb:99:in `block in timeout'
	 1: from /home/byteit101/.rvm/rubies/ruby-head/lib/ruby/2.7.0/timeout.rb:99:in `ensure in block in timeout'
/home/byteit101/.rvm/rubies/ruby-head/lib/ruby/2.7.0/timeout.rb:99:in `join': Interrupt

[1]  + 13423 interrupt  ruby bug.rb
$

The thing that is surprising to me is the explicit print + inspect works, whereas a straight p hangs.

[byteit101 (Patrick Plenefisch)]

• Description updated (diff)

[nobu (Nobuyoshi Nakada)]

As Kernel#p is equivalent to Thread.handle_interrupt(Object => :never) {puts args.map(&:inspect)}, all interrupts never be invoked.

[nobu (Nobuyoshi Nakada)]

• Assignee set to kosaki (Motohiro KOSAKI)

Current implementation is since r38225 (fe6b2e20e9f17ed2c2900aa72994e075ffdc7124).
I think this was discussed in the mailing list (probably ruby-dev), but I can't find it now.
And I think which should be uninterruptible is only printing the argument and a newline.

https://github.com/nobu/ruby/pull/new/bug/16186-allow-interrupts-during-inspect-in-p

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Closed
• Backport changed from 2.5: UNKNOWN, 2.6: UNKNOWN to 2.7: REQUIRED, 3.0: DONTNEED

I tested this and it appears fixed by 63a5412db7138297a2e7513067ef80dad7a3b4b4. It may be worthwhile to backport that commit to Ruby 2.7.