RFR: 7160924: jvmti: GetPhase returns incorrect phase before VMInit event is issued

[Karen Kinnear]

Dmitry,

I hear your point, there is a comment in the VM Initialization Event that "In the case of VM start-up
failure, this event will not be sent".

That said, the goal of the VM initialization event is to inform the agent that it is free
to call any JNI or JMVTI function. Many agents want to be able to start tracking the VM as early as possible.

So there is a trade-off in how early you send this event and risks of VM failures after we send it.
To maximize benefits to users of the API, the current trade-off is to declare the VM initialized, i.e. in live phase,
and to post the VM Initialization event  as soon as we meet the agents' needs.

Yes, it is possible for the VM to exit later, both on additional subsystem startup operations and of course
due to things like out of memory errors at any time. So the "consistency" is that if we have a failure
in starting up the VM for the operations critical to jvmti agents, we exit without sending the event. For
failures later during startup and beyond, we don't. Bootstrapping is a very delicate process and 
we want to optimize for the agents starting as early as they can for the success cases.

While longer term we would like to improve our ability to recover from some of the memory errors,
I think the trade-off of empowering the agents to be functional as early as we can is the right balance
at this time.

So - I would support the bug fix as is.

thanks,
Karen

On Apr 12, 2012, at 9:12 AM, Dmitry Samersoff wrote:

> Rickard,
> 
> As far as I understand the code, after your changes we will
> post JVMTI event
> 
> JvmtiExport::post_vm_initialized();
> 
> ever if later JVM aborts on some error.
> 
> I'm not sure it's a good idea because in couple of other
> places we abort VM without sending the event, so
> behavior of agent become inconsistent.
> 
> -Dmitry
> 
> 
> 
> On 2012-04-12 16:12, Rickard Bäckman wrote:
>> Hi,
>> 
>> can I get review for this small change? The issue is that if we are
>> running tracing startup code inbetween setting the phase to
>> JVMTI_PHASE_LIVE and posting the VMInit event.
>> 
>> Webrev:
>> http://cr.openjdk.java.net/~rbackman/7160924/webrev/
>> 
>> CR: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7160924
>> 
>> Thanks
>> /R
> 
> 
> -- 
> Dmitry Samersoff
> Java Hotspot development team, SPB04
> * There will come soft rains ...