IV20123: JIT CODE CACHE CORRUPTION CAUSING CRASHES

APAR status

• Closed as program error.

Error description

• Error Message: The JVM crashes while executing a JIT-compiled
  Java method that seemingly contains an invalid instruction, or
  takes a wild branch to an unrelated method or invalid memory.
  The invalid instruction typically has been partially overwritten
  with the nibble 0xF. If verbose JIT logging is turned on, the
  crashing method may be shown with a code cache address range
  that overlaps that of another method, e.g.
  
  + (warm) Testcase.foo()V @
  0x52CF4AFC-0x52CF4B20/0x52D62F8C-0x52D63F6C Q_SZ=11 sync
  compThread=1
  + (profiled hot) Testcase.foo()V @
  0x52D0B3FC-0x52D0CD58/0x52D59F7C-0x52D5A7B4 7.01% T Q_SZ=11 sync
  compThread=1
  + (warm) Testcase.bar()V @
  0x52D1FCF4-0x52D1FF30/0x52D6328C-0x52D6349C Q_SZ=7 sync
  compThread=0
  
  In this example, the code cache address range of Testcase.bar
  (0x52D6328C to 0x52D6349C) overlaps that of the first version of
  Testcase.foo (0x52D62F8C to 0x52D63F6C), which has just been
  re-compiled at a higher optimization level.
  
  Stack Trace: N/A
  
  This problem only occurs on System z.
  

Local fix

• This problem can be avoided by disabling AOT compilation support
  with the -Xnoaot option.
  

Problem summary

• The problem can only occur when AOT compilation support is
  enabled. When a method is re-compiled, the JIT code
  cache space occupied by its old version is freed, along with any
  associated run-time assumption data. However, in some situations
  with AOT enabled, the run-time assumption data is not freed,
  causing corruption in the JIT code cache later on.
  

Problem conclusion

• This defect will be fixed in:
  6.0.1 SR3
  7.0.0 SR2
  6.0.0 SR11
  .
  The JIT compiler has been updated to ensure that proper
  assumptions get freed in the scenarios identified.
  

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:

  IV28954

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R260 PSY

     UP

• R600 PSY

     UP