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src/hotspot/share/runtime/continuationFreezeThaw.cpp

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  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "classfile/javaClasses.inline.hpp"
  26 #include "classfile/vmSymbols.hpp"
  27 #include "code/codeCache.inline.hpp"
  28 #include "code/nmethod.inline.hpp"
  29 #include "code/vmreg.inline.hpp"
  30 #include "compiler/oopMap.inline.hpp"
  31 #include "gc/shared/barrierSet.hpp"
  32 #include "gc/shared/continuationGCSupport.inline.hpp"
  33 #include "gc/shared/gc_globals.hpp"
  34 #include "gc/shared/memAllocator.hpp"
  35 #include "gc/shared/threadLocalAllocBuffer.inline.hpp"

  36 #include "interpreter/interpreter.hpp"

  37 #include "jfr/jfrEvents.hpp"
  38 #include "logging/log.hpp"
  39 #include "logging/logStream.hpp"
  40 #include "oops/access.inline.hpp"

  41 #include "oops/method.inline.hpp"
  42 #include "oops/objArrayOop.inline.hpp"
  43 #include "oops/oopsHierarchy.hpp"
  44 #include "oops/stackChunkOop.inline.hpp"
  45 #include "prims/jvmtiThreadState.hpp"
  46 #include "runtime/arguments.hpp"
  47 #include "runtime/continuation.hpp"
  48 #include "runtime/continuationEntry.inline.hpp"
  49 #include "runtime/continuationHelper.inline.hpp"
  50 #include "runtime/continuationJavaClasses.inline.hpp"
  51 #include "runtime/continuationWrapper.inline.hpp"
  52 #include "runtime/frame.inline.hpp"
  53 #include "runtime/interfaceSupport.inline.hpp"
  54 #include "runtime/javaThread.inline.hpp"
  55 #include "runtime/jniHandles.inline.hpp"
  56 #include "runtime/keepStackGCProcessed.hpp"
  57 #include "runtime/objectMonitor.inline.hpp"
  58 #include "runtime/orderAccess.hpp"
  59 #include "runtime/prefetch.inline.hpp"
  60 #include "runtime/sharedRuntime.hpp"
  61 #include "runtime/smallRegisterMap.inline.hpp"
  62 #include "runtime/stackChunkFrameStream.inline.hpp"
  63 #include "runtime/stackFrameStream.inline.hpp"
  64 #include "runtime/stackOverflow.hpp"
  65 #include "runtime/stackWatermarkSet.inline.hpp"


  66 #include "utilities/debug.hpp"
  67 #include "utilities/exceptions.hpp"
  68 #include "utilities/macros.hpp"
  69 #include "utilities/vmError.hpp"
  70 #if INCLUDE_ZGC
  71 #include "gc/z/zStackChunkGCData.inline.hpp"
  72 #endif
  73 #if INCLUDE_JFR
  74 #include "jfr/jfr.inline.hpp"
  75 #endif






  76 
  77 #include <type_traits>
  78 
  79 /*
  80  * This file contains the implementation of continuation freezing (yield) and thawing (run).
  81  *
  82  * This code is very latency-critical and very hot. An ordinary and well-behaved server application
  83  * would likely call these operations many thousands of times per second second, on every core.
  84  *
  85  * Freeze might be called every time the application performs any I/O operation, every time it
  86  * acquires a j.u.c. lock, every time it takes a message from a queue, and thaw can be called
  87  * multiple times in each of those cases, as it is called by the return barrier, which may be
  88  * invoked on method return.
  89  *
  90  * The amortized budget for each of those two operations is ~100-150ns. That is why, for
  91  * example, every effort is made to avoid Java-VM transitions as much as possible.
  92  *
  93  * On the fast path, all frames are known to be compiled, and the chunk requires no barriers
  94  * and so frames simply copied, and the bottom-most one is patched.
  95  * On the slow path, internal pointers in interpreted frames are de/relativized to/from offsets

 165 #endif
 166 
 167 // TODO: See AbstractAssembler::generate_stack_overflow_check,
 168 // Compile::bang_size_in_bytes(), m->as_SafePoint()->jvms()->interpreter_frame_size()
 169 // when we stack-bang, we need to update a thread field with the lowest (farthest) bang point.
 170 
 171 // Data invariants are defined by Continuation::debug_verify_continuation and Continuation::debug_verify_stack_chunk
 172 
 173 // Used to just annotatate cold/hot branches
 174 #define LIKELY(condition)   (condition)
 175 #define UNLIKELY(condition) (condition)
 176 
 177 // debugging functions
 178 #ifdef ASSERT
 179 extern "C" bool dbg_is_safe(const void* p, intptr_t errvalue); // address p is readable and *(intptr_t*)p != errvalue
 180 
 181 static void verify_continuation(oop continuation) { Continuation::debug_verify_continuation(continuation); }
 182 
 183 static void do_deopt_after_thaw(JavaThread* thread);
 184 static bool do_verify_after_thaw(JavaThread* thread, stackChunkOop chunk, outputStream* st);
 185 static void log_frames(JavaThread* thread);
 186 static void log_frames_after_thaw(JavaThread* thread, ContinuationWrapper& cont, intptr_t* sp, bool preempted);
 187 static void print_frame_layout(const frame& f, bool callee_complete, outputStream* st = tty);

 188 
 189 #define assert_pfl(p, ...) \
 190 do {                                           \
 191   if (!(p)) {                                  \
 192     JavaThread* t = JavaThread::active();      \
 193     if (t->has_last_Java_frame()) {            \
 194       tty->print_cr("assert(" #p ") failed:"); \
 195       t->print_frame_layout();                 \
 196     }                                          \
 197   }                                            \
 198   vmassert(p, __VA_ARGS__);                    \
 199 } while(0)
 200 
 201 #else
 202 static void verify_continuation(oop continuation) { }
 203 #define assert_pfl(p, ...)
 204 #endif
 205 
 206 static freeze_result is_pinned0(JavaThread* thread, oop cont_scope, bool safepoint);
 207 template<typename ConfigT, bool preempt> static inline freeze_result freeze_internal(JavaThread* current, intptr_t* const sp);

 496 
 497   assert(!Interpreter::contains(_cont.entryPC()), "");
 498 
 499   _bottom_address = _cont.entrySP() - _cont.entry_frame_extension();
 500 #ifdef _LP64
 501   if (((intptr_t)_bottom_address & 0xf) != 0) {
 502     _bottom_address--;
 503   }
 504   assert(is_aligned(_bottom_address, frame::frame_alignment), "");
 505 #endif
 506 
 507   log_develop_trace(continuations)("bottom_address: " INTPTR_FORMAT " entrySP: " INTPTR_FORMAT " argsize: " PTR_FORMAT,
 508                 p2i(_bottom_address), p2i(_cont.entrySP()), (_cont.entrySP() - _bottom_address) << LogBytesPerWord);
 509   assert(_bottom_address != nullptr, "");
 510   assert(_bottom_address <= _cont.entrySP(), "");
 511   DEBUG_ONLY(_last_write = nullptr;)
 512 
 513   assert(_cont.chunk_invariant(), "");
 514   assert(!Interpreter::contains(_cont.entryPC()), "");
 515 #if !defined(PPC64) || defined(ZERO)
 516   static const int doYield_stub_frame_size = frame::metadata_words;
 517 #else
 518   static const int doYield_stub_frame_size = frame::native_abi_reg_args_size >> LogBytesPerWord;
 519 #endif
 520   // With preemption doYield() might not have been resolved yet
 521   assert(_preempt || SharedRuntime::cont_doYield_stub()->frame_size() == doYield_stub_frame_size, "");
 522 
 523   if (preempt) {
 524     _last_frame = _thread->last_frame();
 525   }
 526 
 527   // properties of the continuation on the stack; all sizes are in words
 528   _cont_stack_top    = frame_sp + (!preempt ? doYield_stub_frame_size : 0); // we don't freeze the doYield stub frame
 529   _cont_stack_bottom = _cont.entrySP() + (_cont.argsize() == 0 ? frame::metadata_words_at_top : 0)
 530       - ContinuationHelper::frame_align_words(_cont.argsize()); // see alignment in thaw
 531 
 532   log_develop_trace(continuations)("freeze size: %d argsize: %d top: " INTPTR_FORMAT " bottom: " INTPTR_FORMAT,
 533     cont_size(), _cont.argsize(), p2i(_cont_stack_top), p2i(_cont_stack_bottom));
 534   assert(cont_size() > 0, "");
 535 
 536   if (LockingMode != LM_LIGHTWEIGHT) {
 537     _monitors_in_lockstack = 0;
 538   } else {
 539     _monitors_in_lockstack = _thread->lock_stack().monitor_count();
 540   }
 541 }
 542 
 543 void FreezeBase::init_rest() { // we want to postpone some initialization after chunk handling
 544   _freeze_size = 0;
 545   _total_align_size = 0;
 546   NOT_PRODUCT(_frames = 0;)
 547 }
 548 

 902   freeze_result res = recurse_freeze(f, caller, 0, false, true);
 903 
 904   if (res == freeze_ok) {
 905     finish_freeze(f, caller);
 906     _cont.write();
 907   }
 908 
 909   return res;
 910 }
 911 
 912 frame FreezeBase::freeze_start_frame() {
 913   if (LIKELY(!_preempt)) {
 914     return freeze_start_frame_yield_stub();
 915   } else {
 916     return freeze_start_frame_on_preempt();
 917   }
 918 }
 919 
 920 frame FreezeBase::freeze_start_frame_yield_stub() {
 921   frame f = _thread->last_frame();
 922   assert(SharedRuntime::cont_doYield_stub()->contains(f.pc()), "must be");
 923   f = sender<ContinuationHelper::NonInterpretedUnknownFrame>(f);
 924   assert(Continuation::is_frame_in_continuation(_thread->last_continuation(), f), "");
 925   return f;
 926 }
 927 
 928 frame FreezeBase::freeze_start_frame_on_preempt() {
 929   assert(_last_frame.sp() == _thread->last_frame().sp(), "_last_frame should be already initialized");
 930   assert(Continuation::is_frame_in_continuation(_thread->last_continuation(), _last_frame), "");
 931   return _last_frame;
 932 }
 933 
 934 // The parameter callee_argsize includes metadata that has to be part of caller/callee overlap.
 935 NOINLINE freeze_result FreezeBase::recurse_freeze(frame& f, frame& caller, int callee_argsize, bool callee_interpreted, bool top) {
 936   assert(f.unextended_sp() < _bottom_address, ""); // see recurse_freeze_java_frame
 937   assert(f.is_interpreted_frame() || ((top && _preempt) == ContinuationHelper::Frame::is_stub(f.cb()))
 938          || ((top && _preempt) == f.is_native_frame()), "");
 939 
 940   if (stack_overflow()) {
 941     return freeze_exception;
 942   }

1098     log_develop_trace(continuations)("Reusing chunk mixed: %d empty: %d", chunk->has_mixed_frames(), chunk->is_empty());
1099     if (chunk->is_empty()) {
1100       int sp = chunk->stack_size() - argsize_md;
1101       chunk->set_sp(sp);
1102       chunk->set_bottom(sp);
1103       _freeze_size += overlap;
1104       assert(chunk->max_thawing_size() == 0, "");
1105     } DEBUG_ONLY(else empty_chunk = false;)
1106   }
1107   assert(!chunk->is_gc_mode(), "");
1108   assert(!chunk->has_bitmap(), "");
1109   chunk->set_has_mixed_frames(true);
1110 
1111   assert(chunk->requires_barriers() == _barriers, "");
1112   assert(!_barriers || chunk->is_empty(), "");
1113 
1114   assert(!chunk->is_empty() || StackChunkFrameStream<ChunkFrames::Mixed>(chunk).is_done(), "");
1115   assert(!chunk->is_empty() || StackChunkFrameStream<ChunkFrames::Mixed>(chunk).to_frame().is_empty(), "");
1116 
1117   if (_preempt) {
1118     frame f = _thread->last_frame();
1119     if (f.is_interpreted_frame()) {
1120       // Some platforms do not save the last_sp in the top interpreter frame on VM calls.
1121       // We need it so that on resume we can restore the sp to the right place, since
1122       // thawing might add an alignment word to the expression stack (see finish_thaw()).
1123       // We do it now that we know freezing will be successful.
1124       prepare_freeze_interpreted_top_frame(f);














1125     }
1126   }
1127 
1128   // We unwind frames after the last safepoint so that the GC will have found the oops in the frames, but before
1129   // writing into the chunk. This is so that an asynchronous stack walk (not at a safepoint) that suspends us here
1130   // will either see no continuation or a consistent chunk.
1131   unwind_frames();
1132 
1133   chunk->set_max_thawing_size(chunk->max_thawing_size() + _freeze_size - _monitors_in_lockstack - frame::metadata_words);
1134 
1135   if (lt.develop_is_enabled()) {
1136     LogStream ls(lt);
1137     ls.print_cr("top chunk:");
1138     chunk->print_on(&ls);
1139   }
1140 
1141   if (_monitors_in_lockstack > 0) {
1142     freeze_lockstack(chunk);
1143   }
1144 

1616       // Some GCs could put direct allocations in old gen for slow-path
1617       // allocations; need to explicitly check if that was the case.
1618       _barriers = chunk->requires_barriers();
1619     }
1620   }
1621 
1622   if (_barriers) {
1623     log_develop_trace(continuations)("allocation requires barriers");
1624   }
1625 
1626   assert(chunk->parent() == nullptr || chunk->parent()->is_stackChunk(), "");
1627 
1628   return chunk;
1629 }
1630 
1631 void FreezeBase::throw_stack_overflow_on_humongous_chunk() {
1632   ContinuationWrapper::SafepointOp so(_thread, _cont); // could also call _cont.done() instead
1633   Exceptions::_throw_msg(_thread, __FILE__, __LINE__, vmSymbols::java_lang_StackOverflowError(), "Humongous stack chunk");
1634 }
1635 



















1636 #if INCLUDE_JVMTI
1637 static int num_java_frames(ContinuationWrapper& cont) {
1638   ResourceMark rm; // used for scope traversal in num_java_frames(nmethod*, address)
1639   int count = 0;
1640   for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
1641     count += chunk->num_java_frames();
1642   }
1643   return count;
1644 }
1645 
1646 static void invalidate_jvmti_stack(JavaThread* thread) {
1647   if (thread->is_interp_only_mode()) {
1648     JvmtiThreadState *state = thread->jvmti_thread_state();
1649     if (state != nullptr)
1650       state->invalidate_cur_stack_depth();
1651   }
1652 }
1653 
1654 static void jvmti_yield_cleanup(JavaThread* thread, ContinuationWrapper& cont) {
1655   if (JvmtiExport::can_post_frame_pop()) {
1656     int num_frames = num_java_frames(cont);
1657 
1658     ContinuationWrapper::SafepointOp so(Thread::current(), cont);
1659     JvmtiExport::continuation_yield_cleanup(JavaThread::current(), num_frames);
1660   }
1661   invalidate_jvmti_stack(thread);
1662 }
1663 
1664 static void jvmti_mount_end(JavaThread* current, ContinuationWrapper& cont, frame top) {
1665   assert(current->vthread() != nullptr, "must be");
1666 
1667   HandleMarkCleaner hm(current);
1668   Handle vth(current, current->vthread());
1669 
1670   ContinuationWrapper::SafepointOp so(current, cont);
1671 
1672   // Since we might safepoint set the anchor so that the stack can be walked.
1673   set_anchor(current, top.sp());
1674 
1675   JRT_BLOCK
1676     JvmtiVTMSTransitionDisabler::VTMS_vthread_mount((jthread)vth.raw_value(), false);
1677 
1678     if (current->pending_contended_entered_event()) {
1679       JvmtiExport::post_monitor_contended_entered(current, current->contended_entered_monitor());



