Uma Maheswara Rao G created HDFS-9137:
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Summary: DeadLock between DataNode#refreshVolumes and
BPOfferService#registrationSucceeded
Key: HDFS-9137
URL: https://issues.apache.org/jira/browse/HDFS-9137
Project: Hadoop HDFS
Issue Type: Bug
Components: datanode
Affects Versions: 3.0.0
Reporter: Uma Maheswara Rao G
Assignee: Uma Maheswara Rao G
I can see this code flows between DataNode#refreshVolumes and
BPOfferService#registrationSucceeded could cause deadLock.
In practice situation may be rare as user calling refreshVolumes at the time DN
registration with NN. But seems like issue can happen.
Reason for deadLock:
1) refreshVolumes will be called with DN lock and after at the end it will
also trigger Block report. In the Block report call,
BPServiceActor#triggerBlockReport calls toString on bpos. Here it takes
readLock on bpos.
DN lock then boos lock
2) BPOfferSetrvice#registrationSucceeded call is taking writeLock on bpos and
calling dn.bpRegistrationSucceeded which is again synchronized call on DN.
bpos lock and then DN lock.
So, this can clearly create dead lock.
I think simple fix could be to move triggerBlockReport call outside out DN lock
and I feel that call may not be really needed inside DN lock.
Thoughts?
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