Round 2: RFR: 8013651 NMT: reserve/release sequence id's in incorrect order due to race

[Zhengyu Gu]

Oops, forgot the link: http://cr.openjdk.java.net/~zgu/8013651/webrev.01/

Thanks,

-Zhengyu

On 5/22/2013 10:28 AM, Zhengyu Gu wrote:
> Based on the discussion with Karen, Coleen and Harold, following 
> changes are made:
>
> 1) Renamed NMTTrackOp to NMTTracker, avoid the confusion with VM 
> operations.
> 2) Used NMTTracker's dtor to discard the tracking operation if no 
> recording is done.
>
> Tests:
>  - JPRT
>  - vm.quick.testlist on Linux 32, Solaris sparcv9 and Windows 32.
>
> Thanks,
>
> -Zhengyu
>
>
> On 5/14/2013 10:01 AM, Zhengyu Gu wrote:
>> There can be race conditions between the memory operations and the 
>> book keeping records are written. For example, thread 1 releases a 
>> virtual memory block, before it can write the release record, thread 
>> 2 reserves the same virtual memory block and writes reservation 
>> first, as result, NMT indicates the block is "released".
>>
>> The solution is that, for those operations that can cause the race 
>> conditions, NMT should pre-reserve sequence number for it, if the 
>> operation succeeds, NMT uses pre-reserved sequence number to write 
>> the record.
>>
>> The tricky part is that, a sequence number is only good for the 
>> generation it is acquired, when there are reserved sequence number, 
>> NMT has to prevent itself from entering so called "sync-point" where 
>> the generation can be advanced.
>>
>>
>> Bug: http://bugs.sun.com/view_bug.do?bug_id=8013651
>> Webrev: http://cr.openjdk.java.net/~zgu/8013651/webrev/ 
>> <http://cr.openjdk.java.net/%7Ezgu/8013651/webrev/>
>>
>>
>> Tests:
>>    1) JPRT
>>    2) vm.quick.testlist on Linux 32, Linux x64 and Solaris Sparcv9
>>    3) Kitchensink on Linux 32, Linux x64, Solaris Sparcv9 and Windows 
>> x64
>>    4) NMT jtreg tests on Linux 32, Linux x64 and Solaris Sparcv9
>>
>>
>> Thanks,
>>
>> -Zhengyu
>