1680       current->set_contended_entered_monitor(nullptr);
1681     }
1682   JRT_BLOCK_END
1683 
1684   clear_anchor(current);
1685 }
1686 #endif // INCLUDE_JVMTI
1687 
1688 #ifdef ASSERT
1689 // There are no interpreted frames if we're not called from the interpreter and we haven't ancountered an i2c
1690 // adapter or called Deoptimization::unpack_frames. As for native frames, upcalls from JNI also go through the
1691 // interpreter (see JavaCalls::call_helper), while the UpcallLinker explicitly sets cont_fastpath.
1692 bool FreezeBase::check_valid_fast_path() {
1693   ContinuationEntry* ce = _thread->last_continuation();
1694   RegisterMap map(_thread,
1695                   RegisterMap::UpdateMap::skip,
1696                   RegisterMap::ProcessFrames::skip,
1697                   RegisterMap::WalkContinuation::skip);
1698   map.set_include_argument_oops(false);
1699   bool is_top_frame = true;
1700   for (frame f = freeze_start_frame(); Continuation::is_frame_in_continuation(ce, f); f = f.sender(&map), is_top_frame = false) {
1701     if (!((f.is_compiled_frame() && !f.is_deoptimized_frame()) || (is_top_frame && (f.is_runtime_frame() || f.is_native_frame())))) {
1702       return false;
1703     }
1704   }
1705   return true;
1706 }































































































1707 #endif // ASSERT
1708 
1709 static inline freeze_result freeze_epilog(ContinuationWrapper& cont) {
1710   verify_continuation(cont.continuation());
1711   assert(!cont.is_empty(), "");
1712 
1713   log_develop_debug(continuations)("=== End of freeze cont ### #" INTPTR_FORMAT, cont.hash());
1714   return freeze_ok;
1715 }
1716 
1717 static freeze_result freeze_epilog(JavaThread* thread, ContinuationWrapper& cont, freeze_result res) {
1718   if (UNLIKELY(res != freeze_ok)) {
1719     JFR_ONLY(thread->set_last_freeze_fail_result(res);)
1720     verify_continuation(cont.continuation());
1721     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
1722     return res;
1723   }
1724 
1725   JVMTI_ONLY(jvmti_yield_cleanup(thread, cont)); // can safepoint
1726   return freeze_epilog(cont);
1727 }
1728 
1729 static freeze_result preempt_epilog(ContinuationWrapper& cont, freeze_result res, frame& old_last_frame) {
1730   if (UNLIKELY(res != freeze_ok)) {
1731     verify_continuation(cont.continuation());
1732     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
1733     return res;
1734   }
1735 

1736   patch_return_pc_with_preempt_stub(old_last_frame);
1737   cont.tail()->set_preempted(true);
1738 
1739   return freeze_epilog(cont);
1740 }
1741 
1742 template<typename ConfigT, bool preempt>
1743 static inline freeze_result freeze_internal(JavaThread* current, intptr_t* const sp) {
1744   assert(!current->has_pending_exception(), "");
1745 
1746 #ifdef ASSERT
1747   log_trace(continuations)("~~~~ freeze sp: " INTPTR_FORMAT "JavaThread: " INTPTR_FORMAT, p2i(current->last_continuation()->entry_sp()), p2i(current));
1748   log_frames(current);
1749 #endif
1750 
1751   CONT_JFR_ONLY(EventContinuationFreeze event;)
1752 
1753   ContinuationEntry* entry = current->last_continuation();
1754 
1755   oop oopCont = entry->cont_oop(current);
1756   assert(oopCont == current->last_continuation()->cont_oop(current), "");
1757   assert(ContinuationEntry::assert_entry_frame_laid_out(current), "");
1758 
1759   verify_continuation(oopCont);
1760   ContinuationWrapper cont(current, oopCont);
1761   log_develop_debug(continuations)("FREEZE #" INTPTR_FORMAT " " INTPTR_FORMAT, cont.hash(), p2i((oopDesc*)oopCont));
1762 
1763   assert(entry->is_virtual_thread() == (entry->scope(current) == java_lang_VirtualThread::vthread_scope()), "");
1764 
1765   assert(LockingMode == LM_LEGACY || (current->held_monitor_count() == 0 && current->jni_monitor_count() == 0),
1766          "Held monitor count should only be used for LM_LEGACY: " INT64_FORMAT " JNI: " INT64_FORMAT, (int64_t)current->held_monitor_count(), (int64_t)current->jni_monitor_count());
1767 
1768   if (entry->is_pinned() || current->held_monitor_count() > 0) {

1922   // 300 is an estimate for stack size taken for this native code, in addition to StackShadowPages
1923   // for the Java frames in the check below.
1924   if (!stack_overflow_check(thread, size + 300, bottom)) {
1925     return 0;
1926   }
1927 
1928   log_develop_trace(continuations)("prepare_thaw bottom: " INTPTR_FORMAT " top: " INTPTR_FORMAT " size: %d",
1929                               p2i(bottom), p2i(bottom - size), size);
1930   return size;
1931 }
1932 
1933 class ThawBase : public StackObj {
1934 protected:
1935   JavaThread* _thread;
1936   ContinuationWrapper& _cont;
1937   CONT_JFR_ONLY(FreezeThawJfrInfo _jfr_info;)
1938 
1939   intptr_t* _fastpath;
1940   bool _barriers;
1941   bool _preempted_case;

1942   intptr_t* _top_unextended_sp_before_thaw;
1943   int _align_size;
1944   DEBUG_ONLY(intptr_t* _top_stack_address);
1945 



1946   StackChunkFrameStream<ChunkFrames::Mixed> _stream;
1947 
1948   NOT_PRODUCT(int _frames;)
1949 
1950 protected:
1951   ThawBase(JavaThread* thread, ContinuationWrapper& cont) :
1952       _thread(thread), _cont(cont),
1953       _fastpath(nullptr) {
1954     DEBUG_ONLY(_top_unextended_sp_before_thaw = nullptr;)
1955     assert (cont.tail() != nullptr, "no last chunk");
1956     DEBUG_ONLY(_top_stack_address = _cont.entrySP() - thaw_size(cont.tail());)
1957   }
1958 
1959   void clear_chunk(stackChunkOop chunk);
1960   template<bool check_stub>
1961   int remove_top_compiled_frame_from_chunk(stackChunkOop chunk, int &argsize);
1962   void copy_from_chunk(intptr_t* from, intptr_t* to, int size);
1963 
1964   void thaw_lockstack(stackChunkOop chunk);
1965 
1966   // fast path
1967   inline void prefetch_chunk_pd(void* start, int size_words);
1968   void patch_return(intptr_t* sp, bool is_last);
1969 
1970   intptr_t* handle_preempted_continuation(intptr_t* sp, Continuation::preempt_kind preempt_kind, bool fast_case);
1971   inline intptr_t* push_cleanup_continuation();


1972   void throw_interrupted_exception(JavaThread* current, frame& top);
1973 
1974   void recurse_thaw(const frame& heap_frame, frame& caller, int num_frames, bool top_on_preempt_case);
1975   void finish_thaw(frame& f);
1976 
1977 private:
1978   template<typename FKind> bool recurse_thaw_java_frame(frame& caller, int num_frames);
1979   void finalize_thaw(frame& entry, int argsize);
1980 
1981   inline bool seen_by_gc();
1982 
1983   inline void before_thaw_java_frame(const frame& hf, const frame& caller, bool bottom, int num_frame);
1984   inline void after_thaw_java_frame(const frame& f, bool bottom);
1985   inline void patch(frame& f, const frame& caller, bool bottom);
1986   void clear_bitmap_bits(address start, address end);
1987 
1988   NOINLINE void recurse_thaw_interpreted_frame(const frame& hf, frame& caller, int num_frames);
1989   void recurse_thaw_compiled_frame(const frame& hf, frame& caller, int num_frames, bool stub_caller);
1990   void recurse_thaw_stub_frame(const frame& hf, frame& caller, int num_frames);
1991   void recurse_thaw_native_frame(const frame& hf, frame& caller, int num_frames);
1992 
1993   void push_return_frame(frame& f);
1994   inline frame new_entry_frame();
1995   template<typename FKind> frame new_stack_frame(const frame& hf, frame& caller, bool bottom);
1996   inline void patch_pd(frame& f, const frame& sender);
1997   inline void patch_pd(frame& f, intptr_t* caller_sp);
1998   inline intptr_t* align(const frame& hf, intptr_t* frame_sp, frame& caller, bool bottom);
1999 
2000   void maybe_set_fastpath(intptr_t* sp) { if (sp > _fastpath) _fastpath = sp; }
2001 
2002   static inline void derelativize_interpreted_frame_metadata(const frame& hf, const frame& f);
2003 
2004  public:
2005   CONT_JFR_ONLY(FreezeThawJfrInfo& jfr_info() { return _jfr_info; })
2006 };
2007 
2008 template <typename ConfigT>

2068   chunk->set_sp(chunk->bottom());
2069   chunk->set_max_thawing_size(0);
2070 }
2071 
2072 template<bool check_stub>
2073 int ThawBase::remove_top_compiled_frame_from_chunk(stackChunkOop chunk, int &argsize) {
2074   bool empty = false;
2075   StackChunkFrameStream<ChunkFrames::CompiledOnly> f(chunk);
2076   DEBUG_ONLY(intptr_t* const chunk_sp = chunk->start_address() + chunk->sp();)
2077   assert(chunk_sp == f.sp(), "");
2078   assert(chunk_sp == f.unextended_sp(), "");
2079 
2080   int frame_size = f.cb()->frame_size();
2081   argsize = f.stack_argsize();
2082 
2083   assert(!f.is_stub() || check_stub, "");
2084   if (check_stub && f.is_stub()) {
2085     // If we don't thaw the top compiled frame too, after restoring the saved
2086     // registers back in Java, we would hit the return barrier to thaw one more
2087     // frame effectively overwriting the restored registers during that call.
2088     f.next(SmallRegisterMap::instance(), true /* stop */);
2089     assert(!f.is_done(), "");
2090 
2091     f.get_cb();
2092     assert(f.is_compiled(), "");
2093     frame_size += f.cb()->frame_size();
2094     argsize = f.stack_argsize();
2095 
2096     if (f.cb()->as_nmethod()->is_marked_for_deoptimization()) {
2097       // The caller of the runtime stub when the continuation is preempted is not at a
2098       // Java call instruction, and so cannot rely on nmethod patching for deopt.
2099       log_develop_trace(continuations)("Deoptimizing runtime stub caller");
2100       f.to_frame().deoptimize(nullptr); // the null thread simply avoids the assertion in deoptimize which we're not set up for
2101     }
2102   }
2103 
2104   f.next(SmallRegisterMap::instance(), true /* stop */);
2105   empty = f.is_done();
2106   assert(!empty || argsize == chunk->argsize(), "");
2107 
2108   if (empty) {
2109     clear_chunk(chunk);
2110   } else {
2111     chunk->set_sp(chunk->sp() + frame_size);
2112     chunk->set_max_thawing_size(chunk->max_thawing_size() - frame_size);
2113     // We set chunk->pc to the return pc into the next frame
2114     chunk->set_pc(f.pc());
2115 #ifdef ASSERT
2116     {
2117       intptr_t* retaddr_slot = (chunk_sp
2118                                 + frame_size
2119                                 - frame::sender_sp_ret_address_offset());
2120       assert(f.pc() == ContinuationHelper::return_address_at(retaddr_slot),
2121              "unexpected pc");
2122     }
2123 #endif
2124   }

2244   return rs.sp();
2245 }
2246 
2247 inline bool ThawBase::seen_by_gc() {
2248   return _barriers || _cont.tail()->is_gc_mode();
2249 }
2250 
2251 static inline void relativize_chunk_concurrently(stackChunkOop chunk) {
2252 #if INCLUDE_ZGC || INCLUDE_SHENANDOAHGC
2253   if (UseZGC || UseShenandoahGC) {
2254     chunk->relativize_derived_pointers_concurrently();
2255   }
2256 #endif
2257 }
2258 
2259 template <typename ConfigT>
2260 NOINLINE intptr_t* Thaw<ConfigT>::thaw_slow(stackChunkOop chunk, Continuation::thaw_kind kind) {
2261   Continuation::preempt_kind preempt_kind;
2262   bool retry_fast_path = false;
2263 

2264   _preempted_case = chunk->preempted();
2265   if (_preempted_case) {
2266     ObjectWaiter* waiter = java_lang_VirtualThread::objectWaiter(_thread->vthread());
2267     if (waiter != nullptr) {
2268       // Mounted again after preemption. Resume the pending monitor operation,
2269       // which will be either a monitorenter or Object.wait() call.
2270       ObjectMonitor* mon = waiter->monitor();
2271       preempt_kind = waiter->is_wait() ? Continuation::freeze_on_wait : Continuation::freeze_on_monitorenter;
2272 
2273       bool mon_acquired = mon->resume_operation(_thread, waiter, _cont);
2274       assert(!mon_acquired || mon->has_owner(_thread), "invariant");
2275       if (!mon_acquired) {
2276         // Failed to acquire monitor. Return to enterSpecial to unmount again.

2277         return push_cleanup_continuation();
2278       }

2279       chunk = _cont.tail();  // reload oop in case of safepoint in resume_operation (if posting JVMTI events).

2280     } else {
2281       // Preemption cancelled in moniterenter case. We actually acquired
2282       // the monitor after freezing all frames so nothing to do.
2283       preempt_kind = Continuation::freeze_on_monitorenter;




2284     }

2285     // Call this first to avoid racing with GC threads later when modifying the chunk flags.
2286     relativize_chunk_concurrently(chunk);







2287     chunk->set_preempted(false);
2288     retry_fast_path = true;
2289   } else {
2290     relativize_chunk_concurrently(chunk);
2291   }
2292 
2293   // On first thaw after freeze restore oops to the lockstack if any.
2294   assert(chunk->lockstack_size() == 0 || kind == Continuation::thaw_top, "");
2295   if (kind == Continuation::thaw_top && chunk->lockstack_size() > 0) {
2296     thaw_lockstack(chunk);
2297     retry_fast_path = true;
2298   }
2299 
2300   // Retry the fast path now that we possibly cleared the FLAG_HAS_LOCKSTACK
2301   // and FLAG_PREEMPTED flags from the stackChunk.
2302   if (retry_fast_path && can_thaw_fast(chunk)) {
2303     intptr_t* sp = thaw_fast<true>(chunk);
2304     if (_preempted_case) {
2305       return handle_preempted_continuation(sp, preempt_kind, true /* fast_case */);
2306     }

2350 
2351   intptr_t* sp = caller.sp();
2352 
2353   if (_preempted_case) {
2354     return handle_preempted_continuation(sp, preempt_kind, false /* fast_case */);
2355   }
2356   return sp;
2357 }
2358 
2359 void ThawBase::recurse_thaw(const frame& heap_frame, frame& caller, int num_frames, bool top_on_preempt_case) {
2360   log_develop_debug(continuations)("thaw num_frames: %d", num_frames);
2361   assert(!_cont.is_empty(), "no more frames");
2362   assert(num_frames > 0, "");
2363   assert(!heap_frame.is_empty(), "");
2364 
2365   if (top_on_preempt_case && (heap_frame.is_native_frame() || heap_frame.is_runtime_frame())) {
2366     heap_frame.is_native_frame() ? recurse_thaw_native_frame(heap_frame, caller, 2) : recurse_thaw_stub_frame(heap_frame, caller, 2);
2367   } else if (!heap_frame.is_interpreted_frame()) {
2368     recurse_thaw_compiled_frame(heap_frame, caller, num_frames, false);
2369   } else {
2370     recurse_thaw_interpreted_frame(heap_frame, caller, num_frames);
2371   }
2372 }
2373 
2374 template<typename FKind>
2375 bool ThawBase::recurse_thaw_java_frame(frame& caller, int num_frames) {
2376   assert(num_frames > 0, "");
2377 
2378   DEBUG_ONLY(_frames++;)
2379 
2380   int argsize = _stream.stack_argsize();
2381 
2382   _stream.next(SmallRegisterMap::instance());
2383   assert(_stream.to_frame().is_empty() == _stream.is_done(), "");
2384 
2385   // we never leave a compiled caller of an interpreted frame as the top frame in the chunk
2386   // as it makes detecting that situation and adjusting unextended_sp tricky
2387   if (num_frames == 1 && !_stream.is_done() && FKind::interpreted && _stream.is_compiled()) {
2388     log_develop_trace(continuations)("thawing extra compiled frame to not leave a compiled interpreted-caller at top");
2389     num_frames++;
2390   }
2391 
2392   if (num_frames == 1 || _stream.is_done()) { // end recursion
2393     finalize_thaw(caller, FKind::interpreted ? 0 : argsize);
2394     return true; // bottom
2395   } else { // recurse
2396     recurse_thaw(_stream.to_frame(), caller, num_frames - 1, false /* top_on_preempt_case */);
2397     return false;
2398   }
2399 }
2400 
2401 void ThawBase::finalize_thaw(frame& entry, int argsize) {
2402   stackChunkOop chunk = _cont.tail();

