Colin Patrick McCabe created HDFS-4522:
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Summary: LightWeightGSet expects incrementing a volatile to be
atomic
Key: HDFS-4522
URL: https://issues.apache.org/jira/browse/HDFS-4522
Project: Hadoop HDFS
Issue Type: Bug
Affects Versions: 2.0.4-beta
Reporter: Colin Patrick McCabe
Assignee: Colin Patrick McCabe
Priority: Minor
LightWeightGSet uses a volatile integer to track the current modification
number (kind of an epoch number).
Unfortunately, it includes code like this, that increments this volatile int:
{code}
//insert the element to the head of the linked list
modification++;
size++;
{code}
The bug here is that in between reading the value of modification, incrementing
it, and storing it back in the variable, another thread may have modified it.
This could lead to lost updates.
We should use {{AtomicInteger}} for these cases.
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