< prev index next >

src/hotspot/share/runtime/continuationFreezeThaw.cpp

Print this page

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

  36 #include "interpreter/interpreter.hpp"

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

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


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






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

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

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

1073     log_develop_trace(continuations)("Reusing chunk mixed: %d empty: %d", chunk->has_mixed_frames(), chunk->is_empty());
1074     if (chunk->is_empty()) {
1075       int sp = chunk->stack_size() - argsize_md;
1076       chunk->set_sp(sp);
1077       chunk->set_bottom(sp);
1078       _freeze_size += overlap;
1079       assert(chunk->max_thawing_size() == 0, "");
1080     } DEBUG_ONLY(else empty_chunk = false;)
1081   }
1082   assert(!chunk->is_gc_mode(), "");
1083   assert(!chunk->has_bitmap(), "");
1084   chunk->set_has_mixed_frames(true);
1085 
1086   assert(chunk->requires_barriers() == _barriers, "");
1087   assert(!_barriers || chunk->is_empty(), "");
1088 
1089   assert(!chunk->is_empty() || StackChunkFrameStream<ChunkFrames::Mixed>(chunk).is_done(), "");
1090   assert(!chunk->is_empty() || StackChunkFrameStream<ChunkFrames::Mixed>(chunk).to_frame().is_empty(), "");
1091 
1092   if (_preempt) {
1093     frame f = _thread->last_frame();
1094     if (f.is_interpreted_frame()) {
1095       // Some platforms do not save the last_sp in the top interpreter frame on VM calls.
1096       // We need it so that on resume we can restore the sp to the right place, since
1097       // thawing might add an alignment word to the expression stack (see finish_thaw()).
1098       // We do it now that we know freezing will be successful.
1099       prepare_freeze_interpreted_top_frame(f);














1100     }
1101   }
1102 
1103   // We unwind frames after the last safepoint so that the GC will have found the oops in the frames, but before
1104   // writing into the chunk. This is so that an asynchronous stack walk (not at a safepoint) that suspends us here
1105   // will either see no continuation or a consistent chunk.
1106   unwind_frames();
1107 
1108   chunk->set_max_thawing_size(chunk->max_thawing_size() + _freeze_size - _monitors_in_lockstack - frame::metadata_words);
1109 
1110   if (lt.develop_is_enabled()) {
1111     LogStream ls(lt);
1112     ls.print_cr("top chunk:");
1113     chunk->print_on(&ls);
1114   }
1115 
1116   if (_monitors_in_lockstack > 0) {
1117     freeze_lockstack(chunk);
1118   }
1119 

1591       // Some GCs could put direct allocations in old gen for slow-path
1592       // allocations; need to explicitly check if that was the case.
1593       _barriers = chunk->requires_barriers();
1594     }
1595   }
1596 
1597   if (_barriers) {
1598     log_develop_trace(continuations)("allocation requires barriers");
1599   }
1600 
1601   assert(chunk->parent() == nullptr || chunk->parent()->is_stackChunk(), "");
1602 
1603   return chunk;
1604 }
1605 
1606 void FreezeBase::throw_stack_overflow_on_humongous_chunk() {
1607   ContinuationWrapper::SafepointOp so(_thread, _cont); // could also call _cont.done() instead
1608   Exceptions::_throw_msg(_thread, __FILE__, __LINE__, vmSymbols::java_lang_StackOverflowError(), "Humongous stack chunk");
1609 }
1610 



















