RFR 10: 8184808 (process) isAlive should use pid for validity, not /proc/pid

[Roger Riggs]

Hi Thomas,

Yes, if there is no access to the pid, then it can't report alive or 
not, and assume not.
If there access restrictions it will apply to the waitid/waitpid in the 
waitForProcessExit0
logic also and the answer will be at least consistent (and avoid a 
possible race
between //proc/pid/psinfo and kill state).

Thanks, Roger

On 7/18/2017 2:53 PM, Thomas Stüfe wrote:
> Hi Roger,
>
> I think this may fail if you have no permission to send a signal to 
> that process. In that case, kill(2) may yield EPERM and isAlive may 
> return false even though the process is alive.
>
> But then, I am not sure if that could happen in that particular 
> scenario, plus it may also mean that you do not have access to 
> /proc/pid either. So, I do not know how much of an issue this could be.
>
> Otherwise, the fix seems straightforward.
>
> Kind Regards, Thomas
>
> On Tue, Jul 18, 2017 at 8:46 PM, Roger Riggs <Roger.Riggs at oracle.com 
> <mailto:Roger.Riggs at oracle.com>> wrote:
>
>     Please review a fix for an intermittent failure in the
>     ProcessHandle OnExitTest
>     that fails frequently on Solaris.
>
>     ProcessHandle.isAlive is using /proc/pid/psinfo to determine if a
>     process is alive and it's start time.
>     However, it appears that the between the process exiting and the
>     reaping of its status, the
>     psinfo file indicates the process is alive but kill(pid, 0)
>     reports that is is not alive.
>     Depending on a race, the ProcessHandler.onExit may determine the
>     process has exited
>     but later isAlive may report it is alive.
>
>     To have a consistent view of the process being alive,
>     ProcessHandle.isAlive in its native implementation
>     should use kill(pid, 0) to determine if the process is
>     definitively determine if the process alive.
>
>     The original issue[1] will be kept open until it is known that it
>     is resolved.
>
>     Webrev:
>     http://cr.openjdk.java.net/~rriggs/webrev-alive-solaris-8184808/
>     <http://cr.openjdk.java.net/%7Erriggs/webrev-alive-solaris-8184808/>
>
>     Issue:
>     https://bugs.openjdk.java.net/browse/JDK-8184808
>     <https://bugs.openjdk.java.net/browse/JDK-8184808>
>
>     Thanks, Roger
>
>     [1] https://bugs.openjdk.java.net/browse/JDK-8177932
>     <https://bugs.openjdk.java.net/browse/JDK-8177932>
>
>
>