[bug#30948] [PATCH core-updates] guix: Reap finished child processes in build containers.

[Carlo Zancanaro <carlo@zancanaro.id.au>]

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Hey,

On Fri, Mar 30 2018, Ludovic Courtès wrote:
>> From what I can understand it's one of pid 1's responsiblities 
>> to reap child processes, so I would expect this to be set up 
>> for every builder, before the builder is run.
>
> True, but for derivations it’s also “optional” because 
> eventually guix-daemon terminates all its child processes.

As long as the build process doesn't rely on behaviour that, 
strictly speaking, it should be allowed to rely on. It's not an 
issue of resource leaking, it's an issue of correctness.

>> Given it's not specific to the gnu-build-system, I don't think 
>> it really fits there.
>
> Yes, but note that it would be inherited by all the build 
> systems.

Except for trivial-build-system, which is probably fine. I still 
don't think it fits in a specific build system, given it's a 
behaviour that transcends the specific action happening within the 
container.

Putting it in gnu-build-system will solve the problem in all 
realistic cases, so that's probably fine. It's still subtly 
incorrect, but will only be a problem if something using the 
trivial build system relies on pid 1 to reap a process, or if we 
make a new build system not deriving from gnu-build-system (which 
seems unlikely, but not impossible).

> The “build side” is fully specified: ‘guix graph’ shows exactly 
> what Guile is used where, and you can see with, say:
>
>   guix graph -t derivation \
>     -e '(@@ (gnu packages commencement) findutils-boot0)'
>
> that the early derivations run on Guile 2.0.9.
>
> For “host side” code, users can use any Guile >= 2.0.13.

Yeah, okay. That makes sense. I guess I just expected 2.0.13 to be 
the minimum version throughout.

Carlo

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