[bug#37510] [PATCH 1/1] compile: Fix race condition on completion progress.

[ericbavier]

From: Eric Bavier <address@hidden>

This prevent a race condition where multiple compilation threads could report
the same completion.

* guix/build/compile.scm (compile-files)<completed>: Increment in same mutex
region as the compilation is reported.


Further reading:

When compiling many scheme files, or with '-j1', this is not usually a
problem, but with multiple build jobs and a handful of scheme files to update,
you may encounter unexpected output.  E.g. I recently saw this from `make -j2`:

```
Compiling Scheme modules...
[ 25%] LOAD     gnu/packages/haskell.scm
;;; note: source file ./gnu/packages/haskell.scm
;;;       newer than compiled /home/bavier/projects/guix/gnu/packages/haskell.go
;;; note: source file ./gnu/packages/haskell.scm
;;;       newer than compiled /home/bavier/projects/guix/gnu/packages/haskell.go
[ 50%] LOAD     gnu/packages/idris.scm
;;; note: source file ./gnu/packages/idris.scm
;;;       newer than compiled /home/bavier/projects/guix/gnu/packages/idris.go
;;; note: source file ./gnu/packages/idris.scm
;;;       newer than compiled /home/bavier/projects/guix/gnu/packages/idris.go
[ 75%] GUILEC   gnu/packages/haskell.go
[ 75%] GUILEC   gnu/packages/idris.go
make[2]: Leaving directory '/home/bavier/projects/guix'
make[1]: Leaving directory '/home/bavier/projects/guix'
```
---
 guix/build/compile.scm | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/guix/build/compile.scm b/guix/build/compile.scm
index c127456fd0..f77e49340a 100644
--- a/guix/build/compile.scm
+++ b/guix/build/compile.scm
@@ -173,7 +173,8 @@ files are for HOST, a GNU triplet such as 
\"x86_64-linux-gnu\"."
 
   (define (build file)
     (with-mutex progress-lock
-      (report-compilation file total completed))
+      (report-compilation file total completed)
+      (set! completed (+ 1 completed)))
 
     ;; Exit as soon as something goes wrong.
     (exit-on-exception
@@ -185,9 +186,7 @@ files are for HOST, a GNU triplet such as 
\"x86_64-linux-gnu\"."
                          #:output-file (string-append build-directory "/"
                                                       (scm->go relative))
                          #:opts (append warning-options
-                                        (optimization-options relative)))))))
-    (with-mutex progress-lock
-      (set! completed (+ 1 completed))))
+                                        (optimization-options relative))))))))
 
   (with-augmented-search-path %load-path source-directory
     (with-augmented-search-path %load-compiled-path build-directory
-- 
2.23.0