On 8/27/14 5:40 AM, serguei.spit...@oracle.com wrote:
On 8/20/14 3:45 PM, Daniel D. Daugherty wrote:
On 8/20/14 2:01 PM, Coleen Phillimore wrote:
On 8/20/14, 3:49 PM, serguei.spit...@oracle.com wrote:
If an EMCP method is not running, should we save it on a previous
version list anyway so that we can make it obsolete if it's
redefined and made obsolete?
I hope, Dan will catch me if I'm wrong...
I think, we should not.
An EMCP method can not be made obsolete if it is not running.
It should be this way otherwise we'd have to hang onto things forever.
An EMCP method should only be made obsolete if a RedefineClasses() or
RetransformClasses() operation made it so. We should not be leveraging
off the obsolete-ness attribute to solve a life-cycle problem.
In the pre-PGR world, we could trust GC to make a completely unused
EMCP method collectible and eventually our weak reference would go
away. Just because an EMCP method is not on a stack does not mean
that it is not used so we need a different way to determine whether
it is OK to no longer track an EMCP method.
Most likely, you are right.
But I'm not convinced yet. Sorry.
A convincing point would be a test that shows this behavior.
I understand that it is not an easy task to write such a test though.
However, such a test would serve nicely if we want a different way
to determine whether it is OK to no longer track an EMCP method.
Running the Serviceability stack of tests with the following
-XX:TraceRedefineClasses=NN flags:
// 0x00001000 | 4096 - detect calls to obsolete methods
// 0x00002000 | 8192 - fail a guarantee() in addition to detection
will show failures of the guarantee(). I used to do this
periodically and then chase down the failures to make sure
only the "legitimate" races were happening. The reason that
we had to add these flags was to find all the places where
folks were caching methods in the VM. I think the last place
I found and fixed was in reflection.
Dan
Thanks,
Serguei
BTW, I'm reviewing the webrev too, but probably it'd be better to
switch to updated webrev after it is ready.
Yes, this is a good idea. I figured out why I made emcp methods
obsolete, and I'm fixing that as well as Dan's comments. Thanks!
Cool! I'm looking forward to the next review.
Dan
Coleen
Thanks,
Serguei
