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

[MiG]

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 =3D 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

 

[Tanaka Akira]

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 <[email protected]>
| 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 <[email protected]>