8369238: Allow virtual thread preemption on some common class initialization paths

src/hotspot/cpu/aarch64/continuationFreezeThaw_aarch64.inline.hpp

@@ -211,6 +211,8 @@ inline intptr_t* AnchorMark::anchor_mark_set_pd() {
     assert(_last_sp_from_frame != nullptr, "");
     _top_frame.interpreter_frame_set_last_sp(nullptr);
     if (sp != _last_sp_from_frame) {
+      // We need to move up return pc and fp. They will be read next in
+      // set_anchor() and set as _last_Java_pc and _last_Java_fp respectively.
       _last_sp_from_frame[-1] = (intptr_t)_top_frame.pc();
       _last_sp_from_frame[-2] = (intptr_t)_top_frame.fp();
     }
@@ -335,15 +337,16 @@ inline intptr_t* ThawBase::push_cleanup_continuation() {
   frame enterSpecial = new_entry_frame();
   intptr_t* sp = enterSpecial.sp();
 
+  // We only need to set the return pc. rfp will be restored back in gen_continuation_enter().
   sp[-1] = (intptr_t)ContinuationEntry::cleanup_pc();
-  sp[-2] = (intptr_t)enterSpecial.fp();
   return sp;
 }
 
 inline intptr_t* ThawBase::push_preempt_adapter() {
   frame enterSpecial = new_entry_frame();
   intptr_t* sp = enterSpecial.sp();
 
+  // We only need to set the return pc. rfp will be restored back in generate_cont_preempt_stub().
   sp[-1] = (intptr_t)StubRoutines::cont_preempt_stub();
   return sp;
 }

src/hotspot/cpu/riscv/continuationFreezeThaw_riscv.inline.hpp

@@ -218,6 +218,8 @@ inline intptr_t* AnchorMark::anchor_mark_set_pd() {
     assert(_last_sp_from_frame != nullptr, "");
     _top_frame.interpreter_frame_set_last_sp(nullptr);
     if (sp != _last_sp_from_frame) {
+      // We need to move up return pc and fp. They will be read next in
+      // set_anchor() and set as _last_Java_pc and _last_Java_fp respectively.
       _last_sp_from_frame[-1] = (intptr_t)_top_frame.pc();
       _last_sp_from_frame[-2] = (intptr_t)_top_frame.fp();
     }
@@ -336,15 +338,16 @@ inline intptr_t* ThawBase::push_cleanup_continuation() {
   frame enterSpecial = new_entry_frame();
   intptr_t* sp = enterSpecial.sp();
 
+  // We only need to set the return pc. fp will be restored back in gen_continuation_enter().
   sp[-1] = (intptr_t)ContinuationEntry::cleanup_pc();
-  sp[-2] = (intptr_t)enterSpecial.fp();
   return sp;
 }
 
 inline intptr_t* ThawBase::push_preempt_adapter() {
   frame enterSpecial = new_entry_frame();
   intptr_t* sp = enterSpecial.sp();
 
+  // We only need to set the return pc. fp will be restored back in generate_cont_preempt_stub().
   sp[-1] = (intptr_t)StubRoutines::cont_preempt_stub();
   return sp;
 }

src/hotspot/cpu/x86/continuationFreezeThaw_x86.inline.hpp

@@ -202,6 +202,8 @@ inline intptr_t* AnchorMark::anchor_mark_set_pd() {
     assert(_last_sp_from_frame != nullptr, "");
     _top_frame.interpreter_frame_set_last_sp(nullptr);
     if (sp != _last_sp_from_frame) {
+      // We need to move up return pc and fp. They will be read next in
+      // set_anchor() and set as _last_Java_pc and _last_Java_fp respectively.
       _last_sp_from_frame[-1] = (intptr_t)_top_frame.pc();
       _last_sp_from_frame[-2] = (intptr_t)_top_frame.fp();
     }
@@ -322,15 +324,16 @@ inline intptr_t* ThawBase::push_cleanup_continuation() {
   frame enterSpecial = new_entry_frame();
   intptr_t* sp = enterSpecial.sp();
 
+  // We only need to set the return pc. rbp will be restored back in gen_continuation_enter().
   sp[-1] = (intptr_t)ContinuationEntry::cleanup_pc();
-  sp[-2] = (intptr_t)enterSpecial.fp();
   return sp;
 }
 
 inline intptr_t* ThawBase::push_preempt_adapter() {
   frame enterSpecial = new_entry_frame();
   intptr_t* sp = enterSpecial.sp();
 
+  // We only need to set the return pc. rbp will be restored back in generate_cont_preempt_stub().
   sp[-1] = (intptr_t)StubRoutines::cont_preempt_stub();
   return sp;
 }

src/hotspot/share/runtime/continuationFreezeThaw.cpp

@@ -1683,10 +1683,9 @@ static void jvmti_yield_cleanup(JavaThread* thread, ContinuationWrapper& cont) {
 static void jvmti_mount_end(JavaThread* current, ContinuationWrapper& cont, frame top, Continuation::preempt_kind pk) {
   assert(current->vthread() != nullptr, "must be");
 
-  HandleMarkCleaner hm(current);  // Cleanup vth and so._conth Handles
+  HandleMarkCleaner hm(current);  // Cleanup all handles (including so._conth) before returning to Java.
   Handle vth(current, current->vthread());
   ContinuationWrapper::SafepointOp so(current, cont);
-
   AnchorMark am(current, top);  // Set anchor so that the stack is walkable.
 
