1 /*
   2  * Copyright (c) 2018, 2024, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  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 "precompiled.hpp"
  26 #include "classfile/javaClasses.inline.hpp"
  27 #include "classfile/vmSymbols.hpp"
  28 #include "code/codeCache.inline.hpp"
  29 #include "code/nmethod.inline.hpp"
  30 #include "code/vmreg.inline.hpp"
  31 #include "compiler/oopMap.inline.hpp"
  32 #include "gc/shared/continuationGCSupport.inline.hpp"
  33 #include "gc/shared/gc_globals.hpp"
  34 #include "gc/shared/barrierSet.hpp"
  35 #include "gc/shared/memAllocator.hpp"
  36 #include "gc/shared/threadLocalAllocBuffer.inline.hpp"
  37 #include "interpreter/interpreter.hpp"
  38 #include "jfr/jfrEvents.hpp"
  39 #include "logging/log.hpp"
  40 #include "logging/logStream.hpp"
  41 #include "oops/access.inline.hpp"
  42 #include "oops/method.inline.hpp"
  43 #include "oops/oopsHierarchy.hpp"
  44 #include "oops/objArrayOop.inline.hpp"
  45 #include "oops/stackChunkOop.inline.hpp"
  46 #include "prims/jvmtiThreadState.hpp"
  47 #include "runtime/arguments.hpp"
  48 #include "runtime/continuation.hpp"
  49 #include "runtime/continuationEntry.inline.hpp"
  50 #include "runtime/continuationHelper.inline.hpp"
  51 #include "runtime/continuationJavaClasses.inline.hpp"
  52 #include "runtime/continuationWrapper.inline.hpp"
  53 #include "runtime/frame.inline.hpp"
  54 #include "runtime/interfaceSupport.inline.hpp"
  55 #include "runtime/javaThread.inline.hpp"
  56 #include "runtime/jniHandles.inline.hpp"
  57 #include "runtime/keepStackGCProcessed.hpp"
  58 #include "runtime/orderAccess.hpp"
  59 #include "runtime/prefetch.inline.hpp"
  60 #include "runtime/smallRegisterMap.inline.hpp"
  61 #include "runtime/sharedRuntime.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 #if INCLUDE_ZGC
  70 #include "gc/z/zStackChunkGCData.inline.hpp"
  71 #endif
  72 
  73 #include <type_traits>
  74 
  75 /*
  76  * This file contains the implementation of continuation freezing (yield) and thawing (run).
  77  *
  78  * This code is very latency-critical and very hot. An ordinary and well-behaved server application
  79  * would likely call these operations many thousands of times per second second, on every core.
  80  *
  81  * Freeze might be called every time the application performs any I/O operation, every time it
  82  * acquires a j.u.c. lock, every time it takes a message from a queue, and thaw can be called
  83  * multiple times in each of those cases, as it is called by the return barrier, which may be
  84  * invoked on method return.
  85  *
  86  * The amortized budget for each of those two operations is ~100-150ns. That is why, for
  87  * example, every effort is made to avoid Java-VM transitions as much as possible.
  88  *
  89  * On the fast path, all frames are known to be compiled, and the chunk requires no barriers
  90  * and so frames simply copied, and the bottom-most one is patched.
  91  * On the slow path, internal pointers in interpreted frames are de/relativized to/from offsets
  92  * and absolute pointers, and barriers invoked.
  93  */
  94 
  95 /************************************************
  96 
  97 Thread-stack layout on freeze/thaw.
  98 See corresponding stack-chunk layout in instanceStackChunkKlass.hpp
  99 
 100             +----------------------------+
 101             |      .                     |
 102             |      .                     |
 103             |      .                     |
 104             |   carrier frames           |
 105             |                            |
 106             |----------------------------|
 107             |                            |
 108             |    Continuation.run        |
 109             |                            |
 110             |============================|
 111             |    enterSpecial frame      |
 112             |  pc                        |
 113             |  rbp                       |
 114             |  -----                     |
 115         ^   |  int argsize               | = ContinuationEntry
 116         |   |  oopDesc* cont             |
 117         |   |  oopDesc* chunk            |
 118         |   |  ContinuationEntry* parent |
 119         |   |  ...                       |
 120         |   |============================| <------ JavaThread::_cont_entry = entry->sp()
 121         |   |  ? alignment word ?        |
 122         |   |----------------------------| <--\
 123         |   |                            |    |
 124         |   |  ? caller stack args ?     |    |   argsize (might not be 2-word aligned) words
 125 Address |   |                            |    |   Caller is still in the chunk.
 126         |   |----------------------------|    |
 127         |   |  pc (? return barrier ?)   |    |  This pc contains the return barrier when the bottom-most frame
 128         |   |  rbp                       |    |  isn't the last one in the continuation.
 129         |   |                            |    |
 130         |   |    frame                   |    |
 131         |   |                            |    |
 132             +----------------------------|     \__ Continuation frames to be frozen/thawed
 133             |                            |     /
 134             |    frame                   |    |
 135             |                            |    |
 136             |----------------------------|    |
 137             |                            |    |
 138             |    frame                   |    |
 139             |                            |    |
 140             |----------------------------| <--/
 141             |                            |
 142             |    doYield/safepoint stub  | When preempting forcefully, we could have a safepoint stub
 143             |                            | instead of a doYield stub
 144             |============================| <- the sp passed to freeze
 145             |                            |
 146             |  Native freeze/thaw frames |
 147             |      .                     |
 148             |      .                     |
 149             |      .                     |
 150             +----------------------------+
 151 
 152 ************************************************/
 153 
 154 static const bool TEST_THAW_ONE_CHUNK_FRAME = false; // force thawing frames one-at-a-time for testing
 155 
 156 #define CONT_JFR false // emit low-level JFR events that count slow/fast path for continuation performance debugging only
 157 #if CONT_JFR
 158   #define CONT_JFR_ONLY(code) code
 159 #else
 160   #define CONT_JFR_ONLY(code)
 161 #endif
 162 
 163 // TODO: See AbstractAssembler::generate_stack_overflow_check,
 164 // Compile::bang_size_in_bytes(), m->as_SafePoint()->jvms()->interpreter_frame_size()
 165 // when we stack-bang, we need to update a thread field with the lowest (farthest) bang point.
 166 
 167 // Data invariants are defined by Continuation::debug_verify_continuation and Continuation::debug_verify_stack_chunk
 168 
 169 // Used to just annotatate cold/hot branches
 170 #define LIKELY(condition)   (condition)
 171 #define UNLIKELY(condition) (condition)
 172 
 173 // debugging functions
 174 #ifdef ASSERT
 175 extern "C" bool dbg_is_safe(const void* p, intptr_t errvalue); // address p is readable and *(intptr_t*)p != errvalue
 176 
 177 static void verify_continuation(oop continuation) { Continuation::debug_verify_continuation(continuation); }
 178 
 179 static void do_deopt_after_thaw(JavaThread* thread);
 180 static bool do_verify_after_thaw(JavaThread* thread, stackChunkOop chunk, outputStream* st);
 181 static void log_frames(JavaThread* thread);
 182 static void print_frame_layout(const frame& f, bool callee_complete, outputStream* st = tty);
 183 
 184 #define assert_pfl(p, ...) \
 185 do {                                           \
 186   if (!(p)) {                                  \
 187     JavaThread* t = JavaThread::active();      \
 188     if (t->has_last_Java_frame()) {            \
 189       tty->print_cr("assert(" #p ") failed:"); \
 190       t->print_frame_layout();                 \
 191     }                                          \
 192   }                                            \
 193   vmassert(p, __VA_ARGS__);                    \
 194 } while(0)
 195 
 196 #else
 197 static void verify_continuation(oop continuation) { }
 198 #define assert_pfl(p, ...)
 199 #endif
 200 
 201 // should match Continuation.preemptStatus() in Continuation.java
 202 enum freeze_result {
 203   freeze_ok = 0,
 204   freeze_ok_bottom = 1,
 205   freeze_pinned_cs = 2,
 206   freeze_pinned_native = 3,
 207   freeze_pinned_monitor = 4,
 208   freeze_exception = 5
 209 };
 210 
 211 const char* freeze_result_names[6] = {
 212   "freeze_ok",
 213   "freeze_ok_bottom",
 214   "freeze_pinned_cs",
 215   "freeze_pinned_native",
 216   "freeze_pinned_monitor",
 217   "freeze_exception"
 218 };
 219 
 220 static freeze_result is_pinned0(JavaThread* thread, oop cont_scope, bool safepoint);
 221 template<typename ConfigT> static inline int freeze_internal(JavaThread* current, intptr_t* const sp);
 222 
 223 static inline int prepare_thaw_internal(JavaThread* thread, bool return_barrier);
 224 template<typename ConfigT> static inline intptr_t* thaw_internal(JavaThread* thread, const Continuation::thaw_kind kind);
 225 
 226 
 227 // Entry point to freeze. Transitions are handled manually
 228 // Called from gen_continuation_yield() in sharedRuntime_<cpu>.cpp through Continuation::freeze_entry();
 229 template<typename ConfigT>
 230 static JRT_BLOCK_ENTRY(int, freeze(JavaThread* current, intptr_t* sp))
 231   assert(sp == current->frame_anchor()->last_Java_sp(), "");
 232 
 233   if (current->raw_cont_fastpath() > current->last_continuation()->entry_sp() || current->raw_cont_fastpath() < sp) {
 234     current->set_cont_fastpath(nullptr);
 235   }
 236 
 237   return ConfigT::freeze(current, sp);
 238 JRT_END
 239 
 240 JRT_LEAF(int, Continuation::prepare_thaw(JavaThread* thread, bool return_barrier))
 241   return prepare_thaw_internal(thread, return_barrier);
 242 JRT_END
 243 
 244 template<typename ConfigT>
 245 static JRT_LEAF(intptr_t*, thaw(JavaThread* thread, int kind))
 246   // TODO: JRT_LEAF and NoHandleMark is problematic for JFR events.
 247   // vFrameStreamCommon allocates Handles in RegisterMap for continuations.
 248   // JRT_ENTRY instead?
 249   ResetNoHandleMark rnhm;
 250 
 251   // we might modify the code cache via BarrierSetNMethod::nmethod_entry_barrier
 252   MACOS_AARCH64_ONLY(ThreadWXEnable __wx(WXWrite, thread));
 253   return ConfigT::thaw(thread, (Continuation::thaw_kind)kind);
 254 JRT_END
 255 
 256 JVM_ENTRY(jint, CONT_isPinned0(JNIEnv* env, jobject cont_scope)) {
 257   JavaThread* thread = JavaThread::thread_from_jni_environment(env);
 258   return is_pinned0(thread, JNIHandles::resolve(cont_scope), false);
 259 }
 260 JVM_END
 261 
 262 ///////////
 263 
 264 enum class oop_kind { NARROW, WIDE };
 265 template <oop_kind oops, typename BarrierSetT>
 266 class Config {
 267 public:
 268   typedef Config<oops, BarrierSetT> SelfT;
 269   using OopT = std::conditional_t<oops == oop_kind::NARROW, narrowOop, oop>;
 270 
 271   static int freeze(JavaThread* thread, intptr_t* const sp) {
 272     return freeze_internal<SelfT>(thread, sp);
 273   }
 274 
 275   static intptr_t* thaw(JavaThread* thread, Continuation::thaw_kind kind) {
 276     return thaw_internal<SelfT>(thread, kind);
 277   }
 278 };
 279 
 280 static bool stack_overflow_check(JavaThread* thread, size_t size, address sp) {
 281   const size_t page_size = os::vm_page_size();
 282   if (size > page_size) {
 283     if (sp - size < thread->stack_overflow_state()->shadow_zone_safe_limit()) {
 284       return false;
 285     }
 286   }
 287   return true;
 288 }
 289 
 290 #ifdef ASSERT
 291 static oop get_continuation(JavaThread* thread) {
 292   assert(thread != nullptr, "");
 293   assert(thread->threadObj() != nullptr, "");
 294   return java_lang_Thread::continuation(thread->threadObj());
 295 }
 296 
 297 inline void clear_anchor(JavaThread* thread) {
 298   thread->frame_anchor()->clear();
 299 }
 300 
 301 static void set_anchor(JavaThread* thread, intptr_t* sp) {
 302   address pc = ContinuationHelper::return_address_at(
 303                  sp - frame::sender_sp_ret_address_offset());
 304   assert(pc != nullptr, "");
 305 
 306   JavaFrameAnchor* anchor = thread->frame_anchor();
 307   anchor->set_last_Java_sp(sp);
 308   anchor->set_last_Java_pc(pc);
 309   ContinuationHelper::set_anchor_pd(anchor, sp);
 310 
 311   assert(thread->has_last_Java_frame(), "");
 312   assert(thread->last_frame().cb() != nullptr, "");
 313 }
 314 #endif // ASSERT
 315 
 316 static void set_anchor_to_entry(JavaThread* thread, ContinuationEntry* entry) {
 317   JavaFrameAnchor* anchor = thread->frame_anchor();
 318   anchor->set_last_Java_sp(entry->entry_sp());
 319   anchor->set_last_Java_pc(entry->entry_pc());
 320   ContinuationHelper::set_anchor_to_entry_pd(anchor, entry);
 321 
 322   assert(thread->has_last_Java_frame(), "");
 323   assert(thread->last_frame().cb() != nullptr, "");
 324 }
 325 
 326 #if CONT_JFR
 327 class FreezeThawJfrInfo : public StackObj {
 328   short _e_size;
 329   short _e_num_interpreted_frames;
 330  public:
 331 
 332   FreezeThawJfrInfo() : _e_size(0), _e_num_interpreted_frames(0) {}
 333   inline void record_interpreted_frame() { _e_num_interpreted_frames++; }
 334   inline void record_size_copied(int size) { _e_size += size << LogBytesPerWord; }
 335   template<typename Event> void post_jfr_event(Event *e, oop continuation, JavaThread* jt);
 336 };
 337 
 338 template<typename Event> void FreezeThawJfrInfo::post_jfr_event(Event* e, oop continuation, JavaThread* jt) {
 339   if (e->should_commit()) {
 340     log_develop_trace(continuations)("JFR event: iframes: %d size: %d", _e_num_interpreted_frames, _e_size);
 341     e->set_carrierThread(JFR_JVM_THREAD_ID(jt));
 342     e->set_continuationClass(continuation->klass());
 343     e->set_interpretedFrames(_e_num_interpreted_frames);
 344     e->set_size(_e_size);
 345     e->commit();
 346   }
 347 }
 348 #endif // CONT_JFR
 349 
 350 /////////////// FREEZE ////
 351 
 352 class FreezeBase : public StackObj {
 353 protected:
 354   JavaThread* const _thread;
 355   ContinuationWrapper& _cont;
 356   bool _barriers; // only set when we allocate a chunk
 357   const bool _preempt; // used only on the slow path
 358   const intptr_t * const _frame_sp; // Top frame sp for this freeze
 359 
 360   intptr_t* _bottom_address;
 361 
 362   int _freeze_size; // total size of all frames plus metadata in words.
