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https://issues.apache.org/jira/browse/HBASE-17872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15959990#comment-15959990
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Chia-Ping Tsai commented on HBASE-17872:
----------------------------------------

bq. Then it becomes how to change a static final setting at test time
The issue is not that complicated. We change the UNSAFE_AVAIL/UNSAFE_UNALIGNED 
before starting up a mini cluster when testing, so they shouldn't be declared 
volatile.

Please see the v3 patch. Thanks. [~anoop.hbase] [~stack] 



> The MSLABImpl generates the invaild cells when unsafe is not availble
> ---------------------------------------------------------------------
>
>                 Key: HBASE-17872
>                 URL: https://issues.apache.org/jira/browse/HBASE-17872
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Chia-Ping Tsai
>            Assignee: Chia-Ping Tsai
>            Priority: Critical
>             Fix For: 2.0.0
>
>         Attachments: HBASE-17872.v0.patch, HBASE-17872.v1.patch, 
> HBASE-17872.v2.patch
>
>
> We will get the wrong position of buffer in multithreaded environment, so the 
> method makes the invalid cell in MSLAB.
> {noformat}
>   public static int copyFromBufferToBuffer(ByteBuffer in, ByteBuffer out, int 
> sourceOffset,
>       int destinationOffset, int length) {
>     if (in.hasArray() && out.hasArray()) {
>       // ...
>     } else if (UNSAFE_AVAIL) {
>       // ...
>     } else {
>       int outOldPos = out.position();
>       out.position(destinationOffset);
>       ByteBuffer inDup = in.duplicate();
>       inDup.position(sourceOffset).limit(sourceOffset + length);
>       out.put(inDup);
>       out.position(outOldPos);
>     }
>     return destinationOffset + length;
>   }
> {noformat}



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