RFR(xs): 8220173: assert(_handle_mark_nesting > 1) failed: memory leak: allocating handle outside HandleMark

[Robbin Ehn]

Hi Dan,

>      L297:     HandleMark hm;
>          This should be "HandleMark hm(thread);".

Thanks, fixed!

> 
> I only took a quick look at clear_handshake() and do_handshake(), but
> I'm not grokking the reason for the CautiouslyPreserveExceptionMark
> helper. You use those when you want to preserve a possible pending
> exception that you have in hand now when you're about to execute code
> that might generate another (unexpected) exception. I'm not seeing
> where clear_handshake() or do_handshake() are doing anything that
> might generate another Java exception. However, I only took a quick
> look so maybe I missed something. So what am I missing?

do_handshake execute unknown code supplied in the ThreadClousure for the 
handshake here:

   // Only actually execute the operation for non terminated threads. 

   if (!thread->is_terminated()) {
     _thread_cl->do_thread(thread); 

   }

The reasoning was that this might generate a second exception.
I think that any code inside a handshake should make sure not generate an 
exception. But for now I just did this.

> 
> Thumbs up on the change itself. Would be good to know the answer to
> my question above.

Thanks, Robbin

> 
> Dan
> 
> 
>>
>> A thread have a pending exception and we try to handleize the oop without a 
>> HandleMark before the handshake.
>> The CautiouslyPreserveExceptionMark should only cover the handshake operation 
>> not the transition, so moved that into proper scope and added HandleMark.
>>
>> Passes t1.
>>
>> Thanks Robbin
>