Bug #1460

IO#select returns wrong fd list after Kernel#sleep (Windows)

Added by romuloceccon (Romulo Ceccon) about 3 years ago. Updated about 1 year ago.

[ruby-core:23431]
Status:Rejected Start date:05/12/2009
Priority:Normal Due date:
Assignee:usa (Usaku NAKAMURA) % Done:

0%
Category:core
Target version:Ruby 1.8.6
ruby -v:ruby 1.8.6 (2008-08-11 patchlevel 287) [i386-mswin32]

Description

The following script never ends on Windows XP/Vista:

  require 'thread'

  a = IO.pipe
  puts "pipe: #{a.inspect}"

  th = Thread.new do
    if res = IO.select([a[0]], [], [], 1)
      puts "select ok: #{res.inspect}"
      c = a[0].read(1)
      puts "read ok: #{c}"
    else
      puts "timeout"
    end
  end

  puts "sleep"
  sleep(1)
  puts "done"

The main thread stops at "sleep(1)" and the secondary thread at "c = a[0].read(1)". This is the output I get:

  pipe: [#<IO:0x2b616f4>, #<IO:0x2b616cc>]
  sleep
  select ok: [[#<IO:0x2b616f4>], [], []]
  (ruby freezes here)

The Kernel#sleep call makes IO#select return with the pipe handle, even though it hasn't signaled. Then the call to IO#read blocks because no data is available. I couldn't come up with a workaround because IO#read_nonblock does not work with pipes in Windows (raises "Bad file descriptor" (calling IO#fcntl with O_NONBLOCK is also not possible)).

History

#1
Updated by nobu (Nobuyoshi Nakada) about 3 years ago

  • Status changed from Open to Assigned
  • Assignee set to usa (Usaku NAKAMURA)
Don't use IO.select with pipes.  It's a known restriction.
If you really need to it, use 1.8.7.

#2
Updated by usa (Usaku NAKAMURA) about 3 years ago

  • Status changed from Assigned to Rejected

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