RFR(s) #2: 6344935: (spec) clarify specifications for Object.wait overloads

[Martin Buchholz]

On Sun, Aug 20, 2017 at 9:53 PM, David Holmes <david.holmes at oracle.com>
wrote:

> On 21/08/2017 2:07 PM, Martin Buchholz wrote:
>
>> On Sun, Aug 20, 2017 at 6:36 PM, David Holmes <david.holmes at oracle.com
>> <mailto:david.holmes at oracle.com>> wrote:
>>
>>     On 20/08/2017 6:37 AM, Martin Buchholz wrote:
>>
>>         Future projects:
>>
>>         377 * <li>The specified amount of real time has elapsed, more or
>>         less.
>>
>>         Replace with
>>
>>         * <li>At least the specified amount of real time has elapsed.
>>
>>         (I think I failed to persuade David last time ...)
>>
>>
>>     And you will continue to do so. :) In the presence of spurious
>>     wakeups it is completely untestable to say "at least the specified
>>     time has elapsed"
>>
>>
>> My view is that spurious wakeup is a separate item in this list. "The
>> specified amount of real time has elapsed" should only be about "normal"
>> timeout.
>>
>
> And if you could perform whitebox testing that peeks inside to be able to
> make the distinction that would be fine. But in terms of the API and any
> conformance test, it is impossible to distinguish between an "early return"
> and a "spurious return". So specifying "at least ..." is meaningless so
> long as spurious wakeups are allowed.
>

The testability difference is that regular timeout is "normal" whereas
spurious wakeup must be "rare" (although of course "rare" is hard to pin
down).
Before we fixed
8065372: Object.wait(ms, ns) timeout returns early
<https://bugs.openjdk.java.net/browse/JDK-8065372>
returning early was unacceptably common