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  1. JDK
  2. JDK-8145204

JVM can hang when ParGCArrayScanChunk=4294967296 and ParallelGC is used

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Details

    • Bug
    • Status: Resolved
    • P4
    • Resolution: Fixed
    • 9
    • 9
    • hotspot
    • None
    • gc
    • b112

    Description

      ParGCArrayScanChunk is assigned to '_array_chunk_size' in PSPromotionManager::PSPromotionManager() constructor(hotspot/src/share/vm/gc/parallel/psPromotionManager.cpp module):
        _array_chunk_size = ParGCArrayScanChunk;

       _array_chunk_size have type uint(hotspot/src/share/vm/gc/parallel/psPromotionManager.hpp module):
      class PSPromotionManager VALUE_OBJ_CLASS_SPEC {
      ...
        uint _array_chunk_size;
      ...

      ParGCArrayScanChunk have intx type. Thus, on 64 bit JVM _array_chunk_size can overflow if ParGCArrayScanChunk is greater than maximum unsigned 32 bit number. For example for ParGCArrayScanChunk=4294967296 the '_array_chunk_size' will be equal to 0 and this leads to the hang of the JVM.

      Can be reproducible by javac:
      javac -J-XX:+UseParallelGC -J-XX:+UseParallelOldGC -J-XX:ParGCArrayScanChunk=4294967296 HelloWorld.java

      Also, _array_chunk_size is then multiplied on 1.5.
      Also, ParGCArrayScanChunk is multiplied on 2 in CMS and G1 code, thus overflow can occur for big values.
      This should be considered for fixing range or constraint for this flag.

      I think that new test is not needed, because this flag will be tested for non-G1 GC mode after fixing JDK-8144578.

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              sangheki Sangheon Kim
              ddmitriev Dmitry Dmitriev
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                Updated:
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