On Wed, 26 Feb 2025 19:46:41 GMT, Alan Bateman <[email protected]> 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
Nice work, Alan
src/java.base/share/classes/jdk/internal/vm/ContinuationSupport.java line 57:
> 55: */
> 56: public static void pinIfSupported() {
> 57: if (ContinuationSupport.isSupported()) {
Suggestion:
if (isSupported()) {
src/java.base/share/classes/jdk/internal/vm/ContinuationSupport.java line 66:
> 64: */
> 65: public static void unpinIfSupported() {
> 66: if (ContinuationSupport.isSupported()) {
Suggestion:
if (isSupported()) {
-------------
Changes requested by vklang (Reviewer).
PR Review: https://git.openjdk.org/jdk/pull/23810#pullrequestreview-2829366716
PR Review Comment: https://git.openjdk.org/jdk/pull/23810#discussion_r2082318599
PR Review Comment: https://git.openjdk.org/jdk/pull/23810#discussion_r2082318783
