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https://issues.apache.org/jira/browse/FLINK-9676?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16533425#comment-16533425
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ASF GitHub Bot commented on FLINK-9676:
---------------------------------------
Github user NicoK commented on a diff in the pull request:
https://github.com/apache/flink/pull/6257#discussion_r200283214
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/io/network/buffer/LocalBufferPool.java
---
@@ -251,27 +257,56 @@ private MemorySegment requestMemorySegment(boolean
isBlocking) throws Interrupte
@Override
public void recycle(MemorySegment segment) {
+ BufferListener listener;
synchronized (availableMemorySegments) {
if (isDestroyed || numberOfRequestedMemorySegments >
currentPoolSize) {
returnMemorySegment(segment);
+ return;
}
else {
- BufferListener listener =
registeredListeners.poll();
+ listener = registeredListeners.poll();
if (listener == null) {
availableMemorySegments.add(segment);
availableMemorySegments.notify();
+ return;
}
- else {
- try {
- boolean needMoreBuffers =
listener.notifyBufferAvailable(new NetworkBuffer(segment, this));
- if (needMoreBuffers) {
-
registeredListeners.add(listener);
- }
+ }
+ }
+
+ // We do not know which locks have been acquired before the
recycle() or are needed in the
+ // notification and which other threads also access them.
+ // -> call notifyBufferAvailable() outside of the synchronized
block to avoid a deadlock (FLINK-9676)
+ boolean success = false;
+ boolean needMoreBuffers = false;
+ try {
+ needMoreBuffers = listener.notifyBufferAvailable(new
NetworkBuffer(segment, this));
+ success = true;
+ } catch (Throwable ignored) {
+ // handled below, under the lock
+ }
+
+ if (!success || needMoreBuffers) {
+ synchronized (availableMemorySegments) {
+ if (isDestroyed) {
+ // cleanup tasks how they would have
been done if we only had one synchronized block
+ if (needMoreBuffers) {
+
listener.notifyBufferDestroyed();
--- End diff --
actually, let's do this in a follow-up PR
> Deadlock during canceling task and recycling exclusive buffer
> -------------------------------------------------------------
>
> Key: FLINK-9676
> URL: https://issues.apache.org/jira/browse/FLINK-9676
> Project: Flink
> Issue Type: Bug
> Components: Network
> Affects Versions: 1.5.0
> Reporter: zhijiang
> Assignee: Nico Kruber
> Priority: Critical
> Labels: pull-request-available
> Fix For: 1.6.0, 1.5.1
>
>
> It may cause deadlock between task canceler thread and task thread.
> The detail is as follows:
> {{Task canceler thread -> IC1#releaseAllResources -> recycle floating buffers
> -> {color:#d04437}lock{color}(LocalBufferPool#availableMemorySegments) ->
> IC2#notifyBufferAvailable}} > {color:#d04437}try to
> lock{color}(IC2#bufferQueue)
> {{Task thread -> IC2#recycle -> {color:#d04437}lock{color}(IC2#bufferQueue)
> -> bufferQueue#addExclusiveBuffer}} -> {{floatingBuffer#recycleBuffer}} ->
> {color:#d04437}try to lock{color}(LocalBufferPool#availableMemorySegments)
> One solution is that {{listener#notifyBufferAvailable}} can be called outside
> the {{synchronized(availableMemorySegments) in }}{{LocalBufferPool#recycle.}}
> The existing RemoteInputChannelTest#testConcurrentOnSenderBacklogAndRecycle
> can cover this case but the deadlock probability is very low, so this UT is
> not stable.
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