 363   int _total_align_size;
 364 
 365   intptr_t* _cont_stack_top;
 366   intptr_t* _cont_stack_bottom;
 367 
 368   CONT_JFR_ONLY(FreezeThawJfrInfo _jfr_info;)
 369 
 370 #ifdef ASSERT
 371   intptr_t* _orig_chunk_sp;
 372   int _fast_freeze_size;
 373   bool _empty;
 374 #endif
 375 
 376   JvmtiSampledObjectAllocEventCollector* _jvmti_event_collector;
 377 
 378   NOT_PRODUCT(int _frames;)
 379   DEBUG_ONLY(intptr_t* _last_write;)
 380 
 381   inline FreezeBase(JavaThread* thread, ContinuationWrapper& cont, intptr_t* sp);
 382 
 383 public:
 384   NOINLINE freeze_result freeze_slow();
 385   void freeze_fast_existing_chunk();
 386 
 387   CONT_JFR_ONLY(FreezeThawJfrInfo& jfr_info() { return _jfr_info; })
 388   void set_jvmti_event_collector(JvmtiSampledObjectAllocEventCollector* jsoaec) { _jvmti_event_collector = jsoaec; }
 389 
 390   inline int size_if_fast_freeze_available();
 391 
 392 #ifdef ASSERT
 393   bool check_valid_fast_path();
 394 #endif
 395 
 396 protected:
 397   inline void init_rest();
 398   void throw_stack_overflow_on_humongous_chunk();
 399 
 400   // fast path
 401   inline void copy_to_chunk(intptr_t* from, intptr_t* to, int size);
 402   inline void unwind_frames();
 403   inline void patch_stack_pd(intptr_t* frame_sp, intptr_t* heap_sp);
 404 
 405   // slow path
 406   virtual stackChunkOop allocate_chunk_slow(size_t stack_size, int argsize_md) = 0;
 407 
 408   int cont_size() { return pointer_delta_as_int(_cont_stack_bottom, _cont_stack_top); }
 409 
 410 private:
 411   // slow path
 412   frame freeze_start_frame();
 413   frame freeze_start_frame_safepoint_stub(frame f);
 414   NOINLINE freeze_result recurse_freeze(frame& f, frame& caller, int callee_argsize, bool callee_interpreted, bool top);
 415   inline frame freeze_start_frame_yield_stub(frame f);
 416   template<typename FKind>
 417   inline freeze_result recurse_freeze_java_frame(const frame& f, frame& caller, int fsize, int argsize);
 418   inline void before_freeze_java_frame(const frame& f, const frame& caller, int fsize, int argsize, bool is_bottom_frame);
 419   inline void after_freeze_java_frame(const frame& hf, bool is_bottom_frame);
 420   freeze_result finalize_freeze(const frame& callee, frame& caller, int argsize);
 421   void patch(const frame& f, frame& hf, const frame& caller, bool is_bottom_frame);
 422   NOINLINE freeze_result recurse_freeze_interpreted_frame(frame& f, frame& caller, int callee_argsize, bool callee_interpreted);
 423   freeze_result recurse_freeze_compiled_frame(frame& f, frame& caller, int callee_argsize, bool callee_interpreted);
 424   NOINLINE freeze_result recurse_freeze_stub_frame(frame& f, frame& caller);
 425   NOINLINE void finish_freeze(const frame& f, const frame& top);
 426 
 427   inline bool stack_overflow();
 428 
 429   static frame sender(const frame& f) { return f.is_interpreted_frame() ? sender<ContinuationHelper::InterpretedFrame>(f)
 430                                                                         : sender<ContinuationHelper::NonInterpretedUnknownFrame>(f); }
 431   template<typename FKind> static inline frame sender(const frame& f);
 432   template<typename FKind> frame new_heap_frame(frame& f, frame& caller);
 433   inline void set_top_frame_metadata_pd(const frame& hf);
 434   inline void patch_pd(frame& callee, const frame& caller);
 435   void adjust_interpreted_frame_unextended_sp(frame& f);
 436   static inline void relativize_interpreted_frame_metadata(const frame& f, const frame& hf);
 437 
 438 protected:
 439   void freeze_fast_copy(stackChunkOop chunk, int chunk_start_sp CONT_JFR_ONLY(COMMA bool chunk_is_allocated));
 440   bool freeze_fast_new_chunk(stackChunkOop chunk);
 441 };
 442 
 443 template <typename ConfigT>
 444 class Freeze : public FreezeBase {
 445 private:
 446   stackChunkOop allocate_chunk(size_t stack_size, int argsize_md);
 447 
 448 public:
 449   inline Freeze(JavaThread* thread, ContinuationWrapper& cont, intptr_t* frame_sp)
 450     : FreezeBase(thread, cont, frame_sp) {}
 451 
 452   freeze_result try_freeze_fast();
 453 
 454 protected:
 455   virtual stackChunkOop allocate_chunk_slow(size_t stack_size, int argsize_md) override { return allocate_chunk(stack_size, argsize_md); }
 456 };
 457 
 458 FreezeBase::FreezeBase(JavaThread* thread, ContinuationWrapper& cont, intptr_t* frame_sp) :
 459     _thread(thread), _cont(cont), _barriers(false), _preempt(false), _frame_sp(frame_sp) {
 460   DEBUG_ONLY(_jvmti_event_collector = nullptr;)
 461 
 462   assert(_thread != nullptr, "");
 463   assert(_thread->last_continuation()->entry_sp() == _cont.entrySP(), "");
 464 
 465   DEBUG_ONLY(_cont.entry()->verify_cookie();)
 466 
 467   assert(!Interpreter::contains(_cont.entryPC()), "");
 468 
 469   _bottom_address = _cont.entrySP() - _cont.entry_frame_extension();
 470 #ifdef _LP64
 471   if (((intptr_t)_bottom_address & 0xf) != 0) {
 472     _bottom_address--;
 473   }
 474   assert(is_aligned(_bottom_address, frame::frame_alignment), "");
 475 #endif
 476 
 477   log_develop_trace(continuations)("bottom_address: " INTPTR_FORMAT " entrySP: " INTPTR_FORMAT " argsize: " PTR_FORMAT,
 478                 p2i(_bottom_address), p2i(_cont.entrySP()), (_cont.entrySP() - _bottom_address) << LogBytesPerWord);
 479   assert(_bottom_address != nullptr, "");
 480   assert(_bottom_address <= _cont.entrySP(), "");
 481   DEBUG_ONLY(_last_write = nullptr;)
 482 
 483   assert(_cont.chunk_invariant(), "");
 484   assert(!Interpreter::contains(_cont.entryPC()), "");
 485 #if !defined(PPC64) || defined(ZERO)
 486   static const int doYield_stub_frame_size = frame::metadata_words;
 487 #else
 488   static const int doYield_stub_frame_size = frame::native_abi_reg_args_size >> LogBytesPerWord;
 489 #endif
 490   assert(SharedRuntime::cont_doYield_stub()->frame_size() == doYield_stub_frame_size, "");
 491 
 492   // properties of the continuation on the stack; all sizes are in words
 493   _cont_stack_top    = frame_sp + doYield_stub_frame_size; // we don't freeze the doYield stub frame
 494   _cont_stack_bottom = _cont.entrySP() + (_cont.argsize() == 0 ? frame::metadata_words_at_top : 0)
 495       - ContinuationHelper::frame_align_words(_cont.argsize()); // see alignment in thaw
 496 
 497   log_develop_trace(continuations)("freeze size: %d argsize: %d top: " INTPTR_FORMAT " bottom: " INTPTR_FORMAT,
 498     cont_size(), _cont.argsize(), p2i(_cont_stack_top), p2i(_cont_stack_bottom));
 499   assert(cont_size() > 0, "");
 500 }
 501 
 502 void FreezeBase::init_rest() { // we want to postpone some initialization after chunk handling
 503   _freeze_size = 0;
 504   _total_align_size = 0;
 505   NOT_PRODUCT(_frames = 0;)
 506 }
 507 
 508 void FreezeBase::copy_to_chunk(intptr_t* from, intptr_t* to, int size) {
 509   stackChunkOop chunk = _cont.tail();
 510   chunk->copy_from_stack_to_chunk(from, to, size);
 511   CONT_JFR_ONLY(_jfr_info.record_size_copied(size);)
 512 
 513 #ifdef ASSERT
 514   if (_last_write != nullptr) {
 515     assert(_last_write == to + size, "Missed a spot: _last_write: " INTPTR_FORMAT " to+size: " INTPTR_FORMAT
 516         " stack_size: %d _last_write offset: " PTR_FORMAT " to+size: " PTR_FORMAT, p2i(_last_write), p2i(to+size),
 517         chunk->stack_size(), _last_write-chunk->start_address(), to+size-chunk->start_address());
 518     _last_write = to;
 519   }
 520 #endif
 521 }
 522 
 523 // Called _after_ the last possible safepoint during the freeze operation (chunk allocation)
 524 void FreezeBase::unwind_frames() {
 525   ContinuationEntry* entry = _cont.entry();
 526   entry->flush_stack_processing(_thread);
 527   set_anchor_to_entry(_thread, entry);
 528 }
 529 
 530 template <typename ConfigT>
 531 freeze_result Freeze<ConfigT>::try_freeze_fast() {
 532   assert(_thread->thread_state() == _thread_in_vm, "");
 533   assert(_thread->cont_fastpath(), "");
 534 
 535   DEBUG_ONLY(_fast_freeze_size = size_if_fast_freeze_available();)
 536   assert(_fast_freeze_size == 0, "");
 537 
 538   stackChunkOop chunk = allocate_chunk(cont_size() + frame::metadata_words, _cont.argsize() + frame::metadata_words_at_top);
 539   if (freeze_fast_new_chunk(chunk)) {
 540     return freeze_ok;
 541   }
 542   if (_thread->has_pending_exception()) {
 543     return freeze_exception;
 544   }
 545 
 546   // TODO R REMOVE when deopt change is fixed
 547   assert(!_thread->cont_fastpath() || _barriers, "");
 548   log_develop_trace(continuations)("-- RETRYING SLOW --");
 549   return freeze_slow();
 550 }
 551 
 552 // Returns size needed if the continuation fits, otherwise 0.
 553 int FreezeBase::size_if_fast_freeze_available() {
 554   stackChunkOop chunk = _cont.tail();
 555   if (chunk == nullptr || chunk->is_gc_mode() || chunk->requires_barriers() || chunk->has_mixed_frames()) {
 556     log_develop_trace(continuations)("chunk available %s", chunk == nullptr ? "no chunk" : "chunk requires barriers");
 557     return 0;
 558   }
 559 
 560   int total_size_needed = cont_size();
 561   const int chunk_sp = chunk->sp();
 562 
 563   // argsize can be nonzero if we have a caller, but the caller could be in a non-empty parent chunk,
 564   // so we subtract it only if we overlap with the caller, i.e. the current chunk isn't empty.
 565   // Consider leaving the chunk's argsize set when emptying it and removing the following branch,
 566   // although that would require changing stackChunkOopDesc::is_empty
 567   if (!chunk->is_empty()) {
 568     total_size_needed -= _cont.argsize() + frame::metadata_words_at_top;
 569   }
 570 
 571   int chunk_free_room = chunk_sp - frame::metadata_words_at_bottom;
 572   bool available = chunk_free_room >= total_size_needed;
 573   log_develop_trace(continuations)("chunk available: %s size: %d argsize: %d top: " INTPTR_FORMAT " bottom: " INTPTR_FORMAT,
 574     available ? "yes" : "no" , total_size_needed, _cont.argsize(), p2i(_cont_stack_top), p2i(_cont_stack_bottom));
 575   return available ? total_size_needed : 0;
 576 }
 577 
 578 void FreezeBase::freeze_fast_existing_chunk() {
 579   stackChunkOop chunk = _cont.tail();
 580 
 581   DEBUG_ONLY(_fast_freeze_size = size_if_fast_freeze_available();)
 582   assert(_fast_freeze_size > 0, "");
 583 
 584   if (!chunk->is_empty()) { // we are copying into a non-empty chunk
 585     DEBUG_ONLY(_empty = false;)
 586     DEBUG_ONLY(_orig_chunk_sp = chunk->sp_address();)
 587 #ifdef ASSERT
 588     {
 589       intptr_t* retaddr_slot = (chunk->sp_address()
 590                                 - frame::sender_sp_ret_address_offset());
 591       assert(ContinuationHelper::return_address_at(retaddr_slot) == chunk->pc(),
 592              "unexpected saved return address");
 593     }
 594 #endif
 595 
 596     // the chunk's sp before the freeze, adjusted to point beyond the stack-passed arguments in the topmost frame
 597     // we overlap; we'll overwrite the chunk's top frame's callee arguments
 598     const int chunk_start_sp = chunk->sp() + _cont.argsize() + frame::metadata_words_at_top;
 599     assert(chunk_start_sp <= chunk->stack_size(), "sp not pointing into stack");
 600 
 601     // increase max_size by what we're freezing minus the overlap
 602     chunk->set_max_thawing_size(chunk->max_thawing_size() + cont_size() - _cont.argsize() - frame::metadata_words_at_top);
 603 
 604     intptr_t* const bottom_sp = _cont_stack_bottom - _cont.argsize() - frame::metadata_words_at_top;
 605     assert(bottom_sp == _bottom_address, "");
 606     // Because the chunk isn't empty, we know there's a caller in the chunk, therefore the bottom-most frame
 607     // should have a return barrier (installed back when we thawed it).
 608 #ifdef ASSERT
 609     {
 610       intptr_t* retaddr_slot = (bottom_sp
 611                                 - frame::sender_sp_ret_address_offset());
 612       assert(ContinuationHelper::return_address_at(retaddr_slot)
 613              == StubRoutines::cont_returnBarrier(),
 614              "should be the continuation return barrier");
 615     }
 616 #endif
 617     // We copy the fp from the chunk back to the stack because it contains some caller data,
 618     // including, possibly, an oop that might have gone stale since we thawed.
 619     patch_stack_pd(bottom_sp, chunk->sp_address());
 620     // we don't patch the return pc at this time, so as not to make the stack unwalkable for async walks
 621 
 622     freeze_fast_copy(chunk, chunk_start_sp CONT_JFR_ONLY(COMMA false));
 623   } else { // the chunk is empty
 624     const int chunk_start_sp = chunk->stack_size();
 625 
 626     DEBUG_ONLY(_empty = true;)
 627     DEBUG_ONLY(_orig_chunk_sp = chunk->start_address() + chunk_start_sp;)
 628 
 629     chunk->set_max_thawing_size(cont_size());
 630     chunk->set_bottom(chunk_start_sp - _cont.argsize() - frame::metadata_words_at_top);
 631     chunk->set_sp(chunk->bottom());
 632 
 633     freeze_fast_copy(chunk, chunk_start_sp CONT_JFR_ONLY(COMMA false));
 634   }
 635 }
 636 
 637 bool FreezeBase::freeze_fast_new_chunk(stackChunkOop chunk) {
 638   DEBUG_ONLY(_empty = true;)
 639 
 640   // Install new chunk
 641   _cont.set_tail(chunk);
 642 
 643   if (UNLIKELY(chunk == nullptr || !_thread->cont_fastpath() || _barriers)) { // OOME/probably humongous
 644     log_develop_trace(continuations)("Retrying slow. Barriers: %d", _barriers);
 645     return false;
 646   }
 647 
 648   chunk->set_max_thawing_size(cont_size());
 649 
 650   // in a fresh chunk, we freeze *with* the bottom-most frame's stack arguments.
 651   // They'll then be stored twice: in the chunk and in the parent chunk's top frame
 652   const int chunk_start_sp = cont_size() + frame::metadata_words;
 653   assert(chunk_start_sp == chunk->stack_size(), "");
 654 
 655   DEBUG_ONLY(_orig_chunk_sp = chunk->start_address() + chunk_start_sp;)
 656 
 657   freeze_fast_copy(chunk, chunk_start_sp CONT_JFR_ONLY(COMMA true));
 658 
 659   return true;
 660 }
 661 
 662 void FreezeBase::freeze_fast_copy(stackChunkOop chunk, int chunk_start_sp CONT_JFR_ONLY(COMMA bool chunk_is_allocated)) {
 663   assert(chunk != nullptr, "");
 664   assert(!chunk->has_mixed_frames(), "");
 665   assert(!chunk->is_gc_mode(), "");
 666   assert(!chunk->has_bitmap(), "");
 667   assert(!chunk->requires_barriers(), "");
 668   assert(chunk == _cont.tail(), "");
 669 
 670   // We unwind frames after the last safepoint so that the GC will have found the oops in the frames, but before
 671   // writing into the chunk. This is so that an asynchronous stack walk (not at a safepoint) that suspends us here
 672   // will either see no continuation on the stack, or a consistent chunk.
