[systemd-devel] [PATCH 0/5] kdbus: allow multiple policies

Simon McVittie simon.mcvittie at collabora.co.uk
Fri Aug 1 04:13:05 PDT 2014

On 31/07/14 21:38, Kay Sievers wrote:
> We have one .busname file per name and it will get really complicated
> to start stop a busname, when it has multiple names per connection. We
> should really avoid that and require one connection per name and allow
> only name.

I might be misunderstanding what you're getting at here (unfortunately I
still haven't had time to review the kdbus design or codebase in detail)
but are you saying that under kdbus, each connection to the bus (thing
with a unique name like :1.42, analogous to DBusConnection) is only
allowed to own one well-known name (thing like org.freedesktop.systemd1)?

If that's true, then I need to raise a red flag here: that would be a
significant regression compared with traditional D-Bus, and is going to
break the semantics of currently-working applications if an existing
library like GDBus or libdbus moves from traditional D-Bus to kdbus. We
have always advised applications to try to avoid having more than one
connection to the same bus, because messages received from different
buses arrive in an undefined order, breaking total or even causal
ordering (and I've seen this cause real-world bugs). So if an
application needs more than one name, for which there are many
real-world uses, it would currently use one connection to the bus to own
all those names, preserving total ordering of messages to all of those

I hope I'm just misunderstanding your message, though.


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