RFR (s) 8059100: SIGSEGV VirtualMemoryTracker::remove_released_region

[George Triantafillou]

Hi Coleen,

Looks good.  Thanks for fixing this.

-George

On 10/10/2014 10:16 AM, Coleen Phillimore wrote:
> Summary: Disallow increasing native memory tracking level
>
> There was support in the code for increasing NMT reporting level, 
> which causes inconsistencies when called by multiple threads. There 
> was also a shutdown() call in final_report() which turned NMT off 
> while other threads could be running.  The final_report() function 
> modified the running baseline in place but other threads calling NMT 
> while it is running could see the wrong data.
>
> Made final_report() snapshot a baseline which is safe enough during 
> error handling and not call shutdown().  Removed the reset() function 
> because it's unnecessary at best, and at worst, dangerous to do to the 
> running baseline.
>
> Also if final_report calls shutdown() it can hang getting the malloc 
> site table lock if the error reported is in the malloc site table, 
> while holding the lock.
>
> Tested with an aurora ad-hoc (thanks George) and linux-x64 testbase, 
> jck and jtreg tests.  All with nmt=detail and PrintNMTStatistics.
>
> open webrev at http://cr.openjdk.java.net/~coleenp/8059100/
> bug link https://bugs.openjdk.java.net/browse/JDK-8059100
>
> Thanks,
> Coleen
>