On Tue, 15 Oct 2024 21:21:07 GMT, Alex Menkov <amen...@openjdk.org> wrote:
>> Serguei Spitsyn has updated the pull request incrementally with one
>> additional commit since the last revision:
>>
>> Disallow NotifyFramePop for
>> enter/enter0/VirtualThread.run/VThreadContinuation.run
>
> src/hotspot/share/prims/jvmtiExport.cpp line 1814:
>
>> 1812: }
>> 1813: // pure continuations have no VTMS transitions but they use methods
>> annotated with JvmtiMountTransition
>> 1814: if ((mh->jvmti_mount_transition() && state->is_virtual()) ||
>> thread->is_in_any_VTMS_transition()) {
>
> Could you please explain the change (and other similar changes in
> jvmtiExport.cpp)
> Before events were not posted for any `@JvmtiMountTransition` methods, and
> now only for virtual threads? I.e. events for `@JvmtiMountTransition` methods
> of carrier threads are posted?
Good question. Some `jvmtiNotify*` notifications can be called in a context of
carrier thread and exited in a context of virtual thread and vice versa. So,
you are right we should not post these events for `@JvmtiMountTransition`
methods, in a context of carrier threads.
So, we need to adjust these conditions even more with something like below:
- if ((mh->jvmti_mount_transition() && state->is_virtual()) ||
thread->is_in_any_VTMS_transition()) {
+ if ((mh->jvmti_mount_transition() && (state->is_virtual() ||
thread->last_continuation() == nullptr)) ||
+ thread->is_in_any_VTMS_transition()) {
return; // no events should be posted if thread is in any VTMS transition
}
The check for `thread->last_continuation() == nullptr` will help to skip these
events for carrier threads as well but won't skip them for pure continuations.
In fact, I do not like the complexity of this check. :(
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/21397#discussion_r1803512093
