RFR: 8010151 nsk/regression/b6653214 fails "assert(snapshot != NULL) failed: Worker should not be started"

[Zhengyu Gu]

Updated webrev based on David's comment:

http://cr.openjdk.java.net/~zgu/8010151/webrev.02/

Thanks,

-Zhengyu

On Apr 9, 2013, at 9:45 AM, Zhengyu Gu wrote:

> Hi David,
> 
> On Apr 8, 2013, at 8:44 PM, David Holmes wrote:
> 
>> Hi Zhengyu,
>> 
>> On 9/04/2013 6:44 AM, Zhengyu Gu wrote:
>>> Second round.
>>> 
>>> It fixed a racing condition when NMT is being shutdown while worker thread just started. The race causes get_snapshot() to return NULL, that triggers the assertion.
>> 
>> I can't see where get_snapshot() is now called such that we know we have a snapshot when calling start_worker() ??
>> 
> Now, snapshot is passed to MemTrackWorker from MemTracker::start(), the method ensures that snapshot is properly created and initialized before calling start_worker().
> 
>>> It also fixed a few volatile pointers that were mistakenly declared as volatile objects.
>> 
>> There is some further cleanup here:
>> 
>> 209 // delete all pooled recorders
>> 210 void MemTracker::delete_all_pooled_recorders() {
>> 211   // free all pooled recorders
>> 212   volatile MemRecorder* cur_head = _pooled_recorders;
>> 
>> cur_head declaration is no longer correct.
>> 
> 
> Thanks for finding this, I will fix it.
> 
> Thanks,
> 
> -Zhengyu
> 
>> David
>> -----
>> 
>>> 
>>> Bug:       http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8010151
>>> Webrev: http://cr.openjdk.java.net/~zgu/8010151/webrev.01/
>>> 
>>> Tests:
>>>  - JPRT
>>>  - vm.quick.testlist on Linux x86 and Windows x64
>>>  - The approach described by Christian in bug report. I were able to reproduce on prior the fix, and it is no longer reproducible after.
>>> 
>>> 
>>> 
>>> Thanks,
>>> 
>>> -Zhengyu
>>> 
>