From b2a45606481a6da6e1f68d14d1095a8dcf2a0e57 Mon Sep 17 00:00:00 2001
From: Liwei Lin <lwlin7@gmail.com>
Date: Tue, 26 Apr 2016 23:08:40 -0700
Subject: [PATCH] [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 most recent value.
This patch makes `acquiredButNotUsed` volatile to fix this.
## How was this patch tested?
This should be covered by existing suits.
Author: Liwei Lin <lwlin7@gmail.com>
Closes #12681 from lw-lin/fix-acquiredButNotUsed.
---
.../main/java/org/apache/spark/memory/TaskMemoryManager.java | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/core/src/main/java/org/apache/spark/memory/TaskMemoryManager.java b/core/src/main/java/org/apache/spark/memory/TaskMemoryManager.java
index 6b7d9aa20f..2796114fc5 100644
--- a/core/src/main/java/org/apache/spark/memory/TaskMemoryManager.java
+++ b/core/src/main/java/org/apache/spark/memory/TaskMemoryManager.java
@@ -114,7 +114,7 @@ public class TaskMemoryManager {
/**
* The amount of memory that is acquired but not used.
*/
- private long acquiredButNotUsed = 0L;
+ private volatile long acquiredButNotUsed = 0L;
/**
* Construct a new TaskMemoryManager.
--
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