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

Thomas Schatzl thomas.schatzl at oracle.com
Wed Nov 22 16:32:54 UTC 2017


Hi Erik,

On Wed, 2017-11-22 at 16:49 +0100, Erik Helin wrote:
> 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.

Thanks.

> 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.

Fine with me. I will push it tomorrow together with the others that are
finished by then.

Thanks,
  Thomas



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