2467 
2468 void ThawBase::clear_bitmap_bits(address start, address end) {
2469   assert(is_aligned(start, wordSize), "should be aligned: " PTR_FORMAT, p2i(start));
2470   assert(is_aligned(end, VMRegImpl::stack_slot_size), "should be aligned: " PTR_FORMAT, p2i(end));
2471 
2472   // we need to clear the bits that correspond to arguments as they reside in the caller frame
2473   // or they will keep objects that are otherwise unreachable alive.
2474 
2475   // Align `end` if UseCompressedOops is not set to avoid UB when calculating the bit index, since
2476   // `end` could be at an odd number of stack slots from `start`, i.e might not be oop aligned.
2477   // If that's the case the bit range corresponding to the last stack slot should not have bits set
2478   // anyways and we assert that before returning.
2479   address effective_end = UseCompressedOops ? end : align_down(end, wordSize);
2480   log_develop_trace(continuations)("clearing bitmap for " INTPTR_FORMAT " - " INTPTR_FORMAT, p2i(start), p2i(effective_end));
2481   stackChunkOop chunk = _cont.tail();
2482   chunk->bitmap().clear_range(chunk->bit_index_for(start), chunk->bit_index_for(effective_end));
2483   assert(effective_end == end || !chunk->bitmap().at(chunk->bit_index_for(effective_end)), "bit should not be set");
2484 }
2485 
2486 intptr_t* ThawBase::handle_preempted_continuation(intptr_t* sp, Continuation::preempt_kind preempt_kind, bool fast_case) {
2487   assert(preempt_kind == Continuation::freeze_on_wait || preempt_kind == Continuation::freeze_on_monitorenter, "");
2488   frame top(sp);
2489   assert(top.pc() == *(address*)(sp - frame::sender_sp_ret_address_offset()), "");


2490 
2491 #if INCLUDE_JVMTI
2492   // Finish the VTMS transition.
2493   assert(_thread->is_in_VTMS_transition(), "must be");
2494   bool is_vthread = Continuation::continuation_scope(_cont.continuation()) == java_lang_VirtualThread::vthread_scope();
2495   if (is_vthread) {
2496     if (JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events()) {
2497       jvmti_mount_end(_thread, _cont, top);
2498     } else {
2499       _thread->set_is_in_VTMS_transition(false);
2500       java_lang_Thread::set_is_in_VTMS_transition(_thread->vthread(), false);
2501     }
2502   }
2503 #endif
2504 
2505   if (fast_case) {
2506     // If we thawed in the slow path the runtime stub/native wrapper frame already
2507     // has the correct fp (see ThawBase::new_stack_frame). On the fast path though,
2508     // we copied the fp patched during freeze, which will now have to be fixed.
2509     assert(top.is_runtime_frame() || top.is_native_frame(), "");
2510     int fsize = top.cb()->frame_size();
2511     patch_pd(top, sp + fsize);
2512   }
2513 
2514   if (preempt_kind == Continuation::freeze_on_wait) {
2515     // Check now if we need to throw IE exception.
2516     if (_thread->pending_interrupted_exception()) {

2517       throw_interrupted_exception(_thread, top);
2518       _thread->set_pending_interrupted_exception(false);
2519     }
2520   } else if (top.is_runtime_frame()) {
2521     // The continuation might now run on a different platform thread than the previous time so
2522     // we need to adjust the current thread saved in the stub frame before restoring registers.
2523     JavaThread** thread_addr = frame::saved_thread_address(top);
2524     if (thread_addr != nullptr) *thread_addr = _thread;































































2525   }
2526   return sp;
2527 }
2528 
2529 void ThawBase::throw_interrupted_exception(JavaThread* current, frame& top) {

2530   ContinuationWrapper::SafepointOp so(current, _cont);
2531   // Since we might safepoint set the anchor so that the stack can be walked.
2532   set_anchor(current, top.sp());
2533   JRT_BLOCK
2534     THROW(vmSymbols::java_lang_InterruptedException());
2535   JRT_BLOCK_END
2536   clear_anchor(current);
2537 }
2538 
2539 NOINLINE void ThawBase::recurse_thaw_interpreted_frame(const frame& hf, frame& caller, int num_frames) {
2540   assert(hf.is_interpreted_frame(), "");
2541 
2542   if (UNLIKELY(seen_by_gc())) {
2543     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance());





2544   }
2545 
2546   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::InterpretedFrame>(caller, num_frames);
2547 
2548   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2549 
2550   _align_size += frame::align_wiggle; // possible added alignment for internal interpreted frame alignment om AArch64
2551 
2552   frame f = new_stack_frame<ContinuationHelper::InterpretedFrame>(hf, caller, is_bottom_frame);
2553 
2554   intptr_t* const stack_frame_top = f.sp() + frame::metadata_words_at_top;
2555   intptr_t* const stack_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(f);
2556   intptr_t* const heap_frame_top = hf.unextended_sp() + frame::metadata_words_at_top;
2557   intptr_t* const heap_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(hf);
2558 
2559   assert(hf.is_heap_frame(), "should be");
2560   assert(!f.is_heap_frame(), "should not be");
2561 
2562   const int fsize = pointer_delta_as_int(heap_frame_bottom, heap_frame_top);
2563   assert((stack_frame_bottom == stack_frame_top + fsize), "");

2568 
2569   // Make sure the relativized locals is already set.
2570   assert(f.interpreter_frame_local_at(0) == stack_frame_bottom - 1, "invalid frame bottom");
2571 
2572   derelativize_interpreted_frame_metadata(hf, f);
2573   patch(f, caller, is_bottom_frame);
2574 
2575   assert(f.is_interpreted_frame_valid(_cont.thread()), "invalid thawed frame");
2576   assert(stack_frame_bottom <= ContinuationHelper::Frame::frame_top(caller), "");
2577 
2578   CONT_JFR_ONLY(_jfr_info.record_interpreted_frame();)
2579 
2580   maybe_set_fastpath(f.sp());
2581 
2582   Method* m = hf.interpreter_frame_method();
2583   assert(!m->is_native() || !is_bottom_frame, "should be top frame of thaw_top case; missing caller frame");
2584   const int locals = m->max_locals();
2585 
2586   if (!is_bottom_frame) {
2587     // can only fix caller once this frame is thawed (due to callee saved regs)
2588     _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance());
2589   } else if (_cont.tail()->has_bitmap() && locals > 0) {
2590     assert(hf.is_heap_frame(), "should be");
2591     address start = (address)(heap_frame_bottom - locals);
2592     address end = (address)heap_frame_bottom;
2593     clear_bitmap_bits(start, end);
2594   }
2595 
2596   DEBUG_ONLY(after_thaw_java_frame(f, is_bottom_frame);)
2597   caller = f;
2598 }
2599 
2600 void ThawBase::recurse_thaw_compiled_frame(const frame& hf, frame& caller, int num_frames, bool stub_caller) {
2601   assert(hf.is_compiled_frame(), "");
2602   assert(_preempted_case || !stub_caller, "stub caller not at preemption");
2603 
2604   if (!stub_caller && UNLIKELY(seen_by_gc())) { // recurse_thaw_stub_frame already invoked our barriers with a full regmap
2605     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance());
2606   }
2607 
2608   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::CompiledFrame>(caller, num_frames);
2609 
2610   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2611 
2612   assert(caller.sp() == caller.unextended_sp(), "");
2613 
2614   if ((!is_bottom_frame && caller.is_interpreted_frame()) || (is_bottom_frame && Interpreter::contains(_cont.tail()->pc()))) {
2615     _align_size += frame::align_wiggle; // we add one whether or not we've aligned because we add it in recurse_freeze_compiled_frame
2616   }
2617 
2618   // new_stack_frame must construct the resulting frame using hf.pc() rather than hf.raw_pc() because the frame is not
2619   // yet laid out in the stack, and so the original_pc is not stored in it.
2620   // As a result, f.is_deoptimized_frame() is always false and we must test hf to know if the frame is deoptimized.
2621   frame f = new_stack_frame<ContinuationHelper::CompiledFrame>(hf, caller, is_bottom_frame);
2622   intptr_t* const stack_frame_top = f.sp();
2623   intptr_t* const heap_frame_top = hf.unextended_sp();
2624 
2625   const int added_argsize = (is_bottom_frame || caller.is_interpreted_frame()) ? hf.compiled_frame_stack_argsize() : 0;

2644   assert(!f.is_deoptimized_frame(), "");
2645   if (hf.is_deoptimized_frame()) {
2646     maybe_set_fastpath(f.sp());
2647   } else if (_thread->is_interp_only_mode()
2648               || (stub_caller && f.cb()->as_nmethod()->is_marked_for_deoptimization())) {
2649     // The caller of the safepoint stub when the continuation is preempted is not at a call instruction, and so
2650     // cannot rely on nmethod patching for deopt.
2651     assert(_thread->is_interp_only_mode() || stub_caller, "expected a stub-caller");
2652 
2653     log_develop_trace(continuations)("Deoptimizing thawed frame");
2654     DEBUG_ONLY(ContinuationHelper::Frame::patch_pc(f, nullptr));
2655 
2656     f.deoptimize(nullptr); // the null thread simply avoids the assertion in deoptimize which we're not set up for
2657     assert(f.is_deoptimized_frame(), "");
2658     assert(ContinuationHelper::Frame::is_deopt_return(f.raw_pc(), f), "");
2659     maybe_set_fastpath(f.sp());
2660   }
2661 
2662   if (!is_bottom_frame) {
2663     // can only fix caller once this frame is thawed (due to callee saved regs); this happens on the stack
2664     _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance());
2665   } else if (_cont.tail()->has_bitmap() && added_argsize > 0) {
2666     address start = (address)(heap_frame_top + ContinuationHelper::CompiledFrame::size(hf) + frame::metadata_words_at_top);
2667     int stack_args_slots = f.cb()->as_nmethod()->num_stack_arg_slots(false /* rounded */);
2668     int argsize_in_bytes = stack_args_slots * VMRegImpl::stack_slot_size;
2669     clear_bitmap_bits(start, start + argsize_in_bytes);
2670   }
2671 
2672   DEBUG_ONLY(after_thaw_java_frame(f, is_bottom_frame);)
2673   caller = f;
2674 }
2675 
2676 void ThawBase::recurse_thaw_stub_frame(const frame& hf, frame& caller, int num_frames) {
2677   DEBUG_ONLY(_frames++;)
2678 
2679   if (UNLIKELY(seen_by_gc())) {
2680     // Process the stub's caller here since we might need the full map.
2681     RegisterMap map(nullptr,
2682                     RegisterMap::UpdateMap::include,
2683                     RegisterMap::ProcessFrames::skip,
2684                     RegisterMap::WalkContinuation::skip);
2685     map.set_include_argument_oops(false);
2686     _stream.next(&map);
2687     assert(!_stream.is_done(), "");
2688     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, &map);
2689   } else {
2690     _stream.next(SmallRegisterMap::instance());
2691     assert(!_stream.is_done(), "");
2692   }
2693 
2694   recurse_thaw_compiled_frame(_stream.to_frame(), caller, num_frames, true);
2695 
2696   assert(caller.is_compiled_frame(), "");
2697   assert(caller.sp() == caller.unextended_sp(), "");
2698 
2699   DEBUG_ONLY(before_thaw_java_frame(hf, caller, false /*is_bottom_frame*/, num_frames);)
2700 
2701   frame f = new_stack_frame<ContinuationHelper::StubFrame>(hf, caller, false);
2702   intptr_t* stack_frame_top = f.sp();
2703   intptr_t* heap_frame_top = hf.sp();
2704   int fsize = ContinuationHelper::StubFrame::size(hf);
2705 
2706   copy_from_chunk(heap_frame_top - frame::metadata_words, stack_frame_top - frame::metadata_words,
2707                   fsize + frame::metadata_words);
2708 
2709   patch(f, caller, false /*is_bottom_frame*/);
2710 
2711   // can only fix caller once this frame is thawed (due to callee saved regs)
2712   RegisterMap map(nullptr,
2713                   RegisterMap::UpdateMap::include,
2714                   RegisterMap::ProcessFrames::skip,
2715                   RegisterMap::WalkContinuation::skip);
2716   map.set_include_argument_oops(false);
2717   f.oop_map()->update_register_map(&f, &map);
2718   ContinuationHelper::update_register_map_with_callee(caller, &map);
2719   _cont.tail()->fix_thawed_frame(caller, &map);
2720 
2721   DEBUG_ONLY(after_thaw_java_frame(f, false /*is_bottom_frame*/);)
2722   caller = f;
2723 }
2724 
2725 void ThawBase::recurse_thaw_native_frame(const frame& hf, frame& caller, int num_frames) {
2726   assert(hf.is_native_frame(), "");
2727   assert(_preempted_case && hf.cb()->as_nmethod()->method()->is_object_wait0(), "");
2728 
2729   if (UNLIKELY(seen_by_gc())) { // recurse_thaw_stub_frame already invoked our barriers with a full regmap
2730     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance());
2731   }
2732 
2733   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::NativeFrame>(caller, num_frames);
2734   assert(!is_bottom_frame, "");
2735 
2736   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2737 
2738   assert(caller.sp() == caller.unextended_sp(), "");
2739 
2740   if (caller.is_interpreted_frame()) {
2741     _align_size += frame::align_wiggle; // we add one whether or not we've aligned because we add it in recurse_freeze_native_frame
2742   }
2743 
2744   // new_stack_frame must construct the resulting frame using hf.pc() rather than hf.raw_pc() because the frame is not
2745   // yet laid out in the stack, and so the original_pc is not stored in it.
2746   // As a result, f.is_deoptimized_frame() is always false and we must test hf to know if the frame is deoptimized.
2747   frame f = new_stack_frame<ContinuationHelper::NativeFrame>(hf, caller, false /* bottom */);
2748   intptr_t* const stack_frame_top = f.sp();
2749   intptr_t* const heap_frame_top = hf.unextended_sp();
2750 
2751   int fsize = ContinuationHelper::NativeFrame::size(hf);
2752   assert(fsize <= (int)(caller.unextended_sp() - f.unextended_sp()), "");
2753 
2754   intptr_t* from = heap_frame_top - frame::metadata_words_at_bottom;
2755   intptr_t* to   = stack_frame_top - frame::metadata_words_at_bottom;
2756   int sz = fsize + frame::metadata_words_at_bottom;
2757 
2758   copy_from_chunk(from, to, sz); // copying good oops because we invoked barriers above
2759 
2760   patch(f, caller, false /* bottom */);
2761 
2762   // f.is_deoptimized_frame() is always false and we must test hf.is_deoptimized_frame() (see comment above)
2763   assert(!f.is_deoptimized_frame(), "");
2764   assert(!hf.is_deoptimized_frame(), "");
2765   assert(!f.cb()->as_nmethod()->is_marked_for_deoptimization(), "");
2766 
2767   // can only fix caller once this frame is thawed (due to callee saved regs); this happens on the stack
2768   _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance());
2769 
2770   DEBUG_ONLY(after_thaw_java_frame(f, false /* bottom */);)
2771   caller = f;
2772 }
2773 
2774 void ThawBase::finish_thaw(frame& f) {
2775   stackChunkOop chunk = _cont.tail();
2776 
2777   if (chunk->is_empty()) {
2778     // Only remove chunk from list if it can't be reused for another freeze
2779     if (seen_by_gc()) {
2780       _cont.set_tail(chunk->parent());
2781     } else {
2782       chunk->set_has_mixed_frames(false);
2783     }
2784     chunk->set_max_thawing_size(0);
2785   } else {
2786     chunk->set_max_thawing_size(chunk->max_thawing_size() - _align_size);
2787   }
2788   assert(chunk->is_empty() == (chunk->max_thawing_size() == 0), "");
2789 
2790   if (!is_aligned(f.sp(), frame::frame_alignment)) {
2791     assert(f.is_interpreted_frame(), "");
2792     f.set_sp(align_down(f.sp(), frame::frame_alignment));
2793   }
2794   push_return_frame(f);
2795   chunk->fix_thawed_frame(f, SmallRegisterMap::instance()); // can only fix caller after push_return_frame (due to callee saved regs)






