RFR 9: 8143876 : test/java/lang/ProcessHandle/TreeTest.java failed intermittently with assertion error

[joe darcy]

Hi Roger,

On 12/1/2015 6:05 PM, Roger Riggs wrote:
> Hi Joe,
>
> I do not know of any specific skew issues at the resolutions used. For 
> example,
> Linux records the start time in ticks  (1/60th to 100th of a second), 
> not the full resolution
> of the time of day clock. Typically, the child start time is at least 
> a bit later
> than the parent. If the maximum possible skew was known or estimated, 
> the comparison
> could take that into account.  For example, I would expect the skew 
> across processors
> to be less than 1sec (or more likely 10ms) or there would be bigger 
> issues among native processes.

Okay; if the start time precision is relatively coarse that reduces the 
hazard of a problem here.

I think it is reasonable to go ahead with the current changes if is this 
kind of issue comes up in the future, a "fuzz" factor is determined and 
taken into consideration.

Thanks,

-Joe

>
> Thanks, Roger
>
>
> On 12/1/15 8:54 PM, Joseph D. Darcy wrote:
>> Hi Roger,
>>
>> Looks fine.
>>
>> Do you know if there are clock skew issues to be concerned with if 
>> the parent and child are spawned on different CPUs?
>>
>> Thanks,
>>
>> -Joe
>>
>> On 12/1/2015 5:49 PM, Roger Riggs wrote:
>>> Please review this change in ProcessHandle to validate parent pids 
>>> provided by the OS.
>>> Children of a process have start times that are the same or later 
>>> than the parent.
>>> The implementation of descendants(), and children(), and getParent()
>>> are updated to validate the parent pid.
>>>
>>> The problem is most pronounced on Windows; the parent pid reported 
>>> for a
>>> process may be stale if the parent exited.  The validation is 
>>> applied in
>>> platform neutral code and used on all platforms.  Platform specific 
>>> code
>>> is used on Windows for getParent(); the Linux platforms do the right 
>>> thing.
>>>
>>> Webrev:
>>> http://cr.openjdk.java.net/~rriggs/webrev-validate-ppid-8143879/
>>>
>>> Issue:
>>>    https://bugs.openjdk.java.net/browse/JDK-8143876
>>>
>>> Thanks, Roger
>>>
>>
>