RFR: 8153749 - New capability can_generate_early_class_hook_events

[Daniel D. Daugherty]

 > Testing:
 >    Altered the nsk.jvmti co-located test 
nsk/jvmti/ClassFileLoadHook/classfloadhk002
 >    to enable the can_generate_early_class_hook_events and checked 
that new CFLH events
 >    are posted in the primordial phase and also they are not posted 
otherwise.

Sorry for looping back on this...

I've been re-reading this thread off and on for a while now...

I'm okay with this part of the testing statement:

 > checked that new CFLH events are posted in the primordial phase

but this part bothers me:

 > and also they are not posted otherwise

I'm not sure what that last part means exactly. I think it might
be saying that there are certain CFLH events that the test expects
to be posted in the primordial phase and the test verifies that
those CFLH events are posted in the primordial phase and not in
the next phase (the start phase). I'm hoping that the testable
assertion is more clear than the above text.

One other possible issue: if the primordial phase is still
single threaded, then there is no race between a thread doing
this early class loading (and posting of the CFLH events) and
the thread that is changing the JVM/TI phase from "primordial
phase" to "start phase". However, if the primordial phase is
now multi-threaded, then there might be a race between the
thread posting the CFLH event and JVM/TI phase switch...

Dan


On 4/14/16 2:24 AM, serguei.spitsyn at oracle.com wrote:
> Please, review the Jigsaw-related fix for:
>   https://bugs.openjdk.java.net/browse/JDK-8153749
>
>
> Hotspot webrev:
> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8153749-Jigsaw-newcap.hs1/ 
>
>
> Jdk webrev:
> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/jdk/8153749-Jigsaw-newcap.jdk1/ 
>
>
>
> Summary:
>
>    This is a Jigsaw related enhancement.
>    Some agents need to get a CFLH event for classes loaded in the 
> primordial phase.
>    This is not possible in JDK 9 because existing agents may 
> instrument code in the
>    primordial or start phase before the module system has completed 
> initialization.
>
>    We introduce a new capability: can_generate_early_class_hook_events.
>    If this capability and can_generate_all_class_hook_events are 
> enabled then
>    the CFLH event could be posted for classes loaded in the primordial 
> phase.
>    We leave can_generate_early_vmstart as is, no changes.
>
>    This enhancement needs a CCC request filed.
>    I will file it once the JVMTI spec changes are reviewed.
>
>
> Testing:
>    Altered the nsk.jvmti co-located test 
> nsk/jvmti/ClassFileLoadHook/classfloadhk002
>    to enable the can_generate_early_class_hook_events and checked that 
> new CFLH events
>    are posted in the primordial phase and also they are not posted 
> otherwise.
>
>
> Thanks,
> Serguei
>