2796 
2797   assert(_cont.is_empty() == _cont.last_frame().is_empty(), "");
2798 
2799   log_develop_trace(continuations)("thawed %d frames", _frames);
2800 
2801   LogTarget(Trace, continuations) lt;
2802   if (lt.develop_is_enabled()) {
2803     LogStream ls(lt);
2804     ls.print_cr("top hframe after (thaw):");
2805     _cont.last_frame().print_value_on(&ls);
2806   }
2807 }
2808 
2809 void ThawBase::push_return_frame(frame& f) { // see generate_cont_thaw
2810   assert(!f.is_compiled_frame() || f.is_deoptimized_frame() == f.cb()->as_nmethod()->is_deopt_pc(f.raw_pc()), "");
2811   assert(!f.is_compiled_frame() || f.is_deoptimized_frame() == (f.pc() != f.raw_pc()), "");
2812 
2813   LogTarget(Trace, continuations) lt;
2814   if (lt.develop_is_enabled()) {
2815     LogStream ls(lt);

2837 
2838   ContinuationEntry* entry = thread->last_continuation();
2839   assert(entry != nullptr, "");
2840   oop oopCont = entry->cont_oop(thread);
2841 
2842   assert(!jdk_internal_vm_Continuation::done(oopCont), "");
2843   assert(oopCont == get_continuation(thread), "");
2844   verify_continuation(oopCont);
2845 
2846   assert(entry->is_virtual_thread() == (entry->scope(thread) == java_lang_VirtualThread::vthread_scope()), "");
2847 
2848   ContinuationWrapper cont(thread, oopCont);
2849   log_develop_debug(continuations)("THAW #" INTPTR_FORMAT " " INTPTR_FORMAT, cont.hash(), p2i((oopDesc*)oopCont));
2850 
2851 #ifdef ASSERT
2852   set_anchor_to_entry(thread, cont.entry());
2853   log_frames(thread);
2854   clear_anchor(thread);
2855 #endif
2856 
2857   DEBUG_ONLY(bool preempted = cont.tail()->preempted();)
2858   Thaw<ConfigT> thw(thread, cont);
2859   intptr_t* const sp = thw.thaw(kind);
2860   assert(is_aligned(sp, frame::frame_alignment), "");
2861   DEBUG_ONLY(log_frames_after_thaw(thread, cont, sp, preempted);)
2862 
2863   CONT_JFR_ONLY(thw.jfr_info().post_jfr_event(&event, cont.continuation(), thread);)
2864 
2865   verify_continuation(cont.continuation());
2866   log_develop_debug(continuations)("=== End of thaw #" INTPTR_FORMAT, cont.hash());
2867 
2868   return sp;
2869 }
2870 
2871 #ifdef ASSERT
2872 static void do_deopt_after_thaw(JavaThread* thread) {
2873   int i = 0;
2874   StackFrameStream fst(thread, true, false);
2875   fst.register_map()->set_include_argument_oops(false);
2876   ContinuationHelper::update_register_map_with_callee(*fst.current(), fst.register_map());
2877   for (; !fst.is_done(); fst.next()) {
2878     if (fst.current()->cb()->is_nmethod()) {
2879       nmethod* nm = fst.current()->cb()->as_nmethod();
2880       if (!nm->method()->is_continuation_native_intrinsic()) {
2881         nm->make_deoptimized();

2938       if (!fr.is_interpreted_frame()) {
2939         st->print_cr("size: %d argsize: %d",
2940                      ContinuationHelper::NonInterpretedUnknownFrame::size(fr),
2941                      ContinuationHelper::NonInterpretedUnknownFrame::stack_argsize(fr));
2942       }
2943       VMReg reg = fst.register_map()->find_register_spilled_here(cl.p(), fst.current()->sp());
2944       if (reg != nullptr) {
2945         st->print_cr("Reg %s %d", reg->name(), reg->is_stack() ? (int)reg->reg2stack() : -99);
2946       }
2947       cl.reset();
2948       DEBUG_ONLY(thread->print_frame_layout();)
2949       if (chunk != nullptr) {
2950         chunk->print_on(true, st);
2951       }
2952       return false;
2953     }
2954   }
2955   return true;
2956 }
2957 
2958 static void log_frames(JavaThread* thread) {
2959   const static int show_entry_callers = 3;
2960   LogTarget(Trace, continuations) lt;
2961   if (!lt.develop_is_enabled()) {
2962     return;
2963   }
2964   LogStream ls(lt);
2965 
2966   ls.print_cr("------- frames --------- for thread " INTPTR_FORMAT, p2i(thread));
2967   if (!thread->has_last_Java_frame()) {
2968     ls.print_cr("NO ANCHOR!");
2969   }
2970 
2971   RegisterMap map(thread,
2972                   RegisterMap::UpdateMap::include,
2973                   RegisterMap::ProcessFrames::include,
2974                   RegisterMap::WalkContinuation::skip);
2975   map.set_include_argument_oops(false);
2976 
2977   if (false) {
2978     for (frame f = thread->last_frame(); !f.is_entry_frame(); f = f.sender(&map)) {
2979       f.print_on(&ls);
2980     }
2981   } else {

2983     ResetNoHandleMark rnhm;
2984     ResourceMark rm;
2985     HandleMark hm(Thread::current());
2986     FrameValues values;
2987 
2988     int i = 0;
2989     int post_entry = -1;
2990     for (frame f = thread->last_frame(); !f.is_first_frame(); f = f.sender(&map), i++) {
2991       f.describe(values, i, &map, i == 0);
2992       if (post_entry >= 0 || Continuation::is_continuation_enterSpecial(f))
2993         post_entry++;
2994       if (post_entry >= show_entry_callers)
2995         break;
2996     }
2997     values.print_on(thread, &ls);
2998   }
2999 
3000   ls.print_cr("======= end frames =========");
3001 }
3002 
3003 static void log_frames_after_thaw(JavaThread* thread, ContinuationWrapper& cont, intptr_t* sp, bool preempted) {
3004   intptr_t* sp0 = sp;
3005   address pc0 = *(address*)(sp - frame::sender_sp_ret_address_offset());
3006 
3007   if (preempted && sp0 == cont.entrySP()) {


3008     // Still preempted (monitor not acquired) so no frames were thawed.
3009     assert(cont.tail()->preempted(), "");
3010     set_anchor(thread, cont.entrySP(), cont.entryPC());

3011   } else {
3012     set_anchor(thread, sp0);
3013   }
3014 
3015   log_frames(thread);
3016   if (LoomVerifyAfterThaw) {
3017     assert(do_verify_after_thaw(thread, cont.tail(), tty), "");
3018   }
3019   assert(ContinuationEntry::assert_entry_frame_laid_out(thread), "");
3020   clear_anchor(thread);
3021 
3022   LogTarget(Trace, continuations) lt;
3023   if (lt.develop_is_enabled()) {
3024     LogStream ls(lt);
3025     ls.print_cr("Jumping to frame (thaw):");
3026     frame(sp).print_value_on(&ls);
3027   }
3028 }
3029 #endif // ASSERT
3030 
3031 #include CPU_HEADER_INLINE(continuationFreezeThaw)
3032 
3033 #ifdef ASSERT
3034 static void print_frame_layout(const frame& f, bool callee_complete, outputStream* st) {
3035   ResourceMark rm;
3036   FrameValues values;
3037   assert(f.get_cb() != nullptr, "");
3038   RegisterMap map(f.is_heap_frame() ?
3039                     nullptr :

  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "classfile/javaClasses.inline.hpp"
  26 #include "classfile/vmSymbols.hpp"
  27 #include "code/codeCache.inline.hpp"
  28 #include "code/nmethod.inline.hpp"
  29 #include "code/vmreg.inline.hpp"
  30 #include "compiler/oopMap.inline.hpp"
  31 #include "gc/shared/barrierSet.hpp"
  32 #include "gc/shared/continuationGCSupport.inline.hpp"
  33 #include "gc/shared/gc_globals.hpp"
  34 #include "gc/shared/memAllocator.hpp"
  35 #include "gc/shared/threadLocalAllocBuffer.inline.hpp"
  36 #include "interpreter/bytecodeStream.hpp"
  37 #include "interpreter/interpreter.hpp"
  38 #include "interpreter/interpreterRuntime.hpp"
  39 #include "jfr/jfrEvents.hpp"
  40 #include "logging/log.hpp"
  41 #include "logging/logStream.hpp"
  42 #include "oops/access.inline.hpp"
  43 #include "oops/constantPool.inline.hpp"
  44 #include "oops/method.inline.hpp"
  45 #include "oops/objArrayOop.inline.hpp"
  46 #include "oops/oopsHierarchy.hpp"
  47 #include "oops/stackChunkOop.inline.hpp"
  48 #include "prims/jvmtiThreadState.hpp"
  49 #include "runtime/arguments.hpp"
  50 #include "runtime/continuation.hpp"
  51 #include "runtime/continuationEntry.inline.hpp"
  52 #include "runtime/continuationHelper.inline.hpp"
  53 #include "runtime/continuationJavaClasses.inline.hpp"
  54 #include "runtime/continuationWrapper.inline.hpp"
  55 #include "runtime/frame.inline.hpp"
  56 #include "runtime/interfaceSupport.inline.hpp"
  57 #include "runtime/javaThread.inline.hpp"
  58 #include "runtime/jniHandles.inline.hpp"
  59 #include "runtime/keepStackGCProcessed.hpp"
  60 #include "runtime/objectMonitor.inline.hpp"
  61 #include "runtime/orderAccess.hpp"
  62 #include "runtime/prefetch.inline.hpp"
  63 #include "runtime/sharedRuntime.hpp"
  64 #include "runtime/smallRegisterMap.inline.hpp"
  65 #include "runtime/stackChunkFrameStream.inline.hpp"
  66 #include "runtime/stackFrameStream.inline.hpp"
  67 #include "runtime/stackOverflow.hpp"
  68 #include "runtime/stackWatermarkSet.inline.hpp"
  69 #include "runtime/vframe.inline.hpp"
  70 #include "runtime/vframe_hp.hpp"
  71 #include "utilities/debug.hpp"
  72 #include "utilities/exceptions.hpp"
  73 #include "utilities/macros.hpp"
  74 #include "utilities/vmError.hpp"
  75 #if INCLUDE_ZGC
  76 #include "gc/z/zStackChunkGCData.inline.hpp"
  77 #endif
  78 #if INCLUDE_JFR
  79 #include "jfr/jfr.inline.hpp"
  80 #endif
  81 #ifdef COMPILER1
  82 #include "c1/c1_Runtime1.hpp"
  83 #endif
  84 #ifdef COMPILER2
  85 #include "opto/runtime.hpp"
  86 #endif
  87 
  88 #include <type_traits>
  89 
  90 /*
  91  * This file contains the implementation of continuation freezing (yield) and thawing (run).
  92  *
  93  * This code is very latency-critical and very hot. An ordinary and well-behaved server application
  94  * would likely call these operations many thousands of times per second second, on every core.
  95  *
  96  * Freeze might be called every time the application performs any I/O operation, every time it
  97  * acquires a j.u.c. lock, every time it takes a message from a queue, and thaw can be called
  98  * multiple times in each of those cases, as it is called by the return barrier, which may be
  99  * invoked on method return.
 100  *
 101  * The amortized budget for each of those two operations is ~100-150ns. That is why, for
 102  * example, every effort is made to avoid Java-VM transitions as much as possible.
 103  *
 104  * On the fast path, all frames are known to be compiled, and the chunk requires no barriers
 105  * and so frames simply copied, and the bottom-most one is patched.
 106  * On the slow path, internal pointers in interpreted frames are de/relativized to/from offsets

 176 #endif
 177 
 178 // TODO: See AbstractAssembler::generate_stack_overflow_check,
 179 // Compile::bang_size_in_bytes(), m->as_SafePoint()->jvms()->interpreter_frame_size()
 180 // when we stack-bang, we need to update a thread field with the lowest (farthest) bang point.
 181 
 182 // Data invariants are defined by Continuation::debug_verify_continuation and Continuation::debug_verify_stack_chunk
 183 
 184 // Used to just annotatate cold/hot branches
 185 #define LIKELY(condition)   (condition)
 186 #define UNLIKELY(condition) (condition)
 187 
 188 // debugging functions
 189 #ifdef ASSERT
 190 extern "C" bool dbg_is_safe(const void* p, intptr_t errvalue); // address p is readable and *(intptr_t*)p != errvalue
 191 
 192 static void verify_continuation(oop continuation) { Continuation::debug_verify_continuation(continuation); }
 193 
 194 static void do_deopt_after_thaw(JavaThread* thread);
 195 static bool do_verify_after_thaw(JavaThread* thread, stackChunkOop chunk, outputStream* st);
 196 static void log_frames(JavaThread* thread, bool dolog = false);
 197 static void log_frames_after_thaw(JavaThread* thread, ContinuationWrapper& cont, intptr_t* sp);
 198 static void print_frame_layout(const frame& f, bool callee_complete, outputStream* st = tty);
 199 static void verify_frame_kind(const frame& top, Continuation::preempt_kind preempt_kind, Method** m_ptr = nullptr, const char** code_name_ptr = nullptr, int* bci_ptr = nullptr);
 200 
 201 #define assert_pfl(p, ...) \
 202 do {                                           \
 203   if (!(p)) {                                  \
 204     JavaThread* t = JavaThread::active();      \
 205     if (t->has_last_Java_frame()) {            \
 206       tty->print_cr("assert(" #p ") failed:"); \
 207       t->print_frame_layout();                 \
 208     }                                          \
 209   }                                            \
 210   vmassert(p, __VA_ARGS__);                    \
 211 } while(0)
 212 
 213 #else
 214 static void verify_continuation(oop continuation) { }
 215 #define assert_pfl(p, ...)
 216 #endif
 217 
 218 static freeze_result is_pinned0(JavaThread* thread, oop cont_scope, bool safepoint);
 219 template<typename ConfigT, bool preempt> static inline freeze_result freeze_internal(JavaThread* current, intptr_t* const sp);

