From mboxrd@z Thu Jan  1 00:00:00 1970
From: Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 1/1] proc: make /proc/self point to thread
Date: Tue, 27 Aug 2013 11:15:56 -0700
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Cc: Andrew Morton <akpm@linux-foundation.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Willy Tarreau <w@1wt.eu>, Al Viro <viro@zeniv.linux.org.uk>,
	Andy Lutomirski <luto@amacapital.net>,
	Ingo Molnar <mingo@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	Brad Spengler <spender@grsecurity.net>
To: Oleg Nesterov <oleg@redhat.com>
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On Tue, Aug 27, 2013 at 10:49 AM, Oleg Nesterov <oleg@redhat.com> wrote:
>
> Why? To me /proc/self == /proc/$((sys_gettid)) looks more natural.
> Say, /proc/self/task... But this is subjective.

Actually, you're right - I incorrectly thought we had removed the
thread id lookup from the top level in /proc. But we never actually
did that. We only removed them from readdir.

So while you won't see thread id's in the directory listing, we *do*
successfully look up thread id's when specified explicitly. It's
confusing, but it happens to work. So you can do

   ls -l /proc/<tid>/

and get the expected result, but if you do

   ls -l /proc | grep <tid>

it won't actually show up unless the thread ID is also the thread group leader.

> Although to be honest, I was seduced by "Worth testing". I mean I am
> just curious, who can suffer from this change? Nevermind, please
> ignore.

Yeah, if we were to redesign /proc I'd do it differently, but I think
we should just accept that it works "well enough" and there's just too
much risk from making changes that aren't strictly required.

            Linus