IJ58601: JAVA JIT: OVERLAPPING MEMORY COPY CAUSES CORRUPTION ON IBM Z

APAR status

• Closed as program error.

Error description

• Error Message: java.io.IOException: BZip2 CRC error
  .
  Stack Trace: Caused by: java.io.IOException: BZip2 CRC error
  at
  org.apache.commons.compress.compressors.bzip2.BZip2CompressorInp
  utStream.endBlock(BZip2CompressorInputStream.java:349)
  at
  org.apache.commons.compress.compressors.bzip2.BZip2CompressorInp
  utStream.setupNoRandPartA(BZip2CompressorInputStream.java:819)
  at
  org.apache.commons.compress.compressors.bzip2.BZip2CompressorInp
  utStream.setupNoRandPartB(BZip2CompressorInputStream.java:868)
  at
  org.apache.commons.compress.compressors.bzip2.BZip2CompressorInp
  utStream.read0(BZip2CompressorInputStream.java:229)
  at
  org.apache.commons.compress.compressors.bzip2.BZip2CompressorInp
  utStream.read(BZip2CompressorInputStream.java:177)
  at
  org.apache.avro.file.BZip2Codec.decompress(BZip2Codec.java:73)
  at
  org.apache.avro.file.DataFileStream$DataBlock.decompressUsing(Da
  taFileStream.java:355)
  at
  org.apache.avro.file.DataFileStream.hasNext(DataFileStream.java:
  199)
  .
  The issue is a small scale corruption, typically within a 64bit
  memory write. How this corruption presents from a failure
  perspective depends on the context. The failure may not always
  present as an exception.
  The issue is caused by the JIT compiler Z code generator and
  therefore can only occur on IBM Z (zOS and zLinux).
  It is possible that the issue is easier to appear when using the
  "Balanced" GC policy with the "offHeap" enhancement (introduced
  in Java 8.0.8.50).
  

Local fix

• There is no way to prevent the Z code generator from using the
  failing code sequence, but if the problem is occurring when
  using the "Balanced" GC policy, switching to the default
  "Gencon" policy will likely avoid the problem.
  

Problem summary

• The JIT can use the "MVC" IBM Z instruction to performance a
  memory to memory copy, but in some rare cases we failed to
  ensure that the source and destination of the copy do not
  overlap. When there is overlapping, trailing parts of the source
  
  could get overwritten when writing to the destination.
  

Problem conclusion

• The JIT was modified so that when we are unable to guarantee
  that no overlapping exist, we will not use a MVC instruction and
  
  instead use a load/store instruction pair.
  https://github.com/eclipse-omr/omr/pull/8273
  .
  This APAR will be fixed in the following Releases:
  .
  IBM Semeru Runtimes
    25              25.0.4.0
    21              21.0.12.0
    17              17.0.20.0
    11              11.0.32.0
  IBM SDK, Java Technology Edition
    8    SR8 FP70  (8.0.8.70)
  .
  Downloads and supplementary documentation can be found at the
  following locations:
  - For non z/OS operating systems:
   - IBM Semeru Runtimes, Version 11 and later
     https://www.ibm.com/semeru-runtimes/downloads/
   - IBM SDK, Java Technology Edition, Version 8
     https://www.ibm.com/support/pages/java-sdk-downloads/
  - For the z/OS operating system:
   - Java SDK Products on z/OS
     https://www.ibm.com/support/pages/java-sdk-products-zos
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels