To: Richard Weinberger <richard@nod.at>
Cc: Austin S Hemmelgarn <ahferroin7@gmail.com>,
        "Theodore Ts'o" <tytso@mit.edu>, Harald Hoyer <harald@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [GIT PULL] kdbus for 4.1-rc1
References: <21824.5086.446831.189915@quad.stoffel.home>
 <5540D2F9.2010704@redhat.com>
 <CAFLxGvzz3ac19J=dC_gWrrY=BG4h-LO+uRn2rOr1eWyVnk3vzg@mail.gmail.com>
 <5540DEEB.2060405@redhat.com> <5540E0C7.3050106@nod.at>
 <5540E432.9020606@redhat.com> <5540E4D9.6000007@nod.at>
 <5540E684.4070606@redhat.com> <5540E821.8050204@nod.at>
 <5540F081.9090005@redhat.com> <20150429150341.GA12374@thunk.org>
 <5540F6E3.8000706@gmail.com> <871tj2ouk2.fsf%l.stelmach@samsung.com>
 <5541F209.8070302@nod.at>
From: =?utf-8?Q?=C5=81ukasz_Stelmach?= <l.stelmach@samsung.com>
Date: Thu, 30 Apr 2015 12:19:00 +0200
In-reply-to: <5541F209.8070302@nod.at>
Message-id: <87wq0tor57.fsf%l.stelmach@samsung.com>
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It was <2015-04-30 czw 11:12>, when Richard Weinberger wrote:
> Am 30.04.2015 um 11:05 schrieb =C5=81ukasz Stelmach:
>> Regardless, of initrd issues I feel there is a need of a local IPC
>> that is more capable than UDS. Linus Torvalds is probably right that
>> dbus-daemon is everything but effictient. I disagree, however, that
>> it can be optimised and therefore solve *all* issues kdbus is trying
>> to address. dbus-deamon, by design, can't some things. It can't
>> transmitt large payloads without copying them. It can't be made
>> race-free.
>
> This is true.
> But as long dbus-deamon is not optimized as much as possible there is
> no reason to force push kdbus.
> As soon dbus-deamon exploits all kernel interfaces as much it can and
> it still needs work (may it performance or other stuff) we can think
> of new kernel features which can help dbus-deamon.

I may not be well informed about kernel interfaces, but there are some
use cases no dbus-daemon optimisation can make work properly because of
rece-conditons introduced by the user-space based message router.

For example, a service can't aquire credentials of a client process that
actually sent a request (it can, but it can't trust them). The service
can't be protected by LSM on a bus that is driven by dbus-daemon. Yes,
dbus-daemon, can check client's and srevice's labels and enforce a
policy but it is going to be the daemon and not the LSM code in the
kernel.

=2D-=20
=C5=81ukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics

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