 673   unwind_frames();
 674 
 675   log_develop_trace(continuations)("freeze_fast start: chunk " INTPTR_FORMAT " size: %d orig sp: %d argsize: %d",
 676     p2i((oopDesc*)chunk), chunk->stack_size(), chunk_start_sp, _cont.argsize());
 677   assert(chunk_start_sp <= chunk->stack_size(), "");
 678   assert(chunk_start_sp >= cont_size(), "no room in the chunk");
 679 
 680   const int chunk_new_sp = chunk_start_sp - cont_size(); // the chunk's new sp, after freeze
 681   assert(!(_fast_freeze_size > 0) || _orig_chunk_sp - (chunk->start_address() + chunk_new_sp) == _fast_freeze_size, "");
 682 
 683   intptr_t* chunk_top = chunk->start_address() + chunk_new_sp;
 684 #ifdef ASSERT
 685   if (!_empty) {
 686     intptr_t* retaddr_slot = (_orig_chunk_sp
 687                               - frame::sender_sp_ret_address_offset());
 688     assert(ContinuationHelper::return_address_at(retaddr_slot) == chunk->pc(),
 689            "unexpected saved return address");
 690   }
 691 #endif
 692 
 693   log_develop_trace(continuations)("freeze_fast start: " INTPTR_FORMAT " sp: %d chunk_top: " INTPTR_FORMAT,
 694                               p2i(chunk->start_address()), chunk_new_sp, p2i(chunk_top));
 695   intptr_t* from = _cont_stack_top - frame::metadata_words_at_bottom;
 696   intptr_t* to   = chunk_top - frame::metadata_words_at_bottom;
 697   copy_to_chunk(from, to, cont_size() + frame::metadata_words_at_bottom);
 698   // Because we're not patched yet, the chunk is now in a bad state
 699 
 700   // patch return pc of the bottom-most frozen frame (now in the chunk)
 701   // with the actual caller's return address
 702   intptr_t* chunk_bottom_retaddr_slot = (chunk_top + cont_size()
 703                                          - _cont.argsize()
 704                                          - frame::metadata_words_at_top
 705                                          - frame::sender_sp_ret_address_offset());
 706 #ifdef ASSERT
 707   if (!_empty) {
 708     assert(ContinuationHelper::return_address_at(chunk_bottom_retaddr_slot)
 709            == StubRoutines::cont_returnBarrier(),
 710            "should be the continuation return barrier");
 711   }
 712 #endif
 713   ContinuationHelper::patch_return_address_at(chunk_bottom_retaddr_slot,
 714                                               chunk->pc());
 715 
 716   // We're always writing to a young chunk, so the GC can't see it until the next safepoint.
 717   chunk->set_sp(chunk_new_sp);
 718   // set chunk->pc to the return address of the topmost frame in the chunk
 719   chunk->set_pc(ContinuationHelper::return_address_at(
 720                   _cont_stack_top - frame::sender_sp_ret_address_offset()));
 721 
 722   _cont.write();
 723 
 724   log_develop_trace(continuations)("FREEZE CHUNK #" INTPTR_FORMAT " (young)", _cont.hash());
 725   LogTarget(Trace, continuations) lt;
 726   if (lt.develop_is_enabled()) {
 727     LogStream ls(lt);
 728     chunk->print_on(true, &ls);
 729   }
 730 
 731   // Verification
 732   assert(_cont.chunk_invariant(), "");
 733   chunk->verify();
 734 
 735 #if CONT_JFR
 736   EventContinuationFreezeFast e;
 737   if (e.should_commit()) {
 738     e.set_id(cast_from_oop<u8>(chunk));
 739     DEBUG_ONLY(e.set_allocate(chunk_is_allocated);)
 740     e.set_size(cont_size() << LogBytesPerWord);
 741     e.commit();
 742   }
 743 #endif
 744 }
 745 
 746 NOINLINE freeze_result FreezeBase::freeze_slow() {
 747 #ifdef ASSERT
 748   ResourceMark rm;
 749 #endif
 750 
 751   log_develop_trace(continuations)("freeze_slow  #" INTPTR_FORMAT, _cont.hash());
 752   assert(_thread->thread_state() == _thread_in_vm || _thread->thread_state() == _thread_blocked, "");
 753 
 754 #if CONT_JFR
 755   EventContinuationFreezeSlow e;
 756   if (e.should_commit()) {
 757     e.set_id(cast_from_oop<u8>(_cont.continuation()));
 758     e.commit();
 759   }
 760 #endif
 761 
 762   init_rest();
 763 
 764   HandleMark hm(Thread::current());
 765 
 766   frame f = freeze_start_frame();
 767 
 768   LogTarget(Debug, continuations) lt;
 769   if (lt.develop_is_enabled()) {
 770     LogStream ls(lt);
 771     f.print_on(&ls);
 772   }
 773 
 774   frame caller; // the frozen caller in the chunk
 775   freeze_result res = recurse_freeze(f, caller, 0, false, true);
 776 
 777   if (res == freeze_ok) {
 778     finish_freeze(f, caller);
 779     _cont.write();
 780   }
 781 
 782   return res;
 783 }
 784 
 785 frame FreezeBase::freeze_start_frame() {
 786   frame f = _thread->last_frame();
 787   if (LIKELY(!_preempt)) {
 788     return freeze_start_frame_yield_stub(f);
 789   } else {
 790     return freeze_start_frame_safepoint_stub(f);
 791   }
 792 }
 793 
 794 frame FreezeBase::freeze_start_frame_yield_stub(frame f) {
 795   assert(SharedRuntime::cont_doYield_stub()->contains(f.pc()), "must be");
 796   f = sender<ContinuationHelper::NonInterpretedUnknownFrame>(f);
 797   assert(Continuation::is_frame_in_continuation(_thread->last_continuation(), f), "");
 798   return f;
 799 }
 800 
 801 frame FreezeBase::freeze_start_frame_safepoint_stub(frame f) {
 802 #if (defined(X86) || defined(AARCH64) || defined(RISCV64)) && !defined(ZERO)
 803   f.set_fp(f.real_fp()); // f.set_fp(*Frame::callee_link_address(f)); // ????
 804 #else
 805   Unimplemented();
 806 #endif
 807   if (!Interpreter::contains(f.pc())) {
 808     assert(ContinuationHelper::Frame::is_stub(f.cb()), "must be");
 809     assert(f.oop_map() != nullptr, "must be");
 810 
 811     if (Interpreter::contains(ContinuationHelper::StubFrame::return_pc(f))) {
 812       f = sender<ContinuationHelper::StubFrame>(f); // Safepoint stub in interpreter
 813     }
 814   }
 815   assert(Continuation::is_frame_in_continuation(_thread->last_continuation(), f), "");
 816   return f;
 817 }
 818 
 819 // The parameter callee_argsize includes metadata that has to be part of caller/callee overlap.
 820 NOINLINE freeze_result FreezeBase::recurse_freeze(frame& f, frame& caller, int callee_argsize, bool callee_interpreted, bool top) {
 821   assert(f.unextended_sp() < _bottom_address, ""); // see recurse_freeze_java_frame
 822   assert(f.is_interpreted_frame() || ((top && _preempt) == ContinuationHelper::Frame::is_stub(f.cb())), "");
 823 
 824   if (stack_overflow()) {
 825     return freeze_exception;
 826   }
 827 
 828   if (f.is_compiled_frame()) {
 829     if (UNLIKELY(f.oop_map() == nullptr)) {
 830       // special native frame
 831       return freeze_pinned_native;
 832     }
 833     return recurse_freeze_compiled_frame(f, caller, callee_argsize, callee_interpreted);
 834   } else if (f.is_interpreted_frame()) {
 835     assert((_preempt && top) || !f.interpreter_frame_method()->is_native(), "");
 836     if (_preempt && top && f.interpreter_frame_method()->is_native()) {
 837       // int native entry
 838       return freeze_pinned_native;
 839     }
 840 
 841     return recurse_freeze_interpreted_frame(f, caller, callee_argsize, callee_interpreted);
 842   } else if (_preempt && top && ContinuationHelper::Frame::is_stub(f.cb())) {
 843     return recurse_freeze_stub_frame(f, caller);
 844   } else {
 845     return freeze_pinned_native;
 846   }
 847 }
 848 
 849 // The parameter callee_argsize includes metadata that has to be part of caller/callee overlap.
 850 // See also StackChunkFrameStream<frame_kind>::frame_size()
 851 template<typename FKind>
 852 inline freeze_result FreezeBase::recurse_freeze_java_frame(const frame& f, frame& caller, int fsize, int argsize) {
 853   assert(FKind::is_instance(f), "");
 854 
 855   assert(fsize > 0, "");
 856   assert(argsize >= 0, "");
 857   _freeze_size += fsize;
 858   NOT_PRODUCT(_frames++;)
 859 
 860   assert(FKind::frame_bottom(f) <= _bottom_address, "");
 861 
 862   // We don't use FKind::frame_bottom(f) == _bottom_address because on x64 there's sometimes an extra word between
 863   // enterSpecial and an interpreted frame
 864   if (FKind::frame_bottom(f) >= _bottom_address - 1) {
 865     return finalize_freeze(f, caller, argsize); // recursion end
 866   } else {
 867     frame senderf = sender<FKind>(f);
 868     assert(FKind::interpreted || senderf.sp() == senderf.unextended_sp(), "");
 869     freeze_result result = recurse_freeze(senderf, caller, argsize, FKind::interpreted, false); // recursive call
 870     return result;
 871   }
 872 }
 873 
 874 inline void FreezeBase::before_freeze_java_frame(const frame& f, const frame& caller, int fsize, int argsize, bool is_bottom_frame) {
 875   LogTarget(Trace, continuations) lt;
 876   if (lt.develop_is_enabled()) {
 877     LogStream ls(lt);
 878     ls.print_cr("======== FREEZING FRAME interpreted: %d bottom: %d", f.is_interpreted_frame(), is_bottom_frame);
 879     ls.print_cr("fsize: %d argsize: %d", fsize, argsize);
 880     f.print_value_on(&ls, nullptr);
 881   }
 882   assert(caller.is_interpreted_frame() == Interpreter::contains(caller.pc()), "");
 883 }
 884 
 885 inline void FreezeBase::after_freeze_java_frame(const frame& hf, bool is_bottom_frame) {
 886   LogTarget(Trace, continuations) lt;
 887   if (lt.develop_is_enabled()) {
 888     LogStream ls(lt);
 889     DEBUG_ONLY(hf.print_value_on(&ls, nullptr);)
 890     assert(hf.is_heap_frame(), "should be");
 891     DEBUG_ONLY(print_frame_layout(hf, false, &ls);)
 892     if (is_bottom_frame) {
 893       ls.print_cr("bottom h-frame:");
 894       hf.print_on(&ls);
 895     }
 896   }
 897 }
 898 
 899 // The parameter argsize_md includes metadata that has to be part of caller/callee overlap.
 900 // See also StackChunkFrameStream<frame_kind>::frame_size()
 901 freeze_result FreezeBase::finalize_freeze(const frame& callee, frame& caller, int argsize_md) {
 902   int argsize = argsize_md - frame::metadata_words_at_top;
 903   assert(callee.is_interpreted_frame()
 904     || callee.cb()->as_nmethod()->is_osr_method()
 905     || argsize == _cont.argsize(), "argsize: %d cont.argsize: %d", argsize, _cont.argsize());
 906   log_develop_trace(continuations)("bottom: " INTPTR_FORMAT " count %d size: %d argsize: %d",
 907     p2i(_bottom_address), _frames, _freeze_size << LogBytesPerWord, argsize);
 908 
 909   LogTarget(Trace, continuations) lt;
 910 
 911 #ifdef ASSERT
 912   bool empty = _cont.is_empty();
 913   log_develop_trace(continuations)("empty: %d", empty);
 914 #endif
 915 
 916   stackChunkOop chunk = _cont.tail();
 917 
 918   assert(chunk == nullptr || (chunk->max_thawing_size() == 0) == chunk->is_empty(), "");
 919 
 920   _freeze_size += frame::metadata_words; // for top frame's metadata
 921 
 922   int overlap = 0; // the args overlap the caller -- if there is one in this chunk and is of the same kind
 923   int unextended_sp = -1;
 924   if (chunk != nullptr) {
 925     if (!chunk->is_empty()) {
 926       StackChunkFrameStream<ChunkFrames::Mixed> last(chunk);
 927       unextended_sp = chunk->to_offset(StackChunkFrameStream<ChunkFrames::Mixed>(chunk).unextended_sp());
 928       bool top_interpreted = Interpreter::contains(chunk->pc());
 929       if (callee.is_interpreted_frame() == top_interpreted) {
 930         overlap = argsize_md;
 931       }
 932     } else {
 933       unextended_sp = chunk->stack_size() - frame::metadata_words_at_top;
 934     }
 935   }
 936 
 937   log_develop_trace(continuations)("finalize _size: %d overlap: %d unextended_sp: %d", _freeze_size, overlap, unextended_sp);
 938 
 939   _freeze_size -= overlap;
 940   assert(_freeze_size >= 0, "");
 941 
 942   assert(chunk == nullptr || chunk->is_empty()
 943           || unextended_sp == chunk->to_offset(StackChunkFrameStream<ChunkFrames::Mixed>(chunk).unextended_sp()), "");
 944   assert(chunk != nullptr || unextended_sp < _freeze_size, "");
 945 
 946   // _barriers can be set to true by an allocation in freeze_fast, in which case the chunk is available
 947   bool allocated_old_in_freeze_fast = _barriers;
 948   assert(!allocated_old_in_freeze_fast || (unextended_sp >= _freeze_size && chunk->is_empty()),
 949     "Chunk allocated in freeze_fast is of insufficient size "
 950     "unextended_sp: %d size: %d is_empty: %d", unextended_sp, _freeze_size, chunk->is_empty());
 951   assert(!allocated_old_in_freeze_fast || (!UseZGC && !UseG1GC), "Unexpected allocation");
 952 
 953   DEBUG_ONLY(bool empty_chunk = true);
 954   if (unextended_sp < _freeze_size || chunk->is_gc_mode() || (!allocated_old_in_freeze_fast && chunk->requires_barriers())) {
 955     // ALLOCATE NEW CHUNK
 956 
 957     if (lt.develop_is_enabled()) {
 958       LogStream ls(lt);
 959       if (chunk == nullptr) {
 960         ls.print_cr("no chunk");
 961       } else {
 962         ls.print_cr("chunk barriers: %d _size: %d free size: %d",
 963           chunk->requires_barriers(), _freeze_size, chunk->sp() - frame::metadata_words);
 964         chunk->print_on(&ls);
 965       }
 966     }
 967 
 968     _freeze_size += overlap; // we're allocating a new chunk, so no overlap
 969     // overlap = 0;
 970 
 971     chunk = allocate_chunk_slow(_freeze_size, argsize_md);
 972     if (chunk == nullptr) {
 973       return freeze_exception;
 974     }
 975 
 976     // Install new chunk
 977     _cont.set_tail(chunk);
 978     assert(chunk->is_empty(), "");
 979   } else {
 980     // REUSE EXISTING CHUNK
 981     log_develop_trace(continuations)("Reusing chunk mixed: %d empty: %d", chunk->has_mixed_frames(), chunk->is_empty());
 982     if (chunk->is_empty()) {
 983       int sp = chunk->stack_size() - argsize_md;
 984       chunk->set_sp(sp);
 985       chunk->set_bottom(sp);
 986       _freeze_size += overlap;
 987       assert(chunk->max_thawing_size() == 0, "");
 988     } DEBUG_ONLY(else empty_chunk = false;)
 989   }
 990   assert(!chunk->is_gc_mode(), "");
 991   assert(!chunk->has_bitmap(), "");
 992   chunk->set_has_mixed_frames(true);
 993 
 994   assert(chunk->requires_barriers() == _barriers, "");
 995   assert(!_barriers || chunk->is_empty(), "");
 996 
 997   assert(!chunk->is_empty() || StackChunkFrameStream<ChunkFrames::Mixed>(chunk).is_done(), "");
 998   assert(!chunk->is_empty() || StackChunkFrameStream<ChunkFrames::Mixed>(chunk).to_frame().is_empty(), "");
 999 
1000   // We unwind frames after the last safepoint so that the GC will have found the oops in the frames, but before
1001   // writing into the chunk. This is so that an asynchronous stack walk (not at a safepoint) that suspends us here
1002   // will either see no continuation or a consistent chunk.
