From 1db46909c94438a3818c7826f00a21a292bf4a0e Mon Sep 17 00:00:00 2001
From: Rui Fan <1996fanrui@gmail.com>
Date: Mon, 31 Aug 2026 17:29:45 +0200
Subject: [PATCH] [FLINK-40521][network] Document potential lost
 priority-barrier wakeup in LocalInputChannel during
 checkpointing-during-recovery

---
 .../io/network/partition/consumer/LocalInputChannel.java      | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/LocalInputChannel.java b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/LocalInputChannel.java
index 9a7aa4b96dfc15..5c2000fef58261 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/LocalInputChannel.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/LocalInputChannel.java
@@ -666,7 +666,9 @@ private Optional<BufferAndAvailability> pullPriorityFromSubpartitionView() throw
 
         Buffer.DataType expectedNextDataType = next.getNextDataType();
         if (!expectedNextDataType.hasPriority()) {
-            // Reset hasPendingPriorityEvent to false if no more priority event.
+            // Latent lost-wakeup: this lock-free clear can clobber a concurrent set-true in
+            // notifyPriorityEvent(). Safe today only because Flink runs no concurrent unaligned
+            // checkpoints, so at most one priority barrier is ever pending.
             hasPendingPriorityEvent = false;
             // Correct nextDataType: if recoveredBuffers is not empty, the actual next element to
             // consume is from recoveredBuffers, not from subpartitionView.