Subject: [bug#66387] [PATCH] home: services: Fix race condition when detecting first login

From: Andrew Tropin <[email-masked]>
Date: Fri, 20 Oct 2023 10:55:46 +0400

On 2023-10-19 22:29, Ludovic Courtès wrote:

> Hi Carlo,
>
> Carlo Zancanaro <[email-masked]> skribis:
>
>> * gnu/home/services.scm (compute-on-first-login-script): Use open to
>> atomically check whether a file exists and create it if not.
>
> Good catch!
>
> I made the following cosmetic changes (‘open-fdes’ is cheaper than
> ‘open’) and applied it.
>
> Thanks!
>
> Ludo’.
>
> diff --git a/gnu/home/services.scm b/gnu/home/services.scm
> index 7137925b30..651c068f79 100644
> --- a/gnu/home/services.scm
> +++ b/gnu/home/services.scm
> @@ -414,15 +414,15 @@ (define (compute-on-first-login-script _ gexps)
>           (use-modules (guix i18n)
>                        (guix diagnostics))
>  
> -       (define (claim-first-run file-name)
> +       (define (claim-first-run file)

Very nice trick!  Carol, Ludo, Thank you for the fix!

>           (catch #t
>             (lambda ()
> -             ;; This incantation will raise an error if the file at
> -             ;; flag-file-path already exists, and will create it otherwise.
> -             (close (open file-name (logior O_CREAT O_EXCL)))
> +             ;; This incantation raises an error if FILE already exists, and
> +             ;; creates it otherwise.
> +             (close-fdes
> +              (open-fdes file (logior O_CREAT O_EXCL O_CLOEXEC)))
>               #t)
> -           (lambda _
> -             #f)))
> +           (const #f)))
>  
>         #$%initialize-gettext
>  

-- 
Best regards,
Andrew Tropin