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

John Cuthbertson john.cuthbertson at oracle.com
Thu Sep 13 17:43:21 UTC 2012


Hi Hal,

The changes look good to me.

JohnC

On 09/13/12 08:55, Jianhao Mo wrote:
> 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 <mailto: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/
>     <http://cr.openjdk.java.net/%7Ebrutisso/7197906/webrev.01/>
>     Contributed-by: 
>     Hal Mo <kungu.mjh at taobao.com <mailto: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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