> JDK-8364343 upgraded the virtual thread transition management to be > independent of JVMTI. We can update java_lang_Thread::async_get_stack_trace > to use it and remove the suspend + retry code from Thread.getStackTrace. > > A summary of the changes: > > - java_lang_Thread::async_get_stack_trace is changed to use the new handshake > op so it can be called to get the stack trace of a started thread in any state > - Thread::getStackTrace is changed to use async_get_stack_trace for all cases > - The SUSPENDED substate in VirtualThread is removed > - JVM_CreateThreadSnapshot is changed to be usable when JVMTI is not compiled > in > - ThreadSnapshotFactory::get_thread_snapshot is changed to not upcall to > StackTraceElement to complete the init of the stack trace > > The changes mean that Thread::getStackTrace may be slower when sampling a > virtual thread in transition. This case should be rare, and it isn't really a > performance critical op anyway. I prototyped use a spin loop and an > increasing wait time in MountUnmountDisabler::disable_transition_for_one to > avoid the wait(10) but decided to leave it out for now. Future work may > examine this issue as there may be other cases (with JVMTI) that would > benefit from avoiding the wait. > > A future PR might propose to change Thread.getStackTrace to use > ThreadSnapshot and allow java_lang_Thread::async_get_stack_trace be removed. > This requires more extensive changes to ThreadSnapshotFactory to reduce > overhead when only the stack trace is required. > > Testing: tier1-5. The changes has been already been tested in the loom repo > for a few months.
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 six additional commits since the last revision: - Merge branch 'master' into JDK-8376568 - Review feedback - Improve asserts - Cleanup - Merge branch 'master' into Thread.getStackTrace - Initial commit ------------- Changes: - all: https://git.openjdk.org/jdk/pull/29461/files - new: https://git.openjdk.org/jdk/pull/29461/files/12214cd8..1b7c9ad7 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=29461&range=02 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29461&range=01-02 Stats: 5098 lines in 109 files changed: 3579 ins; 1148 del; 371 mod Patch: https://git.openjdk.org/jdk/pull/29461.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/29461/head:pull/29461 PR: https://git.openjdk.org/jdk/pull/29461
