On Thu, 31 Aug 2023 10:37:26 GMT, Markus Grönlund <[email protected]> wrote:
>> In the virtual thread implementation, thread identity switches to the
>> carrier before freezing and switches back to the virtual thread after
>> thawing. This was a forced move due to issues getting JVMTI to work with
>> virtual threads. JVMTI can now hide events during transitions so we can
>> invert the sequence back to mounting before running the continuation,
>> unmounting after freezing, and re-mounting after thawing. This sequence is
>> important for future changes that will initiate the freezing from the VM.
>>
>> The change requires an update to the JFR thread sampler to skip sampling
>> when it samples during a transition.
>>
>> Testing: tier1-5
>
> src/hotspot/share/jfr/periodic/sampling/jfrThreadSampler.cpp line 415:
>
>> 413: } else {
>> 414: assert(NATIVE_SAMPLE == type, "invariant");
>> 415: if (thread_state_in_native(thread) &&
>> !is_vthread_in_transition(thread)) {
>
> Is this possible? I assume the thread is in _thread_in_Java during the
> transition?
There are some native methods that we execute during mount/unmount transitions.
From what I see they all seem to be defined as `@IntrinsicCandidate`, but if
for some reason we don't execute the intrinsic version (interp only mode for
instance) then we would call a normal native method.
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PR Review Comment: https://git.openjdk.org/jdk/pull/15492#discussion_r1311970316
