John Doe created HADOOP-15429:
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Summary: unsynchronized index causes
DataInputByteBuffer$Buffer.read hangs
Key: HADOOP-15429
URL: https://issues.apache.org/jira/browse/HADOOP-15429
Project: Hadoop Common
Issue Type: Bug
Components: io
Affects Versions: 0.23.0
Reporter: John Doe
In DataInputByteBuffer$Buffer class, the fields bidx and buffers, etc are
unsynchronized when used in read() and reset() function. In certain
circumstances, e.g., the reset() is invoked in a loop, the unsynchronized bidx
and buffers triggers a concurrency bug.
Here is the code snippet.
{code:java}
ByteBuffer[] buffers = new ByteBuffer[0];
int bidx, pos, length;
@Override
public int read(byte[] b, int off, int len) {
if (bidx >= buffers.length) {
return -1;
}
int cur = 0;
do {
int rem = Math.min(len, buffers[bidx].remaining());
buffers[bidx].get(b, off, rem);
cur += rem;
off += rem;
len -= rem;
} while (len > 0 && ++bidx < buffers.length); //bidx is unsynchronized
pos += cur;
return cur;
}
public void reset(ByteBuffer[] buffers) {//if one thread keeps calling
reset() in a loop
bidx = pos = length = 0;
this.buffers = buffers;
for (ByteBuffer b : buffers) {
length += b.remaining();
}
}
{code}
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