On Wed, 30 Aug 2023 13:56:42 GMT, Alan Bateman <al...@openjdk.org> 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 410:
> 408: }
> 409: if (JAVA_SAMPLE == type) {
> 410: if (thread_state_in_java(thread) &&
> !is_vthread_in_transition(thread)) {
I think this check can be postponed until after the thread is suspended.
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?
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PR Review Comment: https://git.openjdk.org/jdk/pull/15492#discussion_r1311439052
PR Review Comment: https://git.openjdk.org/jdk/pull/15492#discussion_r1311437865