1003   unwind_frames();
1004 
1005   chunk->set_max_thawing_size(chunk->max_thawing_size() + _freeze_size - frame::metadata_words);
1006 
1007   if (lt.develop_is_enabled()) {
1008     LogStream ls(lt);
1009     ls.print_cr("top chunk:");
1010     chunk->print_on(&ls);
1011   }
1012 
1013   // The topmost existing frame in the chunk; or an empty frame if the chunk is empty
1014   caller = StackChunkFrameStream<ChunkFrames::Mixed>(chunk).to_frame();
1015 
1016   DEBUG_ONLY(_last_write = caller.unextended_sp() + (empty_chunk ? argsize_md : overlap);)
1017 
1018   assert(chunk->is_in_chunk(_last_write - _freeze_size),
1019     "last_write-size: " INTPTR_FORMAT " start: " INTPTR_FORMAT, p2i(_last_write-_freeze_size), p2i(chunk->start_address()));
1020 #ifdef ASSERT
1021   if (lt.develop_is_enabled()) {
1022     LogStream ls(lt);
1023     ls.print_cr("top hframe before (freeze):");
1024     assert(caller.is_heap_frame(), "should be");
1025     caller.print_on(&ls);
1026   }
1027 
1028   assert(!empty || Continuation::is_continuation_entry_frame(callee, nullptr), "");
1029 
1030   frame entry = sender(callee);
1031 
1032   assert(Continuation::is_return_barrier_entry(entry.pc()) || Continuation::is_continuation_enterSpecial(entry), "");
1033   assert(callee.is_interpreted_frame() || entry.sp() == entry.unextended_sp(), "");
1034 #endif
1035 
1036   return freeze_ok_bottom;
1037 }
1038 
1039 void FreezeBase::patch(const frame& f, frame& hf, const frame& caller, bool is_bottom_frame) {
1040   if (is_bottom_frame) {
1041     // If we're the bottom frame, we need to replace the return barrier with the real
1042     // caller's pc.
1043     address last_pc = caller.pc();
1044     assert((last_pc == nullptr) == _cont.tail()->is_empty(), "");
1045     ContinuationHelper::Frame::patch_pc(caller, last_pc);
1046   } else {
1047     assert(!caller.is_empty(), "");
1048   }
1049 
1050   patch_pd(hf, caller);
1051 
1052   if (f.is_interpreted_frame()) {
1053     assert(hf.is_heap_frame(), "should be");
1054     ContinuationHelper::InterpretedFrame::patch_sender_sp(hf, caller);
1055   }
1056 
1057 #ifdef ASSERT
1058   if (hf.is_compiled_frame()) {
1059     if (f.is_deoptimized_frame()) { // TODO DEOPT: long term solution: unroll on freeze and patch pc
1060       log_develop_trace(continuations)("Freezing deoptimized frame");
1061       assert(f.cb()->as_nmethod()->is_deopt_pc(f.raw_pc()), "");
1062       assert(f.cb()->as_nmethod()->is_deopt_pc(ContinuationHelper::Frame::real_pc(f)), "");
1063     }
1064   }
1065 #endif
1066 }
1067 
1068 #ifdef ASSERT
1069 static void verify_frame_top(const frame& f, intptr_t* top) {
1070   ResourceMark rm;
1071   InterpreterOopMap mask;
1072   f.interpreted_frame_oop_map(&mask);
1073   assert(top <= ContinuationHelper::InterpretedFrame::frame_top(f, &mask),
1074          "frame_top: " INTPTR_FORMAT " Interpreted::frame_top: " INTPTR_FORMAT,
1075            p2i(top), p2i(ContinuationHelper::InterpretedFrame::frame_top(f, &mask)));
1076 }
1077 #endif // ASSERT
1078 
1079 // The parameter callee_argsize includes metadata that has to be part of caller/callee overlap.
1080 // See also StackChunkFrameStream<frame_kind>::frame_size()
1081 NOINLINE freeze_result FreezeBase::recurse_freeze_interpreted_frame(frame& f, frame& caller,
1082                                                                     int callee_argsize /* incl. metadata */,
1083                                                                     bool callee_interpreted) {
1084   adjust_interpreted_frame_unextended_sp(f);
1085 
1086   // The frame's top never includes the stack arguments to the callee
1087   intptr_t* const stack_frame_top = ContinuationHelper::InterpretedFrame::frame_top(f, callee_argsize, callee_interpreted);
1088   intptr_t* const stack_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(f);
1089   const int fsize = pointer_delta_as_int(stack_frame_bottom, stack_frame_top);
1090 
1091   DEBUG_ONLY(verify_frame_top(f, stack_frame_top));
1092 
1093   Method* frame_method = ContinuationHelper::Frame::frame_method(f);
1094   // including metadata between f and its args
1095   const int argsize = ContinuationHelper::InterpretedFrame::stack_argsize(f) + frame::metadata_words_at_top;
1096 
1097   log_develop_trace(continuations)("recurse_freeze_interpreted_frame %s _size: %d fsize: %d argsize: %d",
1098     frame_method->name_and_sig_as_C_string(), _freeze_size, fsize, argsize);
1099   // we'd rather not yield inside methods annotated with @JvmtiMountTransition
1100   assert(!ContinuationHelper::Frame::frame_method(f)->jvmti_mount_transition(), "");
1101 
1102   freeze_result result = recurse_freeze_java_frame<ContinuationHelper::InterpretedFrame>(f, caller, fsize, argsize);
1103   if (UNLIKELY(result > freeze_ok_bottom)) {
1104     return result;
1105   }
1106 
1107   bool is_bottom_frame = result == freeze_ok_bottom;
1108   assert(!caller.is_empty() || is_bottom_frame, "");
1109 
1110   DEBUG_ONLY(before_freeze_java_frame(f, caller, fsize, 0, is_bottom_frame);)
1111 
1112   frame hf = new_heap_frame<ContinuationHelper::InterpretedFrame>(f, caller);
1113   _total_align_size += frame::align_wiggle; // add alignment room for internal interpreted frame alignment on AArch64/PPC64
1114 
1115   intptr_t* heap_frame_top = ContinuationHelper::InterpretedFrame::frame_top(hf, callee_argsize, callee_interpreted);
1116   intptr_t* heap_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(hf);
1117   assert(heap_frame_bottom == heap_frame_top + fsize, "");
1118 
1119   // Some architectures (like AArch64/PPC64/RISC-V) add padding between the locals and the fixed_frame to keep the fp 16-byte-aligned.
1120   // On those architectures we freeze the padding in order to keep the same fp-relative offsets in the fixed_frame.
1121   copy_to_chunk(stack_frame_top, heap_frame_top, fsize);
1122   assert(!is_bottom_frame || !caller.is_interpreted_frame() || (heap_frame_top + fsize) == (caller.unextended_sp() + argsize), "");
1123 
1124   relativize_interpreted_frame_metadata(f, hf);
1125 
1126   patch(f, hf, caller, is_bottom_frame);
1127 
1128   CONT_JFR_ONLY(_jfr_info.record_interpreted_frame();)
1129   DEBUG_ONLY(after_freeze_java_frame(hf, is_bottom_frame);)
1130   caller = hf;
1131 
1132   // Mark frame_method's GC epoch for class redefinition on_stack calculation.
1133   frame_method->record_gc_epoch();
1134 
1135   return freeze_ok;
1136 }
1137 
1138 // The parameter callee_argsize includes metadata that has to be part of caller/callee overlap.
1139 // See also StackChunkFrameStream<frame_kind>::frame_size()
1140 freeze_result FreezeBase::recurse_freeze_compiled_frame(frame& f, frame& caller,
1141                                                         int callee_argsize /* incl. metadata */,
1142                                                         bool callee_interpreted) {
1143   // The frame's top never includes the stack arguments to the callee
1144   intptr_t* const stack_frame_top = ContinuationHelper::CompiledFrame::frame_top(f, callee_argsize, callee_interpreted);
1145   intptr_t* const stack_frame_bottom = ContinuationHelper::CompiledFrame::frame_bottom(f);
1146   // including metadata between f and its stackargs
1147   const int argsize = ContinuationHelper::CompiledFrame::stack_argsize(f) + frame::metadata_words_at_top;
1148   const int fsize = pointer_delta_as_int(stack_frame_bottom + argsize, stack_frame_top);
1149 
1150   log_develop_trace(continuations)("recurse_freeze_compiled_frame %s _size: %d fsize: %d argsize: %d",
1151                              ContinuationHelper::Frame::frame_method(f) != nullptr ?
1152                              ContinuationHelper::Frame::frame_method(f)->name_and_sig_as_C_string() : "",
1153                              _freeze_size, fsize, argsize);
1154   // we'd rather not yield inside methods annotated with @JvmtiMountTransition
1155   assert(!ContinuationHelper::Frame::frame_method(f)->jvmti_mount_transition(), "");
1156 
1157   freeze_result result = recurse_freeze_java_frame<ContinuationHelper::CompiledFrame>(f, caller, fsize, argsize);
1158   if (UNLIKELY(result > freeze_ok_bottom)) {
1159     return result;
1160   }
1161 
1162   bool is_bottom_frame = result == freeze_ok_bottom;
1163   assert(!caller.is_empty() || is_bottom_frame, "");
1164 
1165   DEBUG_ONLY(before_freeze_java_frame(f, caller, fsize, argsize, is_bottom_frame);)
1166 
1167   frame hf = new_heap_frame<ContinuationHelper::CompiledFrame>(f, caller);
1168 
1169   intptr_t* heap_frame_top = ContinuationHelper::CompiledFrame::frame_top(hf, callee_argsize, callee_interpreted);
1170 
1171   copy_to_chunk(stack_frame_top, heap_frame_top, fsize);
1172   assert(!is_bottom_frame || !caller.is_compiled_frame() || (heap_frame_top + fsize) == (caller.unextended_sp() + argsize), "");
1173 
1174   if (caller.is_interpreted_frame()) {
1175     _total_align_size += frame::align_wiggle; // See Thaw::align
1176   }
1177 
1178   patch(f, hf, caller, is_bottom_frame);
1179 
1180   assert(is_bottom_frame || Interpreter::contains(ContinuationHelper::CompiledFrame::real_pc(caller)) == caller.is_interpreted_frame(), "");
1181 
1182   DEBUG_ONLY(after_freeze_java_frame(hf, is_bottom_frame);)
1183   caller = hf;
1184   return freeze_ok;
1185 }
1186 
1187 NOINLINE freeze_result FreezeBase::recurse_freeze_stub_frame(frame& f, frame& caller) {
1188   intptr_t* const stack_frame_top = ContinuationHelper::StubFrame::frame_top(f, 0, 0);
1189   const int fsize = f.cb()->frame_size();
1190 
1191   log_develop_trace(continuations)("recurse_freeze_stub_frame %s _size: %d fsize: %d :: " INTPTR_FORMAT " - " INTPTR_FORMAT,
1192     f.cb()->name(), _freeze_size, fsize, p2i(stack_frame_top), p2i(stack_frame_top+fsize));
1193 
1194   // recurse_freeze_java_frame and freeze inlined here because we need to use a full RegisterMap for lock ownership
1195   NOT_PRODUCT(_frames++;)
1196   _freeze_size += fsize;
1197 
1198   RegisterMap map(_cont.thread(),
1199                   RegisterMap::UpdateMap::include,
1200                   RegisterMap::ProcessFrames::skip,
1201                   RegisterMap::WalkContinuation::skip);
1202   map.set_include_argument_oops(false);
1203   ContinuationHelper::update_register_map<ContinuationHelper::StubFrame>(f, &map);
1204   f.oop_map()->update_register_map(&f, &map); // we have callee-save registers in this case
1205   frame senderf = sender<ContinuationHelper::StubFrame>(f);
1206   assert(senderf.unextended_sp() < _bottom_address - 1, "");
1207   assert(senderf.is_compiled_frame(), "");
1208 
1209   if (UNLIKELY(senderf.oop_map() == nullptr)) {
1210     // native frame
1211     return freeze_pinned_native;
1212   }
1213 
1214   freeze_result result = recurse_freeze_compiled_frame(senderf, caller, 0, 0); // This might be deoptimized
1215   if (UNLIKELY(result > freeze_ok_bottom)) {
1216     return result;
1217   }
1218   assert(result != freeze_ok_bottom, "");
1219   assert(!caller.is_interpreted_frame(), "");
1220 
1221   DEBUG_ONLY(before_freeze_java_frame(f, caller, fsize, 0, false);)
1222   frame hf = new_heap_frame<ContinuationHelper::StubFrame>(f, caller);
1223   intptr_t* heap_frame_top = ContinuationHelper::StubFrame::frame_top(hf, 0, 0);
1224   copy_to_chunk(stack_frame_top, heap_frame_top, fsize);
1225   DEBUG_ONLY(after_freeze_java_frame(hf, false);)
1226 
1227   caller = hf;
1228   return freeze_ok;
1229 }
1230 
1231 NOINLINE void FreezeBase::finish_freeze(const frame& f, const frame& top) {
1232   stackChunkOop chunk = _cont.tail();
1233 
1234   LogTarget(Trace, continuations) lt;
1235   if (lt.develop_is_enabled()) {
1236     LogStream ls(lt);
1237     assert(top.is_heap_frame(), "should be");
1238     top.print_on(&ls);
1239   }
1240 
1241   set_top_frame_metadata_pd(top);
1242 
1243   chunk->set_sp(chunk->to_offset(top.sp()));
1244   chunk->set_pc(top.pc());
1245 
1246   chunk->set_max_thawing_size(chunk->max_thawing_size() + _total_align_size);
1247 
1248   // At this point the chunk is consistent
1249 
1250   if (UNLIKELY(_barriers)) {
1251     log_develop_trace(continuations)("do barriers on old chunk");
1252     // Serial and Parallel GC can allocate objects directly into the old generation.
1253     // Then we want to relativize the derived pointers eagerly so that
1254     // old chunks are all in GC mode.
1255     assert(!UseG1GC, "G1 can not deal with allocating outside of eden");
1256     assert(!UseZGC, "ZGC can not deal with allocating chunks visible to marking");
1257     if (UseShenandoahGC) {
1258       _cont.tail()->relativize_derived_pointers_concurrently();
1259     } else {
1260       ContinuationGCSupport::transform_stack_chunk(_cont.tail());
1261     }
1262     // For objects in the old generation we must maintain the remembered set
1263     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>();
1264   }
1265 
1266   log_develop_trace(continuations)("finish_freeze: has_mixed_frames: %d", chunk->has_mixed_frames());
1267   if (lt.develop_is_enabled()) {
1268     LogStream ls(lt);
1269     chunk->print_on(true, &ls);
1270   }
1271 
1272   if (lt.develop_is_enabled()) {
1273     LogStream ls(lt);
1274     ls.print_cr("top hframe after (freeze):");
1275     assert(_cont.last_frame().is_heap_frame(), "should be");
1276     _cont.last_frame().print_on(&ls);
1277   }
1278 
1279   assert(_cont.chunk_invariant(), "");
1280 }
1281 
1282 inline bool FreezeBase::stack_overflow() { // detect stack overflow in recursive native code
1283   JavaThread* t = !_preempt ? _thread : JavaThread::current();
1284   assert(t == JavaThread::current(), "");
1285   if (os::current_stack_pointer() < t->stack_overflow_state()->shadow_zone_safe_limit()) {
1286     if (!_preempt) {
1287       ContinuationWrapper::SafepointOp so(t, _cont); // could also call _cont.done() instead
1288       Exceptions::_throw_msg(t, __FILE__, __LINE__, vmSymbols::java_lang_StackOverflowError(), "Stack overflow while freezing");
1289     }
1290     return true;
1291   }
1292   return false;
1293 }
1294 
1295 class StackChunkAllocator : public MemAllocator {
1296   const size_t                                 _stack_size;
1297   int                                          _argsize_md;
1298   ContinuationWrapper&                         _continuation_wrapper;
1299   JvmtiSampledObjectAllocEventCollector* const _jvmti_event_collector;
1300   mutable bool                                 _took_slow_path;
1301 
1302   // Does the minimal amount of initialization needed for a TLAB allocation.
1303   // We don't need to do a full initialization, as such an allocation need not be immediately walkable.
1304   virtual oop initialize(HeapWord* mem) const override {
1305     assert(_stack_size > 0, "");
1306     assert(_stack_size <= max_jint, "");
1307     assert(_word_size > _stack_size, "");
1308 
1309     // zero out fields (but not the stack)
1310     const size_t hs = oopDesc::header_size();
1311     Copy::fill_to_aligned_words(mem + hs, vmClasses::StackChunk_klass()->size_helper() - hs);
1312 
1313     int bottom = (int)_stack_size - _argsize_md;
1314 
1315     jdk_internal_vm_StackChunk::set_size(mem, (int)_stack_size);
1316     jdk_internal_vm_StackChunk::set_bottom(mem, bottom);
1317     jdk_internal_vm_StackChunk::set_sp(mem, bottom);
1318 
1319     return finish(mem);
1320   }
1321 
1322   stackChunkOop allocate_fast() const {
1323     if (!UseTLAB) {
1324       return nullptr;
1325     }
1326 
1327     HeapWord* const mem = MemAllocator::mem_allocate_inside_tlab_fast();
1328     if (mem == nullptr) {
1329       return nullptr;
1330     }
1331 
1332     oop obj = initialize(mem);
1333     return stackChunkOopDesc::cast(obj);
1334   }
1335 
1336 public:
1337   StackChunkAllocator(Klass* klass,
1338                       size_t word_size,
1339                       Thread* thread,
1340                       size_t stack_size,
1341                       int argsize_md,
1342                       ContinuationWrapper& continuation_wrapper,
1343                       JvmtiSampledObjectAllocEventCollector* jvmti_event_collector)
1344     : MemAllocator(klass, word_size, thread),
1345       _stack_size(stack_size),
1346       _argsize_md(argsize_md),
1347       _continuation_wrapper(continuation_wrapper),
1348       _jvmti_event_collector(jvmti_event_collector),
1349       _took_slow_path(false) {}
1350 
1351   // Provides it's own, specialized allocation which skips instrumentation
1352   // if the memory can be allocated without going to a slow-path.
1353   stackChunkOop allocate() const {
1354     // First try to allocate without any slow-paths or instrumentation.
1355     stackChunkOop obj = allocate_fast();
1356     if (obj != nullptr) {
1357       return obj;
1358     }
1359 
1360     // Now try full-blown allocation with all expensive operations,
1361     // including potentially safepoint operations.
1362     _took_slow_path = true;
1363 
1364     // Protect unhandled Loom oops
1365     ContinuationWrapper::SafepointOp so(_thread, _continuation_wrapper);
1366 
1367     // Can safepoint
1368     _jvmti_event_collector->start();
1369 
1370     // Can safepoint
1371     return stackChunkOopDesc::cast(MemAllocator::allocate());
1372   }
1373 
1374   bool took_slow_path() const {
1375     return _took_slow_path;
1376   }
1377 };
1378 
1379 template <typename ConfigT>
1380 stackChunkOop Freeze<ConfigT>::allocate_chunk(size_t stack_size, int argsize_md) {
1381   log_develop_trace(continuations)("allocate_chunk allocating new chunk");
1382 
1383   InstanceStackChunkKlass* klass = InstanceStackChunkKlass::cast(vmClasses::StackChunk_klass());
1384   size_t size_in_words = klass->instance_size(stack_size);
1385 
1386   if (CollectedHeap::stack_chunk_max_size() > 0 && size_in_words >= CollectedHeap::stack_chunk_max_size()) {
1387     if (!_preempt) {
1388       throw_stack_overflow_on_humongous_chunk();
1389     }
1390     return nullptr;
1391   }
1392 
1393   JavaThread* current = _preempt ? JavaThread::current() : _thread;
1394   assert(current == JavaThread::current(), "should be current");
1395 
1396   // Allocate the chunk.
1397   //
1398   // This might safepoint while allocating, but all safepointing due to
1399   // instrumentation have been deferred. This property is important for
1400   // some GCs, as this ensures that the allocated object is in the young
1401   // generation / newly allocated memory.
1402   StackChunkAllocator allocator(klass, size_in_words, current, stack_size, argsize_md, _cont, _jvmti_event_collector);
1403   stackChunkOop chunk = allocator.allocate();
1404 
1405   if (chunk == nullptr) {
1406     return nullptr; // OOME
1407   }
1408 
1409   // assert that chunk is properly initialized
1410   assert(chunk->stack_size() == (int)stack_size, "");
1411   assert(chunk->size() >= stack_size, "chunk->size(): %zu size: %zu", chunk->size(), stack_size);
1412   assert(chunk->sp() == chunk->bottom(), "");
1413   assert((intptr_t)chunk->start_address() % 8 == 0, "");
1414   assert(chunk->max_thawing_size() == 0, "");
1415   assert(chunk->pc() == nullptr, "");
1416   assert(chunk->is_empty(), "");
1417   assert(chunk->flags() == 0, "");
1418   assert(chunk->is_gc_mode() == false, "");
1419 
1420   // fields are uninitialized
1421   chunk->set_parent_access<IS_DEST_UNINITIALIZED>(_cont.last_nonempty_chunk());
1422   chunk->set_cont_access<IS_DEST_UNINITIALIZED>(_cont.continuation());
1423 
1424 #if INCLUDE_ZGC
1425   if (UseZGC) {
1426     if (ZGenerational) {
1427       ZStackChunkGCData::initialize(chunk);
1428     }
1429     assert(!chunk->requires_barriers(), "ZGC always allocates in the young generation");
1430     _barriers = false;
1431   } else
1432 #endif
1433 #if INCLUDE_SHENANDOAHGC
1434   if (UseShenandoahGC) {
1435     _barriers = chunk->requires_barriers();
1436   } else
1437 #endif
1438   {
1439     if (!allocator.took_slow_path()) {
1440       // Guaranteed to be in young gen / newly allocated memory
1441       assert(!chunk->requires_barriers(), "Unfamiliar GC requires barriers on TLAB allocation");
1442       _barriers = false;
1443     } else {
1444       // Some GCs could put direct allocations in old gen for slow-path
1445       // allocations; need to explicitly check if that was the case.
1446       _barriers = chunk->requires_barriers();
1447     }
1448   }
1449 
1450   if (_barriers) {
1451     log_develop_trace(continuations)("allocation requires barriers");
1452   }
1453 
1454   assert(chunk->parent() == nullptr || chunk->parent()->is_stackChunk(), "");
1455 
1456   return chunk;
1457 }
1458 
1459 void FreezeBase::throw_stack_overflow_on_humongous_chunk() {
1460   ContinuationWrapper::SafepointOp so(_thread, _cont); // could also call _cont.done() instead
1461   Exceptions::_throw_msg(_thread, __FILE__, __LINE__, vmSymbols::java_lang_StackOverflowError(), "Humongous stack chunk");
1462 }
1463 
1464 #if INCLUDE_JVMTI
1465 static int num_java_frames(ContinuationWrapper& cont) {
1466   ResourceMark rm; // used for scope traversal in num_java_frames(nmethod*, address)
1467   int count = 0;
1468   for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
1469     count += chunk->num_java_frames();
1470   }
1471   return count;
1472 }
1473 
1474 static void invalidate_jvmti_stack(JavaThread* thread) {
1475   if (thread->is_interp_only_mode()) {
1476     JvmtiThreadState *state = thread->jvmti_thread_state();
1477     if (state != nullptr)
1478       state->invalidate_cur_stack_depth();
1479   }
1480 }
1481 
1482 static void jvmti_yield_cleanup(JavaThread* thread, ContinuationWrapper& cont) {
1483   if (JvmtiExport::can_post_frame_pop()) {
1484     int num_frames = num_java_frames(cont);
1485 
1486     ContinuationWrapper::SafepointOp so(Thread::current(), cont);
1487     JvmtiExport::continuation_yield_cleanup(JavaThread::current(), num_frames);
1488   }
1489   invalidate_jvmti_stack(thread);
1490 }
1491 #endif // INCLUDE_JVMTI
1492 
1493 #ifdef ASSERT
1494 static bool monitors_on_stack(JavaThread* thread) {
1495   ContinuationEntry* ce = thread->last_continuation();
1496   RegisterMap map(thread,
1497                   RegisterMap::UpdateMap::include,
1498                   RegisterMap::ProcessFrames::include,
1499                   RegisterMap::WalkContinuation::skip);
1500   map.set_include_argument_oops(false);
1501   for (frame f = thread->last_frame(); Continuation::is_frame_in_continuation(ce, f); f = f.sender(&map)) {
1502     if ((f.is_interpreted_frame() && ContinuationHelper::InterpretedFrame::is_owning_locks(f)) ||
1503         (f.is_compiled_frame() && ContinuationHelper::CompiledFrame::is_owning_locks(map.thread(), &map, f))) {
1504       return true;
1505     }
1506   }
1507   return false;
1508 }
1509 
1510 // There are no interpreted frames if we're not called from the interpreter and we haven't ancountered an i2c
1511 // adapter or called Deoptimization::unpack_frames. As for native frames, upcalls from JNI also go through the
1512 // interpreter (see JavaCalls::call_helper), while the UpcallLinker explicitly sets cont_fastpath.
1513 bool FreezeBase::check_valid_fast_path() {
1514   ContinuationEntry* ce = _thread->last_continuation();
1515   RegisterMap map(_thread,
1516                   RegisterMap::UpdateMap::skip,
1517                   RegisterMap::ProcessFrames::skip,
1518                   RegisterMap::WalkContinuation::skip);
1519   map.set_include_argument_oops(false);
1520   for (frame f = freeze_start_frame(); Continuation::is_frame_in_continuation(ce, f); f = f.sender(&map)) {
1521     if (!f.is_compiled_frame() || f.is_deoptimized_frame()) {
1522       return false;
1523     }
1524   }
1525   return true;
1526 }
1527 #endif // ASSERT
1528 
1529 static inline int freeze_epilog(JavaThread* thread, ContinuationWrapper& cont) {
1530   verify_continuation(cont.continuation());
1531   assert(!cont.is_empty(), "");
1532   // This is done for the sake of the enterSpecial frame
1533   StackWatermarkSet::after_unwind(thread);
1534 
1535   log_develop_debug(continuations)("=== End of freeze cont ### #" INTPTR_FORMAT, cont.hash());
1536 
1537   return 0;
1538 }
1539 
1540 static int freeze_epilog(JavaThread* thread, ContinuationWrapper& cont, freeze_result res) {
1541   if (UNLIKELY(res != freeze_ok)) {
1542     verify_continuation(cont.continuation());
1543     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
1544     return res;
1545   }
1546 
1547   JVMTI_ONLY(jvmti_yield_cleanup(thread, cont)); // can safepoint
1548   return freeze_epilog(thread, cont);
1549 }
1550 
1551 template<typename ConfigT>
1552 static inline int freeze_internal(JavaThread* current, intptr_t* const sp) {
1553   assert(!current->has_pending_exception(), "");
1554 
1555 #ifdef ASSERT
1556   log_trace(continuations)("~~~~ freeze sp: " INTPTR_FORMAT, p2i(current->last_continuation()->entry_sp()));
1557   log_frames(current);
1558 #endif
1559 
1560   CONT_JFR_ONLY(EventContinuationFreeze event;)
1561 
1562   ContinuationEntry* entry = current->last_continuation();
1563 
1564   oop oopCont = entry->cont_oop(current);
1565   assert(oopCont == current->last_continuation()->cont_oop(current), "");
1566   assert(ContinuationEntry::assert_entry_frame_laid_out(current), "");
1567 
1568   verify_continuation(oopCont);
1569   ContinuationWrapper cont(current, oopCont);
1570   log_develop_debug(continuations)("FREEZE #" INTPTR_FORMAT " " INTPTR_FORMAT, cont.hash(), p2i((oopDesc*)oopCont));
1571 
1572   assert(entry->is_virtual_thread() == (entry->scope(current) == java_lang_VirtualThread::vthread_scope()), "");
1573 
1574   assert(monitors_on_stack(current) == ((current->held_monitor_count() - current->jni_monitor_count()) > 0),
1575          "Held monitor count and locks on stack invariant: " INT64_FORMAT " JNI: " INT64_FORMAT, (int64_t)current->held_monitor_count(), (int64_t)current->jni_monitor_count());
1576 
1577   if (entry->is_pinned() || current->held_monitor_count() > 0) {
1578     log_develop_debug(continuations)("PINNED due to critical section/hold monitor");
1579     verify_continuation(cont.continuation());
1580     freeze_result res = entry->is_pinned() ? freeze_pinned_cs : freeze_pinned_monitor;
1581     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
1582     // Avoid Thread.yield() loops without safepoint polls.
1583     if (SafepointMechanism::should_process(current)) {
1584       cont.done(); // allow safepoint
1585       ThreadInVMfromJava tivmfj(current);
1586     }
1587     return res;
1588   }
1589 
1590   Freeze<ConfigT> freeze(current, cont, sp);
1591 
1592   assert(!current->cont_fastpath() || freeze.check_valid_fast_path(), "");
1593   bool fast = UseContinuationFastPath && current->cont_fastpath();
1594   if (fast && freeze.size_if_fast_freeze_available() > 0) {
1595     freeze.freeze_fast_existing_chunk();
1596     CONT_JFR_ONLY(freeze.jfr_info().post_jfr_event(&event, oopCont, current);)
1597     freeze_epilog(current, cont);
1598     return 0;
1599   }
1600 
1601   log_develop_trace(continuations)("chunk unavailable; transitioning to VM");
1602   assert(current == JavaThread::current(), "must be current thread except for preempt");
1603   JRT_BLOCK
1604     // delays a possible JvmtiSampledObjectAllocEventCollector in alloc_chunk
1605     JvmtiSampledObjectAllocEventCollector jsoaec(false);
1606     freeze.set_jvmti_event_collector(&jsoaec);
1607 
1608     freeze_result res = fast ? freeze.try_freeze_fast() : freeze.freeze_slow();
1609 
1610     CONT_JFR_ONLY(freeze.jfr_info().post_jfr_event(&event, oopCont, current);)
1611     freeze_epilog(current, cont, res);
1612     cont.done(); // allow safepoint in the transition back to Java
1613     return res;
1614   JRT_BLOCK_END
1615 }
1616 
1617 static freeze_result is_pinned0(JavaThread* thread, oop cont_scope, bool safepoint) {
1618   ContinuationEntry* entry = thread->last_continuation();
1619   if (entry == nullptr) {
1620     return freeze_ok;
1621   }
1622   if (entry->is_pinned()) {
1623     return freeze_pinned_cs;
1624   } else if (thread->held_monitor_count() > 0) {
1625     return freeze_pinned_monitor;
1626   }
1627 
1628   RegisterMap map(thread,
1629                   RegisterMap::UpdateMap::include,
1630                   RegisterMap::ProcessFrames::skip,
1631                   RegisterMap::WalkContinuation::skip);
1632   map.set_include_argument_oops(false);
1633   frame f = thread->last_frame();
1634 
1635   if (!safepoint) {
1636     f = f.sender(&map); // this is the yield frame
1637   } else { // safepoint yield
1638 #if (defined(X86) || defined(AARCH64) || defined(RISCV64)) && !defined(ZERO)
1639     f.set_fp(f.real_fp()); // Instead of this, maybe in ContinuationWrapper::set_last_frame always use the real_fp?
1640 #else
1641     Unimplemented();
1642 #endif
1643     if (!Interpreter::contains(f.pc())) {
1644       assert(ContinuationHelper::Frame::is_stub(f.cb()), "must be");
1645       assert(f.oop_map() != nullptr, "must be");
1646       f.oop_map()->update_register_map(&f, &map); // we have callee-save registers in this case
1647     }
1648   }
1649 
1650   while (true) {
1651     if ((f.is_interpreted_frame() && f.interpreter_frame_method()->is_native()) || f.is_native_frame()) {
1652       return freeze_pinned_native;
1653     }
1654 
1655     f = f.sender(&map);
1656     if (!Continuation::is_frame_in_continuation(entry, f)) {
1657       oop scope = jdk_internal_vm_Continuation::scope(entry->cont_oop(thread));
1658       if (scope == cont_scope) {
1659         break;
1660       }
1661       intx monitor_count = entry->parent_held_monitor_count();
1662       entry = entry->parent();
1663       if (entry == nullptr) {
1664         break;
1665       }
1666       if (entry->is_pinned()) {
1667         return freeze_pinned_cs;
1668       } else if (monitor_count > 0) {
1669         return freeze_pinned_monitor;
1670       }
1671     }
1672   }
1673   return freeze_ok;
1674 }
1675 
1676 /////////////// THAW ////
1677 
1678 static int thaw_size(stackChunkOop chunk) {
1679   int size = chunk->max_thawing_size();
1680   size += frame::metadata_words; // For the top pc+fp in push_return_frame or top = stack_sp - frame::metadata_words in thaw_fast
1681   size += 2*frame::align_wiggle; // in case of alignments at the top and bottom
1682   return size;
1683 }
1684 
1685 // make room on the stack for thaw
1686 // returns the size in bytes, or 0 on failure
1687 static inline int prepare_thaw_internal(JavaThread* thread, bool return_barrier) {
1688   log_develop_trace(continuations)("~~~~ prepare_thaw return_barrier: %d", return_barrier);
1689 
1690   assert(thread == JavaThread::current(), "");
1691 
1692   ContinuationEntry* ce = thread->last_continuation();
1693   assert(ce != nullptr, "");
1694   oop continuation = ce->cont_oop(thread);
1695   assert(continuation == get_continuation(thread), "");
1696   verify_continuation(continuation);
1697 
1698   stackChunkOop chunk = jdk_internal_vm_Continuation::tail(continuation);
1699   assert(chunk != nullptr, "");
1700 
1701   // The tail can be empty because it might still be available for another freeze.
1702   // However, here we want to thaw, so we get rid of it (it will be GCed).
1703   if (UNLIKELY(chunk->is_empty())) {
1704     chunk = chunk->parent();
1705     assert(chunk != nullptr, "");
1706     assert(!chunk->is_empty(), "");
1707     jdk_internal_vm_Continuation::set_tail(continuation, chunk);
1708   }
1709 
1710   // Verification
1711   chunk->verify();
1712   assert(chunk->max_thawing_size() > 0, "chunk invariant violated; expected to not be empty");
1713 
1714   // Only make space for the last chunk because we only thaw from the last chunk
1715   int size = thaw_size(chunk) << LogBytesPerWord;
1716 
1717   const address bottom = (address)thread->last_continuation()->entry_sp();
1718   // 300 is an estimate for stack size taken for this native code, in addition to StackShadowPages
1719   // for the Java frames in the check below.
1720   if (!stack_overflow_check(thread, size + 300, bottom)) {
1721     return 0;
1722   }
1723 
1724   log_develop_trace(continuations)("prepare_thaw bottom: " INTPTR_FORMAT " top: " INTPTR_FORMAT " size: %d",
1725                               p2i(bottom), p2i(bottom - size), size);
1726   return size;
1727 }
1728 
1729 class ThawBase : public StackObj {
1730 protected:
1731   JavaThread* _thread;
1732   ContinuationWrapper& _cont;
1733   CONT_JFR_ONLY(FreezeThawJfrInfo _jfr_info;)
1734 
1735   intptr_t* _fastpath;
1736   bool _barriers;
1737   intptr_t* _top_unextended_sp_before_thaw;
1738   int _align_size;
1739   DEBUG_ONLY(intptr_t* _top_stack_address);
1740 
1741   StackChunkFrameStream<ChunkFrames::Mixed> _stream;
1742 
1743   NOT_PRODUCT(int _frames;)
1744 
1745 protected:
1746   ThawBase(JavaThread* thread, ContinuationWrapper& cont) :
1747       _thread(thread), _cont(cont),
1748       _fastpath(nullptr) {
1749     DEBUG_ONLY(_top_unextended_sp_before_thaw = nullptr;)
1750     assert (cont.tail() != nullptr, "no last chunk");
1751     DEBUG_ONLY(_top_stack_address = _cont.entrySP() - thaw_size(cont.tail());)
1752   }
1753 
1754   void clear_chunk(stackChunkOop chunk);
1755   int remove_top_compiled_frame_from_chunk(stackChunkOop chunk, int &argsize);
1756   void copy_from_chunk(intptr_t* from, intptr_t* to, int size);
1757 
1758   // fast path
1759   inline void prefetch_chunk_pd(void* start, int size_words);
1760   void patch_return(intptr_t* sp, bool is_last);
1761 
1762   // slow path
1763   NOINLINE intptr_t* thaw_slow(stackChunkOop chunk, bool return_barrier);
1764 
1765 private:
1766   void recurse_thaw(const frame& heap_frame, frame& caller, int num_frames, bool top);
1767   template<typename FKind> bool recurse_thaw_java_frame(frame& caller, int num_frames);
1768   void finalize_thaw(frame& entry, int argsize);
1769 
1770   inline bool seen_by_gc();
1771 
1772   inline void before_thaw_java_frame(const frame& hf, const frame& caller, bool bottom, int num_frame);
1773   inline void after_thaw_java_frame(const frame& f, bool bottom);
1774   inline void patch(frame& f, const frame& caller, bool bottom);
1775   void clear_bitmap_bits(address start, address end);
1776 
1777   NOINLINE void recurse_thaw_interpreted_frame(const frame& hf, frame& caller, int num_frames);
1778   void recurse_thaw_compiled_frame(const frame& hf, frame& caller, int num_frames, bool stub_caller);
1779   void recurse_thaw_stub_frame(const frame& hf, frame& caller, int num_frames);
1780   void finish_thaw(frame& f);
1781 
1782   void push_return_frame(frame& f);
1783   inline frame new_entry_frame();
1784   template<typename FKind> frame new_stack_frame(const frame& hf, frame& caller, bool bottom);
1785   inline void patch_pd(frame& f, const frame& sender);
1786   inline intptr_t* align(const frame& hf, intptr_t* frame_sp, frame& caller, bool bottom);
1787 
1788   void maybe_set_fastpath(intptr_t* sp) { if (sp > _fastpath) _fastpath = sp; }
1789 
1790   static inline void derelativize_interpreted_frame_metadata(const frame& hf, const frame& f);
1791 
1792  public:
1793   CONT_JFR_ONLY(FreezeThawJfrInfo& jfr_info() { return _jfr_info; })
1794 };
1795 
1796 template <typename ConfigT>
1797 class Thaw : public ThawBase {
1798 public:
1799   Thaw(JavaThread* thread, ContinuationWrapper& cont) : ThawBase(thread, cont) {}
1800 
1801   inline bool can_thaw_fast(stackChunkOop chunk) {
1802     return    !_barriers
1803            &&  _thread->cont_fastpath_thread_state()
1804            && !chunk->has_thaw_slowpath_condition()
1805            && !PreserveFramePointer;
1806   }
1807 
1808   inline intptr_t* thaw(Continuation::thaw_kind kind);
1809   NOINLINE intptr_t* thaw_fast(stackChunkOop chunk);
1810   inline void patch_caller_links(intptr_t* sp, intptr_t* bottom);
1811 };
1812 
1813 template <typename ConfigT>
1814 inline intptr_t* Thaw<ConfigT>::thaw(Continuation::thaw_kind kind) {
1815   verify_continuation(_cont.continuation());
1816   assert(!jdk_internal_vm_Continuation::done(_cont.continuation()), "");
1817   assert(!_cont.is_empty(), "");
1818 
1819   stackChunkOop chunk = _cont.tail();
1820   assert(chunk != nullptr, "guaranteed by prepare_thaw");
1821   assert(!chunk->is_empty(), "guaranteed by prepare_thaw");
1822 
1823   _barriers = chunk->requires_barriers();
1824   return (LIKELY(can_thaw_fast(chunk))) ? thaw_fast(chunk)
1825                                         : thaw_slow(chunk, kind != Continuation::thaw_top);
1826 }
1827 
1828 class ReconstructedStack : public StackObj {
1829   intptr_t* _base;  // _cont.entrySP(); // top of the entry frame
1830   int _thaw_size;
1831   int _argsize;
1832 public:
1833   ReconstructedStack(intptr_t* base, int thaw_size, int argsize)
1834   : _base(base), _thaw_size(thaw_size - (argsize == 0 ? frame::metadata_words_at_top : 0)), _argsize(argsize) {
1835     // The only possible source of misalignment is stack-passed arguments b/c compiled frames are 16-byte aligned.
1836     assert(argsize != 0 || (_base - _thaw_size) == ContinuationHelper::frame_align_pointer(_base - _thaw_size), "");
1837     // We're at most one alignment word away from entrySP
1838     assert(_base - 1 <= top() + total_size() + frame::metadata_words_at_bottom, "missed entry frame");
1839   }
1840 
1841   int entry_frame_extension() const { return _argsize + (_argsize > 0 ? frame::metadata_words_at_top : 0); }
1842 
1843   // top and bottom stack pointers
1844   intptr_t* sp() const { return ContinuationHelper::frame_align_pointer(_base - _thaw_size); }
1845   intptr_t* bottom_sp() const { return ContinuationHelper::frame_align_pointer(_base - entry_frame_extension()); }
1846 
1847   // several operations operate on the totality of the stack being reconstructed,
1848   // including the metadata words
1849   intptr_t* top() const { return sp() - frame::metadata_words_at_bottom;  }
1850   int total_size() const { return _thaw_size + frame::metadata_words_at_bottom; }
1851 };
1852 
1853 inline void ThawBase::clear_chunk(stackChunkOop chunk) {
1854   chunk->set_sp(chunk->bottom());
1855   chunk->set_max_thawing_size(0);
1856 }
1857 
1858 int ThawBase::remove_top_compiled_frame_from_chunk(stackChunkOop chunk, int &argsize) {
1859   bool empty = false;
1860   StackChunkFrameStream<ChunkFrames::CompiledOnly> f(chunk);
1861   DEBUG_ONLY(intptr_t* const chunk_sp = chunk->start_address() + chunk->sp();)
1862   assert(chunk_sp == f.sp(), "");
1863   assert(chunk_sp == f.unextended_sp(), "");
1864 
1865   const int frame_size = f.cb()->frame_size();
1866   argsize = f.stack_argsize();
1867 
1868   f.next(SmallRegisterMap::instance, true /* stop */);
1869   empty = f.is_done();
1870   assert(!empty || argsize == chunk->argsize(), "");
1871 
1872   if (empty) {
1873     clear_chunk(chunk);
1874   } else {
1875     chunk->set_sp(chunk->sp() + frame_size);
1876     chunk->set_max_thawing_size(chunk->max_thawing_size() - frame_size);
1877     // We set chunk->pc to the return pc into the next frame
1878     chunk->set_pc(f.pc());
1879 #ifdef ASSERT
1880     {
1881       intptr_t* retaddr_slot = (chunk_sp
1882                                 + frame_size
1883                                 - frame::sender_sp_ret_address_offset());
1884       assert(f.pc() == ContinuationHelper::return_address_at(retaddr_slot),
1885              "unexpected pc");
1886     }
1887 #endif
1888   }
1889   assert(empty == chunk->is_empty(), "");
1890   // returns the size required to store the frame on stack, and because it is a
1891   // compiled frame, it must include a copy of the arguments passed by the caller
1892   return frame_size + argsize + frame::metadata_words_at_top;
1893 }
1894 
1895 void ThawBase::copy_from_chunk(intptr_t* from, intptr_t* to, int size) {
1896   assert(to >= _top_stack_address, "overwrote past thawing space"
1897     " to: " INTPTR_FORMAT " top_address: " INTPTR_FORMAT, p2i(to), p2i(_top_stack_address));
1898   assert(to + size <= _cont.entrySP(), "overwrote past thawing space");
1899   _cont.tail()->copy_from_chunk_to_stack(from, to, size);
1900   CONT_JFR_ONLY(_jfr_info.record_size_copied(size);)
1901 }
1902 
1903 void ThawBase::patch_return(intptr_t* sp, bool is_last) {
1904   log_develop_trace(continuations)("thaw_fast patching -- sp: " INTPTR_FORMAT, p2i(sp));
1905 
1906   address pc = !is_last ? StubRoutines::cont_returnBarrier() : _cont.entryPC();
1907   ContinuationHelper::patch_return_address_at(
1908     sp - frame::sender_sp_ret_address_offset(),
1909     pc);
1910 }
1911 
1912 template <typename ConfigT>
1913 NOINLINE intptr_t* Thaw<ConfigT>::thaw_fast(stackChunkOop chunk) {
1914   assert(chunk == _cont.tail(), "");
1915   assert(!chunk->has_mixed_frames(), "");
1916   assert(!chunk->requires_barriers(), "");
1917   assert(!chunk->has_bitmap(), "");
1918   assert(!_thread->is_interp_only_mode(), "");
1919 
1920   LogTarget(Trace, continuations) lt;
1921   if (lt.develop_is_enabled()) {
1922     LogStream ls(lt);
1923     ls.print_cr("thaw_fast");
1924     chunk->print_on(true, &ls);
1925   }
1926 
1927   // Below this heuristic, we thaw the whole chunk, above it we thaw just one frame.