 508 
 509   assert(!Interpreter::contains(_cont.entryPC()), "");
 510 
 511   _bottom_address = _cont.entrySP() - _cont.entry_frame_extension();
 512 #ifdef _LP64
 513   if (((intptr_t)_bottom_address & 0xf) != 0) {
 514     _bottom_address--;
 515   }
 516   assert(is_aligned(_bottom_address, frame::frame_alignment), "");
 517 #endif
 518 
 519   log_develop_trace(continuations)("bottom_address: " INTPTR_FORMAT " entrySP: " INTPTR_FORMAT " argsize: " PTR_FORMAT,
 520                 p2i(_bottom_address), p2i(_cont.entrySP()), (_cont.entrySP() - _bottom_address) << LogBytesPerWord);
 521   assert(_bottom_address != nullptr, "");
 522   assert(_bottom_address <= _cont.entrySP(), "");
 523   DEBUG_ONLY(_last_write = nullptr;)
 524 
 525   assert(_cont.chunk_invariant(), "");
 526   assert(!Interpreter::contains(_cont.entryPC()), "");
 527 #if !defined(PPC64) || defined(ZERO)
 528   static const int do_yield_frame_size = frame::metadata_words;
 529 #else
 530   static const int do_yield_frame_size = frame::native_abi_reg_args_size >> LogBytesPerWord;
 531 #endif
 532   // With preemption doYield() might not have been resolved yet
 533   assert(_preempt || ContinuationEntry::do_yield_nmethod()->frame_size() == do_yield_frame_size, "");
 534 
 535   if (preempt) {
 536     _last_frame = _thread->last_frame();
 537   }
 538 
 539   // properties of the continuation on the stack; all sizes are in words
 540   _cont_stack_top    = frame_sp + (!preempt ? do_yield_frame_size : 0); // we don't freeze the doYield stub frame
 541   _cont_stack_bottom = _cont.entrySP() + (_cont.argsize() == 0 ? frame::metadata_words_at_top : 0)
 542       - ContinuationHelper::frame_align_words(_cont.argsize()); // see alignment in thaw
 543 
 544   log_develop_trace(continuations)("freeze size: %d argsize: %d top: " INTPTR_FORMAT " bottom: " INTPTR_FORMAT,
 545     cont_size(), _cont.argsize(), p2i(_cont_stack_top), p2i(_cont_stack_bottom));
 546   assert(cont_size() > 0, "");
 547 
 548   if (LockingMode != LM_LIGHTWEIGHT) {
 549     _monitors_in_lockstack = 0;
 550   } else {
 551     _monitors_in_lockstack = _thread->lock_stack().monitor_count();
 552   }
 553 }
 554 
 555 void FreezeBase::init_rest() { // we want to postpone some initialization after chunk handling
 556   _freeze_size = 0;
 557   _total_align_size = 0;
 558   NOT_PRODUCT(_frames = 0;)
 559 }
 560 

 914   freeze_result res = recurse_freeze(f, caller, 0, false, true);
 915 
 916   if (res == freeze_ok) {
 917     finish_freeze(f, caller);
 918     _cont.write();
 919   }
 920 
 921   return res;
 922 }
 923 
 924 frame FreezeBase::freeze_start_frame() {
 925   if (LIKELY(!_preempt)) {
 926     return freeze_start_frame_yield_stub();
 927   } else {
 928     return freeze_start_frame_on_preempt();
 929   }
 930 }
 931 
 932 frame FreezeBase::freeze_start_frame_yield_stub() {
 933   frame f = _thread->last_frame();
 934   assert(ContinuationEntry::do_yield_nmethod()->contains(f.pc()), "must be");
 935   f = sender<ContinuationHelper::NonInterpretedUnknownFrame>(f);
 936   assert(Continuation::is_frame_in_continuation(_thread->last_continuation(), f), "");
 937   return f;
 938 }
 939 
 940 frame FreezeBase::freeze_start_frame_on_preempt() {
 941   assert(_last_frame.sp() == _thread->last_frame().sp(), "_last_frame should be already initialized");
 942   assert(Continuation::is_frame_in_continuation(_thread->last_continuation(), _last_frame), "");
 943   return _last_frame;
 944 }
 945 
 946 // The parameter callee_argsize includes metadata that has to be part of caller/callee overlap.
 947 NOINLINE freeze_result FreezeBase::recurse_freeze(frame& f, frame& caller, int callee_argsize, bool callee_interpreted, bool top) {
 948   assert(f.unextended_sp() < _bottom_address, ""); // see recurse_freeze_java_frame
 949   assert(f.is_interpreted_frame() || ((top && _preempt) == ContinuationHelper::Frame::is_stub(f.cb()))
 950          || ((top && _preempt) == f.is_native_frame()), "");
 951 
 952   if (stack_overflow()) {
 953     return freeze_exception;
 954   }

1110     log_develop_trace(continuations)("Reusing chunk mixed: %d empty: %d", chunk->has_mixed_frames(), chunk->is_empty());
1111     if (chunk->is_empty()) {
1112       int sp = chunk->stack_size() - argsize_md;
1113       chunk->set_sp(sp);
1114       chunk->set_bottom(sp);
1115       _freeze_size += overlap;
1116       assert(chunk->max_thawing_size() == 0, "");
1117     } DEBUG_ONLY(else empty_chunk = false;)
1118   }
1119   assert(!chunk->is_gc_mode(), "");
1120   assert(!chunk->has_bitmap(), "");
1121   chunk->set_has_mixed_frames(true);
1122 
1123   assert(chunk->requires_barriers() == _barriers, "");
1124   assert(!_barriers || chunk->is_empty(), "");
1125 
1126   assert(!chunk->is_empty() || StackChunkFrameStream<ChunkFrames::Mixed>(chunk).is_done(), "");
1127   assert(!chunk->is_empty() || StackChunkFrameStream<ChunkFrames::Mixed>(chunk).to_frame().is_empty(), "");
1128 
1129   if (_preempt) {
1130     frame top_frame = _thread->last_frame();
1131     if (top_frame.is_interpreted_frame()) {
1132       // Some platforms do not save the last_sp in the top interpreter frame on VM calls.
1133       // We need it so that on resume we can restore the sp to the right place, since
1134       // thawing might add an alignment word to the expression stack (see finish_thaw()).
1135       // We do it now that we know freezing will be successful.
1136       prepare_freeze_interpreted_top_frame(top_frame);
1137     }
1138 
1139     // Do this now so should_process_args_at_top() is set before calling finish_freeze
1140     // in case we might need to apply GC barriers to frames in this stackChunk.
1141     if (_thread->at_preemptable_init()) {
1142       assert(top_frame.is_interpreted_frame(), "only InterpreterRuntime::_new/resolve_from_cache allowed");
1143       chunk->set_at_klass_init(true);
1144       Method* m = top_frame.interpreter_frame_method();
1145       Bytecode current_bytecode = Bytecode(m, top_frame.interpreter_frame_bcp());
1146       Bytecodes::Code code = current_bytecode.code();
1147       int exp_size = top_frame.interpreter_frame_expression_stack_size();
1148       if (code == Bytecodes::Code::_invokestatic && exp_size > 0) {
1149         chunk->set_has_args_at_top(true);
1150       }
1151     }
1152   }
1153 
1154   // We unwind frames after the last safepoint so that the GC will have found the oops in the frames, but before
1155   // writing into the chunk. This is so that an asynchronous stack walk (not at a safepoint) that suspends us here
1156   // will either see no continuation or a consistent chunk.
1157   unwind_frames();
1158 
1159   chunk->set_max_thawing_size(chunk->max_thawing_size() + _freeze_size - _monitors_in_lockstack - frame::metadata_words);
1160 
1161   if (lt.develop_is_enabled()) {
1162     LogStream ls(lt);
1163     ls.print_cr("top chunk:");
1164     chunk->print_on(&ls);
1165   }
1166 
1167   if (_monitors_in_lockstack > 0) {
1168     freeze_lockstack(chunk);
1169   }
1170 

1642       // Some GCs could put direct allocations in old gen for slow-path
1643       // allocations; need to explicitly check if that was the case.
1644       _barriers = chunk->requires_barriers();
1645     }
1646   }
1647 
1648   if (_barriers) {
1649     log_develop_trace(continuations)("allocation requires barriers");
1650   }
1651 
1652   assert(chunk->parent() == nullptr || chunk->parent()->is_stackChunk(), "");
1653 
1654   return chunk;
1655 }
1656 
1657 void FreezeBase::throw_stack_overflow_on_humongous_chunk() {
1658   ContinuationWrapper::SafepointOp so(_thread, _cont); // could also call _cont.done() instead
1659   Exceptions::_throw_msg(_thread, __FILE__, __LINE__, vmSymbols::java_lang_StackOverflowError(), "Humongous stack chunk");
1660 }
1661 
1662 class AnchorMark : public StackObj {
1663   JavaThread* _current;
1664   frame& _top_frame;
1665   intptr_t* _last_sp_from_frame;
1666   bool _is_interpreted;
1667 
1668  public:
1669   AnchorMark(JavaThread* current, frame& f) : _current(current), _top_frame(f), _is_interpreted(false) {
1670     intptr_t* sp = anchor_mark_set_pd();
1671     set_anchor(_current, sp);
1672   }
1673   ~AnchorMark() {
1674     clear_anchor(_current);
1675     anchor_mark_clear_pd();
1676   }
1677   inline intptr_t* anchor_mark_set_pd();
1678   inline void anchor_mark_clear_pd();
1679 };
1680 
1681 #if INCLUDE_JVMTI
1682 static int num_java_frames(ContinuationWrapper& cont) {
1683   ResourceMark rm; // used for scope traversal in num_java_frames(nmethod*, address)
1684   int count = 0;
1685   for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
1686     count += chunk->num_java_frames();
1687   }
1688   return count;
1689 }
1690 
1691 static void invalidate_jvmti_stack(JavaThread* thread) {
1692   if (thread->is_interp_only_mode()) {
1693     JvmtiThreadState *state = thread->jvmti_thread_state();
1694     if (state != nullptr)
1695       state->invalidate_cur_stack_depth();
1696   }
1697 }
1698 
1699 static void jvmti_yield_cleanup(JavaThread* thread, ContinuationWrapper& cont) {
1700   if (JvmtiExport::can_post_frame_pop()) {
1701     int num_frames = num_java_frames(cont);
1702 
1703     ContinuationWrapper::SafepointOp so(Thread::current(), cont);
1704     JvmtiExport::continuation_yield_cleanup(JavaThread::current(), num_frames);
1705   }
1706   invalidate_jvmti_stack(thread);
1707 }
1708 
1709 static void jvmti_mount_end(JavaThread* current, ContinuationWrapper& cont, frame top, Continuation::preempt_kind pk) {
1710   assert(current->vthread() != nullptr, "must be");
1711 
1712   HandleMarkCleaner hm(current);  // Cleanup vth and so._conth Handles
1713   Handle vth(current, current->vthread());

1714   ContinuationWrapper::SafepointOp so(current, cont);
1715 
1716   AnchorMark am(current, top);  // Set anchor so that the stack is walkable.

1717 
1718   JRT_BLOCK
1719     JvmtiVTMSTransitionDisabler::VTMS_vthread_mount((jthread)vth.raw_value(), false);
1720 
1721     if (current->pending_contended_entered_event()) {
1722       // No monitor JVMTI events for ObjectLocker case.
1723       if (pk != Continuation::object_locker) {
1724         JvmtiExport::post_monitor_contended_entered(current, current->contended_entered_monitor());
1725       }
1726       current->set_contended_entered_monitor(nullptr);
1727     }
1728   JRT_BLOCK_END


