linux-kernel - Re: [GIT PULL] kdbus for 4.1-rc1

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Date:	Thu, 23 Apr 2015 09:46:22 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Tom Gundersen <teg@...m.no>, Jiri Kosina <jkosina@...e.cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Daniel Mack <daniel@...que.org>,
	David Herrmann <dh.herrmann@...il.com>,
	Djalal Harouni <tixxdz@...ndz.org>
Subject: Re: [GIT PULL] kdbus for 4.1-rc1

On Thu, Apr 23, 2015 at 9:36 AM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Thu, Apr 23, 2015 at 03:05:48PM +0200, Greg Kroah-Hartman wrote:
>>
>> Andy's concerns about the capability stuff has been hashed out in
>> multiple threads here.  The kernel code isn't buggy as-designed or
>> implemented from what we can all tell, it's just that the new
>> functionality isn't liked by everyone, which is totally fair, but not a
>> reason to declare that the function isn't useful.
>
> Andy, did I capture your existing position correctly?  If we drop the
> caps metadata, I'm guessing that you are ok with the code as you have
> reviewed it and tested it out.  So should I just add a small patch that
> removes this for now?  After that, we can discuss the addition of
> capabilities to the metadata as an add-on feature with a future patch
> and not hold up this larger merge request?

No.  I can fish out lists I've posted of what I personally dislike.
To repeat from my not-yet-awake memory, briefly:

 - starttime, cmdline, and possibly other pieces of metadata are also
problematic.  I think starttime is especially bad because it both
breaks CRIU and is IMO completely unnecessary -- I sent out draft
"highpid" patches a while ago to give a much better alternative that
isn't racy and won't break CRIU.  But cmdline is also IMO ridiculous.

 - There's still an open performance question.  Namely: is kdbus performant?

 - The policy system still sucks.  Now, if we give up on the idea of
anyone ever using it for anything other than dbus as it currently
works, maybe this isn't a real problem.

 - Someone should probably convince someone who understands memory
accounting that the pool mechanism accounts memory acceptably.  I
don't know much about mm stuff, but I think it's subject to all kinds
of nasty latency and accounting abuses, some of which might even be
exploited by accident.

I haven't reviewed most of it.  I've reviewed the metadata code (and
not recently) and the pool *docs*.

Shouldn't the bulk of this code have actual review before it gets
merged?  I've only reviewed some of it, and I didn't like what I found
in that small fraction, hence my objections to caps.

--Andy

>
> thanks,
>
> greg k-h



-- 
Andy Lutomirski
AMA Capital Management, LLC
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