RFR: 8367725: Incorrect reading of oop in SuspendResumeManager::suspend while thread is blocked [v5]

[Patricio Chilano Mateo]

On Tue, 16 Sep 2025 19:11:49 GMT, Leonid Mesnik <lmesnik at openjdk.org> wrote:

>> The
>> `SuspendResumeManager::suspend(bool register_vthread_SR)`
>> has an issue while suspend current virtual thread. The suspend tries to access vthread oop field to read vthread id after thread is blocked. 
>> 
>> Seems, that this case is not used by our debugger and was not covered by tests. I found it using jtreg test thread virtual factory plugin. I updated existing test to reproduce this problem. The easiest way is to suspend current virtual thread using plain SuspendThread. 
>> 
>> The fix added some "asymmetry"  in suspend/resume mechanism which is required because self-suspend doesn't have resume counterpart.
>
> Leonid Mesnik has updated the pull request incrementally with one additional commit since the last revision:
> 
>   ident fixed

Thanks for finding and fixing this Leonid.

src/hotspot/share/runtime/suspendResumeManager.cpp line 89:

> 87:   int64_t id = java_lang_Thread::thread_id(_target->vthread());
> 88:   ThreadBlockInVM tbivm(current);
> 89:   MutexLocker ml(_state_lock, Mutex::_no_safepoint_check_flag);

Transitioning to the blocked state and acquiring the monitor should still be executed without JVMTI included. We won’t see any issues today because suspend/resume is only used by JVMTI code.

src/hotspot/share/runtime/suspendResumeManager.cpp line 105:

> 103:     // If target is the current thread we can bypass the handshake machinery
> 104:     // and just suspend directly
> 105:     self_suspend(register_vthread_SR, self);

Since `self_suspend()` is a very short method and only called from here, I would keep the method as it was and if anything define `set_suspended_with_id(int64_t id, bool register_vthread_SR)` instead.

-------------

PR Review: https://git.openjdk.org/jdk/pull/27317#pullrequestreview-3231325205
PR Review Comment: https://git.openjdk.org/jdk/pull/27317#discussion_r2353407110
PR Review Comment: https://git.openjdk.org/jdk/pull/27317#discussion_r2353410713