StefanRRichter commented on a change in pull request #8443:
[FLINK-12510][network] Fix deadlock in InputGates
URL: https://github.com/apache/flink/pull/8443#discussion_r284155595
##########
File path:
flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/UnionInputGate.java
##########
@@ -210,12 +211,16 @@ public void requestPartitions() throws IOException,
InterruptedException {
}
Iterator<InputGate> inputGateIterator =
inputGatesWithData.iterator();
- final InputGate inputGate =
inputGateIterator.next();
+ inputGate = inputGateIterator.next();
inputGateIterator.remove();
+ }
- // In case of inputGatesWithData being
inaccurate do not block on an empty inputGate, but just poll the data.
- Optional<BufferOrEvent> bufferOrEvent =
inputGate.pollNextBufferOrEvent();
+ // In case of inputGatesWithData being inaccurate do
not block on an empty inputGate, but just poll the data.
+ // Do not poll the gate under inputGatesWithData lock,
since this can trigger notifications
+ // that could deadlock because of wrong locks taking
order.
+ Optional<BufferOrEvent> bufferOrEvent =
inputGate.pollNextBufferOrEvent();
+ synchronized (inputGatesWithData) {
Review comment:
I can see that this can fix the deadlock, but it also splits up a previously
atomic operation into two parts. I could not spot a concrete problem with it,
just wanted to make sure that we don't miss a potential problem here.
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