1729 }
1730 #endif // INCLUDE_JVMTI
1731 
1732 #ifdef ASSERT
1733 // There are no interpreted frames if we're not called from the interpreter and we haven't ancountered an i2c
1734 // adapter or called Deoptimization::unpack_frames. As for native frames, upcalls from JNI also go through the
1735 // interpreter (see JavaCalls::call_helper), while the UpcallLinker explicitly sets cont_fastpath.
1736 bool FreezeBase::check_valid_fast_path() {
1737   ContinuationEntry* ce = _thread->last_continuation();
1738   RegisterMap map(_thread,
1739                   RegisterMap::UpdateMap::skip,
1740                   RegisterMap::ProcessFrames::skip,
1741                   RegisterMap::WalkContinuation::skip);
1742   map.set_include_argument_oops(false);
1743   bool is_top_frame = true;
1744   for (frame f = freeze_start_frame(); Continuation::is_frame_in_continuation(ce, f); f = f.sender(&map), is_top_frame = false) {
1745     if (!((f.is_compiled_frame() && !f.is_deoptimized_frame()) || (is_top_frame && (f.is_runtime_frame() || f.is_native_frame())))) {
1746       return false;
1747     }
1748   }
1749   return true;
1750 }
1751 
1752 static void verify_frame_kind(const frame& top, Continuation::preempt_kind preempt_kind, Method** m_ptr, const char** code_name_ptr, int* bci_ptr) {
1753   JavaThread* current = JavaThread::current();
1754   ResourceMark rm(current);
1755 
1756   Method* m;
1757   const char* code_name;
1758   int bci;
1759   if (preempt_kind == Continuation::monitorenter) {
1760     assert(top.is_interpreted_frame() || top.is_runtime_frame(), "");
1761     bool at_sync_method;
1762     if (top.is_interpreted_frame()) {
1763       m = top.interpreter_frame_method();
1764       assert(!m->is_native() || m->is_synchronized(), "invalid method %s", m->external_name());
1765       address bcp = top.interpreter_frame_bcp();
1766       assert(bcp != 0 || m->is_native(), "");
1767       at_sync_method = m->is_synchronized() && (bcp == 0 || bcp == m->code_base());
1768       // bcp is advanced on monitorenter before making the VM call, adjust for that.
1769       bool at_sync_bytecode = bcp > m->code_base() && Bytecode(m, bcp - 1).code() == Bytecodes::Code::_monitorenter;
1770       assert(at_sync_method || at_sync_bytecode, "");
1771       bci = at_sync_method ? -1 : top.interpreter_frame_bci();
1772     } else {
1773       CodeBlob* cb = top.cb();
1774       RegisterMap reg_map(current,
1775                   RegisterMap::UpdateMap::skip,
1776                   RegisterMap::ProcessFrames::skip,
1777                   RegisterMap::WalkContinuation::skip);
1778       frame fr = top.sender(&reg_map);
1779       vframe*  vf  = vframe::new_vframe(&fr, &reg_map, current);
1780       compiledVFrame* cvf = compiledVFrame::cast(vf);
1781       m = cvf->method();
1782       bci = cvf->scope()->bci();
1783       at_sync_method = bci == SynchronizationEntryBCI;
1784       assert(!at_sync_method || m->is_synchronized(), "bci is %d but method %s is not synchronized", bci, m->external_name());
1785       bool is_c1_monitorenter = false, is_c2_monitorenter = false;
1786       COMPILER1_PRESENT(is_c1_monitorenter = cb == Runtime1::blob_for(StubId::c1_monitorenter_id) ||
1787                                              cb == Runtime1::blob_for(StubId::c1_monitorenter_nofpu_id);)
1788       COMPILER2_PRESENT(is_c2_monitorenter = cb == CodeCache::find_blob(OptoRuntime::complete_monitor_locking_Java());)
1789       assert(is_c1_monitorenter || is_c2_monitorenter, "wrong runtime stub frame");
1790     }
1791     code_name = at_sync_method ? "synchronized method" : "monitorenter";
1792   } else if (preempt_kind == Continuation::object_wait) {
1793     assert(top.is_interpreted_frame() || top.is_native_frame(), "");
1794     m  = top.is_interpreted_frame() ? top.interpreter_frame_method() : top.cb()->as_nmethod()->method();
1795     assert(m->is_object_wait0(), "");
1796     bci = 0;
1797     code_name = "";
1798   } else {
1799     assert(preempt_kind == Continuation::object_locker, "invalid preempt kind");
1800     assert(top.is_interpreted_frame(), "");
1801     m = top.interpreter_frame_method();
1802     Bytecode current_bytecode = Bytecode(m, top.interpreter_frame_bcp());
1803     Bytecodes::Code code = current_bytecode.code();
1804     assert(code == Bytecodes::Code::_new || code == Bytecodes::Code::_invokestatic ||
1805            (code == Bytecodes::Code::_getstatic || code == Bytecodes::Code::_putstatic), "invalid bytecode");
1806     bci = top.interpreter_frame_bci();
1807     code_name = Bytecodes::name(current_bytecode.code());
1808   }
1809   assert(bci >= 0 || m->is_synchronized(), "invalid bci:%d at method %s", bci, m->external_name());
1810 
1811   if (m_ptr != nullptr) {
1812     *m_ptr = m;
1813     *code_name_ptr = code_name;
1814     *bci_ptr = bci;
1815   }
1816 }
1817 
1818 static void log_preempt_after_freeze(ContinuationWrapper& cont) {
1819   JavaThread* current = cont.thread();
1820   StackChunkFrameStream<ChunkFrames::Mixed> sfs(cont.tail());
1821   frame top_frame = sfs.to_frame();
1822   bool at_init = current->at_preemptable_init();
1823   bool at_enter = current->current_pending_monitor() != nullptr;
1824   bool at_wait = current->current_waiting_monitor() != nullptr;
1825   assert((at_enter && !at_wait) || (!at_enter && at_wait), "");
1826   Continuation::preempt_kind pk = at_init ? Continuation::object_locker : at_enter ? Continuation::monitorenter : Continuation::object_wait;
1827 
1828   Method* m = nullptr;
1829   const char* code_name = nullptr;
1830   int bci = InvalidFrameStateBci;
1831   verify_frame_kind(top_frame, pk, &m, &code_name, &bci);
1832   assert(m != nullptr && code_name != nullptr && bci != InvalidFrameStateBci, "should be set");
1833 
1834   ResourceMark rm(current);
1835   if (bci < 0) {
1836     log_trace(continuations, preempt)("Preempted " INT64_FORMAT " while synchronizing on %smethod %s", current->monitor_owner_id(), m->is_native() ? "native " : "", m->external_name());
1837   } else if (m->is_object_wait0()) {
1838     log_trace(continuations, preempt)("Preempted " INT64_FORMAT " at native method %s", current->monitor_owner_id(), m->external_name());
1839   } else {
1840     Klass* k = current->preempt_init_klass();
1841     assert(k != nullptr || !at_init, "");
1842     log_trace(continuations, preempt)("Preempted " INT64_FORMAT " at %s(bci:%d) in method %s %s%s", current->monitor_owner_id(),
1843             code_name, bci, m->external_name(), at_init ? "trying to initialize klass " : "", at_init ? k->external_name() : "");
1844   }
1845 }
1846 #endif // ASSERT
1847 
1848 static inline freeze_result freeze_epilog(ContinuationWrapper& cont) {
1849   verify_continuation(cont.continuation());
1850   assert(!cont.is_empty(), "");
1851 
1852   log_develop_debug(continuations)("=== End of freeze cont ### #" INTPTR_FORMAT, cont.hash());
1853   return freeze_ok;
1854 }
1855 
1856 static freeze_result freeze_epilog(JavaThread* thread, ContinuationWrapper& cont, freeze_result res) {
1857   if (UNLIKELY(res != freeze_ok)) {
1858     JFR_ONLY(thread->set_last_freeze_fail_result(res);)
1859     verify_continuation(cont.continuation());
1860     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
1861     return res;
1862   }
1863 
1864   JVMTI_ONLY(jvmti_yield_cleanup(thread, cont)); // can safepoint
1865   return freeze_epilog(cont);
1866 }
1867 
1868 static freeze_result preempt_epilog(ContinuationWrapper& cont, freeze_result res, frame& old_last_frame) {
1869   if (UNLIKELY(res != freeze_ok)) {
1870     verify_continuation(cont.continuation());
1871     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
1872     return res;
1873   }
1874 
1875   // Set up things so that on return to Java we jump to preempt stub.
1876   patch_return_pc_with_preempt_stub(old_last_frame);
1877   cont.tail()->set_preempted(true);
1878   DEBUG_ONLY(log_preempt_after_freeze(cont);)
1879   return freeze_epilog(cont);
1880 }
1881 
1882 template<typename ConfigT, bool preempt>
1883 static inline freeze_result freeze_internal(JavaThread* current, intptr_t* const sp) {
1884   assert(!current->has_pending_exception(), "");
1885 
1886 #ifdef ASSERT
1887   log_trace(continuations)("~~~~ freeze sp: " INTPTR_FORMAT "JavaThread: " INTPTR_FORMAT, p2i(current->last_continuation()->entry_sp()), p2i(current));
1888   log_frames(current, false);
1889 #endif
1890 
1891   CONT_JFR_ONLY(EventContinuationFreeze event;)
1892 
1893   ContinuationEntry* entry = current->last_continuation();
1894 
1895   oop oopCont = entry->cont_oop(current);
1896   assert(oopCont == current->last_continuation()->cont_oop(current), "");
1897   assert(ContinuationEntry::assert_entry_frame_laid_out(current), "");
1898 
1899   verify_continuation(oopCont);
1900   ContinuationWrapper cont(current, oopCont);
1901   log_develop_debug(continuations)("FREEZE #" INTPTR_FORMAT " " INTPTR_FORMAT, cont.hash(), p2i((oopDesc*)oopCont));
1902 
1903   assert(entry->is_virtual_thread() == (entry->scope(current) == java_lang_VirtualThread::vthread_scope()), "");
1904 
1905   assert(LockingMode == LM_LEGACY || (current->held_monitor_count() == 0 && current->jni_monitor_count() == 0),
1906          "Held monitor count should only be used for LM_LEGACY: " INT64_FORMAT " JNI: " INT64_FORMAT, (int64_t)current->held_monitor_count(), (int64_t)current->jni_monitor_count());
1907 
1908   if (entry->is_pinned() || current->held_monitor_count() > 0) {

2062   // 300 is an estimate for stack size taken for this native code, in addition to StackShadowPages
2063   // for the Java frames in the check below.
2064   if (!stack_overflow_check(thread, size + 300, bottom)) {
2065     return 0;
2066   }
2067 
2068   log_develop_trace(continuations)("prepare_thaw bottom: " INTPTR_FORMAT " top: " INTPTR_FORMAT " size: %d",
2069                               p2i(bottom), p2i(bottom - size), size);
2070   return size;
2071 }
2072 
2073 class ThawBase : public StackObj {
2074 protected:
2075   JavaThread* _thread;
2076   ContinuationWrapper& _cont;
2077   CONT_JFR_ONLY(FreezeThawJfrInfo _jfr_info;)
2078 
2079   intptr_t* _fastpath;
2080   bool _barriers;
2081   bool _preempted_case;
2082   bool _process_args_at_top;
2083   intptr_t* _top_unextended_sp_before_thaw;
2084   int _align_size;
2085   DEBUG_ONLY(intptr_t* _top_stack_address);
2086 
2087   // Only used for some preemption cases.
2088   ObjectMonitor* _monitor;
2089 
2090   StackChunkFrameStream<ChunkFrames::Mixed> _stream;
2091 
2092   NOT_PRODUCT(int _frames;)
2093 
2094 protected:
2095   ThawBase(JavaThread* thread, ContinuationWrapper& cont) :
2096       _thread(thread), _cont(cont),
2097       _fastpath(nullptr) {
2098     DEBUG_ONLY(_top_unextended_sp_before_thaw = nullptr;)
2099     assert (cont.tail() != nullptr, "no last chunk");
2100     DEBUG_ONLY(_top_stack_address = _cont.entrySP() - thaw_size(cont.tail());)
2101   }
2102 
2103   void clear_chunk(stackChunkOop chunk);
2104   template<bool check_stub>
2105   int remove_top_compiled_frame_from_chunk(stackChunkOop chunk, int &argsize);
2106   void copy_from_chunk(intptr_t* from, intptr_t* to, int size);
2107 
2108   void thaw_lockstack(stackChunkOop chunk);
2109 
2110   // fast path
2111   inline void prefetch_chunk_pd(void* start, int size_words);
2112   void patch_return(intptr_t* sp, bool is_last);
2113 
2114   intptr_t* handle_preempted_continuation(intptr_t* sp, Continuation::preempt_kind preempt_kind, bool fast_case);
2115   inline intptr_t* push_cleanup_continuation();
2116   inline intptr_t* push_preempt_adapter();
2117   intptr_t* redo_vmcall(JavaThread* current, frame& top);
2118   void throw_interrupted_exception(JavaThread* current, frame& top);
2119 
2120   void recurse_thaw(const frame& heap_frame, frame& caller, int num_frames, bool top_on_preempt_case);
2121   void finish_thaw(frame& f);
2122 
2123 private:
2124   template<typename FKind> bool recurse_thaw_java_frame(frame& caller, int num_frames);
2125   void finalize_thaw(frame& entry, int argsize);
2126 
2127   inline bool seen_by_gc();
2128 
2129   inline void before_thaw_java_frame(const frame& hf, const frame& caller, bool bottom, int num_frame);
2130   inline void after_thaw_java_frame(const frame& f, bool bottom);
2131   inline void patch(frame& f, const frame& caller, bool bottom);
2132   void clear_bitmap_bits(address start, address end);
2133 
2134   NOINLINE void recurse_thaw_interpreted_frame(const frame& hf, frame& caller, int num_frames, bool is_top);
2135   void recurse_thaw_compiled_frame(const frame& hf, frame& caller, int num_frames, bool stub_caller);
2136   void recurse_thaw_stub_frame(const frame& hf, frame& caller, int num_frames);
2137   void recurse_thaw_native_frame(const frame& hf, frame& caller, int num_frames);
2138 
2139   void push_return_frame(frame& f);
2140   inline frame new_entry_frame();
2141   template<typename FKind> frame new_stack_frame(const frame& hf, frame& caller, bool bottom);
2142   inline void patch_pd(frame& f, const frame& sender);
2143   inline void patch_pd(frame& f, intptr_t* caller_sp);
2144   inline intptr_t* align(const frame& hf, intptr_t* frame_sp, frame& caller, bool bottom);
2145 
2146   void maybe_set_fastpath(intptr_t* sp) { if (sp > _fastpath) _fastpath = sp; }
2147 
2148   static inline void derelativize_interpreted_frame_metadata(const frame& hf, const frame& f);
2149 
2150  public:
2151   CONT_JFR_ONLY(FreezeThawJfrInfo& jfr_info() { return _jfr_info; })
2152 };
2153 
2154 template <typename ConfigT>

2214   chunk->set_sp(chunk->bottom());
2215   chunk->set_max_thawing_size(0);
2216 }
2217 
2218 template<bool check_stub>
2219 int ThawBase::remove_top_compiled_frame_from_chunk(stackChunkOop chunk, int &argsize) {
2220   bool empty = false;
2221   StackChunkFrameStream<ChunkFrames::CompiledOnly> f(chunk);
2222   DEBUG_ONLY(intptr_t* const chunk_sp = chunk->start_address() + chunk->sp();)
2223   assert(chunk_sp == f.sp(), "");
2224   assert(chunk_sp == f.unextended_sp(), "");
2225 
2226   int frame_size = f.cb()->frame_size();
2227   argsize = f.stack_argsize();
2228 
2229   assert(!f.is_stub() || check_stub, "");
2230   if (check_stub && f.is_stub()) {
2231     // If we don't thaw the top compiled frame too, after restoring the saved
2232     // registers back in Java, we would hit the return barrier to thaw one more
2233     // frame effectively overwriting the restored registers during that call.
2234     f.next(SmallRegisterMap::instance_no_args(), true /* stop */);
2235     assert(!f.is_done(), "");
2236 
2237     f.get_cb();
2238     assert(f.is_compiled(), "");
2239     frame_size += f.cb()->frame_size();
2240     argsize = f.stack_argsize();
2241 
2242     if (f.cb()->as_nmethod()->is_marked_for_deoptimization()) {
2243       // The caller of the runtime stub when the continuation is preempted is not at a
2244       // Java call instruction, and so cannot rely on nmethod patching for deopt.
2245       log_develop_trace(continuations)("Deoptimizing runtime stub caller");
2246       f.to_frame().deoptimize(nullptr); // the null thread simply avoids the assertion in deoptimize which we're not set up for
2247     }
2248   }
2249 
2250   f.next(SmallRegisterMap::instance_no_args(), true /* stop */);
2251   empty = f.is_done();
2252   assert(!empty || argsize == chunk->argsize(), "");
2253 
2254   if (empty) {
2255     clear_chunk(chunk);
2256   } else {
2257     chunk->set_sp(chunk->sp() + frame_size);
2258     chunk->set_max_thawing_size(chunk->max_thawing_size() - frame_size);
2259     // We set chunk->pc to the return pc into the next frame
2260     chunk->set_pc(f.pc());
2261 #ifdef ASSERT
2262     {
2263       intptr_t* retaddr_slot = (chunk_sp
2264                                 + frame_size
2265                                 - frame::sender_sp_ret_address_offset());
2266       assert(f.pc() == ContinuationHelper::return_address_at(retaddr_slot),
2267              "unexpected pc");
2268     }
2269 #endif
2270   }

2390   return rs.sp();
2391 }
2392 
2393 inline bool ThawBase::seen_by_gc() {
2394   return _barriers || _cont.tail()->is_gc_mode();
2395 }
2396 
2397 static inline void relativize_chunk_concurrently(stackChunkOop chunk) {
2398 #if INCLUDE_ZGC || INCLUDE_SHENANDOAHGC
2399   if (UseZGC || UseShenandoahGC) {
2400     chunk->relativize_derived_pointers_concurrently();
2401   }
2402 #endif
2403 }
2404 
2405 template <typename ConfigT>
2406 NOINLINE intptr_t* Thaw<ConfigT>::thaw_slow(stackChunkOop chunk, Continuation::thaw_kind kind) {
2407   Continuation::preempt_kind preempt_kind;
2408   bool retry_fast_path = false;
2409 
2410   _process_args_at_top = false;
2411   _preempted_case = chunk->preempted();
2412   if (_preempted_case) {
2413     ObjectWaiter* waiter = java_lang_VirtualThread::objectWaiter(_thread->vthread());
2414     if (waiter != nullptr) {
2415       // Mounted again after preemption. Resume the pending monitor operation,
2416       // which will be either a monitorenter or Object.wait() call.
2417       ObjectMonitor* mon = waiter->monitor();
2418       preempt_kind = waiter->is_wait() ? Continuation::object_wait : Continuation::monitorenter;
2419 
2420       bool mon_acquired = mon->resume_operation(_thread, waiter, _cont);
2421       assert(!mon_acquired || mon->has_owner(_thread), "invariant");
2422       if (!mon_acquired) {
2423         // Failed to acquire monitor. Return to enterSpecial to unmount again.
2424         log_trace(continuations, tracking)("Failed to acquire monitor, unmounting again");
2425         return push_cleanup_continuation();
2426       }
2427       _monitor = mon;        // remember monitor since we might need it on handle_preempted_continuation()
2428       chunk = _cont.tail();  // reload oop in case of safepoint in resume_operation (if posting JVMTI events).
2429       JVMTI_ONLY(assert(_thread->contended_entered_monitor() == nullptr || _thread->contended_entered_monitor() == _monitor, ""));
2430     } else {
2431       // Preemption cancelled on moniterenter or ObjectLocker case. We
2432       // actually acquired the monitor after freezing all frames so no
2433       // need to call resume_operation. If this is the ObjectLocker case
2434       // we released the monitor already at ~ObjectLocker, so here we set
2435       // _monitor to nullptr to indicate there is no need to release it later.
2436       preempt_kind = Continuation::monitorenter;
2437       _monitor = nullptr;
2438     }
2439 
2440     // Call this first to avoid racing with GC threads later when modifying the chunk flags.
2441     relativize_chunk_concurrently(chunk);
2442 
2443     if (chunk->at_klass_init()) {
2444       preempt_kind = Continuation::object_locker;
2445       chunk->set_at_klass_init(false);
2446       _process_args_at_top = chunk->has_args_at_top();
2447       if (_process_args_at_top) chunk->set_has_args_at_top(false);
2448     }
2449     chunk->set_preempted(false);
2450     retry_fast_path = true;
2451   } else {
2452     relativize_chunk_concurrently(chunk);
2453   }
2454 
2455   // On first thaw after freeze restore oops to the lockstack if any.
2456   assert(chunk->lockstack_size() == 0 || kind == Continuation::thaw_top, "");
2457   if (kind == Continuation::thaw_top && chunk->lockstack_size() > 0) {
2458     thaw_lockstack(chunk);
2459     retry_fast_path = true;
2460   }
2461 
2462   // Retry the fast path now that we possibly cleared the FLAG_HAS_LOCKSTACK
2463   // and FLAG_PREEMPTED flags from the stackChunk.
2464   if (retry_fast_path && can_thaw_fast(chunk)) {
2465     intptr_t* sp = thaw_fast<true>(chunk);
2466     if (_preempted_case) {
2467       return handle_preempted_continuation(sp, preempt_kind, true /* fast_case */);
2468     }

