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

[Florian Weimer]

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 --no-hard-links, the separate touch invocation is no longer
required.

---
 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..b0ce27fbae 100644
--- a/localedata/gen-locale.sh
+++ b/localedata/gen-locale.sh
@@ -32,15 +32,23 @@ generate_locale ()
   out=$3
   flags=$4
   ret=0
+
+  # Use a staging area to avoid writing to locales concurrently.
+  # While this process is running, $$ is sufficiently unique.
+  # Use --no-hard-links to prevent localedef from accessing
+  # other staging areas.
+  stage="${common_objpfx}localedata/gen-locale.$$.tmp"
+
   ${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
+	${localedef_after_env} $flags --no-hard-links -f $charmap -i $input \
+	$stage || ret=$?
+  if [ $ret -eq 0 ] ; then
+      # Ignore errors in case some other process has created the same locale.
+      # (Some versions of mv do not report an error here.)
+      mv -Tn $stage ${common_objpfx}localedata/$out 2>/dev/null || true
+      rm -rf $stage
   else
+    rm -rf $stage
     echo "Charmap: \"${charmap}\" Inputfile: \"${input}\"" \
 	 "Outputdir: \"${out}\" failed"
     exit 1