[GitHub] [httpcomponents-core] rschmitt commented on a change in pull request #293: Fix data race in StrictConnPool

[GitBox <gi...@apache.org>]

rschmitt commented on a change in pull request #293:
URL: https://github.com/apache/httpcomponents-core/pull/293#discussion_r654649739



##########
File path: httpcore5/src/main/java/org/apache/hc/core5/pool/StrictConnPool.java
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@@ -699,14 +699,18 @@ public boolean isDone() {
         }
 
         public void failed(final Exception ex) {
-            if (this.completed.compareAndSet(false, true)) {
-                this.ex = ex;
+            synchronized (this.completed) {

Review comment:
       |Thread A | Thread B|
   |-|-|
   |Set `completed` to true ||
   ||Call `isDone()`, which returns `true`|
   ||Call `getResult()`/`getException()`, which return `null`|
   |Set `ex`/`result`||
   
   I found this race condition by inspection. I'm trying to track down a connection leak that we're continuing to get reports about. In the absence of a repro, I've resorted to auditing the code. I don't know if this race condition results in an actual bug, or is just benign, but either way there's no reason not to fix it.




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