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https://issues.apache.org/jira/browse/HDFS-16422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17520310#comment-17520310
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Takanobu Asanuma commented on HDFS-16422:
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Hi [~cndaimin],
bq. In conclusion: RSRawDecoder seems to be thread safe, NativeRSRawDecoder is
not thread safe, the read/write lock seems unable to protect the native
decodeImpl method.
Do you mean HDFS-16422 also made NativeRSRawDecoder thread safe? Or
NativeRSRawDecoder is still not thread safe after HDFS-16422?
> Fix thread safety of EC decoding during concurrent preads
> ---------------------------------------------------------
>
> Key: HDFS-16422
> URL: https://issues.apache.org/jira/browse/HDFS-16422
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: dfsclient, ec, erasure-coding
> Affects Versions: 3.3.0, 3.3.1
> Reporter: daimin
> Assignee: daimin
> Priority: Critical
> Labels: pull-request-available
> Fix For: 3.4.0, 3.2.3, 3.3.3
>
> Time Spent: 3h 40m
> Remaining Estimate: 0h
>
> Reading data on an erasure-coded file with missing replicas(internal block of
> block group) will cause online reconstruction: read dataUnits part of data
> and decode them into the target missing data. Each DFSStripedInputStream
> object has a RawErasureDecoder object, and when we doing pread concurrently,
> RawErasureDecoder.decode will be invoked concurrently too.
> RawErasureDecoder.decode is not thread safe, as a result of that we get wrong
> data from pread occasionally.
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