-Djdk.tracePinnedThreads is a debugging option that dates from early development in the loom repo to identify pinned threads. It has several issues and this tracing option will eventually be removed (use JFR events instead). Several hangs have been reported when running with the system property set. The "hangs" stem from the onPinned callback executing while the virtual thread is in a transition state (typically parking). If the virtual parks while printing the stack trace then it works like a nested park where the thread state is never restored. Contention on the System.out can also lead to deadlock when there are platform and pinned virtual threads printing to System.out around the same time.
This PR brings over the changes from the loom repo to avoid these hangs. The changes mean the stack trace is only printed to System.out when the PrintStream lock can be acquired without blocking. It also restores the thread state after printing. ------------- Commit messages: - Initial commit Changes: https://git.openjdk.org/jdk/pull/17221/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17221&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8322846 Stats: 126 lines in 3 files changed: 98 ins; 12 del; 16 mod Patch: https://git.openjdk.org/jdk/pull/17221.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/17221/head:pull/17221 PR: https://git.openjdk.org/jdk/pull/17221
