RFR [6853696] (ref) ReferenceQueue.remove(timeout) may return null even if timeout has not expired

[Ivan Gerasimov]

Thank you Roger for looking at the fix!

On 24.02.2014 18:37, roger riggs wrote:
> Hi Ivan,
>
> The code is correct as written but there might be some creep in the 
> end time due to the sampling of System.nanoTime.
>
> I would be inclined to calculate the final time of the timeout once
> and then compare simply with the current nanotime.
>
> long end = (timeout == 0) ? Long.MAX_VALUE : (System.nanoTime() + 
> timeout * 1000000);
>
I don't think it is always correct.
According to the documentation, "The value returned represents 
nanoseconds since some fixed but *arbitrary* origin time".
http://download.java.net/jdk8/docs/api/java/lang/System.html#nanoTime--

Thus, Long.MAX_VALUE may just happen to represent some valid time in the 
near future, and we'll achieve wrong result.

Sincerely yours,
Ivan

> Then the test in the loop can be:
>
>   if (System.nanoTime() > end) {
>      return null;
>   }
>
> Roger (Not a Reviewer)
>
> On 2/24/2014 12:59 AM, Ivan Gerasimov wrote:
>> Hello!
>>
>> ReferenceQueue.remove(timeout) may return too early, i.e. before the 
>> specified timeout has elapsed.
>>
>> Would you please review the fix?
>> The change also includes a regression test, which can be used to 
>> demonstrate the issue.
>>
>> BUGURL: https://bugs.openjdk.java.net/browse/JDK-6853696
>> WEBREV: http://cr.openjdk.java.net/~igerasim/6853696/0/webrev/
>>
>> Sincerely yours,
>> Ivan
>
>