[foreign-memaccess+abi] Integrated: 8270851: Logic for attaching/detaching native threads could be improved

[Maurizio Cimadamore]

On Fri, 16 Jul 2021 15:59:18 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> For a complete description of the issue, please refer to:
> 
> https://bugs.openjdk.java.net/browse/JDK-8270851
> 
> This patch makes the logic for detaching native threads more lazy - by only doing the detach when a native thread has completed. This is achieved by using some thread local storage, which is used to keep track of the Java thread associated to a given native thread. If, by the time the thread local storage is destroyed, we see that a Java thread has been attached, we do a detach operation. This trick effectively minimizes the number of Thread instances created when interacting with multi-threaded native code.
> 
> This patch also tweaks the logic for attaching native threads to the VM by using the "daemon" attach variant. That is, native threads registered against the VM (because of Panama upcalls) should not prevent the JVM to shut down in an orderly fashion (in cases where the native threads might outlive the JVM).

This pull request has now been integrated.

Changeset: 0c14a6d5
Author:    Maurizio Cimadamore <mcimadamore at openjdk.org>
URL:       https://git.openjdk.java.net/panama-foreign/commit/0c14a6d503386e12282f12388b7f4c67840077a3
Stats:     33 lines in 3 files changed: 22 ins; 8 del; 3 mod

8270851: Logic for attaching/detaching native threads could be improved

Reviewed-by: jvernee, dholmes

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PR: https://git.openjdk.java.net/panama-foreign/pull/570