RFR(s): 8171449" [aarch64] store_klass needs to use store release

Andrew Haley aph at redhat.com
Tue Dec 20 10:27:51 UTC 2016

On 20/12/16 10:21, Thomas Schatzl wrote:
> Derek can very likely tell you more about the protocol between CMS'
> concurrent threads and the mutators, but both collectors have protocols
> to ensure that the memory contains valid information, either retrying
> later (G1), or busy waiting (CMS, afaics from code around a "bugfix for
> systems with weak memory model" comment) until this is the case.

Yeah.  This stuff doesn't make any sense: I need to see the code.  I
guess that what's going on is that a humongous object is allocated,
the memory is zeroed, and the memory is then returned to the Java
thread, which then initializes the object.  So, the object is
reachable from the GC thread even before it has been initialized.  But
instances of Class aren't humongous... or are they?


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