From: Jason Gladish <jason@...>
Date: 2013-03-30T02:16:18+09:00
Subject: [ruby-core:53825] Thread/fork issue

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Hello all,

I've found an issue where calling fork inside a thread, and passing a block
to the fork, causes the forked process to continue after the block.  I've
reproduced the issue on the following versions of ruby:
ruby 2.0.0p100 (2013-03-27 revision 39954) [x86_64-darwin10.8.0]
ruby 1.9.3p392 (2013-02-22 revision 39386) [x86_64-darwin10.8.0]

Here is the script I used to reproduce:

1000.times do |j|
  puts "run #{j}"
  threads = []
  100.times do |i|
    threads << Thread.new(i) do |local_i|
      opid = fork do
        # exit!(true) # fixes the issue
        # exit(true) # doesn't fix the issue
        # no 'exit' also exhibits issue
      end
      ::Process.waitpid(opid, 0)
      File.open("/tmp/test_thread_fork_#{local_i}.pid", "w") {|f| f.write
"1" }
    end
  end
  threads.map { |t| t.join }

  borked = false
  100.times do |i|
    fn = "/tmp/test_thread_fork_#{i}.pid"
    contents = File.read(fn)
    if contents.size > 1
      puts "file #{fn} was written to many times (#{contents})"
      borked = true
    end
  end
  exit(false) if borked
end

As you can see from the comments inside the fork I can work around the
issue by using "exit!".  I am correct in understanding that there should be
no case in which the file is written to multiple times, correct?

Thank you,
Jason Gladish

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<div dir=3D"ltr">Hello all,<div><br></div><div>I&#39;ve found an issue wher=
e calling fork inside a thread, and passing a block to the fork, causes the=
 forked process to continue after the block. =A0I&#39;ve reproduced the iss=
ue on the following versions of ruby:</div>

<div><div>ruby 2.0.0p100 (2013-03-27 revision 39954) [x86_64-darwin10.8.0]<=
/div></div><div><div>ruby 1.9.3p392 (2013-02-22 revision 39386) [x86_64-dar=
win10.8.0]</div></div><div><br></div><div>Here is the script I used to repr=
oduce:</div>

<div><br></div><div><div>1000.times do |j|</div><div>=A0 puts &quot;run #{j=
}&quot;</div><div>=A0 threads =3D []</div><div>=A0 100.times do |i|</div><d=
iv>=A0 =A0 threads &lt;&lt; Thread.new(i) do |local_i|</div><div>=A0 =A0 =
=A0 opid =3D fork do</div>

<div>=A0 =A0 =A0 =A0 # exit!(true) # fixes the issue</div><div>=A0 =A0 =A0 =
=A0 # exit(true) # doesn&#39;t fix the issue</div><div>=A0 =A0 =A0 =A0 # no=
 &#39;exit&#39; also exhibits issue</div><div>=A0 =A0 =A0 end</div><div>=A0=
 =A0 =A0 ::Process.waitpid(opid, 0)</div>

<div>=A0 =A0 =A0 File.open(&quot;/tmp/test_thread_fork_#{local_i}.pid&quot;=
, &quot;w&quot;) {|f| f.write &quot;1&quot; }</div><div>=A0 =A0 end</div><d=
iv>=A0 end</div><div>=A0 threads.map { |t| t.join }</div><div>=A0 =A0</div>=
<div>=A0 borked =3D false</div>

<div>=A0 100.times do |i|</div><div>=A0 =A0 fn =3D &quot;/tmp/test_thread_f=
ork_#{i}.pid&quot;</div><div>=A0 =A0 contents =3D File.read(fn)</div><div>=
=A0 =A0 if contents.size &gt; 1</div><div>=A0 =A0 =A0 puts &quot;file #{fn}=
 was written to many times (#{contents})&quot;</div>

<div>=A0 =A0 =A0 borked =3D true</div><div>=A0 =A0 end</div><div>=A0 end</d=
iv><div>=A0 exit(false) if borked</div><div>end</div></div><div><br></div><=
div>As you can see from the comments inside the fork I can work around the =
issue by using &quot;exit!&quot;. =A0I am correct in understanding that the=
re should be no case in which the file is written to multiple times, correc=
t?</div>

<div><br></div><div>Thank you,</div><div>Jason Gladish</div><div><br></div>=
</div>

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