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From: ludo@gnu.org (Ludovic Courtès)
To: Caleb Ristvedt <caleb.ristvedt@cune.org>
Cc: guix-devel@gnu.org
Subject: Re: Latest guile-daemon changes and bewilderment
Date: Tue, 01 Aug 2017 14:46:50 +0200	[thread overview]
Message-ID: <87k22no3ph.fsf@gnu.org> (raw)
In-Reply-To: <87wp6sbygq.fsf@cune.org> (Caleb Ristvedt's message of "Fri, 28 Jul 2017 06:19:33 -0500")

Hi reepca,

Caleb Ristvedt <caleb.ristvedt@cune.org> skribis:

>> Is there a line above or below the backtrace mentioning the uncaught
>> exception?  Could you ‘strace -f’ the daemon process?
>
> No, no line above or below. Very strange.

And strace?  :-)  It could be that it fails to load some of the
(system *) helper modules when displaying the error, something like
that.

>> BTW, I see the code uses ‘clone’ directly.  It would be safer to use
>> ‘call-with-container’, which already handles bind mounts, non-local
>> exits, and so on.  Would it be an option?
>
> There are a couple of issues with using call-with-container. In
> decreasing order of perceived difficulty to solve:

[...]

> ... and then I paused writing this for 2 days while I checked whether my
> in-theory solutions would work in practice. And it seems like they
> actually do (see recent branch update). Mostly. I need to figure out why
> it fails when a new user namespace is created - for some reason
> pivot-root fails when new-root was mounted from a different user
> namespace.

Heheh.  :-)

The commit “build-derivations: use call-with-container” does two things:
adjust ‘call-with-container’, and actually use it in the new daemon
code.  I think it would be great to split this into two logical changes.

I don’t get the use of ‘try-umount’ in an unwind handler of
‘call-with-container’.  Since ‘call-with-container’ uses
‘call-with-temporary-directory’, ROOT is never a mount point, no?

> But on the bright side, it somehow solved the bug I described earlier. I
> still haven't managed to make it all the way to building hello (a
> libunistring test hangs), but it's getting much farther.

If the hanging test is ‘test-lock’, that’s a “known problem” on machines
with more than ~8 cores, and it’s fixed in core-updates.

>> Let’s maybe try to further debug this interactively on IRC.
>
> ... and then I promptly fell asleep and spent the next few days
> (nights?) tinkering. Oops.

No problem.  :-)

Next time feel free to ping me when you’re at the peak of your debugging
activity, in case I can help out!

Thanks,
Ludo’.

  reply	other threads:[~2017-08-01 12:46 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-24 10:18 Latest guile-daemon changes and bewilderment Caleb Ristvedt
2017-07-25  8:44 ` Ludovic Courtès
2017-07-28 11:19   ` Caleb Ristvedt
2017-08-01 12:46     ` Ludovic Courtès [this message]
2017-08-20  6:30     ` Ricardo Wurmus
2017-07-25 20:05 ` Mark H Weaver

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