1611 #if INCLUDE_JVMTI
1612 static int num_java_frames(ContinuationWrapper& cont) {
1613   ResourceMark rm; // used for scope traversal in num_java_frames(nmethod*, address)
1614   int count = 0;
1615   for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
1616     count += chunk->num_java_frames();
1617   }
1618   return count;
1619 }
1620 
1621 static void invalidate_jvmti_stack(JavaThread* thread) {
1622   JvmtiThreadState *state = thread->jvmti_thread_state();
1623   if (state != nullptr) {
1624     state->invalidate_cur_stack_depth();
1625   }
1626 }
1627 
1628 static void jvmti_yield_cleanup(JavaThread* thread, ContinuationWrapper& cont) {
1629   if (JvmtiExport::has_frame_pops(thread)) {
1630     int num_frames = num_java_frames(cont);
1631 
1632     ContinuationWrapper::SafepointOp so(Thread::current(), cont);
1633     JvmtiExport::continuation_yield_cleanup(JavaThread::current(), num_frames);
1634   }
1635   invalidate_jvmti_stack(thread);
1636 }
1637 
1638 static void jvmti_mount_end(JavaThread* current, ContinuationWrapper& cont, frame top) {
1639   assert(current->vthread() != nullptr, "must be");
1640 
1641   HandleMarkCleaner hm(current);
1642   Handle vth(current, current->vthread());
1643 
1644   ContinuationWrapper::SafepointOp so(current, cont);
1645 
1646   // Since we might safepoint set the anchor so that the stack can be walked.
1647   set_anchor(current, top.sp());
1648 
1649   JRT_BLOCK
1650     JvmtiVTMSTransitionDisabler::VTMS_vthread_mount((jthread)vth.raw_value(), false);
1651 
1652     if (current->pending_contended_entered_event()) {
1653       JvmtiExport::post_monitor_contended_entered(current, current->contended_entered_monitor());



1654       current->set_contended_entered_monitor(nullptr);
1655     }
1656   JRT_BLOCK_END
1657 
1658   clear_anchor(current);
1659 }
1660 #endif // INCLUDE_JVMTI
1661 
1662 #ifdef ASSERT
1663 // There are no interpreted frames if we're not called from the interpreter and we haven't ancountered an i2c
1664 // adapter or called Deoptimization::unpack_frames. As for native frames, upcalls from JNI also go through the
1665 // interpreter (see JavaCalls::call_helper), while the UpcallLinker explicitly sets cont_fastpath.
1666 bool FreezeBase::check_valid_fast_path() {
1667   ContinuationEntry* ce = _thread->last_continuation();
1668   RegisterMap map(_thread,
1669                   RegisterMap::UpdateMap::skip,
1670                   RegisterMap::ProcessFrames::skip,
1671                   RegisterMap::WalkContinuation::skip);
1672   map.set_include_argument_oops(false);
1673   bool is_top_frame = true;
1674   for (frame f = freeze_start_frame(); Continuation::is_frame_in_continuation(ce, f); f = f.sender(&map), is_top_frame = false) {
1675     if (!((f.is_compiled_frame() && !f.is_deoptimized_frame()) || (is_top_frame && (f.is_runtime_frame() || f.is_native_frame())))) {
1676       return false;
1677     }
1678   }
1679   return true;
1680 }
































































































1681 #endif // ASSERT
1682 
1683 static inline freeze_result freeze_epilog(ContinuationWrapper& cont) {
1684   verify_continuation(cont.continuation());
1685   assert(!cont.is_empty(), "");
1686 
1687   log_develop_debug(continuations)("=== End of freeze cont ### #" INTPTR_FORMAT, cont.hash());
1688   return freeze_ok;
1689 }
1690 
1691 static freeze_result freeze_epilog(JavaThread* thread, ContinuationWrapper& cont, freeze_result res) {
1692   if (UNLIKELY(res != freeze_ok)) {
1693     JFR_ONLY(thread->set_last_freeze_fail_result(res);)
1694     verify_continuation(cont.continuation());
1695     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
1696     return res;
1697   }
1698 
1699   JVMTI_ONLY(jvmti_yield_cleanup(thread, cont)); // can safepoint
1700   return freeze_epilog(cont);
1701 }
1702 
1703 static freeze_result preempt_epilog(ContinuationWrapper& cont, freeze_result res, frame& old_last_frame) {
1704   if (UNLIKELY(res != freeze_ok)) {
1705     verify_continuation(cont.continuation());
1706     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
1707     return res;
1708   }
1709 

