Integrated: 8350765: Need to pin when accessing thread container from virtual thread

[Alan Bateman]

On Wed, 26 Feb 2025 19:46:41 GMT, Alan Bateman <alanb at openjdk.org> wrote:

> Data structures that are accessed by both virtual threads and their carriers require the virtual thread to pin the continuation to avoid potential deadlock. A deadlock can arise when a virtual thread is preempted, is selected and scheduled to be the next owner of the lock/resource, but can't execute because all carriers are blocking on the same lock/resource. There are a small number of places that need to pin. One that was missed is the the notification to the thread container when threads are started or terminate. This is not currently an issue at this time but it is a potential hazard for ongoing and future work that will add further scheduling points to the code.  Continuation.pin/unpin have intrinsics since JDK-8338745, and Continuation is initialized early in startup. Finally, the changes have been in the loom repo for several months with no issues.
> 
> Testing tier1-5, quick statup/footprint, noreg-hard

This pull request has now been integrated.

Changeset: fa419489
Author:    Alan Bateman <alanb at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/fa419489d3769a989ee5bd948eeda0ed9be071e2
Stats:     94 lines in 6 files changed: 50 ins; 25 del; 19 mod

8350765: Need to pin when accessing thread container from virtual thread

Reviewed-by: vklang, jpai

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PR: https://git.openjdk.org/jdk/pull/23810