Bug#918764: udev: "udevadm control --reload-rules" kills all processes except init

[Axel Beckert]

Control: tag -1 moreinfo

Hi!

Gedalya wrote:
> > It just happened again, triggered by wireshark-dkms
> s/wireshark/wireguard/

Ehm, yes. :-)

> Also, on my router, ntpd is moved to another cgroup (for routing
> purposes). This is done in cgroup2, old cgroup is not mounted at
> all. ntpd remains the only running process apart from init.
> 
> Moving udev into its own special cgroup didn't change anything: udev
> is still running, same PID, and and the same goes for ntpd.
> Everything else is killed.

And here you gave me the right hint: cgroups!

I don't have systemd, but I wanted to play with anbox, which
pulled in lxc and cgroupfs-mount besides others. And while I was able
to kill all processes with "udevadm control --reload-rules" just
beforehand, removing these packages made the issue vanish for me:

[REMOVE, NOT USED] bridge-utils:amd64 1.6-2
[REMOVE, NOT USED] dnsmasq-base:amd64 2.80-1
[REMOVE, NOT USED] liblinux-lvm-perl:amd64 0.17-2
[REMOVE, NOT USED] redir:amd64 3.2-1
[REMOVE, DEPENDENCIES] anbox:amd64 0.0~git20181210-1
[REMOVE, DEPENDENCIES] liblxc1:amd64 1:3.1.0+really3.0.3-2
[REMOVE, DEPENDENCIES] lxc:amd64 1:3.1.0+really3.0.3-2
[REMOVE, DEPENDENCIES] lxctl:amd64 0.3.1+debian-4
[REMOVE, DEPENDENCIES] python3-lxc:amd64 1:3.0.3-1
[REMOVE, DEPENDENCIES] vagrant-lxc:amd64 1.4.3-1
[REMOVE] cgroupfs-mount:amd64 1.4

(from /var/log/aptitude)

So I tried to figure out which of these packages actually trigger the
change and installed one by one again. Inbetween each package
installation run I did the following three commands to see if anything
killed my SSH session:

# udevadm control --reload-rules
# service udev restart
# udevadm control --reload-rules

But none did directly. The issue came back later. though and I
rebooted.

Then I uninstalled not all of them at once but each of them one by
one. And the one after whose purging

# service udev restart
# udevadm control --reload-rules

didn't kill my processes anymore was cgroupfs-mount.

So for some reason this killing only seems to happen on my box if
cgroupfs-mount is installed. Then again, this is only necessary if
systemd is not installed. But we also had reports where this happend
with systemd, so this doesn't seem to be depend on the init system (at
most at the init system's default features) and hence also the package
cgroupfs-mount can't be held guilty for this.

Which IMHO again leaves either src:systemd or src:linux as rc-buggy
package.

I've allowed myself to remove at least the moreinfo tag as there are
now multiple hints on how to reproduce this issue.

Will now run my systemd without cgroupfs-mount and see if I ran into
this issue again soon.

		Regards, Axel
-- 
 ,''`.  |  Axel Beckert <abe at debian.org>, https://people.debian.org/~abe/
: :' :  |  Debian Developer, ftp.ch.debian.org Admin
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