1710   patch_return_pc_with_preempt_stub(old_last_frame);
1711   cont.tail()->set_preempted(true);
1712 
1713   return freeze_epilog(cont);
1714 }
1715 
1716 template<typename ConfigT, bool preempt>
1717 static inline freeze_result freeze_internal(JavaThread* current, intptr_t* const sp) {
1718   assert(!current->has_pending_exception(), "");
1719 
1720 #ifdef ASSERT
1721   log_trace(continuations)("~~~~ freeze sp: " INTPTR_FORMAT "JavaThread: " INTPTR_FORMAT, p2i(current->last_continuation()->entry_sp()), p2i(current));
1722   log_frames(current);
1723 #endif
1724 
1725   CONT_JFR_ONLY(EventContinuationFreeze event;)
1726 
1727   ContinuationEntry* entry = current->last_continuation();
1728 
1729   oop oopCont = entry->cont_oop(current);
1730   assert(oopCont == current->last_continuation()->cont_oop(current), "");
1731   assert(ContinuationEntry::assert_entry_frame_laid_out(current), "");
1732 

1888   // 300 is an estimate for stack size taken for this native code, in addition to StackShadowPages
1889   // for the Java frames in the check below.
1890   if (!stack_overflow_check(thread, size + 300, bottom)) {
1891     return 0;
1892   }
1893 
1894   log_develop_trace(continuations)("prepare_thaw bottom: " INTPTR_FORMAT " top: " INTPTR_FORMAT " size: %d",
1895                               p2i(bottom), p2i(bottom - size), size);
1896   return size;
1897 }
1898 
1899 class ThawBase : public StackObj {
1900 protected:
1901   JavaThread* _thread;
1902   ContinuationWrapper& _cont;
1903   CONT_JFR_ONLY(FreezeThawJfrInfo _jfr_info;)
1904 
1905   intptr_t* _fastpath;
1906   bool _barriers;
1907   bool _preempted_case;

1908   intptr_t* _top_unextended_sp_before_thaw;
1909   int _align_size;
1910   DEBUG_ONLY(intptr_t* _top_stack_address);
1911 



1912   StackChunkFrameStream<ChunkFrames::Mixed> _stream;
1913 
1914   NOT_PRODUCT(int _frames;)
1915 
1916 protected:
1917   ThawBase(JavaThread* thread, ContinuationWrapper& cont) :
1918       _thread(thread), _cont(cont),
1919       _fastpath(nullptr) {
1920     DEBUG_ONLY(_top_unextended_sp_before_thaw = nullptr;)
1921     assert (cont.tail() != nullptr, "no last chunk");
1922     DEBUG_ONLY(_top_stack_address = _cont.entrySP() - thaw_size(cont.tail());)
1923   }
1924 
1925   void clear_chunk(stackChunkOop chunk);
1926   template<bool check_stub>
1927   int remove_top_compiled_frame_from_chunk(stackChunkOop chunk, int &argsize);
1928   void copy_from_chunk(intptr_t* from, intptr_t* to, int size);
1929 
1930   void thaw_lockstack(stackChunkOop chunk);
1931 
1932   // fast path
1933   inline void prefetch_chunk_pd(void* start, int size_words);
1934   void patch_return(intptr_t* sp, bool is_last);
1935 
1936   intptr_t* handle_preempted_continuation(intptr_t* sp, Continuation::preempt_kind preempt_kind, bool fast_case);
1937   inline intptr_t* push_cleanup_continuation();


