[GitHub] [lucene-solr] gus-asf commented on a change in pull request #838: SOLR-13705 Double-checked locking bug is fixed.

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gus-asf commented on a change in pull request #838: SOLR-13705 Double-checked locking bug is fixed.
URL: https://github.com/apache/lucene-solr/pull/838#discussion_r321050422
 
 

 ##########
 File path: solr/core/src/java/org/apache/solr/handler/admin/SecurityConfHandler.java
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 @@ -260,22 +260,25 @@ public String toString() {
 
   @Override
   public Collection<Api> getApis() {
-    if (apis == null) {
+    Collection<Api> syncedApis = apis;
+    if (syncedApis == null) {
       synchronized (this) {
-        if (apis == null) {
-          Collection<Api> apis = new ArrayList<>();
+        syncedApis = apis;
+        if (syncedApis == null) {
+          syncedApis = new ArrayList<>();
+          apis = syncedApis;
 
 Review comment:
   Is this correct? Doesn't this line assigning syncedApis to apis expose the partially configured empty list to the rest of the world as a non-immutable collection while the rest of this method executes (which was the original complaint)? I think without this line the patch is an improvement...(the existing code has this problem too).

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