netdev - Re: bpfilter causes a leftover kernel process

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Date:   Tue, 28 Aug 2018 13:23:38 +0200
From:   Olivier Brunel <jjk@...cky.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     netdev@...r.kernel.org, daniel@...earbox.net
Subject: Re: bpfilter causes a leftover kernel process

On Mon, 27 Aug 2018 20:35:02 -0700
Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:

> I'm also running Arch Linux in my VM, but I'm not able to reproduce
> umount issue. I'm guessing it's somehow related to non-static build
> and libc.so being busy with old systemd.

Oh, I mentioned it in a previous draft of my original mail but it
seems it got lost in rewrites, I don't actually use systemd. Not that
it should matter here though.

> Typical shutdown should have done:
> [   73.498022] shutdown[1]: Sending SIGTERM to remaining processes...
> [   73.505501] shutdown[1]: Sending SIGKILL to remaining processes...
> [   73.512783] shutdown[1]: Unmounting file systems.
> And at the time of umount / no processes are alive other than systemd.

Yeah, I have a similar thing happening on shutdown, except that we're
talking about a kernel thread here, so that process is ignored by the
mentionned killing spree as a result, thus leaving that process running.

>From a shell opened after the umounting fails I can see that only my
pid1 & the opened shell are running, except of course that this
bpfilter process is there, as a kernel thread "[none]"

Manually killing it at that point works, i.e. allows the umounting to
succeed and a proper shutdown to complete.