IJ55766: JAVA JIT: CRASH IN ASPARSEBITVECTOR DESTRUCTOR

APAR status

• Closed as program error.

Error description

• Error Message: A segmentation fault during Java JIT compile time
  while executing in the destructor method for the
  ASparseBitVector class.
  .
  Stack Trace: CS2::ASparseBitVector<...>::__dftdt()() at
  0x90000000807cc6c
  invokedtr.__Invoke__Destructor() at 0x9000000008150e0
  __DoThrowV6() at 0x900000000817c3c
  J9::SystemSegmentProvider::request(...)() at 0x900000008ffa590
  TR::Region::allocate(...)() at 0x900000008032e24
  TR_Memory::allocateMemory(...)() at 0x900000008045108
  TR_AliasSetInterface<0>::getAliasesAndUnionWith(...)() at
  0x9000000081d2e2c
  RematTools::walkNodesCalculatingRematSafety(...)() at
  0x9000000081cd424
  ...
  .
  The problem occurs after the JIT reaches its memory limit during
  a Java method compile. Therefore the problem is most likely to
  occur during the compilation of very large methods. All current
  examples of this problem have occurred while compiling methods
  with 10,000+ bytes of bytecodes and reach that size because they
  are machine generated methods.
  The problem can occur on any J9 platform.
  

Local fix

• The issue can not be eliminated using a java command line
  option, but the chances of hitting the problem can be reduced by
  increasing the JIT scratch space limit above the default of
  256MB. In this example we increase the limit by 50% to 384MB,
  but it can be set even higher if need be. The value is specified
  in KB.
  -Xjit:scratchSpaceLimit=393216
  It is also possible to avoid specific instances of the issue by
  preventing the compilation of affected methods, but this will
  not prevent the same issue from affecting the compilation of
  other methods in the Java application.
  -Xjit:exclude={<method_full_signature>}
  Where <method_full_signature> is the method name as seen in the
  javacore labeled "Compiling method".
  

Problem summary

• At a point where the JIT is manipulating the structure of an
  ASparseBitVector C++ object, the compile time scratch memory
  space limit is reached causing a C++ exception to be thrown. The
  
  C++ runtime then calls the destructor for the ASparseBitVector
  C++ object, but the object structure is in an inconsistent state
  
  resulting in a crash while the destructor is attempting to free
  the memory associated with the object.
  

Problem conclusion

• The JIT was modified so that the ASparseBitVector C++ object is
  in a consistent state when running the destructor.
  .
  This APAR will be fixed in the following Releases:
  .
  IBM Semeru Runtimes
    25              25.0.2.0
    21              21.0.10.0
    17              17.0.18.0
    11              11.0.30.0
  IBM SDK, Java Technology Edition
    8    SR8 FP60   (8.0.8.60)
  .
  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