linux-kernel - Re: 2.6.24-rc3: find complains about /proc/net

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Message-ID: <m1ve7wr28z.fsf@ebiederm.dsl.xmission.com>
Date:	Tue, 20 Nov 2007 15:17:00 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Pavel Emelyanov <xemul@...nvz.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Pavel Machek <pavel@....cz>,
	kernel list <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: 2.6.24-rc3: find complains about /proc/net

Ingo Molnar <mingo@...e.hu> writes:

> * Eric W. Biederman <ebiederm@...ssion.com> wrote:
>
>> > lr-x------  1 root root 64 Nov 20 18:03 3 -> /proc/net
>> > ...
>> 
>> Yes all of those are nasty.  So much for my clever way of implementing 
>> these things.  Grr. Simple hacks that almost work!
>
> btw., in case you feel inclined, i recently did some userspace coding 
> and found to my surprise that /proc/self points to the parent task, not 
> the thread itself (giving threads no real way to examine themselves). If 
> you are hacking in this area, would it be a big trouble to add something 
> like /proc/self-task/ or something like that? I had to use a raw gettid 
> syscall to figure out the TID to get to /proc/*/tasks/TID/sched 
> instrumentation info - which is quite a PITA.

Agreed.  I have been debating with myself in the last couple of days
if it is a bug that /proc/self uses the tgid and not the actual pid/tid
value.

If I can be convinced that posix threads don't care I will happily just
switch /proc/self, calling the current implementation a bug.

I think it is a bug the real question is what are the backwards
compatibility implications.  Do posix threads care?

It appears to me that either we need to fix /proc/self or we need
to add /proc/task-self and fix /proc/mounts to point at that.

In the normal case we share all of the same things so I think it is
a don't care.  Except that /proc/self/status | grep Pid returns the
tgid.

Hmm.  I think I am just going to send Andrew a patch for 2.6.25 that
just fixes /proc/self.  I just fail to see how using the tgid is correct.
The only cases we could care seem to do the wrong thing when we use the
tgid.

Eric
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