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Date:	Tue, 20 Nov 2007 17:41:35 -0700
From: (Eric W. Biederman)
To:	Ulrich Drepper <>
Cc:	Roland McGrath <>,
	Guillaume Chazarain <>,
	Ingo Molnar <>,
	Pavel Emelyanov <>,
	"Rafael J. Wysocki" <>, Pavel Machek <>,
	kernel list <>,
	netdev <>
Subject: Re: 2.6.24-rc3: find complains about /proc/net

Ulrich Drepper <> writes:

> Roland McGrath wrote:
>> Oh, it seems it has indeed been that way for a very long time, so I was
>> mistaken.  It still seems a little odd to me.  Ulrich can say definitively
>> whether the kind of concern I mentioned really matters one way or the other
>> for glibc.
> glibc cannot survive (at least NPTL) if somebody uses funny CLONE_*
> flags to separate various pieces of information, e.g., file descriptors.
>  So, all the information in each thread's /proc/self should be identical.

Which seems to confirm that glibc and native pthread can't care.

> When the information is not the same, the current semantics seems to be
> more useful.  So I guess, no change is the way to go here.

Could you elaborate a bit on how the semantics of returning the
wrong information are more useful?

In particular if a thread does the logical equivalent of:
grep Pid: /proc/self/status.  It always get the tgid despite
having a different process id.

How can that possibly be useful or correct?

>From the kernel side I really think the current semantics of /proc/self
in the context of threads is a bug and confusing.  All of the kernel
developers first reaction when this was pointed out was that this
is a regression.

If it is truly useful to user space we can preserve this API design
bug forever.  I just want to make certain we are not being bug
compatible without a good reason.

Currently we have several kernel side bugs with threaded
programs because /proc/self does not do the intuitive thing.  Unless
something has changed recently selinux will cause accesses by a
non-leader thread to fail when accessing files through /proc/self.

So far the more I look at the current /proc/self behavior the
more I am convinced it is broken, and useless.  Please help me see
where it is useful, so we can justify keeping it.

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