> -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 the 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. An alternative to not printing traces would of > course be to queue the traces so they are printed by another thread but this > is just adding complexity for a debugging option that we want to go away.
Alan Bateman has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision: - Expand TracePinnedThreads.testContention test description - Merge - Initial commit ------------- Changes: - all: https://git.openjdk.org/jdk/pull/17221/files - new: https://git.openjdk.org/jdk/pull/17221/files/15993866..ab8a2bcb Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=17221&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17221&range=00-01 Stats: 2985 lines in 239 files changed: 1868 ins; 364 del; 753 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
