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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-7499) double buffer release in SpillableSubpartitionView
Date Tue, 21 Nov 2017 17:12:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-7499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16261077#comment-16261077
] 

ASF GitHub Bot commented on FLINK-7499:
---------------------------------------

Github user NicoK commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4581#discussion_r152342531
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/SpillableSubpartitionView.java
---
    @@ -108,11 +108,7 @@ int releaseMemory() throws IOException {
     				for (int i = 0; i < numBuffers; i++) {
     					Buffer buffer = buffers.remove();
     					spilledBytes += buffer.getSize();
    -					try {
    -						spillWriter.writeBlock(buffer);
    -					} finally {
    -						buffer.recycle();
    -					}
    +					spillWriter.writeBlock(buffer);
    --- End diff --
    
    Actually, if I see this correctly, here the original code is wrong since it is already
recycling a buffer which was added to an asynchronous file write operation. This would lead
to data corruption if the buffer is re-used in the meanwhile, wouldn't it?!


> double buffer release in SpillableSubpartitionView
> --------------------------------------------------
>
>                 Key: FLINK-7499
>                 URL: https://issues.apache.org/jira/browse/FLINK-7499
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Network
>    Affects Versions: 1.2.0, 1.1.4, 1.3.0, 1.1.5, 1.2.1, 1.2.2, 1.3.1, 1.4.0, 1.3.2, 1.3.3
>            Reporter: Nico Kruber
>            Assignee: Nico Kruber
>            Priority: Blocker
>
> {{SpillableSubpartitionView#releaseMemory()}} recycles its buffers twice: once asynchronously
after the write operation and once in {{SpillableSubpartitionView#releaseMemory()}} after
adding the write operation to the queue.
> 1) if {{SpillableSubpartitionView#releaseMemory()}} hits first and the buffer is recycled,
the memory region may already be reused despite the pending write
> 2) If, for some reason (probably only in tests like {{SpillableSubpartitionTest#testConsumeSpillablePartitionSpilledDuringConsume()}}?),
the buffer is retained and to be used in parallel somewhere else it may also not be available
anymore or contain corrupt data.



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