RFR: 8204170: MXBeanException.java assumes the existence of a pool that doesn't support usage threshold

[mandy chung]

Hi Stefan,

I think a better fix is to find another operation that will throw an 
exception.  ThreadMXBean::getThreadInfo throws IAE and it can be a 
candidate.

Mandy

On 5/31/18 6:38 AM, Stefan Karlsson wrote:
> Hi all,
> 
> Please review this patch to deal with the case when all available 
> MemoryPoolMXBeans support usage thresholds.
> 
> http://cr.openjdk.java.net/~stefank/8204170/webrev.01/
> https://bugs.openjdk.java.net/browse/JDK-8204170
> 
> The tests searches for a MemoryPoolMXBean that returns false for 
> isUsageThresholdSupported(), and then uses one of those pools to trigger 
> UnsupportedOperationExceptions when setUsageThreshold is used.
> 
> ZGC doesn't provide a pool that doesn't support usage threshold, and the 
> test therefore throws an NPE.
> 
> The suggested fix is to add:
>          if (pool == null) {
>            return; // All pools support usage threshold
>          }
> 
> An alternative fix would be to filter out the test if ZGC is used.
> 
> Thanks,
> StefanK