RFR: 8210889: Some service thread cleanups can be starved

[Kim Barrett]

> On Sep 19, 2018, at 9:29 AM, coleen.phillimore at oracle.com wrote:
> 
> Looks good!  Thanks for noticing and fixing this!
> Coleen

Thanks.

> On 9/18/18 8:46 PM, Kim Barrett wrote:
>> Please review this small change to the ServiceThread.  When checking
>> for work to be done, rather than immediately doing the first kind of
>> work found, instead determine all pending work and then do all known
>> pending work.  This avoids the possibility of frequently available
>> work early in the sequence of checks from leading to starvation of
>> work associated with later checks.
>> 
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8210889
>> 
>> Webrev:
>> http://cr.openjdk.java.net/~kbarrett/8210889/open.00/
>> 
>> Testing:
>> mach5 tier1-3