Yang Jie created HADOOP-20067:
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Summary: RawLocalFileSystem: broken double-checked locking in
LocalFSFileInputStream#getAsyncChannel() can leak AsynchronousFileChannels
Key: HADOOP-20067
URL: https://issues.apache.org/jira/browse/HADOOP-20067
Project: Hadoop Common
Issue Type: Bug
Components: fs
Reporter: Yang Jie
LocalFSFileInputStream#getAsyncChannel() checks {{asyncChannel == null}}
outside the lock but not again inside it, and the field is not volatile. When
two threads make the first readVectored() call on the same stream, both can
open an AsynchronousFileChannel. The last assignment wins and close() only
closes that channel, so the other one keeps its file descriptor open until the
JVM exits. PositionedReadable requires positioned reads, readVectored included,
to be thread-safe.
The fix makes the field volatile and checks it again inside the synchronized
block. This was pointed out in the review of HADOOP-19901:
https://github.com/apache/hadoop/pull/8511#discussion_r4452981403. A
readVectored() call after close() still opens a new channel; this change does
not touch that.
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