[glibc] localedata: Avoid concurrently written locales in gen-locale.sh

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=20b13fa08b2831ee67fcc92edf2d89288bcc2c93

commit 20b13fa08b2831ee67fcc92edf2d89288bcc2c93
Author: Florian Weimer <[email protected]>
Date:   Wed Jul 8 17:38:42 2026 +0200

    localedata: Avoid concurrently written locales in gen-locale.sh
    
    There is no cross-directory exclusion of concurrent $(gen-locales)
    usage.  Parallel localedef calls can clobber locale data as it is
    being loaded by tests.
    
    With the separate staging areas, there are no peer directories,
    so hard-linking no longer happens.  The touch command is therefore
    unnecessary.
    
    Reviewed-by: Sam James <[email protected]>

Diff:
---
 localedata/gen-locale.sh | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/localedata/gen-locale.sh b/localedata/gen-locale.sh
index 4762c04284..c449efe125 100644
--- a/localedata/gen-locale.sh
+++ b/localedata/gen-locale.sh
@@ -32,17 +32,25 @@ generate_locale ()
   out=$3
   flags=$4
   ret=0
+
+  # Use a staging area to avoid writing to locales concurrently.
+  # While this process is running, $$ is sufficiently unique.
+  stage="${common_objpfx}localedata/gen-locale.$$.tmp"
+  mkdir "$stage" 2>/dev/null || true
+
   ${localedef_before_env} ${run_program_env} I18NPATH=../localedata \
 	${localedef_after_env} $flags -f $charmap -i $input \
-	${common_objpfx}localedata/$out || ret=$?
-  if [ $ret -eq 0 ]; then
-    # The makefile checks the timestamp of the LC_CTYPE file,
-    # but localedef won't have touched it if it was able to
-    # hard-link it to an existing file.
-    touch ${common_objpfx}localedata/$out/LC_CTYPE
+	$stage/$out || ret=$?
+  if [ $ret -eq 0 ] ; then
+      # Ignore errors in case some other process has created the same locale.
+      # This rename operation should be atomic, and it should fail if the
+      # $out locale already exists (rename fails with ENOTEMPTY).
+      mv $stage/$out ${common_objpfx}localedata/. 2>/dev/null || true
+      rm -rf $stage
   else
+    rm -rf $stage
     echo "Charmap: \"${charmap}\" Inputfile: \"${input}\"" \
-	 "Outputdir: \"${out}\" failed"
+	 "Outputdir: \"${out}\" failed (exit status $ret)"
     exit 1
   fi
 }