From: mame@...
Date: 2021-05-21T05:38:19+00:00
Subject: [ruby-core:103934] [Ruby master Bug#13876] Tempfile's finalizer can be interrupted by a Timeout exception which can cause the process to hang

Issue #13876 has been updated by mame (Yusuke Endoh).


I'm neutral for this proposal, but just like to add two comments.

1. The proposed change will break a program that uses `Timeout.timeout` in a finalizer. Such a program may get stuck. I don't think that it is a good program, though.
2. The patch adds an ad-hoc field to disable interrupt, but it may be good to reuse the mechanism of `handle_interrupt`.

----------------------------------------
Bug #13876: Tempfile's finalizer can be interrupted by a Timeout exception which can cause the process to hang
https://bugs.ruby-lang.org/issues/13876#change-92064

* Author: jrafanie (Joe Rafaniello)
* Status: Open
* Priority: Normal
* ruby -v: ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin15]
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
Ruby hangs if a Timeout is raised when a Tempfile's finalizer is run.

This also happens on ruby 2.3.4 on OSX.  I could only recreate this on linux once but not reliably.  Maybe the finalizer runs at a different and unpredictable time on Linux.

See the following script:

```ruby
require 'tempfile'
require 'timeout'
Tempfile.new("x")

# this empty method is needed for some reason, maybe scope/GC related
def stuff
  ""
end

2.times do |i|
  begin
    Timeout.timeout(1e-9) do
      loop do
        begin
          "result"
        ensure
        end
      end
    end
  rescue Timeout::Error
  end
end
```

When run, I get the following output and it hangs ~4 out of 5 times on OSX:

```
$ ruby -d test.rb
Exception `LoadError' at /Users/joerafaniello/.rubies/ruby-2.4.1/lib/ruby/2.4.0/rubygems.rb:1345 - cannot load such file -- rubygems/defaults/operating_system
Exception `LoadError' at /Users/joerafaniello/.rubies/ruby-2.4.1/lib/ruby/2.4.0/rubygems.rb:1354 - cannot load such file -- rubygems/defaults/ruby
removing /var/folders/fq/blrz820d3qz7nm7vj8mbtfs40000gq/T/x20170906-72981-1ttdgpr...
<HANGS>
```

When it doesn't hang (~1 in 5 tries), it looks like this (the exception seems to be raised after the file cleanup is done):

```
$ ruby -d test.rb
Exception `LoadError' at /Users/joerafaniello/.rubies/ruby-2.4.1/lib/ruby/2.4.0/rubygems.rb:1345 - cannot load such file -- rubygems/defaults/operating_system
Exception `LoadError' at /Users/joerafaniello/.rubies/ruby-2.4.1/lib/ruby/2.4.0/rubygems.rb:1354 - cannot load such file -- rubygems/defaults/ruby
removing /var/folders/fq/blrz820d3qz7nm7vj8mbtfs40000gq/T/x20170906-72963-164cw8j...
done
Exception `Timeout::Error' at /Users/joerafaniello/.rubies/ruby-2.4.1/lib/ruby/2.4.0/timeout.rb:114 - execution expired
Exception `Timeout::Error' at /Users/joerafaniello/.rubies/ruby-2.4.1/lib/ruby/2.4.0/timeout.rb:114 - execution expired
```

When it hangs, it seems to be this code:
https://github.com/ruby/ruby/blob/0f25c6d7d59ff9744d1ca5dc908cc12c8ce79e25/lib/tempfile.rb#L253-L261







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