RFR: 8364314: java_lang_Thread::get_thread_status fails assert(base != nullptr) failed: Invalid base [v2]
David Holmes
dholmes at openjdk.org
Wed Jul 30 06:24:39 UTC 2025
> After the changes in JDK-8361912 we could "return " the carrier thread from `cv_internal_thread_to_JavaThread`, but before we hit the transition disabler the virtual thread could unmount. As a result when we execute this code:
>
> if (is_virtual) {
> // 1st need to disable mount/unmount transitions
> transition_disabler.init(jthread);
>
> carrier_thread = Handle(THREAD, java_lang_VirtualThread::carrier_thread(thread_h()));
> if (carrier_thread != nullptr) {
> java_thread = java_lang_Thread::thread(carrier_thread());
> }
> }
>
> we hit the implicit else where "`carrier_thread == nullptr`" and we do nothing, but `java_thread` still holds the old carrier, which we then perform the handshake operation with:
>
> void do_thread(Thread* th) override {
> Thread* current = Thread::current();
>
> bool is_virtual = java_lang_VirtualThread::is_instance(_thread_h());
> if (_java_thread != nullptr) {
> if (is_virtual) {
> // mounted vthread, use carrier thread state
> oop carrier_thread = java_lang_VirtualThread::carrier_thread(_thread_h());
> _thread_status = java_lang_Thread::get_thread_status(carrier_thread);
> } else {
>
> But the `_java_thread` no longer has a carrier, so `get_thread_status` is passed null and we crash.
>
> Simple fix is to clear `java_thread` when we find a null carrier oop. Also added an assert to guard against a null carrier oop in the handshake code, and added some additional commentary.
>
> Testing:
> - com/sun/management/HotSpotDiagnosticMXBean/DumpThreads.java
> - tier 5 and 6
>
> Thanks
David Holmes 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:
- Remove from ProblemList
- Merge branch 'master' into 8364314-threadSMR
- 8364314: java_lang_Thread::get_thread_status fails assert(base != nullptr) failed: Invalid base
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/26544/files
- new: https://git.openjdk.org/jdk/pull/26544/files/ad497497..610186f1
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=26544&range=01
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=26544&range=00-01
Stats: 20 lines in 6 files changed: 12 ins; 2 del; 6 mod
Patch: https://git.openjdk.org/jdk/pull/26544.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/26544/head:pull/26544
PR: https://git.openjdk.org/jdk/pull/26544
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