[11u]: RFR CSR backport: JDK-8220362: Add "POSIX_SPAWN" as valid value to jdk.lang.Process.launchMechanism on Linux

[Thomas Stüfe]

Hi Andrew,

This would be good to have in jdk11 for the following reason:

The established (since decades) method of forking off on Linux JDKs has
been to use vfork(3). Using vfork is risky. There are chances of crashing
the parent process. The risk of this happening is very low, but not zero.
Since analyzing those crashes and attributing them to vfork(3) is very
difficult, there may be a number of reported cases not associated with
vfork(3) but in fact caused by it.

The patch adds a second, safer way to fork off childs, using
posix_spawn(3). This one has been the default on other platforms for quite
some while. The patch does not change the default fork mode - which remains
vfork(3). So installations would not be affected unless they explicitely
choose to use vfork(3).

Having this possibility would allow us to use posix_spawn(3) in situations
where we are analysing crashes and want to exclude vfork(3) as a cause. It
also would enable us to use posix_spawn(3) as a safe alternative by default
if we choose to do so.

In addition to that, as David Loyd mentioned, vfork(3) is marked as
obsolete and may be vanish at some point in the life span of JDK 11. I
admit the chance of this happening is low.

Kind Regards, Thomas

On Fri, Mar 8, 2019 at 4:20 PM Andrew Haley <aph at redhat.com> wrote:

> On 3/8/19 2:39 PM, Langer, Christoph wrote:
> > please review the CSR backport
> https://bugs.openjdk.java.net/browse/JDK-8220362.
> >
> > It is the backport of https://bugs.openjdk.java.net/browse/JDK-8214511
> to JDK11.
> >
> > We want to backport JDK-8212828<
> https://bugs.openjdk.java.net/browse/JDK-8212828> to jdk11u and hence
> backporting the CSR is a prerequisite. The CSR is, however, more or less
> identical for 11u.
>
> I don't see any explanation of why this should go into jdk11.
>
> --
> Andrew Haley
> Java Platform Lead Engineer
> Red Hat UK Ltd. <https://www.redhat.com>
> EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671
>