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

[Jason Mehrens]

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?
 
Jason
 

> Date: Tue, 17 Apr 2012 15:56:30 +0100
> From: rob.mckenna at oracle.com
> To: Alan.Bateman at oracle.com
> Subject: Re: review request: 4244896: (process) Provide System.getPid(), System.killProcess(String pid)
> CC: core-libs-dev at openjdk.java.net
> 
> New webrev at:
> 
> http://cr.openjdk.java.net/~robm/4244896/webrev.01/
> 
> Differences:
> - implemented Process.waitFor(long timeout). I figured I'd throw it in 
> and let you decide if you want to keep it / replace isAlive.
> - implemented defaults in Process.java
> - destroyForcibly now returns the Process object
> - Updated documentation
> - Added @Override to all new overrides.
> - Fixed long line in UNIXProcess_md.c consistent with other functions in 
> that file.
> - Replaced WaitForSingleObject with GetExitCodeProcess: given the 
> concerns raised it seems to make more sense to leave users who return 
> STILL_ACTIVE as an error code on their own.
> - Test updated to allow for proper execution of shell script.
> 
> -Rob
> 
> On 12/04/12 10:05, Alan Bateman wrote:
> > On 12/04/2012 00:48, Rob McKenna wrote:
> >> Hi folks,
> >>
> >> I'm hoping for some feedback on the above. Webrev:
> >>
> >> http://cr.openjdk.java.net/~robm/4244896/webrev.00/
> > Thanks for taking this one on, a destroyForcibly is really useful to 
> > have (destroy was always misleading given that that is was actually a 
> > SIGTERM). The isAlive is also useful, another choice would be a 
> > waitFor that takes a timeout.
> >
> > As this patch adds two abstract methods it means there will be a 
> > source compatibility issue. Process has been in the platform since 
> > JDK1.0 so it likely there are other implementation, perhaps mocked. 
> > For destroyForcibly then a reasonable default could invoke the 
> > existing destroy but this would need to be specified. A possible 
> > default for isAlive is to invoke exitValue and mask the IAE when it 
> > hasn't terminated.
> >
> > On the javadoc then destroyForcibly needs to specify the return value, 
> > I think I missed this in the original patch that I gave you off-list. 
> > Having it return the Process is very useful as it allows for method 
> > invocation chaining, exitCode = p.destroyForcibly().waitFor(). I also 
> > think destroyForcibly needs to set expectation that the process may 
> > not terminate immediately (isAlive might still return true for a brief 
> > period for example).
> >
> > The duplicate code in UNIXProcess.java.* is a reminder that we could 
> > combine the common code into something like a private package 
> > AbstractUNIXPorcess that would be extended by UNIXProcess, not for 
> > this patch of course.
> >
> > Looks like there is inconsistent use of @Override, you've added it to 
> > the isAlive implementation but not the others.
> >
> > Looks like UNIXProcess_md.c is straying beyond 80c so you might want 
> > to move the force parameter to the next line.
> >
> > Overall I think the implementation looks okay but one thing to think 
> > about is errors, WaitForSingleObject can fail with other errors, the 
> > return from kill is not checked.
> >
> > I don't have time to study the test is detail just now but I suspect 
> > invoking "./ProcessKillTest.sh" will need to change as the script will 
> > be in test.src and may not have execute permission. Also I see tests 
> > for specific exit codes which may be problematic (and will need to be 
> > updated for MacOSX). For isAlive then it may be better to test it by 
> > adding to existing tests.
> >
> > -Alan.
> >
> >