[systemd-devel] [PATCH] cgtop: useful error messages when bootup fails

[Lennart Poettering]

On Mon, 21.05.12 23:04, shawn (shawnlandden at gmail.com) wrote:

Heya,

> Uggh, sorry for sending that super-buggy patch. Here is a better
> version.
> 
> On Mon, 2012-05-21 at 22:59 -0700, Shawn Landden wrote: 
> > cgtop quits on startup if all the cgroup mounts it expects are not ready.
> > Provide user with some indication of why cgtop failed.

> >From 33fa72fdbed3e82d9910e8ecf4b04502fe266ebf Mon Sep 17 00:00:00 2001
> From: Shawn Landden <shawnlandden at gmail.com>
> Date: Mon, 21 May 2012 22:54:41 -0700
> Subject: [PATCH] cgtop: useful error messages when bootup fails
> 
> cgtop quits on startup if all the cgroup mounts it expects are not ready.
> Provide user with some indication of why cgtop failed.

Hmm, this is misleading. THis has little to do with being ready, as the
cgroup VFS are mounted synchronously very early in PID 1 and it is
basically very hard to run in parallel with that.

So this check actually would check for something different: whether the
system was booted with systemd at all, and whether the respective cgroup
controller has been enabled in the kernel at all. But for the former an
excplicit early check for sd_booted() would probably a nicer choice
(though I must say I shiver at the idea that we add this to all our
tools). And for the latter we should probably fix things so that the
tool works fine even if cpuacct, memory and blkio (or any subset of them
are not available), after all those controllers should be optional.

How did you start cgtop so that you ran into this problem?

Lennart

-- 
Lennart Poettering - Red Hat, Inc.