linux-kernel - Re: [REVIEW][PATCH 0/4] /proc/thread-self

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Message-ID: <871tt08xgs.fsf@x220.int.ebiederm.org>
Date:	Fri, 01 Aug 2014 00:45:23 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Bert Wesarg <bert.wesarg@...glemail.com>
Cc:	Linux Containers <containers@...ts.linux-foundation.org>,
	linux-api@...r.kernel.org,
	"Michael Kerrisk \(man-pages\)" <mtk.manpages@...il.com>,
	linux-fsdevel@...r.kernel.org,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [REVIEW][PATCH 0/4] /proc/thread-self

Bert Wesarg <bert.wesarg@...glemail.com> writes:

> On Fri, Aug 1, 2014 at 2:30 AM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
>>
>> This patchset implements /proc/thread-self a magic symlink that
>> solves a couple of problems.
>
> shouldn't we keep the 'task' in the name, as it points into the 'task'
> directory? And why not mimic the current 'self -> <id>' ideom under
> /proc/<tgid>/task too and put a new 'self' link there:
>
> $ ls -l /proc/self/task/self
>   lrwxrwxrwx 1 root root 0 Aug  1 00:00 /proc/self/task/self -> 484

No particularly good reason.  

Mostly I picked thread-self as I could pick that out as a concept in the
code distinct from self and distinct from thread and it the
implementation was stratighforward.

Your approach requires a bit more symlink recursion than mine so it is
not my first choice.

I almost pointed it at just the sometimes invisible thread directory
directly under /proc so it would be a single number.  But that has the
issue that it you still get the process rollups in the numbers reported
by some of the proc files, which is undesirable.

Frankly I think it was a mistake by the nptl kernel code to have changed
the implementation of self.  But changing /proc/self to return the tid
at this point is more likely than not to beak applications so that I
have avoided.

Eric

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