GitHub user lw-lin opened a pull request:
https://github.com/apache/spark/pull/12681
[SPARK-14911][Core] Fix a potential data race in TaskMemoryManager
## What changes were proposed in this pull request?
[[SPARK-13210][SQL] catch OOM when allocate memory and expand
array](https://github.com/apache/spark/commit/37bc203c8dd5022cb11d53b697c28a737ee85bcc)
introduced an `acquiredButNotUsed` field, but it might not be correctly
synchronized:
- the write `acquiredButNotUsed += acquired` is guarded by `this` lock (see
[here](https://github.com/apache/spark/blame/master/core/src/main/java/org/apache/spark/memory/TaskMemoryManager.java#L271));
- the read `memoryManager.releaseExecutionMemory(acquiredButNotUsed,
taskAttemptId, tungstenMemoryMode)` (see
[here](https://github.com/apache/spark/blame/master/core/src/main/java/org/apache/spark/memory/TaskMemoryManager.java#L400))
might not be correctly synchronized, and thus might not see
`acquiredButNotUsed`'s new written value.
This patch makes `acquiredButNotUsed` to fix this.
## How was this patch tested?
This should be covered by existing suits.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/lw-lin/spark fix-acquiredButNotUsed
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/12681.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #12681
----
commit 6b72b963d54855771dcabc1fca8ed963be28303c
Author: Liwei Lin <lwl...@gmail.com>
Date: 2016-04-26T03:11:53Z
fix a potential data race in TaskMemoryManager
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