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Bug #20461

open

Unreadable pipe included in the readable IO of IO.select

Added by yamam (Masanari Yamamoto) about 1 month ago. Updated 30 days ago.

Status:
Open
Assignee:
-
Target version:
-
ruby -v:
ruby 3.4.0dev (2024-04-27T12:55:28Z master c844968b72) [x86_64-linux]
[ruby-core:117733]

Description

When executing the following script, pipe_r is not supposed to be readable because no writing is done to pipe_w, but pipe_r is included in the return value rs of IO.select. Since it is not possible to read from pipe_r, the IO::EAGAINWaitReadable exception is raised.

pipe_r, pipe_w = IO.pipe
1000.times do |i|
    IO.popen(['seq', '1', '1000']) do |popen_r|
        j = 0
        while true
            rs, ws, = IO.select([popen_r, pipe_r])
            if rs.include?(popen_r)
                unless popen_r.gets
                    break
                end
            end
            if rs.include?(pipe_r)
                puts "IO.select BUG pipe_r is not readable! i = #{i} j = #{j}"
                p pipe_r.read_nonblock(1)
            end
            j += 1
        end
    end
end
$ ruby select.rb
IO.select BUG pipe_r is not readable! i = 0 j = 20
<internal:io>:63:in `read_nonblock': Resource temporarily unavailable - read would block (IO::EAGAINWaitReadable)
        from select.rb:14:in `block (2 levels) in <main>'
        from select.rb:3:in `popen'
        from select.rb:3:in `block in <main>'
        from select.rb:2:in `times'
        from select.rb:2:in `<main>'
[1]    73732 exit 1     ruby select.rb
Actions #1

Updated by yamam (Masanari Yamamoto) about 1 month ago

  • Description updated (diff)

Updated by yamam (Masanari Yamamoto) 30 days ago

Using git bisect, I found that the following commit is the cause of the bug:
https://github.com/ruby/ruby/commit/49a55f28abdcf3dea1f84ec5b59cfbedc37f44bf

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