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Date: Wed, 5 Aug 2015 09:10:50 +0200
Message-ID: <CANq1E4Rek3HXCDU_13OGfRShS7Z0g+fxcTp5C1V3oKC4HgkD_A@mail.gmail.com>
Subject: Re: kdbus: to merge or not to merge?
From: David Herrmann <dh.herrmann@gmail.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Djalal Harouni <tixxdz@opendz.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Havoc Pennington <havoc.pennington@gmail.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        Tom Gundersen <teg@jklm.no>, Daniel Mack <daniel@zonque.org>,
        "Kalle A. Sandstrom" <ksandstr@iki.fi>, Borislav Petkov <bp@alien8.de>,
        cee1 <fykcee1@gmail.com>
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Hi

On Tue, Aug 4, 2015 at 4:47 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> On Tue, Aug 4, 2015 at 7:09 AM, David Herrmann <dh.herrmann@gmail.com> wrote:
>> This is a bug in the proxy (which is already fixed).
>
> Should I expect to see it in Rawhide soon?

Use this workaround until it does:

    $ DBUS_SYSTEM_BUS_ADDRESS="kernel:path=/sys/fs/kdbus/0-system/bus"
./your-binary

> Anyway, the broadcasts that I intended to exercise were
> KDBUS_ITEM_ID_REMOVE.  Those appear to be broadcast to everyone,
> irrespective of "policy", so long as the "match" thingy allows it.

Matches are opt-in, not opt-out. Nobody will get this message unless
they opt in.

> The bloom filter thing won't help at all according to the docs: bloom
> filters don't apply to kernel-generated notifications.

Bloom filters apply to message payloads. Kernel notifications do not
carry a message payload. Message metadata can be filtered for
explicitly (without false-positives).

> So yes, as far as I can tell, kdbus really does track object lifetime
> by broadcasting every single destruction event to every single
> receiver (subject to caveats above) and pokes the data into every
> receiver's tmpfs space.

Broadcast reception is opt-in.

Thanks
David
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