Fix race condition in config maven plugin

The race occur during Maven parallel build where multiple threads will
race to create the output directory.

1 files changed, 3 insertions, 1 deletions

diff --git a/configgen/src/main/scala/com/yahoo/config/codegen/JavaClassBuilder.scala b/configgen/src/main/scala/com/yahoo/config/codegen/JavaClassBuilder.scala
index c346338e543..f2ee4f74157 100644
--- a/configgen/src/main/scala/com/yahoo/config/codegen/JavaClassBuilder.scala
+++ b/configgen/src/main/scala/com/yahoo/config/codegen/JavaClassBuilder.scala
@@ -166,7 +166,9 @@ object JavaClassBuilder {
     val subDirs: Array[String] = (PackagePrefix + namespace).split("""\.""")
     for (subDir <- subDirs) {
       dir = new File(dir, subDir)
-      if (!dir.isDirectory && !dir.mkdir) throw new CodegenRuntimeException("Could not create " + dir.getPath)
+      this.synchronized {
+        if (!dir.isDirectory && !dir.mkdir) throw new CodegenRuntimeException("Could not create " + dir.getPath)
+      }
     }
     dir
   }