1928   static const int threshold = 500; // words
1929 
1930   const int full_chunk_size = chunk->stack_size() - chunk->sp(); // this initial size could be reduced if it's a partial thaw
1931   int argsize, thaw_size;
1932 
1933   intptr_t* const chunk_sp = chunk->start_address() + chunk->sp();
1934 
1935   bool partial, empty;
1936   if (LIKELY(!TEST_THAW_ONE_CHUNK_FRAME && (full_chunk_size < threshold))) {
1937     prefetch_chunk_pd(chunk->start_address(), full_chunk_size); // prefetch anticipating memcpy starting at highest address
1938 
1939     partial = false;
1940     argsize = chunk->argsize(); // must be called *before* clearing the chunk
1941     clear_chunk(chunk);
1942     thaw_size = full_chunk_size;
1943     empty = true;
1944   } else { // thaw a single frame
1945     partial = true;
1946     thaw_size = remove_top_compiled_frame_from_chunk(chunk, argsize);
1947     empty = chunk->is_empty();
1948   }
1949 
1950   // Are we thawing the last frame(s) in the continuation
1951   const bool is_last = empty && chunk->parent() == nullptr;
1952   assert(!is_last || argsize == 0, "");
1953 
1954   log_develop_trace(continuations)("thaw_fast partial: %d is_last: %d empty: %d size: %d argsize: %d entrySP: " PTR_FORMAT,
1955                               partial, is_last, empty, thaw_size, argsize, p2i(_cont.entrySP()));
1956 
1957   ReconstructedStack rs(_cont.entrySP(), thaw_size, argsize);
1958 
1959   // also copy metadata words at frame bottom
1960   copy_from_chunk(chunk_sp - frame::metadata_words_at_bottom, rs.top(), rs.total_size());
1961 
1962   // update the ContinuationEntry
1963   _cont.set_argsize(argsize);
1964   log_develop_trace(continuations)("setting entry argsize: %d", _cont.argsize());
1965   assert(rs.bottom_sp() == _cont.entry()->bottom_sender_sp(), "");
1966 
1967   // install the return barrier if not last frame, or the entry's pc if last
1968   patch_return(rs.bottom_sp(), is_last);
1969 
1970   // insert the back links from callee to caller frames
1971   patch_caller_links(rs.top(), rs.top() + rs.total_size());
1972 
1973   assert(is_last == _cont.is_empty(), "");
1974   assert(_cont.chunk_invariant(), "");
1975 
1976 #if CONT_JFR
1977   EventContinuationThawFast e;
1978   if (e.should_commit()) {
1979     e.set_id(cast_from_oop<u8>(chunk));
1980     e.set_size(thaw_size << LogBytesPerWord);
1981     e.set_full(!partial);
1982     e.commit();
1983   }
1984 #endif
1985 
1986 #ifdef ASSERT
1987   set_anchor(_thread, rs.sp());
1988   log_frames(_thread);
1989   if (LoomDeoptAfterThaw) {
1990     do_deopt_after_thaw(_thread);
1991   }
1992   clear_anchor(_thread);
1993 #endif
1994 
1995   return rs.sp();
1996 }
1997 
1998 inline bool ThawBase::seen_by_gc() {
1999   return _barriers || _cont.tail()->is_gc_mode();
2000 }
2001 
2002 NOINLINE intptr_t* ThawBase::thaw_slow(stackChunkOop chunk, bool return_barrier) {
2003   LogTarget(Trace, continuations) lt;
2004   if (lt.develop_is_enabled()) {
2005     LogStream ls(lt);
2006     ls.print_cr("thaw slow return_barrier: %d " INTPTR_FORMAT, return_barrier, p2i(chunk));
2007     chunk->print_on(true, &ls);
2008   }
2009 
2010 #if CONT_JFR
2011   EventContinuationThawSlow e;
2012   if (e.should_commit()) {
2013     e.set_id(cast_from_oop<u8>(_cont.continuation()));
2014     e.commit();
2015   }
2016 #endif
2017 
2018   DEBUG_ONLY(_frames = 0;)
2019   _align_size = 0;
2020   int num_frames = (return_barrier ? 1 : 2);
2021 
2022   _stream = StackChunkFrameStream<ChunkFrames::Mixed>(chunk);
2023   _top_unextended_sp_before_thaw = _stream.unextended_sp();
2024 
2025   frame heap_frame = _stream.to_frame();
2026   if (lt.develop_is_enabled()) {
2027     LogStream ls(lt);
2028     ls.print_cr("top hframe before (thaw):");
2029     assert(heap_frame.is_heap_frame(), "should have created a relative frame");
2030     heap_frame.print_value_on(&ls, nullptr);
2031   }
2032 
2033 #if INCLUDE_ZGC || INCLUDE_SHENANDOAHGC
2034   if (UseZGC || UseShenandoahGC) {
2035     _cont.tail()->relativize_derived_pointers_concurrently();
2036   }
2037 #endif
2038 
2039   frame caller; // the thawed caller on the stack
2040   recurse_thaw(heap_frame, caller, num_frames, true);
2041   finish_thaw(caller); // caller is now the topmost thawed frame
2042   _cont.write();
2043 
2044   assert(_cont.chunk_invariant(), "");
2045 
2046   JVMTI_ONLY(if (!return_barrier) invalidate_jvmti_stack(_thread));
2047 
2048   _thread->set_cont_fastpath(_fastpath);
2049 
2050   intptr_t* sp = caller.sp();
2051   return sp;
2052 }
2053 
2054 void ThawBase::recurse_thaw(const frame& heap_frame, frame& caller, int num_frames, bool top) {
2055   log_develop_debug(continuations)("thaw num_frames: %d", num_frames);
2056   assert(!_cont.is_empty(), "no more frames");
2057   assert(num_frames > 0, "");
2058   assert(!heap_frame.is_empty(), "");
2059 
2060   if (top && heap_frame.is_safepoint_blob_frame()) {
2061     assert(ContinuationHelper::Frame::is_stub(heap_frame.cb()), "cb: %s", heap_frame.cb()->name());
2062     recurse_thaw_stub_frame(heap_frame, caller, num_frames);
2063   } else if (!heap_frame.is_interpreted_frame()) {
2064     recurse_thaw_compiled_frame(heap_frame, caller, num_frames, false);
2065   } else {
2066     recurse_thaw_interpreted_frame(heap_frame, caller, num_frames);
2067   }
2068 }
2069 
2070 template<typename FKind>
2071 bool ThawBase::recurse_thaw_java_frame(frame& caller, int num_frames) {
2072   assert(num_frames > 0, "");
2073 
2074   DEBUG_ONLY(_frames++;)
2075 
2076   int argsize = _stream.stack_argsize();
2077 
2078   _stream.next(SmallRegisterMap::instance);
2079   assert(_stream.to_frame().is_empty() == _stream.is_done(), "");
2080 
2081   // we never leave a compiled caller of an interpreted frame as the top frame in the chunk
2082   // as it makes detecting that situation and adjusting unextended_sp tricky
2083   if (num_frames == 1 && !_stream.is_done() && FKind::interpreted && _stream.is_compiled()) {
2084     log_develop_trace(continuations)("thawing extra compiled frame to not leave a compiled interpreted-caller at top");
2085     num_frames++;
2086   }
2087 
2088   if (num_frames == 1 || _stream.is_done()) { // end recursion
2089     finalize_thaw(caller, FKind::interpreted ? 0 : argsize);
2090     return true; // bottom
2091   } else { // recurse
2092     recurse_thaw(_stream.to_frame(), caller, num_frames - 1, false);
2093     return false;
2094   }
2095 }
2096 
2097 void ThawBase::finalize_thaw(frame& entry, int argsize) {
2098   stackChunkOop chunk = _cont.tail();
2099 
2100   if (!_stream.is_done()) {
2101     assert(_stream.sp() >= chunk->sp_address(), "");
2102     chunk->set_sp(chunk->to_offset(_stream.sp()));
2103     chunk->set_pc(_stream.pc());
2104   } else {
2105     chunk->set_sp(chunk->bottom());
2106     chunk->set_pc(nullptr);
2107   }
2108   assert(_stream.is_done() == chunk->is_empty(), "");
2109 
2110   int total_thawed = pointer_delta_as_int(_stream.unextended_sp(), _top_unextended_sp_before_thaw);
2111   chunk->set_max_thawing_size(chunk->max_thawing_size() - total_thawed);
2112 
2113   _cont.set_argsize(argsize);
2114   entry = new_entry_frame();
2115 
2116   assert(entry.sp() == _cont.entrySP(), "");
2117   assert(Continuation::is_continuation_enterSpecial(entry), "");
2118   assert(_cont.is_entry_frame(entry), "");
2119 }
2120 
2121 inline void ThawBase::before_thaw_java_frame(const frame& hf, const frame& caller, bool bottom, int num_frame) {
2122   LogTarget(Trace, continuations) lt;
2123   if (lt.develop_is_enabled()) {
2124     LogStream ls(lt);
2125     ls.print_cr("======== THAWING FRAME: %d", num_frame);
2126     assert(hf.is_heap_frame(), "should be");
2127     hf.print_value_on(&ls, nullptr);
2128   }
2129   assert(bottom == _cont.is_entry_frame(caller), "bottom: %d is_entry_frame: %d", bottom, _cont.is_entry_frame(hf));
2130 }
2131 
2132 inline void ThawBase::after_thaw_java_frame(const frame& f, bool bottom) {
2133 #ifdef ASSERT
2134   LogTarget(Trace, continuations) lt;
2135   if (lt.develop_is_enabled()) {
2136     LogStream ls(lt);
2137     ls.print_cr("thawed frame:");
2138     print_frame_layout(f, false, &ls); // f.print_on(&ls);
2139   }
2140 #endif
2141 }
2142 
2143 inline void ThawBase::patch(frame& f, const frame& caller, bool bottom) {
2144   assert(!bottom || caller.fp() == _cont.entryFP(), "");
2145   if (bottom) {
2146     ContinuationHelper::Frame::patch_pc(caller, _cont.is_empty() ? caller.pc()
2147                                                                  : StubRoutines::cont_returnBarrier());
2148   } else {
2149     // caller might have been deoptimized during thaw but we've overwritten the return address when copying f from the heap.
2150     // If the caller is not deoptimized, pc is unchanged.
2151     ContinuationHelper::Frame::patch_pc(caller, caller.raw_pc());
2152   }
2153 
2154   patch_pd(f, caller);
2155 
2156   if (f.is_interpreted_frame()) {
2157     ContinuationHelper::InterpretedFrame::patch_sender_sp(f, caller);
2158   }
2159 
2160   assert(!bottom || !_cont.is_empty() || Continuation::is_continuation_entry_frame(f, nullptr), "");
2161   assert(!bottom || (_cont.is_empty() != Continuation::is_cont_barrier_frame(f)), "");
2162 }
2163 
2164 void ThawBase::clear_bitmap_bits(address start, address end) {
2165   assert(is_aligned(start, wordSize), "should be aligned: " PTR_FORMAT, p2i(start));
2166   assert(is_aligned(end, VMRegImpl::stack_slot_size), "should be aligned: " PTR_FORMAT, p2i(end));
2167 
2168   // we need to clear the bits that correspond to arguments as they reside in the caller frame
2169   // or they will keep objects that are otherwise unreachable alive.
2170 
2171   // Align `end` if UseCompressedOops is not set to avoid UB when calculating the bit index, since
2172   // `end` could be at an odd number of stack slots from `start`, i.e might not be oop aligned.
2173   // If that's the case the bit range corresponding to the last stack slot should not have bits set
2174   // anyways and we assert that before returning.
2175   address effective_end = UseCompressedOops ? end : align_down(end, wordSize);
2176   log_develop_trace(continuations)("clearing bitmap for " INTPTR_FORMAT " - " INTPTR_FORMAT, p2i(start), p2i(effective_end));
2177   stackChunkOop chunk = _cont.tail();
2178   chunk->bitmap().clear_range(chunk->bit_index_for(start), chunk->bit_index_for(effective_end));
2179   assert(effective_end == end || !chunk->bitmap().at(chunk->bit_index_for(effective_end)), "bit should not be set");
2180 }
2181 
2182 NOINLINE void ThawBase::recurse_thaw_interpreted_frame(const frame& hf, frame& caller, int num_frames) {
2183   assert(hf.is_interpreted_frame(), "");
2184 
2185   if (UNLIKELY(seen_by_gc())) {
2186     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance);
2187   }
2188 
2189   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::InterpretedFrame>(caller, num_frames);
2190 
2191   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2192 
2193   _align_size += frame::align_wiggle; // possible added alignment for internal interpreted frame alignment om AArch64
2194 
2195   frame f = new_stack_frame<ContinuationHelper::InterpretedFrame>(hf, caller, is_bottom_frame);
2196 
2197   intptr_t* const stack_frame_top = f.sp() + frame::metadata_words_at_top;
2198   intptr_t* const stack_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(f);
2199   intptr_t* const heap_frame_top = hf.unextended_sp() + frame::metadata_words_at_top;
2200   intptr_t* const heap_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(hf);
2201 
2202   assert(hf.is_heap_frame(), "should be");
2203   assert(!f.is_heap_frame(), "should not be");
2204 
2205   const int fsize = pointer_delta_as_int(heap_frame_bottom, heap_frame_top);
2206   assert((stack_frame_bottom == stack_frame_top + fsize), "");
2207 
2208   // Some architectures (like AArch64/PPC64/RISC-V) add padding between the locals and the fixed_frame to keep the fp 16-byte-aligned.
2209   // On those architectures we freeze the padding in order to keep the same fp-relative offsets in the fixed_frame.
2210   copy_from_chunk(heap_frame_top, stack_frame_top, fsize);
2211 
2212   // Make sure the relativized locals is already set.
2213   assert(f.interpreter_frame_local_at(0) == stack_frame_bottom - 1, "invalid frame bottom");
2214 
2215   derelativize_interpreted_frame_metadata(hf, f);
2216   patch(f, caller, is_bottom_frame);
2217 
2218   assert(f.is_interpreted_frame_valid(_cont.thread()), "invalid thawed frame");
2219   assert(stack_frame_bottom <= ContinuationHelper::Frame::frame_top(caller), "");
2220 
2221   CONT_JFR_ONLY(_jfr_info.record_interpreted_frame();)
2222 
2223   maybe_set_fastpath(f.sp());
2224 
2225   const int locals = hf.interpreter_frame_method()->max_locals();
2226 
2227   if (!is_bottom_frame) {
2228     // can only fix caller once this frame is thawed (due to callee saved regs)
2229     _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance);
2230   } else if (_cont.tail()->has_bitmap() && locals > 0) {
2231     assert(hf.is_heap_frame(), "should be");
2232     address start = (address)(heap_frame_bottom - locals);
2233     address end = (address)heap_frame_bottom;
2234     clear_bitmap_bits(start, end);
2235   }
2236 
2237   DEBUG_ONLY(after_thaw_java_frame(f, is_bottom_frame);)
2238   caller = f;
2239 }
2240 
2241 void ThawBase::recurse_thaw_compiled_frame(const frame& hf, frame& caller, int num_frames, bool stub_caller) {
2242   assert(!hf.is_interpreted_frame(), "");
2243   assert(_cont.is_preempted() || !stub_caller, "stub caller not at preemption");
2244 
2245   if (!stub_caller && UNLIKELY(seen_by_gc())) { // recurse_thaw_stub_frame already invoked our barriers with a full regmap
2246     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance);
2247   }
2248 
2249   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::CompiledFrame>(caller, num_frames);
2250 
2251   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2252 
2253   assert(caller.sp() == caller.unextended_sp(), "");
2254 
2255   if ((!is_bottom_frame && caller.is_interpreted_frame()) || (is_bottom_frame && Interpreter::contains(_cont.tail()->pc()))) {
2256     _align_size += frame::align_wiggle; // we add one whether or not we've aligned because we add it in freeze_interpreted_frame
2257   }
2258 
2259   // new_stack_frame must construct the resulting frame using hf.pc() rather than hf.raw_pc() because the frame is not
2260   // yet laid out in the stack, and so the original_pc is not stored in it.
2261   // As a result, f.is_deoptimized_frame() is always false and we must test hf to know if the frame is deoptimized.
2262   frame f = new_stack_frame<ContinuationHelper::CompiledFrame>(hf, caller, is_bottom_frame);
2263   intptr_t* const stack_frame_top = f.sp();
2264   intptr_t* const heap_frame_top = hf.unextended_sp();
2265 
2266   const int added_argsize = (is_bottom_frame || caller.is_interpreted_frame()) ? hf.compiled_frame_stack_argsize() : 0;
2267   int fsize = ContinuationHelper::CompiledFrame::size(hf) + added_argsize;
2268   assert(fsize <= (int)(caller.unextended_sp() - f.unextended_sp()), "");
2269 
2270   intptr_t* from = heap_frame_top - frame::metadata_words_at_bottom;
2271   intptr_t* to   = stack_frame_top - frame::metadata_words_at_bottom;
2272   // copy metadata, except the metadata at the top of the (unextended) entry frame
2273   int sz = fsize + frame::metadata_words_at_bottom + (is_bottom_frame && added_argsize == 0 ? 0 : frame::metadata_words_at_top);
2274 
2275   // If we're the bottom-most thawed frame, we're writing to within one word from entrySP
2276   // (we might have one padding word for alignment)
2277   assert(!is_bottom_frame || (_cont.entrySP() - 1 <= to + sz && to + sz <= _cont.entrySP()), "");
2278   assert(!is_bottom_frame || hf.compiled_frame_stack_argsize() != 0 || (to + sz && to + sz == _cont.entrySP()), "");
2279 
2280   copy_from_chunk(from, to, sz); // copying good oops because we invoked barriers above
2281 
2282   patch(f, caller, is_bottom_frame);
2283 
2284   // f.is_deoptimized_frame() is always false and we must test hf.is_deoptimized_frame() (see comment above)
2285   assert(!f.is_deoptimized_frame(), "");
2286   if (hf.is_deoptimized_frame()) {
2287     maybe_set_fastpath(f.sp());
2288   } else if (_thread->is_interp_only_mode()
2289               || (_cont.is_preempted() && f.cb()->as_nmethod()->is_marked_for_deoptimization())) {
2290     // The caller of the safepoint stub when the continuation is preempted is not at a call instruction, and so
2291     // cannot rely on nmethod patching for deopt.
