linux-kernel - Re: [!GIT PULL] kdbus for 4.2

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Date:	Thu, 2 Jul 2015 17:39:17 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Tom Gundersen <teg@...m.no>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Jiri Kosina <jkosina@...e.cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Daniel Mack <daniel@...que.org>,
	David Herrmann <dh.herrmann@...il.com>,
	Djalal Harouni <tixxdz@...ndz.org>
Subject: Re: [!GIT PULL] kdbus for 4.2

On Fri, Jun 26, 2015 at 12:36 PM, Tom Gundersen <teg@...m.no> wrote:
> On Fri, Jun 26, 2015 at 9:33 PM, Andy Lutomirski <luto@...capital.net> wrote:
>> What's a good distro on which to poke at a full running system?
>
> Fedora Rawhide is probably currently your best bet.

I won't swear that all of the problems I'm seeing are 100% kdbus'
fault, but Rawhide, updated today, has serious problems with the kdbus
branch in Greg's char-misc tree.

Problem 1: Booting a kdbus-enabled kernel (CONFIG_KDBUS=y) causes gdm
to bail saying "oops, something went wrong" or whatever the useless
standard error message is.

I can work around problem 1 by booting with kdbus=1, but that's not
okay.  Unless this is limited to just some narrow range of Rawhide
versions, I don't think the kernel gets to make changes that break
userspace like that.  Maybe this is a kernel issue, not a user issue,
in which case it's not a big deal as long as it gets fixed.

Problem 2: Running 'sudo mount /mnt/share' from a terminal hangs the
whole graphical session hard.  This is repeatable.  /mnt/share is
virtfs, but I doubt that matters.

If I build exactly the same sources but set CONFIG_KDBUS=n, all is well.

I suspect that there are multiple issues here:

1. The current state of systemd's --disable-kdbus could be buggy.
kdbusfs still gets mounted but isn't set up and then things break.

2. mount generates a bunch of dbus traffic.  Apparently on the latest
char-misc kdbus tree with the latest Rawhide, it blows up somehow.

That's all from me until next week.

--Andy
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