Re: using shepherd's (shepherd service repl) in guix system

[Andy Wingo <wingo@igalia.com>]

On Tue 09 Jan 2024 23:36, Ludovic Courtès <ludo@gnu.org> writes:

> scheme@(shepherd-user)> (+ 2 3)
> $6 = 5
> scheme@(shepherd-user)> (lookup-service 'repl)
> ;;; socket:56:1: warning: possibly unbound variable `lookup-service'
> ice-9/boot-9.scm:1685:16: In procedure raise-exception:
> Unbound variable: lookup-service
>
> Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
> scheme@(shepherd-user) [1]> While reading expression:
> Attempt to suspend fiber within continuation barrier
> scheme@(shepherd-user) [1]> While reading expression:
> Attempt to suspend fiber within continuation barrier
>
>
> The problem here is that the exception is raised C code (in
> libguile/modules.c, then indirectly calling ‘scm_error’), which makes it
> a “continuation barrier” (meaning that it prevents Fibers from switching
> contexts among fibers in the shepherd process, hence the error above.)

Interesting.  I guess the short-term fix is to only enter the debugger
if suspendable-continuation? is true for the fibers prompt, and
otherwise just print a backtrace.

Andy