2512 
2513   intptr_t* sp = caller.sp();
2514 
2515   if (_preempted_case) {
2516     return handle_preempted_continuation(sp, preempt_kind, false /* fast_case */);
2517   }
2518   return sp;
2519 }
2520 
2521 void ThawBase::recurse_thaw(const frame& heap_frame, frame& caller, int num_frames, bool top_on_preempt_case) {
2522   log_develop_debug(continuations)("thaw num_frames: %d", num_frames);
2523   assert(!_cont.is_empty(), "no more frames");
2524   assert(num_frames > 0, "");
2525   assert(!heap_frame.is_empty(), "");
2526 
2527   if (top_on_preempt_case && (heap_frame.is_native_frame() || heap_frame.is_runtime_frame())) {
2528     heap_frame.is_native_frame() ? recurse_thaw_native_frame(heap_frame, caller, 2) : recurse_thaw_stub_frame(heap_frame, caller, 2);
2529   } else if (!heap_frame.is_interpreted_frame()) {
2530     recurse_thaw_compiled_frame(heap_frame, caller, num_frames, false);
2531   } else {
2532     recurse_thaw_interpreted_frame(heap_frame, caller, num_frames, top_on_preempt_case);
2533   }
2534 }
2535 
2536 template<typename FKind>
2537 bool ThawBase::recurse_thaw_java_frame(frame& caller, int num_frames) {
2538   assert(num_frames > 0, "");
2539 
2540   DEBUG_ONLY(_frames++;)
2541 
2542   int argsize = _stream.stack_argsize();
2543 
2544   _stream.next(SmallRegisterMap::instance_no_args());
2545   assert(_stream.to_frame().is_empty() == _stream.is_done(), "");
2546 
2547   // we never leave a compiled caller of an interpreted frame as the top frame in the chunk
2548   // as it makes detecting that situation and adjusting unextended_sp tricky
2549   if (num_frames == 1 && !_stream.is_done() && FKind::interpreted && _stream.is_compiled()) {
2550     log_develop_trace(continuations)("thawing extra compiled frame to not leave a compiled interpreted-caller at top");
2551     num_frames++;
2552   }
2553 
2554   if (num_frames == 1 || _stream.is_done()) { // end recursion
2555     finalize_thaw(caller, FKind::interpreted ? 0 : argsize);
2556     return true; // bottom
2557   } else { // recurse
2558     recurse_thaw(_stream.to_frame(), caller, num_frames - 1, false /* top_on_preempt_case */);
2559     return false;
2560   }
2561 }
2562 
2563 void ThawBase::finalize_thaw(frame& entry, int argsize) {
2564   stackChunkOop chunk = _cont.tail();

2629 
2630 void ThawBase::clear_bitmap_bits(address start, address end) {
2631   assert(is_aligned(start, wordSize), "should be aligned: " PTR_FORMAT, p2i(start));
2632   assert(is_aligned(end, VMRegImpl::stack_slot_size), "should be aligned: " PTR_FORMAT, p2i(end));
2633 
2634   // we need to clear the bits that correspond to arguments as they reside in the caller frame
2635   // or they will keep objects that are otherwise unreachable alive.
2636 
2637   // Align `end` if UseCompressedOops is not set to avoid UB when calculating the bit index, since
2638   // `end` could be at an odd number of stack slots from `start`, i.e might not be oop aligned.
2639   // If that's the case the bit range corresponding to the last stack slot should not have bits set
2640   // anyways and we assert that before returning.
2641   address effective_end = UseCompressedOops ? end : align_down(end, wordSize);
2642   log_develop_trace(continuations)("clearing bitmap for " INTPTR_FORMAT " - " INTPTR_FORMAT, p2i(start), p2i(effective_end));
2643   stackChunkOop chunk = _cont.tail();
2644   chunk->bitmap().clear_range(chunk->bit_index_for(start), chunk->bit_index_for(effective_end));
2645   assert(effective_end == end || !chunk->bitmap().at(chunk->bit_index_for(effective_end)), "bit should not be set");
2646 }
2647 
2648 intptr_t* ThawBase::handle_preempted_continuation(intptr_t* sp, Continuation::preempt_kind preempt_kind, bool fast_case) {

2649   frame top(sp);
2650   assert(top.pc() == *(address*)(sp - frame::sender_sp_ret_address_offset()), "");
2651   DEBUG_ONLY(verify_frame_kind(top, preempt_kind);)
2652   NOT_PRODUCT(int64_t tid = _thread->monitor_owner_id();)
2653 
2654 #if INCLUDE_JVMTI
2655   // Finish the VTMS transition.
2656   assert(_thread->is_in_VTMS_transition(), "must be");
2657   bool is_vthread = Continuation::continuation_scope(_cont.continuation()) == java_lang_VirtualThread::vthread_scope();
2658   if (is_vthread) {
2659     if (JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events()) {
2660       jvmti_mount_end(_thread, _cont, top, preempt_kind);
2661     } else {
2662       _thread->set_is_in_VTMS_transition(false);
2663       java_lang_Thread::set_is_in_VTMS_transition(_thread->vthread(), false);
2664     }
2665   }
2666 #endif
2667 
2668   if (fast_case) {
2669     // If we thawed in the slow path the runtime stub/native wrapper frame already
2670     // has the correct fp (see ThawBase::new_stack_frame). On the fast path though,
2671     // we copied the fp patched during freeze, which will now have to be fixed.
2672     assert(top.is_runtime_frame() || top.is_native_frame(), "");
2673     int fsize = top.cb()->frame_size();
2674     patch_pd(top, sp + fsize);
2675   }
2676 
2677   if (preempt_kind == Continuation::object_wait) {
2678     // Check now if we need to throw IE exception.
2679     bool throw_ie = _thread->pending_interrupted_exception();
2680     if (throw_ie) {
2681       throw_interrupted_exception(_thread, top);
2682       _thread->set_pending_interrupted_exception(false);
2683     }
2684     log_develop_trace(continuations, preempt)("Resuming " INT64_FORMAT" after preemption on Object.wait%s", tid, throw_ie ? "(throwing IE)" : "");
2685   } else if (preempt_kind == Continuation::monitorenter) {
2686     if (top.is_runtime_frame()) {
2687       // The continuation might now run on a different platform thread than the previous time so
2688       // we need to adjust the current thread saved in the stub frame before restoring registers.
2689       JavaThread** thread_addr = frame::saved_thread_address(top);
2690       if (thread_addr != nullptr) *thread_addr = _thread;
2691     }
2692     log_develop_trace(continuations, preempt)("Resuming " INT64_FORMAT " after preemption on monitorenter", tid);
2693   } else {
2694     // We need to redo the original call into the VM. First though, we need
2695     // to exit the monitor we just acquired (except on preemption cancelled
2696     // case where it was already released).
2697     assert(preempt_kind == Continuation::object_locker, "");
2698     if (_monitor != nullptr) _monitor->exit(_thread);
2699     sp = redo_vmcall(_thread, top);
2700   }
2701   return sp;
2702 }
2703 
2704 intptr_t* ThawBase::redo_vmcall(JavaThread* current, frame& top) {
2705   assert(!current->preempting(), "");
2706   NOT_PRODUCT(int64_t tid = current->monitor_owner_id();)
2707   intptr_t* sp = top.sp();
2708 
2709   {
2710     HandleMarkCleaner hmc(current);  // Cleanup so._conth Handle
2711     ContinuationWrapper::SafepointOp so(current, _cont);
2712     AnchorMark am(current, top);    // Set the anchor so that the stack is walkable.
2713 
2714     Method* m = top.interpreter_frame_method();
2715     Bytecode current_bytecode = Bytecode(m, top.interpreter_frame_bcp());
2716     Bytecodes::Code code = current_bytecode.code();
2717     log_develop_trace(continuations, preempt)("Redoing InterpreterRuntime::%s for " INT64_FORMAT, code == Bytecodes::Code::_new ? "_new" : "resolve_from_cache", tid);
2718 
2719     // These InterpreterRuntime entry points use JRT_ENTRY which uses a HandleMarkCleaner.
2720     // Create a HandeMark to avoid destroying so._conth.
2721     HandleMark hm(current);
2722     if (code == Bytecodes::Code::_new) {
2723       InterpreterRuntime::_new(current, m->constants(), current_bytecode.get_index_u2(code));
2724     } else {
2725       InterpreterRuntime::resolve_from_cache(current, code);
2726     }
2727   }
2728 
2729   if (current->preempting()) {
2730     // Preempted again so we just arrange to return to preempt stub to unmount.
2731     sp = push_preempt_adapter();
2732     current->set_preempt_alternate_return(nullptr);
2733     bool cancelled = current->preemption_cancelled();
2734     if (cancelled) {
2735       // Instead of calling thaw again from the preempt stub just unmount anyways with
2736       // state of YIELDING. This will give a chance for other vthreads to run while
2737       // minimizing repeated loops of "thaw->redo_vmcall->try_preempt->preemption_cancelled->thaw..."
2738       // in case of multiple vthreads contending for the same init_lock().
2739       current->set_preemption_cancelled(false);
2740       oop vthread = current->vthread();
2741       assert(java_lang_VirtualThread::state(vthread) == java_lang_VirtualThread::RUNNING, "wrong state for vthread");
2742       java_lang_VirtualThread::set_state(vthread, java_lang_VirtualThread::YIELDING);
2743 #if INCLUDE_JVMTI
2744       if (current->contended_entered_monitor() != nullptr) {
2745         current->set_contended_entered_monitor(nullptr);
2746       }
2747 #endif
2748     }
2749     log_develop_trace(continuations, preempt)("Preempted " INT64_FORMAT " again%s", tid, cancelled ? "(preemption cancelled, setting state to YIELDING)" : "");
2750   } else {
2751     log_develop_trace(continuations, preempt)("Call succesful, resuming " INT64_FORMAT, tid);
2752   }
2753   return sp;
2754 }
2755 
2756 void ThawBase::throw_interrupted_exception(JavaThread* current, frame& top) {
2757   HandleMarkCleaner hm(current);  // Cleanup so._conth Handle
2758   ContinuationWrapper::SafepointOp so(current, _cont);
2759   // Since we might safepoint set the anchor so that the stack can be walked.
2760   set_anchor(current, top.sp());
2761   JRT_BLOCK
2762     THROW(vmSymbols::java_lang_InterruptedException());
2763   JRT_BLOCK_END
2764   clear_anchor(current);
2765 }
2766 
2767 NOINLINE void ThawBase::recurse_thaw_interpreted_frame(const frame& hf, frame& caller, int num_frames, bool is_top) {
2768   assert(hf.is_interpreted_frame(), "");
2769 
2770   if (UNLIKELY(seen_by_gc())) {
2771     if (is_top && _process_args_at_top) {
2772       log_trace(continuations, tracking)("Processing arguments in recurse_thaw_interpreted_frame");
2773       _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance_with_args());  
2774     } else {
2775       _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance_no_args());  
2776     }
2777   }
2778 
2779   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::InterpretedFrame>(caller, num_frames);
2780 
2781   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2782 
2783   _align_size += frame::align_wiggle; // possible added alignment for internal interpreted frame alignment om AArch64
2784 
2785   frame f = new_stack_frame<ContinuationHelper::InterpretedFrame>(hf, caller, is_bottom_frame);
2786 
2787   intptr_t* const stack_frame_top = f.sp() + frame::metadata_words_at_top;
2788   intptr_t* const stack_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(f);
2789   intptr_t* const heap_frame_top = hf.unextended_sp() + frame::metadata_words_at_top;
2790   intptr_t* const heap_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(hf);
2791 
2792   assert(hf.is_heap_frame(), "should be");
2793   assert(!f.is_heap_frame(), "should not be");
2794 
2795   const int fsize = pointer_delta_as_int(heap_frame_bottom, heap_frame_top);
2796   assert((stack_frame_bottom == stack_frame_top + fsize), "");

2801 
2802   // Make sure the relativized locals is already set.
2803   assert(f.interpreter_frame_local_at(0) == stack_frame_bottom - 1, "invalid frame bottom");
2804 
2805   derelativize_interpreted_frame_metadata(hf, f);
2806   patch(f, caller, is_bottom_frame);
2807 
2808   assert(f.is_interpreted_frame_valid(_cont.thread()), "invalid thawed frame");
2809   assert(stack_frame_bottom <= ContinuationHelper::Frame::frame_top(caller), "");
2810 
2811   CONT_JFR_ONLY(_jfr_info.record_interpreted_frame();)
2812 
2813   maybe_set_fastpath(f.sp());
2814 
2815   Method* m = hf.interpreter_frame_method();
2816   assert(!m->is_native() || !is_bottom_frame, "should be top frame of thaw_top case; missing caller frame");
2817   const int locals = m->max_locals();
2818 
2819   if (!is_bottom_frame) {
2820     // can only fix caller once this frame is thawed (due to callee saved regs)
2821     _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance_no_args());
2822   } else if (_cont.tail()->has_bitmap() && locals > 0) {
2823     assert(hf.is_heap_frame(), "should be");
2824     address start = (address)(heap_frame_bottom - locals);
2825     address end = (address)heap_frame_bottom;
2826     clear_bitmap_bits(start, end);
2827   }
2828 
2829   DEBUG_ONLY(after_thaw_java_frame(f, is_bottom_frame);)
2830   caller = f;
2831 }
2832 
2833 void ThawBase::recurse_thaw_compiled_frame(const frame& hf, frame& caller, int num_frames, bool stub_caller) {
2834   assert(hf.is_compiled_frame(), "");
2835   assert(_preempted_case || !stub_caller, "stub caller not at preemption");
2836 
2837   if (!stub_caller && UNLIKELY(seen_by_gc())) { // recurse_thaw_stub_frame already invoked our barriers with a full regmap
2838     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance_no_args());
2839   }
2840 
2841   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::CompiledFrame>(caller, num_frames);
2842 
2843   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2844 
2845   assert(caller.sp() == caller.unextended_sp(), "");
2846 
2847   if ((!is_bottom_frame && caller.is_interpreted_frame()) || (is_bottom_frame && Interpreter::contains(_cont.tail()->pc()))) {
2848     _align_size += frame::align_wiggle; // we add one whether or not we've aligned because we add it in recurse_freeze_compiled_frame
2849   }
2850 
2851   // new_stack_frame must construct the resulting frame using hf.pc() rather than hf.raw_pc() because the frame is not
2852   // yet laid out in the stack, and so the original_pc is not stored in it.
2853   // As a result, f.is_deoptimized_frame() is always false and we must test hf to know if the frame is deoptimized.
2854   frame f = new_stack_frame<ContinuationHelper::CompiledFrame>(hf, caller, is_bottom_frame);
2855   intptr_t* const stack_frame_top = f.sp();
2856   intptr_t* const heap_frame_top = hf.unextended_sp();
2857 
2858   const int added_argsize = (is_bottom_frame || caller.is_interpreted_frame()) ? hf.compiled_frame_stack_argsize() : 0;

