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8369609: Continuations preempt_epilog is missing a call to invalidate_jvmti_stack #27878

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8369609: Continuations preempt_epilog is missing a call to invalidate_jvmti_stack #27878

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8369609: Continuations preempt_epilog is missing a call to invalidate…
sspitsyn Oct 17, 2025
1b5a057
review: remove now unneeded call to invalidate_jvmti_stack
sspitsyn Oct 22, 2025
3edebdb
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sspitsyn Oct 22, 2025
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3 changes: 2 additions & 1 deletion src/hotspot/share/runtime/continuationFreezeThaw.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1632,7 +1632,6 @@ static void jvmti_yield_cleanup(JavaThread* thread, ContinuationWrapper& cont) {
ContinuationWrapper::SafepointOp so(Thread::current(), cont);
JvmtiExport::continuation_yield_cleanup(JavaThread::current(), num_frames);
}
invalidate_jvmti_stack(thread);
}

static void jvmti_mount_end(JavaThread* current, ContinuationWrapper& cont, frame top) {
Expand Down Expand Up @@ -1685,6 +1684,8 @@ static inline freeze_result freeze_epilog(ContinuationWrapper& cont) {
assert(!cont.is_empty(), "");

log_develop_debug(continuations)("=== End of freeze cont ### #" INTPTR_FORMAT, cont.hash());

JVMTI_ONLY(invalidate_jvmti_stack(JavaThread::current()));
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Why not directly in preempt_epilog? Is it to cover the freeze fast case too? If that’s the case we should remove the call to invalidate_jvmti_stack from jvmti_yield_cleanup to avoid calling it twice for the freeze slow case. Also I wonder if this call to invalidate_jvmti_stack should just be moved to JvmtiVTMSTransitionDisabler::VTMS_unmount_end instead.

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@sspitsyn sspitsyn Oct 22, 2025 •
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Thank you for the comment! Yes, I had in mind but forgot to remove the call to invalidate_jvmti_stack() from jvmti_yield_cleanup(). I've pushed the update now.

Also I wonder if this call to invalidate_jvmti_stack should just be moved to JvmtiVTMSTransitionDisabler::VTMS_unmount_end instead.

Unfortunately, this is not going to work for plain/pure continuations as mount/unmount code path does not work for them.

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I see. What do you think about adding invalidate_jvmti_stack in jvmti_yield_cleanup if !cont.entry()->is_virtual_thread() is true to address that case?

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Good idea! It'd be nice to move the invalidate_jvmti_stack() calls out of the continuation code. I'll test it and let you know the results.

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@sspitsyn sspitsyn Oct 22, 2025 •
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Strangely, the test serviceability/jvmti/vthread/ContStackDepthTest is failing with the assert(_cur_stack_depth == num_frames). Obviously, some of the code paths is missed to call invalidate_jvmti_stack().

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@sspitsyn sspitsyn Oct 23, 2025 •
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As I see, the calls to invalidate_jvmti_stack() are needed for plain continuations only (under condition if (!cont.entry()->is_virtual_thread()).

The following patch does not cause regressions in mach5 tier 6 (mach5 tiers 1-5 are in progress):

diff --git a/src/hotspot/share/prims/jvmtiExport.cpp b/src/hotspot/share/prims/jvmtiExport.cpp
index 0884fce2ff7..dbbf5526602 100644
--- a/src/hotspot/share/prims/jvmtiExport.cpp
+++ b/src/hotspot/share/prims/jvmtiExport.cpp
@@ -1711,7 +1711,6 @@ void JvmtiExport::continuation_yield_cleanup(JavaThread* thread, jint continuati
   if (state == nullptr) {
     return;
   }
-  state->invalidate_cur_stack_depth();
 
   // Clear frame_pop requests in frames popped by yield
   if (can_post_frame_pop()) {
diff --git a/src/hotspot/share/runtime/continuationFreezeThaw.cpp b/src/hotspot/share/runtime/continuationFreezeThaw.cpp
index 0750f611876..f8406fb33c1 100644
--- a/src/hotspot/share/runtime/continuationFreezeThaw.cpp
+++ b/src/hotspot/share/runtime/continuationFreezeThaw.cpp
@@ -1626,11 +1626,15 @@ static void invalidate_jvmti_stack(JavaThread* thread) {
 }
 
 static void jvmti_yield_cleanup(JavaThread* thread, ContinuationWrapper& cont) {
-  if (!cont.entry()->is_virtual_thread() && JvmtiExport::has_frame_pops(thread)) {
+  if (cont.entry()->is_virtual_thread()) {
+    return;
+  }
+  invalidate_jvmti_stack(thread);
+  if (JvmtiExport::has_frame_pops(thread)) {
     int num_frames = num_java_frames(cont);
 
     ContinuationWrapper::SafepointOp so(Thread::current(), cont);
-    JvmtiExport::continuation_yield_cleanup(JavaThread::current(), num_frames);
+    JvmtiExport::continuation_yield_cleanup(thread, num_frames);
   }
 }
 
@@ -1685,7 +1689,7 @@ static inline freeze_result freeze_epilog(ContinuationWrapper& cont) {
 
   log_develop_debug(continuations)("=== End of freeze cont ### #" INTPTR_FORMAT, cont.hash());
 
-  JVMTI_ONLY(invalidate_jvmti_stack(JavaThread::current()));
+  JVMTI_ONLY(if (!cont.entry()->is_virtual_thread()) invalidate_jvmti_stack(JavaThread::current()));
   return freeze_ok;
 }
 
@@ -2311,7 +2315,7 @@ NOINLINE intptr_t* Thaw<ConfigT>::thaw_slow(stackChunkOop chunk, Continuation::t
 
   assert(_cont.chunk_invariant(), "");
 
-  JVMTI_ONLY(invalidate_jvmti_stack(_thread));
+  JVMTI_ONLY(if (!_cont.entry()->is_virtual_thread()) invalidate_jvmti_stack(_thread));
 
   _thread->set_cont_fastpath(_fastpath);

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Ah, we need to call invalidate_jvmti_stack at the end in jvmti_yield_cleanup! The problem is that in JvmtiExport::continuation_yield_cleanup we are setting again the stack depth when calling state->cur_stack_depth(). We count the enterSpecial frame at the top but we don’t decrement the depth when removing it (done in assembly code).

return freeze_ok;
}

Expand Down