RFR (XXS): 8179244: Assert failed in instanceMirrorKlass.inline.hpp

Erik Helin erik.helin at oracle.com
Wed Nov 22 15:49:02 UTC 2017

On 11/20/2017 12:56 PM, Thomas Schatzl wrote:
> Hi all,
>    can I have reviews for this small comment update that clarifies that
> the assert in that location is too strong and should be commented out.
> The issue is that an assert fails during CMS precleaning if class
> loading occurred where the mirror ended up in the old generation (in
> some situations CMS allocates directly into old gen). This assert found
> that a klass that has had a NULL value suddenly changed its value to
> something else.
> This is normal behavior in the situation described above.
> Also checked that we do not miss iterating over a CLD for such oops -
> there is actually explicit support in class loading for this, where
> such CLDs (and their mirrors) are kept alive until remark and iterated
> over again there. (Look for "CMS support" in classLoaderData.?pp).
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8179244
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8179244/webrev/

Looks good, Reviewed, I think the comment is on the right level.

Although the comment and the bug (and understanding how this all hangs 
together) is far from trivial, I think this actual patch is trivial (it 
just adds a comment). Therefore, in my opinion, this patch only requires 
one (R)eviewer.


> Testing:
> local compilation (just a comment added)
> Thanks,
>    Thomas

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