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

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Message-ID: <554244CB.10606@nod.at>
Date:	Thu, 30 Apr 2015 17:05:47 +0200
From:	Richard Weinberger <richard@....at>
To:	Łukasz Stelmach <l.stelmach@...sung.com>
CC:	Austin S Hemmelgarn <ahferroin7@...il.com>,
	Theodore Ts'o <tytso@....edu>,
	Harald Hoyer <harald@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [GIT PULL] kdbus for 4.1-rc1

Am 30.04.2015 um 16:52 schrieb Łukasz Stelmach:
>> Sorry, I thought you mean the races while collecting metadata in userspace...
> 
> My bad, some reace conditions *are* associated with collecting metadata
> but ont all. It is impossible (correct me if I am wrong) to implement
> reliable die-on-idle with dbus-daemon.

IIRC Andy gave some ideas howto deal with that.
i.e. https://lkml.org/lkml/2015/4/29/622

>>> AF_UNIX with multicast support wouldn't be AF_UNIX anymore.
>>>
>>> AF_BUS? I haven't followed the discussion back then. Why do you think it
>>> is better than kdbus?
>>
>> Please see https://lwn.net/Articles/641278/
> 
> Thanks. If I understand correctly, the author suggests using EBPF on a
> receiveing socket side for receiving multicast messages. This is nice if
> you care about introducing (or not) (too?) much of new code. However,
> AFAICT it may be more computationally complex than Bloom filters because
> you need to run EBPF on every receiving socket instead of getting a list
> of a few of them to copy data to. Of course for small number of
> receivers the "constant" cost of running the Bloom filter may be higher.

To make the story short, the kdbus *concept* needs much more
thought. There are many ideas out there howto deal with dbus issues without introducing
an ad-hoc solution. AF_BUS is just one of them.
IMHO AF_BUS would be nice but the decision is not up to me.

Thanks,
//richard


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