RFR: JDK-8274320: os::fork_and_exec() should be using posix_spawn
xliu at openjdk.java.net
Thu Oct 14 19:44:54 UTC 2021
On Sat, 25 Sep 2021 16:16:29 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:
> Hi, may I have reviews for this small patch please?
> `os::fork_and_exec()`, used in the hotspot to spawn child programs (scripts etc) in error situations, should be using `posix_spawn()`.
> ATM it uses either `fork()` or `vfork()`. `vfork()` got deprecated on MacOS and we get build errors (JDK-8274293) - even though in this case it would be completely fine to use. This leaves us with `fork()` for MacOS, which has the known problems with large-footprint-parents. This matters here especially since we also use os::fork_and_exec to implement `-XX:OnError` for OOM situations.
> We already use posix_spawn() as default for Runtime.exec() since JDK 15, and it is available on all our Unices. We also should use it here.
> I kept the name of the function (fork_and_exec) since people know it, even though it's more incorrect now than before.
> - manual tests using -XX:OnError with various scripts, including checking that env variables are passed correctly
> - manually ran runtime/ErrorHandling tests
> - GHAs
When it comes to Linux/glibc, Linux kernel has Copy-On-Write feature, doesn't it? So this change can't improve Linux further.
On the other side, Darwin can take benefit from it by changing from fork() to posix_spawn(). If so, why not just use ifdef __APPLE__ posix_spwarn() on Darwin? VMError has already used the macro for the vfork issue.
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