PING: RFR(s): (new approach) 8223777: In posix_spawn mode, failing to exec() jspawnhelper does not result in an error

[Roger Riggs]

Hi Thomas,

A minor concern is the impact of the extra write and read that can cause 
rescheduling
of the parent and child processes.  But that's probably in the noise 
compared to the
real work of exec.  It would raise the complexity quite a bit/too much 
to code a single read
in the parent that could expect 0/4/8 bytes.

At ProcessImpl_md.c: 708: the "Read failed" is less than informative.
(Though it is the same as the pre-existing one at 720).
But I suppose it has never happened.  The 'Exec failed' is more specific 
than 'read'.
And it has probably never been seen.

Thanks, Roger


On 06/04/2019 02:06 AM, Thomas Stüfe wrote:
> Hi all,
>
> may I please have reviews/opinions on this fix?
>
> Fix has been live in our test landscape since some weeks.
>
> If we do not want this fix to be in JDK13, we may want to revert the 
> posix_spawn-by-default-on-Linux change.
>
> Thanks, Thomas
>
>
> On Mon, May 20, 2019 at 4:15 PM Thomas Stüfe <thomas.stuefe at gmail.com 
> <mailto:thomas.stuefe at gmail.com>> wrote:
>
>     Hi all,
>
>     (old mail thread:
>     https://mail.openjdk.java.net/pipermail/core-libs-dev/2019-May/060139.html)
>
>     May I please have your reviews and opinions for the following bug fix:
>
>     issue: https://bugs.openjdk.java.net/browse/JDK-8223777
>     cr:
>     http://cr.openjdk.java.net/~stuefe/webrevs/8223777-posix_spawn-no-exec-error-alternate-impl/webrev.00/webrev/
>     <http://cr.openjdk.java.net/%7Estuefe/webrevs/8223777-posix_spawn-no-exec-error-alternate-impl/webrev.00/webrev/>
>
>     ---
>
>     The fix implements Florians proposal: the jspawnhelper will signal
>     its aliveness to the parent process the moment it gains control.
>     If the parent process does not get the signal, it assumes exec'ing
>     the jspawnhelper never worked.
>
>     I only do this for posix_spawn mode, out of cautiousness.
>
>     (Note that I kept the fix as minimal as possible. I found a minor
>     bug and some improvement possibilities and opened follow up issues
>     to track them: JDK-8224180 and JDK-8224181).
>
>     Thanks, Thomas
>
>