Re: [PATCH] build: container: Use the same clone flags as fork(3).

[ludo@gnu.org (Ludovic Courtès)]

David Thompson <dthompson2@worcester.edu> skribis:

> This patch resolves an issue I was having when working with containers
> at the REPL, which means it probably presented undetected issues
> elsewhere.

Calling ‘primitive-fork’ at the REPL is not very useful anyway since you
end up with two Guiles trying to read from the same tty.

> From 61ebbe55f7f6d4d4eb42db957d6fc7b4eaf282a6 Mon Sep 17 00:00:00 2001
> From: David Thompson <dthompson2@worcester.edu>
> Date: Sat, 5 Sep 2015 14:10:08 -0400
> Subject: [PATCH] build: container: Use the same clone flags as fork(3).
>
> The intent is to make 'clone' behave a lot more like 'primitive-fork', which
> calls clone(2) with SIGCHLD, CLONE_CHILD_CLEARTID, and CLONE_CHILD_SETTID
> flags.  Notably, running 'clone' at the REPL without these flags would break
> the REPL beyond repair.
>
> * guix/build/syscalls.scm (CLONE_CHILD_CLEARTID, CLONE_CHILD_SETTID): New
>   variables.
> * gnu/build/linux-container.scm (namespaces->bit-mask): Add
>   CLONE_CHILD_CLEARTID and CLONE_CHILD_SETTID to bit mask.

Looking at clone(2) and libc, I’m guessing that without these flags, the
child would have a wrong idea of its thread ID, which in turn may cause
all sorts of problems, right?

LGTM.

Thanks,
Ludo’.