IV27141: BAD JIT PROFILING LOGIC CAUSES CRASH

APAR status

• Closed as program error.

Error description

• Error Message: There are a number of possible symptoms, but a
  common one is a an Unhandled Exception during garbage
  collection, with vmState=0x00020002 and Module=j9jit26.dll (or
  of course libj9jit26.so on Linux).
  .
  Stack Trace: ----------- Stack Backtrace -----------
  walkTransitionFrame+0x293 (jswalk.c:471, 0x72FF4653
  <OSB>j9jit26+0x374653<CSB>)
  jitWalkStackFrames+0x1b8 (jswalk.c:216, 0x72FF4858
  <OSB>j9jit26+0x374858<CSB>)
  GC_VMThreadStackSlotIterator::scanSlots+0x7d
  (vmthreadstackslotiterator.cpp:106, 0x735F014D
  <OSB>j9gc26+0xe014d<CSB>)
  MM_RootScanner::scanOneThread+0xd8 (rootscanner.cpp:498,
  0x73521A28 <OSB>j9gc26+0x11a28<CSB>)
  MM_RootScanner::scanThreads+0x8f (rootscanner.cpp:466,
  0x7352189F <OSB>j9gc26+0x1189f<CSB>)
  MM_RootScanner::scanRoots+0x66 (rootscanner.cpp:1078, 0x73522636
  <OSB>j9gc26+0x12636<CSB>)
  MM_MarkingScheme::markLiveObjectsRoots+0x50c
  (markingscheme.cpp:1428, 0x735624CC <OSB>j9gc26+0x524cc<CSB>)
  MM_ParallelMarkTask::run+0x33 (parallelmarktask.cpp:39,
  0x73558DD3 <OSB>j9gc26+0x48dd3<CSB>)
  MM_ParallelDispatcher::slaveEntryPoint+0x77
  (paralleldispatcher.cpp:167, 0x735F2B57
  <OSB>j9gc26+0xe2b57<CSB>)
  dispatcher_thread_proc2+0x10d (paralleldispatcher.cpp:94,
  0x735F29ED <OSB>j9gc26+0xe29ed<CSB>)
  j9sig_protect+0x44 (j9signal.c:150, 0x7422F054
  <OSB>J9PRT26+0xf054<CSB>)
  dispatcher_thread_proc+0x2a (paralleldispatcher.cpp:128,
  0x735F2ACA <OSB>j9gc26+0xe2aca<CSB>)
  thread_wrapper+0xda (j9thread.c:1234, 0x7446464A
  <OSB>J9THR26+0x464a<CSB>)
  _endthread+0x48 (0x73F9C55C <OSB>msvcr100+0x5c55c<CSB>)
  _endthread+0xe8 (0x73F9C5FC <OSB>msvcr100+0x5c5fc<CSB>)
  BaseThreadInitThunk+0xe (0x7568F13C <OSB>kernel32+0x8f13c<CSB>)
  RtlCreateUserProcess+0x8c (0x7778D819 <OSB>ntdll+0x7d819<CSB>)
  RtlCreateProcessParameters+0x4e (0x7778DA2B
  <OSB>ntdll+0x7da2b<CSB>)
  ---------------------------------------
  .
  Only observed to fail with -Xaggressive
  

Local fix

• -Xjit:disableValueProfiling
  

Problem summary

• The jit compiler creates incorrect code for value profiling.
  One common outcome is that jitted code ends up calling a Java
  method on the C stack.  If a stack walk occurs in this state (as
  during garbage collection), the walker gets mighty confused and
  crashes in various ways.
  

Problem conclusion

• This defect will be fixed in:
  7.0.0 SR2
  6.0.1 SR3
  .
  The jit compiler was changed to check for problematic scenarios,
  and decline to perform value profiling if it could possibly
  cause this problem.
  

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

• R260 PSY

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