[aarch64-port-dev ] RFR(S): 8248851: CMS: Missing memory fences between free chunk check and klass read

[Yangfei (Felix)]

Hi,

> -----Original Message-----
> From: Andrew Haley [mailto:aph at redhat.com]
> Sent: Tuesday, July 7, 2020 4:42 PM
> To: Yangfei (Felix) <felix.yang at huawei.com>; 'jdk8u-dev at openjdk.java.net'
> <jdk8u-dev at openjdk.java.net>
> Cc: hotspot-gc-dev at openjdk.java.net; aarch64-port-dev at openjdk.java.net
> Subject: Re: [aarch64-port-dev ] RFR(S): 8248851: CMS: Missing memory
> fences between free chunk check and klass read
> 
> On 07/07/2020 04:22, Yangfei (Felix) wrote:
> 
> > Webrev for jdk8u-dev:
> > http://cr.openjdk.java.net/~fyang/8248851/webrev.00/ JTreg tested on
> > x86_64-linux-gnu &aarch64-linux-gnu with jdk8u release builds.
> > Comments?
> 
> That looks right. I was thinking of arguing that you only need loadload here,
> but other parts of the same function use acquire, so we might as well be
> consistent.
> 
> I'd lose this line:
> 
> // Bugfix for systems with weak memory model (AARCH64).
> 
> It doesn't add anything, and it may mislead people into thinking that it's
> AArch64 specific. Looking at the code, it seems like all the casting to volatile
> was an earlier attempt to fix the same bug.

Good suggestion.
I have prepared a new webrev with the line removed: http://cr.openjdk.java.net/~fyang/8248851/webrev.01/ 
Does it look better?

Thanks,
Felix