   JRT_BLOCK
@@ -2352,12 +2351,12 @@ NOINLINE intptr_t* Thaw<ConfigT>::thaw_fast(stackChunkOop chunk) {
 #endif
 
 #ifdef ASSERT
-  set_anchor(_thread, rs.sp());
-  log_frames(_thread);
   if (LoomDeoptAfterThaw) {
+    frame top(rs.sp());
+    AnchorMark am(_thread, top);
+    log_frames(_thread);
     do_deopt_after_thaw(_thread);
   }
-  clear_anchor(_thread);
 #endif
 
   return rs.sp();
@@ -2684,7 +2683,7 @@ intptr_t* ThawBase::redo_vmcall(JavaThread* current, frame& top) {
   intptr_t* sp = top.sp();
 
   {
-    HandleMarkCleaner hmc(current);  // Cleanup so._conth Handle
+    HandleMarkCleaner hmc(current);  // Cleanup all handles (including so._conth) before returning to Java.
     ContinuationWrapper::SafepointOp so(current, _cont);
     AnchorMark am(current, top);    // Set the anchor so that the stack is walkable.
 
@@ -2731,10 +2730,9 @@ intptr_t* ThawBase::redo_vmcall(JavaThread* current, frame& top) {
 }
 
 void ThawBase::throw_interrupted_exception(JavaThread* current, frame& top) {
-  HandleMarkCleaner hm(current);  // Cleanup so._conth Handle
+  HandleMarkCleaner hm(current);  // Cleanup all handles (including so._conth) before returning to Java.
   ContinuationWrapper::SafepointOp so(current, _cont);
-  // Since we might safepoint set the anchor so that the stack can be walked.
-  set_anchor(current, top.sp());
+  AnchorMark am(current, top);  // Set the anchor so that the stack is walkable.
   JRT_BLOCK
     THROW(vmSymbols::java_lang_InterruptedException());
   JRT_BLOCK_END

src/hotspot/share/runtime/frame.cpp

@@ -939,19 +939,8 @@ void frame::oops_interpreted_do(OopClosure* f, const RegisterMapT* map, bool que
       ResourceMark rm(thread);  // is this right ???
       Symbol* signature = call.signature();
       bool has_receiver = call.has_receiver();
-      // we are at a call site & the expression stack is not empty
-      // => process callee's arguments
-      //
-      // Note: The expression stack can be empty if an exception
-      //       occurred during method resolution/execution. In all
-      //       cases we empty the expression stack completely be-
-      //       fore handling the exception (the exception handling
-      //       code in the interpreter calls a blocking runtime
-      //       routine which can cause this code to be executed).
-      //       (was bug gri 7/27/98)
-      // if (dolog) {
-      //   log_trace(continuations, tracking)("Processing arguments");
-      // }
+      // We are at a call site & the expression stack is not empty
+      // so we might have callee arguments we need to process.
       oops_interpreted_arguments_do(signature, has_receiver, f);
     }
   }

test/jdk/java/lang/Thread/virtual/KlassInit.java

@@ -25,42 +25,49 @@
  * @test id=default
  * @library /test/lib
  * @requires vm.continuations
- * @run junit/othervm/timeout=480 -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit* -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
+ * @run junit/othervm/timeout=480 -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit*
+ *      -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
  */
 
 /*
  * @test id=Xint
  * @library /test/lib
  * @requires vm.continuations
- * @run junit/othervm/timeout=480 -Xint -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit* -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
+ * @run junit/othervm/timeout=480 -Xint -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit*
+ *      -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
  */
 
 /*
  * @test id=Xcomp
  * @library /test/lib
  * @requires vm.continuations
- * @run junit/othervm/timeout=480 -Xcomp -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit* -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
+ * @run junit/othervm/timeout=480 -Xcomp -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit*
+ *      -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
  */
 
 /*
  * @test id=Xcomp-TieredStopAtLevel1
  * @library /test/lib
  * @requires vm.continuations
- * @run junit/othervm/timeout=480 -Xcomp -XX:TieredStopAtLevel=1 -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit* -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
+ * @run junit/othervm/timeout=480 -Xcomp -XX:TieredStopAtLevel=1 -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit*
+ *      -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
  */
 
 /*
  * @test id=Xcomp-noTieredCompilation
  * @library /test/lib
  * @requires vm.continuations
- * @run junit/othervm/timeout=480 -Xcomp -XX:-TieredCompilation -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit* -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
+ * @run junit/othervm/timeout=480 -Xcomp -XX:-TieredCompilation -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit*
+ *      -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
  */
 
 /*
  * @test id=gc
  * @library /test/lib
  * @requires vm.debug == true & vm.continuations
- * @run junit/othervm/timeout=480 -XX:+UnlockDiagnosticVMOptions -XX:+FullGCALot -XX:FullGCALotInterval=1000 -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit* -XX:CompileCommand=exclude,KlassInit$$Lambda*::run -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
+ * @run junit/othervm/timeout=480 -XX:+UnlockDiagnosticVMOptions -XX:+FullGCALot -XX:FullGCALotInterval=1000
+ *      -XX:CompileCommand=exclude,KlassInit::lambda$testReleaseAtKlassInit* -XX:CompileCommand=exclude,KlassInit$$Lambda*::run
+ *      -XX:CompileCommand=exclude,KlassInit$1Driver::foo KlassInit
  */
 
 import java.util.ArrayList;