review request: 4244896: (process) Provide System.getPid(), System.killProcess(String pid)

[David Holmes]

Hi Rob,

This looks good to me. I'm glad to see that destroyForcibly mandates 
that Process instances from ProcessBuilder.start and Runtime.exec must 
do a forcible destroy. That addresses my concern about documenting the 
actual implementations.

Two minor comments:

Process.java:

  236      * {@link ProcessBuilder#start} and {@link Runtime#exec} are 
of type that

"are of type" -> "are of a type ..."

ProcessKillTest.sh:

BIT_FLAG is now unused.

Thanks,
David


On 1/06/2012 1:05 AM, Rob McKenna wrote:
> Latest version including work on the spec language:
>
> http://cr.openjdk.java.net/~robm/4244896/webrev.04/
> <http://cr.openjdk.java.net/%7Erobm/4244896/webrev.03/>
>
> -Rob
>
> On 10/05/12 19:56, Rob McKenna wrote:
>> Hi folks,
>>
>> The latest version is at:
>>
>> http://cr.openjdk.java.net/~robm/4244896/webrev.03/
>> <http://cr.openjdk.java.net/%7Erobm/4244896/webrev.03/>
>>
>> Feedback greatly appreciated.
>>
>> -Rob
>>
>> On 19/04/12 12:05, Alan Bateman wrote:
>>> On 19/04/2012 01:05, David Holmes wrote:
>>>> On 18/04/2012 11:44 PM, Jason Mehrens wrote:
>>>>>
>>>>> Rob,
>>>>>
>>>>> It looks like waitFor is calling Object.wait(long) without owning
>>>>> this objects monitor. If I pass Long.MAX_VALUE to waitFor,
>>>>> shouldn't waitFor return if the early if the process ends?
>>>>
>>>> Also waitFor doesn't call wait() under the guard of a looping
>>>> predicate so it will suffer from lost signals and potentially
>>>> spurious wakeups. I also don't see anything calling notify[All] to
>>>> indicate the process has now terminated. It would appear that
>>>> wait(timeout) is being used as a sleep mechanism and that is wrong
>>>> on a number of levels.
>>> I assume waitFor(timout) will require 3 distinct implementations, one
>>> for Solaris/Linux/Mac, another for Windows, and a default
>>> implementations for Process implementations that exist outside of the
>>> JDK.
>>>
>>> It's likely the Solaris/Linux/Mac implementation will involve two
>>> threads, one to block in waitpid and the other to interrupt it via a
>>> signal if the timeout elapses before the child terminates. The
>>> Windows implementation should be trivial because it can be a timed wait.
>>>
>>> I assume the default implementation (which is what is being discussed
>>> here) will need to loop calling exitValue until the timeout elapses
>>> or the child terminates. Not very efficient but at least it won't be
>>> used when when creating Processes via Runtime.exec or ProcessBuilder.
>>>
>>> I think the question we need to consider is whether waitFor(timeout)
>>> is really needed. If it's something that it pushed out for another
>>> day then it brings up the question as to whether to include isAlive
>>> now or not (as waitFor without timeout gives us an isAlive equivalent
>>> too).
>>>
>>> -Alan.
>>>
>>>
>>>
>>>