Integrated: 8364314: java_lang_Thread::get_thread_status fails assert(base != nullptr) failed: Invalid base
David Holmes
dholmes at openjdk.org
Mon Aug 4 21:51:15 UTC 2025
On Wed, 30 Jul 2025 05:14:29 GMT, David Holmes <dholmes at openjdk.org> wrote:
> 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
This pull request has now been integrated.
Changeset: 84a4a364
Author: David Holmes <dholmes at openjdk.org>
URL: https://git.openjdk.org/jdk/commit/84a4a3647c86baecc07abfa7d1d4b88e06984821
Stats: 14 lines in 2 files changed: 11 ins; 3 del; 0 mod
8364314: java_lang_Thread::get_thread_status fails assert(base != nullptr) failed: Invalid base
Reviewed-by: amenkov, shade, dcubed, pchilanomate, sspitsyn
-------------
PR: https://git.openjdk.org/jdk/pull/26544
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