RFR: JDK-8147026- Convert an assert in ClassLoaderData to a guarantee

[David Holmes]

Hi Shafi,

On 16/02/2016 7:41 PM, Shafi Ahmad wrote:
> Hi All,
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> Please review the trivial change of replacing 'assert' by 'guarantee'
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> Summary: Having a guarantee in method "ClassLoaderDataGraph::find_or_create" ensuring that the classloader is a valid oop will help catch the errors at an early stage during the run rather than crashing the JVM later on in the GC.

I'm not sure I agree with this change on principle. The assert says "we 
never expect this to fail and we expect to weed out any problems during 
testing". I could see the need to expand the assert to also check for it 
being an oop though.

I'll defer approval of this to Coleen and Ioi as they have the expertise 
in this code area.

Thanks,
David

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> Open webrev: http://cr.openjdk.java.net/~csahu/8147026/webrev.00
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> Bug link: https://bugs.openjdk.java.net/browse/JDK-8147026
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> Testing:  JPRT
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> Since we are changing 'assert' by 'guarantee' which will add few instruction into code in product build and I am not sure about the *hotness* of this method.
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> So I run the performance test [refworkload] to make sure the impact of this change in the product build.
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> I am attaching the  performance run report for your reference.
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> Regards,
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> Shafi
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