RFR(s): 8046231: G1: Code root location ... from nmethod ... not in strong code roots for region

[Thomas Schatzl]

Hi Per,

On Tue, 2014-06-17 at 14:12 +0200, Per Liden wrote:
> Could I please have this fix reviewed.
> 
> Summary: nmethods are only registered with the heap if 
> nmethod::detect_scavenge_root_oops() returns true. However, in case the 
> nmethod only contains oops to humongous objects 
> detect_scavenge_root_oops() will return false and the nmethod will not 
> be registered. This will later cause heap verification to fail.
> 
> There are several ways in which this can be fixed. One alternative is to 
> adjust the verification to ignore humongous oops (since these objects 
> will never move). Another alternative is to just register the method 
> regardless of what detect_scavenge_root_oops() says. Since we might want 
> to allow humongous objects to move in the future this is the proposed fix.

I agree that this is the better solution.

> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8046231
> Webrev: http://cr.openjdk.java.net/~pliden/8046231/webrev.0/
> 
> Testing:
> * gc-test-suite
> * manual ad-hoc testing

  looks good.

Thanks,
  Thomas