Request for reviews (S): 6826736: CMS: core dump with -XX:+UseCompressedOops

Vladimir Kozlov Vladimir.Kozlov at Sun.COM
Wed Jul 22 13:33:14 PDT 2009


Thanks, Paul

I will do that.

Thanks,
Vladimir


Paul Hohensee wrote:
> You've got 4 uses of this expression
> 
> Universe::narrow_oop_base() == (address)(void*)(*foo)
> 
> You might write a new method in Universe to factor it out, vis
> 
> bool is_narrow_oop_base(void* addr) {
>  return narrow_oop_base() == (address)addr);
> }
> 
> Paul
> 
> Vladimir Kozlov wrote:
>>
>> http://cr.openjdk.java.net/~kvn/6826736/webrev.01
>>
>> Fixed 6826736: CMS: core dump with -XX:+UseCompressedOops
>>
>> Problem:
>> Compiled code may produce decoded oop = narrow_oop_base
>> when a narrow oop implicit null check is used.
>> The narrow_oop_base could be NULL or be the address
>> of the page below heap depending on the used mode of
>> compressed oops. Such decoded oop could live across
>> a safepoint and as result referenced in oopMap and debug info.
>> The implicit NULL exception code checks for such oop value
>> but deoptimization code and GC does not. And this cause
>> the problem.
>>
>> Solution:
>> Fix deoptimization code and GC to check for such oops values.
>> During deoptimization convert them to NULL.
>> And ignore them for GC (like NULL values are ignored).
>>
>> Added the regression test which shows the problem.
>>
>> Reviewed by:
>>
>> Fix verified (y/n): y, regression test
>>
>> Other testing:
>> JPRT, CTW with/without UseCompressedOops and +/- ScavengeALot
>>



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