Request for review (XS): 7197906: BlockOffsetArray::power_to_cards_back() needs to handle > 32 bit shifts

Jianhao Mo mojianhao at gmail.com
Thu Sep 13 15:55:49 UTC 2012


Hi all,

Attached please find the new patch, modified according to John's advice.

Thanks Bengt again for the help :)

Regards,

Hal

2012/9/12 Jianhao Mo <mojianhao at gmail.com>

> Hi all,
>
> Could I get a couple of reviews for this small patch, please?
>
> 7197906: BlockOffsetArray::power_to_cards_back() needs to handle > 32 bit
> shifts
>
> CR link:
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7197906
> Webrev:
> http://cr.openjdk.java.net/~brutisso/7197906/webrev.01/
> Contributed-by:
> Hal Mo <kungu.mjh at taobao.com> from Alibaba Group(with OCA)
>
> It may take a while before the CR link is publicly accessible.
>
> In blockOffsetTable.hpp, there is an unexpected data truncation in
> power_to_cards_back(uint i), which may lead to crashing the VM on very
> large GC heaps.
> The problem could be reproduced easily on machines, that have enough
> memory, with:
> $ java -Xmx135g -XX:+UseConcMarkSweepGC
>
> The proposed patch fixes this problem, and builds on all OpenJDK supported
> platforms.
>
> I'd like to thank Bengt Rutisson for the initial review and help preparing
> the CR and Webrev.
>
> Regards,
> Hal
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