2877   assert(!f.is_deoptimized_frame(), "");
2878   if (hf.is_deoptimized_frame()) {
2879     maybe_set_fastpath(f.sp());
2880   } else if (_thread->is_interp_only_mode()
2881               || (stub_caller && f.cb()->as_nmethod()->is_marked_for_deoptimization())) {
2882     // The caller of the safepoint stub when the continuation is preempted is not at a call instruction, and so
2883     // cannot rely on nmethod patching for deopt.
2884     assert(_thread->is_interp_only_mode() || stub_caller, "expected a stub-caller");
2885 
2886     log_develop_trace(continuations)("Deoptimizing thawed frame");
2887     DEBUG_ONLY(ContinuationHelper::Frame::patch_pc(f, nullptr));
2888 
2889     f.deoptimize(nullptr); // the null thread simply avoids the assertion in deoptimize which we're not set up for
2890     assert(f.is_deoptimized_frame(), "");
2891     assert(ContinuationHelper::Frame::is_deopt_return(f.raw_pc(), f), "");
2892     maybe_set_fastpath(f.sp());
2893   }
2894 
2895   if (!is_bottom_frame) {
2896     // can only fix caller once this frame is thawed (due to callee saved regs); this happens on the stack
2897     _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance_no_args());
2898   } else if (_cont.tail()->has_bitmap() && added_argsize > 0) {
2899     address start = (address)(heap_frame_top + ContinuationHelper::CompiledFrame::size(hf) + frame::metadata_words_at_top);
2900     int stack_args_slots = f.cb()->as_nmethod()->num_stack_arg_slots(false /* rounded */);
2901     int argsize_in_bytes = stack_args_slots * VMRegImpl::stack_slot_size;
2902     clear_bitmap_bits(start, start + argsize_in_bytes);
2903   }
2904 
2905   DEBUG_ONLY(after_thaw_java_frame(f, is_bottom_frame);)
2906   caller = f;
2907 }
2908 
2909 void ThawBase::recurse_thaw_stub_frame(const frame& hf, frame& caller, int num_frames) {
2910   DEBUG_ONLY(_frames++;)
2911 
2912   if (UNLIKELY(seen_by_gc())) {
2913     // Process the stub's caller here since we might need the full map.
2914     RegisterMap map(nullptr,
2915                     RegisterMap::UpdateMap::include,
2916                     RegisterMap::ProcessFrames::skip,
2917                     RegisterMap::WalkContinuation::skip);
2918     map.set_include_argument_oops(false);
2919     _stream.next(&map);
2920     assert(!_stream.is_done(), "");
2921     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, &map);
2922   } else {
2923     _stream.next(SmallRegisterMap::instance_no_args());
2924     assert(!_stream.is_done(), "");
2925   }
2926 
2927   recurse_thaw_compiled_frame(_stream.to_frame(), caller, num_frames, true);
2928 
2929   assert(caller.is_compiled_frame(), "");
2930   assert(caller.sp() == caller.unextended_sp(), "");
2931 
2932   DEBUG_ONLY(before_thaw_java_frame(hf, caller, false /*is_bottom_frame*/, num_frames);)
2933 
2934   frame f = new_stack_frame<ContinuationHelper::StubFrame>(hf, caller, false);
2935   intptr_t* stack_frame_top = f.sp();
2936   intptr_t* heap_frame_top = hf.sp();
2937   int fsize = ContinuationHelper::StubFrame::size(hf);
2938 
2939   copy_from_chunk(heap_frame_top - frame::metadata_words, stack_frame_top - frame::metadata_words,
2940                   fsize + frame::metadata_words);
2941 
2942   patch(f, caller, false /*is_bottom_frame*/);
2943 
2944   // can only fix caller once this frame is thawed (due to callee saved regs)
2945   RegisterMap map(nullptr,
2946                   RegisterMap::UpdateMap::include,
2947                   RegisterMap::ProcessFrames::skip,
2948                   RegisterMap::WalkContinuation::skip);
2949   map.set_include_argument_oops(false);
2950   f.oop_map()->update_register_map(&f, &map);
2951   ContinuationHelper::update_register_map_with_callee(caller, &map);
2952   _cont.tail()->fix_thawed_frame(caller, &map);
2953 
2954   DEBUG_ONLY(after_thaw_java_frame(f, false /*is_bottom_frame*/);)
2955   caller = f;
2956 }
2957 
2958 void ThawBase::recurse_thaw_native_frame(const frame& hf, frame& caller, int num_frames) {
2959   assert(hf.is_native_frame(), "");
2960   assert(_preempted_case && hf.cb()->as_nmethod()->method()->is_object_wait0(), "");
2961 
2962   if (UNLIKELY(seen_by_gc())) { // recurse_thaw_stub_frame already invoked our barriers with a full regmap
2963     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance_no_args());
2964   }
2965 
2966   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::NativeFrame>(caller, num_frames);
2967   assert(!is_bottom_frame, "");
2968 
2969   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2970 
2971   assert(caller.sp() == caller.unextended_sp(), "");
2972 
2973   if (caller.is_interpreted_frame()) {
2974     _align_size += frame::align_wiggle; // we add one whether or not we've aligned because we add it in recurse_freeze_native_frame
2975   }
2976 
2977   // new_stack_frame must construct the resulting frame using hf.pc() rather than hf.raw_pc() because the frame is not
2978   // yet laid out in the stack, and so the original_pc is not stored in it.
2979   // As a result, f.is_deoptimized_frame() is always false and we must test hf to know if the frame is deoptimized.
2980   frame f = new_stack_frame<ContinuationHelper::NativeFrame>(hf, caller, false /* bottom */);
2981   intptr_t* const stack_frame_top = f.sp();
2982   intptr_t* const heap_frame_top = hf.unextended_sp();
2983 
2984   int fsize = ContinuationHelper::NativeFrame::size(hf);
2985   assert(fsize <= (int)(caller.unextended_sp() - f.unextended_sp()), "");
2986 
2987   intptr_t* from = heap_frame_top - frame::metadata_words_at_bottom;
2988   intptr_t* to   = stack_frame_top - frame::metadata_words_at_bottom;
2989   int sz = fsize + frame::metadata_words_at_bottom;
2990 
2991   copy_from_chunk(from, to, sz); // copying good oops because we invoked barriers above
2992 
2993   patch(f, caller, false /* bottom */);
2994 
2995   // f.is_deoptimized_frame() is always false and we must test hf.is_deoptimized_frame() (see comment above)
2996   assert(!f.is_deoptimized_frame(), "");
2997   assert(!hf.is_deoptimized_frame(), "");
2998   assert(!f.cb()->as_nmethod()->is_marked_for_deoptimization(), "");
2999 
3000   // can only fix caller once this frame is thawed (due to callee saved regs); this happens on the stack
3001   _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance_no_args());
3002 
3003   DEBUG_ONLY(after_thaw_java_frame(f, false /* bottom */);)
3004   caller = f;
3005 }
3006 
3007 void ThawBase::finish_thaw(frame& f) {
3008   stackChunkOop chunk = _cont.tail();
3009 
3010   if (chunk->is_empty()) {
3011     // Only remove chunk from list if it can't be reused for another freeze
3012     if (seen_by_gc()) {
3013       _cont.set_tail(chunk->parent());
3014     } else {
3015       chunk->set_has_mixed_frames(false);
3016     }
3017     chunk->set_max_thawing_size(0);
3018   } else {
3019     chunk->set_max_thawing_size(chunk->max_thawing_size() - _align_size);
3020   }
3021   assert(chunk->is_empty() == (chunk->max_thawing_size() == 0), "");
3022 
3023   if (!is_aligned(f.sp(), frame::frame_alignment)) {
3024     assert(f.is_interpreted_frame(), "");
3025     f.set_sp(align_down(f.sp(), frame::frame_alignment));
3026   }
3027   push_return_frame(f);
3028    // can only fix caller after push_return_frame (due to callee saved regs)
3029   if (_process_args_at_top) {
3030     log_trace(continuations, tracking)("Processing arguments in finish_thaw");
3031     chunk->fix_thawed_frame(f, SmallRegisterMap::instance_with_args());
3032   } else {
3033     chunk->fix_thawed_frame(f, SmallRegisterMap::instance_no_args());  
3034   }
3035 
3036   assert(_cont.is_empty() == _cont.last_frame().is_empty(), "");
3037 
3038   log_develop_trace(continuations)("thawed %d frames", _frames);
3039 
3040   LogTarget(Trace, continuations) lt;
3041   if (lt.develop_is_enabled()) {
3042     LogStream ls(lt);
3043     ls.print_cr("top hframe after (thaw):");
3044     _cont.last_frame().print_value_on(&ls);
3045   }
3046 }
3047 
3048 void ThawBase::push_return_frame(frame& f) { // see generate_cont_thaw
3049   assert(!f.is_compiled_frame() || f.is_deoptimized_frame() == f.cb()->as_nmethod()->is_deopt_pc(f.raw_pc()), "");
3050   assert(!f.is_compiled_frame() || f.is_deoptimized_frame() == (f.pc() != f.raw_pc()), "");
3051 
3052   LogTarget(Trace, continuations) lt;
3053   if (lt.develop_is_enabled()) {
3054     LogStream ls(lt);

3076 
3077   ContinuationEntry* entry = thread->last_continuation();
3078   assert(entry != nullptr, "");
3079   oop oopCont = entry->cont_oop(thread);
3080 
3081   assert(!jdk_internal_vm_Continuation::done(oopCont), "");
3082   assert(oopCont == get_continuation(thread), "");
3083   verify_continuation(oopCont);
3084 
3085   assert(entry->is_virtual_thread() == (entry->scope(thread) == java_lang_VirtualThread::vthread_scope()), "");
3086 
3087   ContinuationWrapper cont(thread, oopCont);
3088   log_develop_debug(continuations)("THAW #" INTPTR_FORMAT " " INTPTR_FORMAT, cont.hash(), p2i((oopDesc*)oopCont));
3089 
3090 #ifdef ASSERT
3091   set_anchor_to_entry(thread, cont.entry());
3092   log_frames(thread);
3093   clear_anchor(thread);
3094 #endif
3095 

3096   Thaw<ConfigT> thw(thread, cont);
3097   intptr_t* const sp = thw.thaw(kind);
3098   assert(is_aligned(sp, frame::frame_alignment), "");
3099   DEBUG_ONLY(log_frames_after_thaw(thread, cont, sp);)
3100 
3101   CONT_JFR_ONLY(thw.jfr_info().post_jfr_event(&event, cont.continuation(), thread);)
3102 
3103   verify_continuation(cont.continuation());
3104   log_develop_debug(continuations)("=== End of thaw #" INTPTR_FORMAT, cont.hash());
3105 
3106   return sp;
3107 }
3108 
3109 #ifdef ASSERT
3110 static void do_deopt_after_thaw(JavaThread* thread) {
3111   int i = 0;
3112   StackFrameStream fst(thread, true, false);
3113   fst.register_map()->set_include_argument_oops(false);
3114   ContinuationHelper::update_register_map_with_callee(*fst.current(), fst.register_map());
3115   for (; !fst.is_done(); fst.next()) {
3116     if (fst.current()->cb()->is_nmethod()) {
3117       nmethod* nm = fst.current()->cb()->as_nmethod();
3118       if (!nm->method()->is_continuation_native_intrinsic()) {
3119         nm->make_deoptimized();

3176       if (!fr.is_interpreted_frame()) {
3177         st->print_cr("size: %d argsize: %d",
3178                      ContinuationHelper::NonInterpretedUnknownFrame::size(fr),
3179                      ContinuationHelper::NonInterpretedUnknownFrame::stack_argsize(fr));
3180       }
3181       VMReg reg = fst.register_map()->find_register_spilled_here(cl.p(), fst.current()->sp());
3182       if (reg != nullptr) {
3183         st->print_cr("Reg %s %d", reg->name(), reg->is_stack() ? (int)reg->reg2stack() : -99);
3184       }
3185       cl.reset();
3186       DEBUG_ONLY(thread->print_frame_layout();)
3187       if (chunk != nullptr) {
3188         chunk->print_on(true, st);
3189       }
3190       return false;
3191     }
3192   }
3193   return true;
3194 }
3195 
3196 static void log_frames(JavaThread* thread, bool dolog) {
3197   const static int show_entry_callers = 3;
3198   LogTarget(Trace, continuations, tracking) lt;
3199   if (!lt.develop_is_enabled() || !dolog) {
3200     return;
3201   }
3202   LogStream ls(lt);
3203 
3204   ls.print_cr("------- frames --------- for thread " INTPTR_FORMAT, p2i(thread));
3205   if (!thread->has_last_Java_frame()) {
3206     ls.print_cr("NO ANCHOR!");
3207   }
3208 
3209   RegisterMap map(thread,
3210                   RegisterMap::UpdateMap::include,
3211                   RegisterMap::ProcessFrames::include,
3212                   RegisterMap::WalkContinuation::skip);
3213   map.set_include_argument_oops(false);
3214 
3215   if (false) {
3216     for (frame f = thread->last_frame(); !f.is_entry_frame(); f = f.sender(&map)) {
3217       f.print_on(&ls);
3218     }
3219   } else {

3221     ResetNoHandleMark rnhm;
3222     ResourceMark rm;
3223     HandleMark hm(Thread::current());
3224     FrameValues values;
3225 
3226     int i = 0;
3227     int post_entry = -1;
3228     for (frame f = thread->last_frame(); !f.is_first_frame(); f = f.sender(&map), i++) {
3229       f.describe(values, i, &map, i == 0);
3230       if (post_entry >= 0 || Continuation::is_continuation_enterSpecial(f))
3231         post_entry++;
3232       if (post_entry >= show_entry_callers)
3233         break;
3234     }
3235     values.print_on(thread, &ls);
3236   }
3237 
3238   ls.print_cr("======= end frames =========");
3239 }
3240 
3241 static void log_frames_after_thaw(JavaThread* thread, ContinuationWrapper& cont, intptr_t* sp) {
3242   intptr_t* sp0 = sp;
3243   address pc0 = *(address*)(sp - frame::sender_sp_ret_address_offset());
3244 
3245   bool preempted = false;
3246   stackChunkOop tail = cont.tail();
3247   if (tail != nullptr && tail->preempted()) {
3248     // Still preempted (monitor not acquired) so no frames were thawed.

3249     set_anchor(thread, cont.entrySP(), cont.entryPC());
3250     preempted = true;
3251   } else {
3252     set_anchor(thread, sp0);
3253   }
3254 
3255   log_frames(thread);
3256   if (LoomVerifyAfterThaw) {
3257     assert(do_verify_after_thaw(thread, cont.tail(), tty), "");
3258   }
3259   assert(ContinuationEntry::assert_entry_frame_laid_out(thread, preempted), "");
3260   clear_anchor(thread);
3261 
3262   LogTarget(Trace, continuations) lt;
3263   if (lt.develop_is_enabled()) {
3264     LogStream ls(lt);
3265     ls.print_cr("Jumping to frame (thaw):");
3266     frame(sp).print_value_on(&ls);
3267   }
3268 }
3269 #endif // ASSERT
3270 
3271 #include CPU_HEADER_INLINE(continuationFreezeThaw)
3272 
3273 #ifdef ASSERT
3274 static void print_frame_layout(const frame& f, bool callee_complete, outputStream* st) {
3275   ResourceMark rm;
3276   FrameValues values;
3277   assert(f.get_cb() != nullptr, "");
3278   RegisterMap map(f.is_heap_frame() ?
3279                     nullptr :
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