RFR: 8230401: ClassLoaderData::_keep_alive is read with wrong type in c2i entry barrier

Ioi Lam ioi.lam at oracle.com
Sat Aug 31 03:13:36 UTC 2019

Looks reasonable to me.

- Ioi

On 8/30/19 8:43 AM, Erik Österlund wrote:
> Hi,
> Zhengyu noticed that the ClassLoaderData::_keep_alive field is a 
> short, but the c2i entry barrier reads it with cmpl, treating it like 
> an int.
> First of all, thanks Zhengyu for spotting that. Nice catch.
> Encoding cmpw is not currently supported for x86_64 extended 
> registers, used in the barriers. So my proposed fix is to simply 
> change the type of _keep_alive to int. Because the 2 extra bytes will 
> become padding anyway, so we are not really saving any bytes by making 
> it s2.
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8230401
> Webrev:
> http://cr.openjdk.java.net/~eosterlund/8230401/webrev.00/
> Thanks,
> /Erik

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