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

Jianhao Mo mojianhao at gmail.com
Wed Sep 12 10:12:11 UTC 2012


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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