Isolating tests from general concurrency

[Jonathan Gibbons]

On 3/19/19 12:03 PM, Gary Adams wrote:
> A recent question came up about how the exclusiveAccess.dirs property 
> was being used to
> prevent concurrent tests from using some critical resource. It appears 
> that some of
> the hotspot/jtreg/vmTestbase tests were setting the property assuming 
> they would get
> a concurrency=1 type of behavior.
>
> I'd like to start the discussion about how the current feature works 
> and see
> if a new feature might be appropriate for other related use cases.
The feature was originally created for tests that needed exclusive 
access to specific system
resources: specifically, fixed ports in RMI/networking tests. To some 
extent, it was a quick
stop-gap measure, to avoid having to rewrite those tests in short order 
to use dynamically
allocated ports.

The need for "concurrency=1" behavior is new/different. Previously, all 
tests wanting
exclusive access had to opt-in to the feature.  To support 
"concurrency=1", there's an
implicit need to check any interlock on all tests that don't request 
"concurrency=1".

-- Jon