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From: Eelco Dolstra <eelco.dolstra@logicblox.com>
To: "Ludovic Courtès" <ludo@gnu.org>
Cc: guix-devel <guix-devel@gnu.org>, nix-dev <nix-dev@lists.science.uu.nl>
Subject: Re: Avoiding threads in the daemon
Date: Fri, 19 Dec 2014 19:20:42 +0100	[thread overview]
Message-ID: <54946C7A.9020804@logicblox.com> (raw)
In-Reply-To: <87mw6lym95.fsf@gnu.org>

Hi,

On 18/12/14 17:32, Ludovic Courtès wrote:

> Thus, I think Nix commit 49fe95 (which introduces monitor-fd.hh, which
> uses std::thread just for convenience) should be reverted, along with
> the subsequent commits to that file; then commit 524f89 can be reverted.

I really don't want to get rid of threads because they're useful and I want to
use them more in the future (e.g. build.cc would be much simpler if it used
threads rather than the current event-driven approach; nix-daemon could handle
client connections with a thread rather than a process; etc.).

I see a few ways to get PID namespaces back:

* Do a regular fork followed by clone(... | CLONE_NEWPID | CLONE_PARENT) (after
which the intermediate process can exit).

* Call setuid/setgid via syscall() to bypass the locking in the Glibc wrappers.
However, there might be other problematic functions so this is not a great solution.

* Get the Glibc folks to provide a way to run at-fork handlers with clone().

Clearly the first option is the easiest.

-- 
Eelco Dolstra | LogicBlox, Inc. | http://nixos.org/~eelco/
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  reply	other threads:[~2014-12-19 18:20 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-18 16:32 Avoiding threads in the daemon Ludovic Courtès
2014-12-19 18:20 ` Eelco Dolstra [this message]
2014-12-19 18:41   ` Shea Levy
2014-12-19 18:46     ` Eelco Dolstra
2014-12-19 21:31   ` Ludovic Courtès
2014-12-19 21:36     ` Luca Bruno
2014-12-20  0:11   ` Alexander Kjeldaas
2014-12-23 16:26   ` Eelco Dolstra
2014-12-26 22:02     ` Ludovic Courtès

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