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Re: 05/07: inferior: Fix concurrent cached-profile calls.
From: |
Ludovic Courtès |
Subject: |
Re: 05/07: inferior: Fix concurrent cached-profile calls. |
Date: |
Wed, 10 Mar 2021 10:48:21 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) |
Hi Mathieu,
guix-commits@gnu.org skribis:
> commit 6ee7e3d26b8f5d2a234518cc2ab1bfeba7cd7c18
> Author: Mathieu Othacehe <othacehe@gnu.org>
> AuthorDate: Fri Mar 5 12:49:06 2021 +0100
>
> inferior: Fix concurrent cached-profile calls.
>
> * guix/inferior.scm (cached-profile): Do not create the profile symlink
> if it
> already exists.
[...]
> +++ b/guix/inferior.scm
> @@ -755,8 +755,9 @@ seconds. This procedure opens a new connection to the
> build daemon."
> (built-derivations (list profile))
> ;; Note: Caching is fine even when AUTHENTICATE? is false because
> ;; we always call 'latest-channel-instances?'.
> - (symlink* (derivation->output-path profile) cached)
> - (add-indirect-root* cached)
> + (unless (file-exists? cached)
> + (symlink* (derivation->output-path profile) cached)
> + (add-indirect-root* cached))
> (return cached))))))
It should be ‘munless’ instead of ‘unless’ since we’re in an ‘mbegin’.
However, there’s already a (file-exists? cached) call a few lines
above. So what you need instead is a TOCTTOU-free ‘symlink’, along
these lines:
(define (symlink/safe old new)
(catch 'system-error
(lambda ()
(symlink old new))
(lambda args
(unless (= EEXIST (system-error-errno args))
(apply throw args)))))
;; …
(define symlink*
(lift2 symlink/safe %store-monad))
WDYT?
Ludo’.
- Re: 05/07: inferior: Fix concurrent cached-profile calls.,
Ludovic Courtès <=