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

[Zhengyu Gu]

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