2292     assert(_thread->is_interp_only_mode() || stub_caller, "expected a stub-caller");
2293 
2294     log_develop_trace(continuations)("Deoptimizing thawed frame");
2295     DEBUG_ONLY(ContinuationHelper::Frame::patch_pc(f, nullptr));
2296 
2297     f.deoptimize(nullptr); // the null thread simply avoids the assertion in deoptimize which we're not set up for
2298     assert(f.is_deoptimized_frame(), "");
2299     assert(ContinuationHelper::Frame::is_deopt_return(f.raw_pc(), f), "");
2300     maybe_set_fastpath(f.sp());
2301   }
2302 
2303   if (!is_bottom_frame) {
2304     // can only fix caller once this frame is thawed (due to callee saved regs); this happens on the stack
2305     _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance);
2306   } else if (_cont.tail()->has_bitmap() && added_argsize > 0) {
2307     address start = (address)(heap_frame_top + ContinuationHelper::CompiledFrame::size(hf) + frame::metadata_words_at_top);
2308     int stack_args_slots = f.cb()->as_nmethod()->num_stack_arg_slots(false /* rounded */);
2309     int argsize_in_bytes = stack_args_slots * VMRegImpl::stack_slot_size;
2310     clear_bitmap_bits(start, start + argsize_in_bytes);
2311   }
2312 
2313   DEBUG_ONLY(after_thaw_java_frame(f, is_bottom_frame);)
2314   caller = f;
2315 }
2316 
2317 void ThawBase::recurse_thaw_stub_frame(const frame& hf, frame& caller, int num_frames) {
2318   DEBUG_ONLY(_frames++;)
2319 
2320   {
2321     RegisterMap map(nullptr,
2322                     RegisterMap::UpdateMap::include,
2323                     RegisterMap::ProcessFrames::skip,
2324                     RegisterMap::WalkContinuation::skip);
2325     map.set_include_argument_oops(false);
2326     _stream.next(&map);
2327     assert(!_stream.is_done(), "");
2328     if (UNLIKELY(seen_by_gc())) { // we're now doing this on the stub's caller
2329       _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, &map);
2330     }
2331     assert(!_stream.is_done(), "");
2332   }
2333 
2334   recurse_thaw_compiled_frame(_stream.to_frame(), caller, num_frames, true); // this could be deoptimized
2335 
2336   DEBUG_ONLY(before_thaw_java_frame(hf, caller, false, num_frames);)
2337 
2338   assert(ContinuationHelper::Frame::is_stub(hf.cb()), "");
2339   assert(caller.sp() == caller.unextended_sp(), "");
2340   assert(!caller.is_interpreted_frame(), "");
2341 
2342   int fsize = ContinuationHelper::StubFrame::size(hf);
2343 
2344   frame f = new_stack_frame<ContinuationHelper::StubFrame>(hf, caller, false);
2345   intptr_t* stack_frame_top = f.sp();
2346   intptr_t* heap_frame_top = hf.sp();
2347 
2348   copy_from_chunk(heap_frame_top - frame::metadata_words, stack_frame_top - frame::metadata_words,
2349                   fsize + frame::metadata_words);
2350 
2351   { // can only fix caller once this frame is thawed (due to callee saved regs)
2352     RegisterMap map(nullptr,
2353                     RegisterMap::UpdateMap::include,
2354                     RegisterMap::ProcessFrames::skip,
2355                     RegisterMap::WalkContinuation::skip); // map.clear();
2356     map.set_include_argument_oops(false);
2357     f.oop_map()->update_register_map(&f, &map);
2358     ContinuationHelper::update_register_map_with_callee(caller, &map);
2359     _cont.tail()->fix_thawed_frame(caller, &map);
2360   }
2361 
2362   DEBUG_ONLY(after_thaw_java_frame(f, false);)
2363   caller = f;
2364 }
2365 
2366 void ThawBase::finish_thaw(frame& f) {
2367   stackChunkOop chunk = _cont.tail();
2368 
2369   if (chunk->is_empty()) {
2370     // Only remove chunk from list if it can't be reused for another freeze
2371     if (seen_by_gc()) {
2372       _cont.set_tail(chunk->parent());
2373     } else {
2374       chunk->set_has_mixed_frames(false);
2375     }
2376     chunk->set_max_thawing_size(0);
2377   } else {
2378     chunk->set_max_thawing_size(chunk->max_thawing_size() - _align_size);
2379   }
2380   assert(chunk->is_empty() == (chunk->max_thawing_size() == 0), "");
2381 
2382   if (!is_aligned(f.sp(), frame::frame_alignment)) {
2383     assert(f.is_interpreted_frame(), "");
2384     f.set_sp(align_down(f.sp(), frame::frame_alignment));
2385   }
2386   push_return_frame(f);
2387   chunk->fix_thawed_frame(f, SmallRegisterMap::instance); // can only fix caller after push_return_frame (due to callee saved regs)
2388 
2389   assert(_cont.is_empty() == _cont.last_frame().is_empty(), "");
2390 
2391   log_develop_trace(continuations)("thawed %d frames", _frames);
2392 
2393   LogTarget(Trace, continuations) lt;
2394   if (lt.develop_is_enabled()) {
2395     LogStream ls(lt);
2396     ls.print_cr("top hframe after (thaw):");
2397     _cont.last_frame().print_value_on(&ls, nullptr);
2398   }
2399 }
2400 
2401 void ThawBase::push_return_frame(frame& f) { // see generate_cont_thaw
2402   assert(!f.is_compiled_frame() || f.is_deoptimized_frame() == f.cb()->as_nmethod()->is_deopt_pc(f.raw_pc()), "");
2403   assert(!f.is_compiled_frame() || f.is_deoptimized_frame() == (f.pc() != f.raw_pc()), "");
2404 
2405   LogTarget(Trace, continuations) lt;
2406   if (lt.develop_is_enabled()) {
2407     LogStream ls(lt);
2408     ls.print_cr("push_return_frame");
2409     f.print_value_on(&ls, nullptr);
2410   }
2411 
2412   assert(f.sp() - frame::metadata_words_at_bottom >= _top_stack_address, "overwrote past thawing space"
2413     " to: " INTPTR_FORMAT " top_address: " INTPTR_FORMAT, p2i(f.sp() - frame::metadata_words), p2i(_top_stack_address));
2414   ContinuationHelper::Frame::patch_pc(f, f.raw_pc()); // in case we want to deopt the frame in a full transition, this is checked.
2415   ContinuationHelper::push_pd(f);
2416 
2417   assert(ContinuationHelper::Frame::assert_frame_laid_out(f), "");
2418 }
2419 
2420 // returns new top sp
2421 // called after preparations (stack overflow check and making room)
2422 template<typename ConfigT>
2423 static inline intptr_t* thaw_internal(JavaThread* thread, const Continuation::thaw_kind kind) {
2424   assert(thread == JavaThread::current(), "Must be current thread");
2425 
2426   CONT_JFR_ONLY(EventContinuationThaw event;)
2427 
2428   log_develop_trace(continuations)("~~~~ thaw kind: %d sp: " INTPTR_FORMAT, kind, p2i(thread->last_continuation()->entry_sp()));
2429 
2430   ContinuationEntry* entry = thread->last_continuation();
2431   assert(entry != nullptr, "");
2432   oop oopCont = entry->cont_oop(thread);
2433 
2434   assert(!jdk_internal_vm_Continuation::done(oopCont), "");
2435   assert(oopCont == get_continuation(thread), "");
2436   verify_continuation(oopCont);
2437 
2438   assert(entry->is_virtual_thread() == (entry->scope(thread) == java_lang_VirtualThread::vthread_scope()), "");
2439 
2440   ContinuationWrapper cont(thread, oopCont);
2441   log_develop_debug(continuations)("THAW #" INTPTR_FORMAT " " INTPTR_FORMAT, cont.hash(), p2i((oopDesc*)oopCont));
2442 
2443 #ifdef ASSERT
2444   set_anchor_to_entry(thread, cont.entry());
2445   log_frames(thread);
2446   clear_anchor(thread);
2447 #endif
2448 
2449   Thaw<ConfigT> thw(thread, cont);
2450   intptr_t* const sp = thw.thaw(kind);
2451   assert(is_aligned(sp, frame::frame_alignment), "");
2452 
2453   // All the frames have been thawed so we know they don't hold any monitors
2454   assert(thread->held_monitor_count() == 0, "Must be");
2455 
2456 #ifdef ASSERT
2457   intptr_t* sp0 = sp;
2458   set_anchor(thread, sp0);
2459   log_frames(thread);
2460   if (LoomVerifyAfterThaw) {
2461     assert(do_verify_after_thaw(thread, cont.tail(), tty), "");
2462   }
2463   assert(ContinuationEntry::assert_entry_frame_laid_out(thread), "");
2464   clear_anchor(thread);
2465 
2466   LogTarget(Trace, continuations) lt;
2467   if (lt.develop_is_enabled()) {
2468     LogStream ls(lt);
2469     ls.print_cr("Jumping to frame (thaw):");
2470     frame(sp).print_value_on(&ls, nullptr);
2471   }
2472 #endif
2473 
2474   CONT_JFR_ONLY(thw.jfr_info().post_jfr_event(&event, cont.continuation(), thread);)
2475 
2476   verify_continuation(cont.continuation());
2477   log_develop_debug(continuations)("=== End of thaw #" INTPTR_FORMAT, cont.hash());
2478 
2479   return sp;
2480 }
2481 
2482 #ifdef ASSERT
2483 static void do_deopt_after_thaw(JavaThread* thread) {
2484   int i = 0;
2485   StackFrameStream fst(thread, true, false);
2486   fst.register_map()->set_include_argument_oops(false);
2487   ContinuationHelper::update_register_map_with_callee(*fst.current(), fst.register_map());
2488   for (; !fst.is_done(); fst.next()) {
2489     if (fst.current()->cb()->is_nmethod()) {
2490       nmethod* nm = fst.current()->cb()->as_nmethod();
2491       if (!nm->method()->is_continuation_native_intrinsic()) {
2492         nm->make_deoptimized();
2493       }
2494     }
2495   }
2496 }
2497 
2498 class ThawVerifyOopsClosure: public OopClosure {
2499   intptr_t* _p;
2500   outputStream* _st;
2501   bool is_good_oop(oop o) {
2502     return dbg_is_safe(o, -1) && dbg_is_safe(o->klass(), -1) && oopDesc::is_oop(o) && o->klass()->is_klass();
2503   }
2504 public:
2505   ThawVerifyOopsClosure(outputStream* st) : _p(nullptr), _st(st) {}
2506   intptr_t* p() { return _p; }
2507   void reset() { _p = nullptr; }
2508 
2509   virtual void do_oop(oop* p) {
2510     oop o = *p;
2511     if (o == nullptr || is_good_oop(o)) {
2512       return;
2513     }
2514     _p = (intptr_t*)p;
2515     _st->print_cr("*** non-oop " PTR_FORMAT " found at " PTR_FORMAT, p2i(*p), p2i(p));
2516   }
2517   virtual void do_oop(narrowOop* p) {
2518     oop o = RawAccess<>::oop_load(p);
2519     if (o == nullptr || is_good_oop(o)) {
2520       return;
2521     }
2522     _p = (intptr_t*)p;
2523     _st->print_cr("*** (narrow) non-oop %x found at " PTR_FORMAT, (int)(*p), p2i(p));
2524   }
2525 };
2526 
2527 static bool do_verify_after_thaw(JavaThread* thread, stackChunkOop chunk, outputStream* st) {
2528   assert(thread->has_last_Java_frame(), "");
2529 
2530   ResourceMark rm;
2531   ThawVerifyOopsClosure cl(st);
2532   NMethodToOopClosure cf(&cl, false);
2533 
2534   StackFrameStream fst(thread, true, false);
2535   fst.register_map()->set_include_argument_oops(false);
2536   ContinuationHelper::update_register_map_with_callee(*fst.current(), fst.register_map());
2537   for (; !fst.is_done() && !Continuation::is_continuation_enterSpecial(*fst.current()); fst.next()) {
2538     if (fst.current()->cb()->is_nmethod() && fst.current()->cb()->as_nmethod()->is_marked_for_deoptimization()) {
2539       st->print_cr(">>> do_verify_after_thaw deopt");
2540       fst.current()->deoptimize(nullptr);
2541       fst.current()->print_on(st);
2542     }
2543 
2544     fst.current()->oops_do(&cl, &cf, fst.register_map());
2545     if (cl.p() != nullptr) {
2546       frame fr = *fst.current();
2547       st->print_cr("Failed for frame barriers: %d",chunk->requires_barriers());
2548       fr.print_on(st);
2549       if (!fr.is_interpreted_frame()) {
2550         st->print_cr("size: %d argsize: %d",
2551                      ContinuationHelper::NonInterpretedUnknownFrame::size(fr),
2552                      ContinuationHelper::NonInterpretedUnknownFrame::stack_argsize(fr));
2553       }
2554       VMReg reg = fst.register_map()->find_register_spilled_here(cl.p(), fst.current()->sp());
2555       if (reg != nullptr) {
2556         st->print_cr("Reg %s %d", reg->name(), reg->is_stack() ? (int)reg->reg2stack() : -99);
2557       }
2558       cl.reset();
2559       DEBUG_ONLY(thread->print_frame_layout();)
2560       if (chunk != nullptr) {
2561         chunk->print_on(true, st);
2562       }
2563       return false;
2564     }
2565   }
2566   return true;
2567 }
2568 
2569 static void log_frames(JavaThread* thread) {
2570   const static int show_entry_callers = 3;
2571   LogTarget(Trace, continuations) lt;
2572   if (!lt.develop_is_enabled()) {
2573     return;
2574   }
2575   LogStream ls(lt);
2576 
2577   ls.print_cr("------- frames ---------");
2578   if (!thread->has_last_Java_frame()) {
2579     ls.print_cr("NO ANCHOR!");
2580   }
2581 
2582   RegisterMap map(thread,
2583                   RegisterMap::UpdateMap::include,
2584                   RegisterMap::ProcessFrames::include,
2585                   RegisterMap::WalkContinuation::skip);
2586   map.set_include_argument_oops(false);
2587 
2588   if (false) {
2589     for (frame f = thread->last_frame(); !f.is_entry_frame(); f = f.sender(&map)) {
2590       f.print_on(&ls);
2591     }
2592   } else {
2593     map.set_skip_missing(true);
2594     ResetNoHandleMark rnhm;
2595     ResourceMark rm;
2596     HandleMark hm(Thread::current());
2597     FrameValues values;
2598 
2599     int i = 0;
2600     int post_entry = -1;
2601     for (frame f = thread->last_frame(); !f.is_entry_frame(); f = f.sender(&map)) {
2602       f.describe(values, i++, &map);
2603       if (post_entry >= 0 || Continuation::is_continuation_enterSpecial(f))
2604         post_entry++;
2605       if (post_entry >= show_entry_callers)
2606         break;
2607     }
2608     values.print_on(thread, &ls);
2609   }
2610 
2611   ls.print_cr("======= end frames =========");
2612 }
2613 #endif // ASSERT
2614 
2615 #include CPU_HEADER_INLINE(continuationFreezeThaw)
2616 
2617 #ifdef ASSERT
2618 static void print_frame_layout(const frame& f, bool callee_complete, outputStream* st) {
2619   ResourceMark rm;
2620   FrameValues values;
2621   assert(f.get_cb() != nullptr, "");
2622   RegisterMap map(f.is_heap_frame() ?
2623                     nullptr :
2624                     JavaThread::current(),
2625                   RegisterMap::UpdateMap::include,
2626                   RegisterMap::ProcessFrames::skip,
2627                   RegisterMap::WalkContinuation::skip);
2628   map.set_include_argument_oops(false);
2629   map.set_skip_missing(true);
2630   if (callee_complete) {
2631     frame::update_map_with_saved_link(&map, ContinuationHelper::Frame::callee_link_address(f));
2632   }
2633   const_cast<frame&>(f).describe(values, 0, &map);
2634   values.print_on(static_cast<JavaThread*>(nullptr), st);
2635 }
2636 #endif
2637 
2638 static address thaw_entry   = nullptr;
2639 static address freeze_entry = nullptr;
2640 
2641 address Continuation::thaw_entry() {
2642   return ::thaw_entry;
2643 }
2644 
2645 address Continuation::freeze_entry() {
2646   return ::freeze_entry;
2647 }
2648 
2649 class ConfigResolve {
2650 public:
2651   static void resolve() { resolve_compressed(); }
2652 
2653   static void resolve_compressed() {
2654     UseCompressedOops ? resolve_gc<true>()
2655                       : resolve_gc<false>();
2656   }
2657 
2658 private:
2659   template <bool use_compressed>
2660   static void resolve_gc() {
2661     BarrierSet* bs = BarrierSet::barrier_set();
2662     assert(bs != nullptr, "freeze/thaw invoked before BarrierSet is set");
2663     switch (bs->kind()) {
2664 #define BARRIER_SET_RESOLVE_BARRIER_CLOSURE(bs_name)                    \
2665       case BarrierSet::bs_name: {                                       \
2666         resolve<use_compressed, typename BarrierSet::GetType<BarrierSet::bs_name>::type>(); \
2667       }                                                                 \
2668         break;
2669       FOR_EACH_CONCRETE_BARRIER_SET_DO(BARRIER_SET_RESOLVE_BARRIER_CLOSURE)
2670 #undef BARRIER_SET_RESOLVE_BARRIER_CLOSURE
2671 
2672     default:
2673       fatal("BarrierSet resolving not implemented");
2674     };
2675   }
2676 
2677   template <bool use_compressed, typename BarrierSetT>
2678   static void resolve() {
2679     typedef Config<use_compressed ? oop_kind::NARROW : oop_kind::WIDE, BarrierSetT> SelectedConfigT;
2680 
2681     freeze_entry = (address)freeze<SelectedConfigT>;
2682 
2683     // If we wanted, we could templatize by kind and have three different thaw entries
2684     thaw_entry   = (address)thaw<SelectedConfigT>;
2685   }
2686 };
2687 
2688 void Continuation::init() {
2689   ConfigResolve::resolve();
2690 }