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IV86745: JIT OPTIMIZATION ALLOCATES UNALIGNED OBJECTS CAUSING NULL POINTE R EXCEPTIONS OR A CRASH IN GC

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APAR status

  • Closed as program error.

Error description

  • Error Message: A crash in gc or null pointer exceptions is
observed.
.
Stack Trace: The exception is not limited to a particular
method. So stack trace may vary. A crash in gc usually occurs
after the exceptions. An example for the crash is:
----------- Stack Backtrace -----------
(0x00007FE6C350D371 <OSB>libj9gc28.so+0x3b371<CSB>)
(0x00007FE6C8F20DFA <OSB>libj9jit28.so+0x971dfa<CSB>)
(0x00007FE6C8F213DA <OSB>libj9jit28.so+0x9723da<CSB>)
(0x00007FE6C8F2273A <OSB>libj9jit28.so+0x97373a<CSB>)
(0x00007FE6CA1EAEF1 <OSB>libj9vm28.so+0xacef1<CSB>)
0000000000BE8000: Object neither in heap nor stack-allocated in
thread Pooled Thread <thread ID>
.
This issue could be observed on X86, Power, or Z. This only
happens when a heap larger than 32G is configured and the jvm is
running in compressedrefs mode

Local fix

  • Normally using -Xjit:disableEscapeAnalysis could stop the crash
from happening.

Problem summary

  • In compressedrefs mode, a special memory alignment should be
enforced. In this case, when a heap is larger than 32G, JIT
didn't align some objects, most likely primitive arrays. JIT
compiled method or GC would assume all objects are aligned and
try to access the memory, resulting in a NPE or a crash.

Problem conclusion

  • JIT has been fixed to properly align all objects.
.
This APAR will be fixed in the following Java Releases:
   8    SR3 FP10  (8.0.3.10)
.
Contact your IBM Product's Service Team for these Service
Refreshes and Fix Packs.
For those running stand-alone, information about the available
Service Refreshes and Fix Packs can be found at:
           https://www.ibm.com/developerworks/java/jdk/

Temporary fix

  • 



Comments


    

  • 



APAR Information




    

  • APAR number
    IV86745
    • 

  • Reported component name
    JIT
    • 

  • Reported component ID
    620700124
    • 

  • Reported release
    130
    • 

  • Status
    CLOSED  PER
    • 

  • PE
    NoPE
    • 

  • HIPER
    NoHIPER
    • 

  • Special Attention
    NoSpecatt / Xsystem
    • 

  • Submitted date
    2016-07-08
    • 

  • Closed date
    2016-07-08
    • 

  • Last modified date
    2016-07-08
    • 





    

  • 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


    

  • R130  PSY
       UP
    • 








      
              
                            

              

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Document Information


            

            


                        

            Modified date:
            

            08 July 2016
            

            
                      

        


        

        


      

    

  



    

  

  
    
            

          
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