Re: [GIT PULL] kdbus for 4.1-rc1

Al Viro
2015-04-15T20:42:10Z

On Wed, Apr 15, 2015 at 01:22:12PM -0700, Andy Lutomirski wrote:

> This leads me to a potentially interesting question: where's the
> buffering? If there's a bus with lots of untrusted clients and one of
> them broadcasts data faster than all receivers can process it, where
> does it go?
>
> At least with a userspace solution, it's clear what the OOM killer
> should kill when this happens. Unless it's PID 1. Sigh.

... and there is a PID 1 specimen that really likes to spew over dbus.
A lot. I had never been able to find out _why_ does systemd feel like
broadcasting all kinds of stuff from PID 1 - maybe somebody in this
thread can answer that. For example, what's the point of broadcasting
mount table updates, when
* it can't hope to catch all individual changes - they _can_ get
lumped together, no matter what it tries.
* any process can just as easily keep track of that data on its
own as it could by watching those broadcasts; parsing /proc/self/mountinfo
isn't harder than parsing notifications.
* you need to start with obtaining the original state somehow, or
what would you apply those updates to?
* if one insists on having a daemon doing such broadcasts, what
the hell is the point of having PID 1 do that? Exact same logics would
do just fine. Moreover, you could have one running in a namespace of
your session, which is something PID 1 won't see.

Sure, I understand why it wants to be aware of what's mounted and where it's
mounted. Just as it wants to know what time it is. Should it broadcast
a dbus message every second, just to tell everyone what had it found about
the time?

I'm somewhat tempted to propose AF_TWITTER - would match the style... ;-/
And frankly, this really looks like a social media braindamage - complete
with status update broadcast every time a plane flies by...