From: William Morgan <wmorgan-ruby-talk@...>
Date: 2004-08-18T21:23:55+09:00
Subject: ruby + linux /proc/acpi deadlock?

Hi Rubyists,

I'm working on a predictive battery monitor in Ruby. One issue I've
found is that when I read /proc/acpi/battery/BAT1/state and there are
other Ruby threads running, the read seems to freeze.  This doesn't
happen with other files in /proc/acpi (that I've tried, at least) and
doesn't happen if there's no threading going on.

Here's some code that hangs on the read for me:

PROC_FILE = "/proc/acpi/battery/BAT1/state"         # freezes
#PROC_FILE = "/proc/acpi/power_resource/PFAN/state" # doesn't freeze
FREEZE = true # when this is true, the "read" thread freezes for me

def read
  puts "=== starting to read at #{Time.now}"
  IO.foreach(PROC_FILE) { |l| puts "> #{l}" }
  puts "===     done reading at #{Time.now}"
end

Thread.new do
  while true
    puts "zzz..."
    sleep 1
  end
end if FREEZE

while true
  read
  sleep 1
end

This might be some weird kernel interaction thing that's specific to my
buggy BIOS, but I thought I'd check and see if others experienced the
same behavior.

Thanks,

-- 
William <wmorgan-ruby-talk@masanjin.net>