linux-kernel - Re: Linux messages full of `random: get_random

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Date:   Thu, 26 Apr 2018 22:47:49 +0200
From:   Christian Brauner <christian.brauner@...onical.com>
To:     Sultan Alsawaf <sultanxda@...il.com>
Cc:     "Theodore Y. Ts'o" <tytso@....edu>, linux-kernel@...r.kernel.org,
        Jann Horn <jannh@...gle.com>
Subject: Re: Linux messages full of `random: get_random_u32 called from`

On Thu, Apr 26, 2018 at 01:22:02PM -0700, Sultan Alsawaf wrote:
> > Hmm, it looks like the multiuser startup is getting blocked on snapd:
> >
> >          29.060s snapd.service
> >
> > graphical.target @1min 32.145s
> > └─multi-user.target @1min 32.145s
> >   └─hddtemp.service @6.512s +28ms
> >     └─network-online.target @6.508s
> >       └─NetworkManager-wait-online.service @2.428s +4.079s
> >         └─NetworkManager.service @2.016s +404ms
> >           └─dbus.service @1.869s
> >             └─basic.target @1.824s
> >               └─sockets.target @1.824s
> >                 └─snapd.socket @1.821s +1ms
> >                   └─sysinit.target @1.812s
> >                     └─apparmor.service @587ms +1.224s
> >                       └─local-fs.target @585ms
> >                         └─local-fs-pre.target @585ms
> >                           └─keyboard-setup.service @235ms +346ms
> >                             └─systemd-journald.socket @226ms
> >                               └─system.slice @225ms
> >                                 └─-.slice @220ms
> >
> > This appears to be some kind of new package management system for
> > Ubuntu:
> >
> > Description-en: Tool to interact with Ubuntu Core Snappy.
> >  Install, configure, refresh and remove snap packages. Snaps are
> >  'universal' packages that work across many different Linux systems,
> >  enabling secure distribution of the latest apps and utilities for
> >  cloud, servers, desktops and the internet of things.
> >
> > Why it the Ubuntu package believes it needs to be fully started before
> > the login screen can display is unclear to me.  It might be worth
> > using systemctl to disable snapd.serivce and see if that makes things
> > work better for you.
> >
> > 				- Ted
> 
> I removed snapd completely which did nothing.
> 
> Here are new logs:
> systemd-analyze blame: https://hastebin.com/edehikuyeb.css
> systemd-analyze critical-chain: https://hastebin.com/vedufafema.pl
> dmesg: https://hastebin.com/zuwuwoxadu.vbs
> 
> I should also note that leaving the system untouched does not result in it booting: I must
> provide a source of entropy, otherwise it just stays stuck. In both of the dmesgs I've given, I

We have observed a similiar problem  with libvirt. As soon as entropy is
provided the boot finishes otherwise it hangs for a long time.
This is not happening with v4.17-rc1 afaict.

Christian

> manually provided entropy to the system after about 5 minutes of waiting.
> 
> Also, regardless of what's hanging on CRNG init, CRNG should be able to init on its own in a timely
> manner without the need for user-provided entropy. Userspace was working fine before the recent CRNG
> kernel changes, so I don't think this is a userspace bug.
> 
> -Sultan
>