RFR 9: 8064932: test java/lang/ProcessBuilder/Basic.java: waitFor didn't take long enough

[David Holmes]

On 19/11/2014 2:02 AM, Martin Buchholz wrote:
> On Mon, Nov 17, 2014 at 9:02 PM, David Holmes <david.holmes at oracle.com> wrote:
>> Hi Martin,
>>
>> On 18/11/2014 2:49 PM, Martin Buchholz wrote:
>>>
>>> Hi David,
>>>
>>> I'm still hoping to persuade you (and others) to fix the long-standing
>>> return-early bug in Object.wait.
>>
>>
>> Are you referring to the low level mechanics or specifically to the
>> nanosecond version below?
>
> Here I'm just trying to fix the problem that Object.wait(millis,nanos)
> trivially returns early.
>
>> That seems overly complex - after checking for valid values of timeout and
>> nanos you simply need:
>>
>> if (nanos > 0) timeout++;
>>
>> to ensure the >= requirement.
>
> Sure, the miminal diff is:
>
> diff --git a/src/java.base/share/classes/java/lang/Object.java
> b/src/java.base/share/classes/java/lang/Object.java
> --- a/src/java.base/share/classes/java/lang/Object.java
> +++ b/src/java.base/share/classes/java/lang/Object.java
> @@ -453,7 +453,7 @@
>                                   "nanosecond timeout value out of range");
>           }
>
> -        if (nanos >= 500000 || (nanos != 0 && timeout == 0)) {
> +        if (nanos != 0) {
>               timeout++;
>           }

I can live with that. Though given spurious wakeups it doesn't add much.

>> But seriously we should just deprecate this version as we're not likely to
>> get any underlying OS mechanisms for doing nanosecond resolution timed
>> blocking actions.
>
> Object.wait(millis, nanos) is an ugly API (I wish for both a public
> and hotspot internal API that simply operated on nanoseconds), but
> it's not totally awful.  It's not obvious to me that computing
> advances over the lifetime of the java platform won't allow
> sub-millisecond scheduling, and other APIs that do operate on
> nanoseconds (like Process.waitFor) should call this API.

I'm sure the same thing was said 20 years ago, yet the OS seem stuck at 
microsecond resolution. Maybe one day ...

David