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

[Rob McKenna]

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.
>>
>>
>>
>>