Shuyan Zhang created HDFS-15963:
-----------------------------------
Summary: Unreleased volume references cause an infinite loop
Key: HDFS-15963
URL: https://issues.apache.org/jira/browse/HDFS-15963
Project: Hadoop HDFS
Issue Type: Bug
Components: datanode
Reporter: Shuyan Zhang
When BlockSender throws an exception because the meta-data cannot be found, the
volume reference obtained by the thread is not released, which causes the
thread trying to remove the volume to wait and fall into an infinite loop.
{code:java}
boolean checkVolumesRemoved() {
Iterator<FsVolumeImpl> it = volumesBeingRemoved.iterator();
while (it.hasNext()) {
FsVolumeImpl volume = it.next();
if (!volume.checkClosed()) {
return false;
}
it.remove();
}
return true;
}
boolean checkClosed() {
// always be true.
if (this.reference.getReferenceCount() > 0) {
FsDatasetImpl.LOG.debug("The reference count for {} is {}, wait to be 0.",
this, reference.getReferenceCount());
return false;
}
return true;
}
{code}
At the same time, because the thread has been holding checkDirsLock when
removing the volume, other threads trying to acquire the same lock will be
permanently blocked.
Similar problems also occur in RamDiskAsyncLazyPersistService and
FsDatasetAsyncDiskService.
This patch releases the three previously unreleased volume references.
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