[concurrency-interest] CompletableFuture.get() swallows thread interrupt flag on Java 11

Doug Lea dl at cs.oswego.edu
Fri Oct 16 07:49:19 EDT 2020


Thanks for reporting this; sorry for problems. As David noticed, there 
was a path that did not re-establish interrupt status. Now updated to 
place this check along common path.

(While I'm at it: sorry that teaching and CS dept chairing during 
pandemic make for  slow response to just about everything.)



@@ -1855,25 +1855,25 @@
              }
              else if (!queued)
                  queued = tryPushStack(q);
+            else if (interruptible && q.interrupted) {
+                q.thread = null;
+                cleanStack();
+                return null;
+            }
              else {
                  try {
                      ForkJoinPool.managedBlock(q);
                  } catch (InterruptedException ie) { // currently 
cannot happen
                      q.interrupted = true;
                  }
-                if (q.interrupted && interruptible)
-                    break;
              }
          }
-        if (q != null && queued) {
+        if (q != null) {
              q.thread = null;
-            if (!interruptible && q.interrupted)
+            if (q.interrupted)
                  Thread.currentThread().interrupt();
-            if (r == null)
-                cleanStack();
          }
-        if (r != null || (r = result) != null)
-            postComplete();
+        postComplete();
          return r;
      }



On 10/14/20 11:33 PM, Jens Wilke via Concurrency-interest wrote:
> Hello everyone,
>
> finally I am using more of the Java 8 concurrency code (yay!) and 
> found something strange.
>
> Here is the test code:
>
>     Executor executor = Executors.newCachedThreadPool();
>     Thread t = new Thread(() -> {
>       while (!Thread.interrupted()) {
>         CompletableFuture<Void> future = new CompletableFuture<>();
>         executor.execute(() -> future.complete(null));
>         try {
>           future.get();
>         } catch (InterruptedException e) {
>           return;
>         } catch (ExecutionException e) {
>           e.printStackTrace();
>         }
>       }
>     });
>     t.start();
>     Thread.sleep(1000);
>     t.interrupt();
>     t.join();
>
> This is supposed to terminate after 1s.
>
> Java version which does not terminate:
> openjdk version "11.0.8" 2020-07-14
> OpenJDK Runtime Environment (build 11.0.8+10-post-Ubuntu-0ubuntu120.04)
> OpenJDK 64-Bit Server VM (build 11.0.8+10-post-Ubuntu-0ubuntu120.04, 
> mixed mode, sharing)
>
> Java version which does terminate:
> java version "1.8.0_162"
> Java(TM) SE Runtime Environment (build 1.8.0_162-b12)
> Java HotSpot(TM) 64-Bit Server VM (build 25.162-b12, mixed mode)
>
> Debugging into the CompletableFuture.get() in Java 11 I can find a 
> code path that resets the interrupt flag but neither restores it or 
> throws the InterruptedException.
>
> Can "someone" give that a closer look?
>
> Warm regards,
>
> Jens
> _______________________________________________
> Concurrency-interest mailing list
> Concurrency-interest at cs.oswego.edu
> http://cs.oswego.edu/mailman/listinfo/concurrency-interest


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