Script hangs while opening a file from /proc in a thread

ruby-talk
1

Hello,
I have a problem with opening a file under /proc in a thread.

This works fine:
File.open('/proc/locks').readlines

But this hangs on open:
t = Thread.new { File.open('/proc/locks').readlines }
t.join

It happens on Linux 2.6, Linux 2.4 seems ok.

It looks the same as
http://www.ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-core/3798

Is there any workaround (other than `cat`) ?

Thank you,
jan molic

2

In article <op.swzfm2axs1a91r@localhost>,
  MiG <mig@1984.cz> writes:

I have a problem with opening a file under /proc in a thread.

This works fine:
File.open('/proc/locks').readlines

But this hangs on open:
t = Thread.new { File.open('/proc/locks').readlines }
t.join

It happens on Linux 2.6, Linux 2.4 seems ok.

It looks the same as
http://www.ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-core/3798

Is there any workaround (other than `cat`) ?

Upgrade the Linux kernel to 2.6.13.

http://kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.13

···

commit e334016fc1735e491385e14157a0360cd85c321b
Author: Luke Kosewski <lkosewsk@nit.ca>
Date: Wed Jun 1 02:39:28 2005 -0500

    Input: do not corrupt system-wide procfs fops.
    
    entry->proc_fops is a pointer to struct file_operations. When we
    call create_proc_entry(...), it pointis to proc_file_operations,
    deep in fs/proc/generic.c. By adding a 'poll' member to this struct
    we effectively force the 'poll' member on every file in /proc,
    which is wrong (they all fail select(...) calls).
    
    This patch changes a copy of entry->proc_fops and reassigns it rather
    than changing the original member.

    Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

--
Tanaka Akira