1938   void throw_interrupted_exception(JavaThread* current, frame& top);
1939 
1940   void recurse_thaw(const frame& heap_frame, frame& caller, int num_frames, bool top_on_preempt_case);
1941   void finish_thaw(frame& f);
1942 
1943 private:
1944   template<typename FKind> bool recurse_thaw_java_frame(frame& caller, int num_frames);
1945   void finalize_thaw(frame& entry, int argsize);
1946 
1947   inline bool seen_by_gc();
1948 
1949   inline void before_thaw_java_frame(const frame& hf, const frame& caller, bool bottom, int num_frame);
1950   inline void after_thaw_java_frame(const frame& f, bool bottom);
1951   inline void patch(frame& f, const frame& caller, bool bottom);
1952   void clear_bitmap_bits(address start, address end);
1953 
1954   NOINLINE void recurse_thaw_interpreted_frame(const frame& hf, frame& caller, int num_frames);
1955   void recurse_thaw_compiled_frame(const frame& hf, frame& caller, int num_frames, bool stub_caller);
1956   void recurse_thaw_stub_frame(const frame& hf, frame& caller, int num_frames);
1957   void recurse_thaw_native_frame(const frame& hf, frame& caller, int num_frames);
1958 
1959   void push_return_frame(frame& f);
1960   inline frame new_entry_frame();
1961   template<typename FKind> frame new_stack_frame(const frame& hf, frame& caller, bool bottom);
1962   inline void patch_pd(frame& f, const frame& sender);
1963   inline void patch_pd(frame& f, intptr_t* caller_sp);
1964   inline intptr_t* align(const frame& hf, intptr_t* frame_sp, frame& caller, bool bottom);
1965 
1966   void maybe_set_fastpath(intptr_t* sp) { if (sp > _fastpath) _fastpath = sp; }
1967 
1968   static inline void derelativize_interpreted_frame_metadata(const frame& hf, const frame& f);
1969 
1970  public:
1971   CONT_JFR_ONLY(FreezeThawJfrInfo& jfr_info() { return _jfr_info; })
1972 };
1973 
1974 template <typename ConfigT>

2034   chunk->set_sp(chunk->bottom());
2035   chunk->set_max_thawing_size(0);
2036 }
2037 
2038 template<bool check_stub>
2039 int ThawBase::remove_top_compiled_frame_from_chunk(stackChunkOop chunk, int &argsize) {
2040   bool empty = false;
2041   StackChunkFrameStream<ChunkFrames::CompiledOnly> f(chunk);
2042   DEBUG_ONLY(intptr_t* const chunk_sp = chunk->start_address() + chunk->sp();)
2043   assert(chunk_sp == f.sp(), "");
2044   assert(chunk_sp == f.unextended_sp(), "");
2045 
2046   int frame_size = f.cb()->frame_size();
2047   argsize = f.stack_argsize();
2048 
2049   assert(!f.is_stub() || check_stub, "");
2050   if (check_stub && f.is_stub()) {
2051     // If we don't thaw the top compiled frame too, after restoring the saved
2052     // registers back in Java, we would hit the return barrier to thaw one more
2053     // frame effectively overwriting the restored registers during that call.
2054     f.next(SmallRegisterMap::instance(), true /* stop */);
2055     assert(!f.is_done(), "");
2056 
2057     f.get_cb();
2058     assert(f.is_compiled(), "");
2059     frame_size += f.cb()->frame_size();
2060     argsize = f.stack_argsize();
2061 
2062     if (f.cb()->as_nmethod()->is_marked_for_deoptimization()) {
2063       // The caller of the runtime stub when the continuation is preempted is not at a
2064       // Java call instruction, and so cannot rely on nmethod patching for deopt.
2065       log_develop_trace(continuations)("Deoptimizing runtime stub caller");
2066       f.to_frame().deoptimize(nullptr); // the null thread simply avoids the assertion in deoptimize which we're not set up for
2067     }
2068   }
2069 
2070   f.next(SmallRegisterMap::instance(), true /* stop */);
2071   empty = f.is_done();
2072   assert(!empty || argsize == chunk->argsize(), "");
2073 
2074   if (empty) {
2075     clear_chunk(chunk);
2076   } else {
2077     chunk->set_sp(chunk->sp() + frame_size);
2078     chunk->set_max_thawing_size(chunk->max_thawing_size() - frame_size);
2079     // We set chunk->pc to the return pc into the next frame
2080     chunk->set_pc(f.pc());
2081 #ifdef ASSERT
2082     {
2083       intptr_t* retaddr_slot = (chunk_sp
2084                                 + frame_size
2085                                 - frame::sender_sp_ret_address_offset());
2086       assert(f.pc() == ContinuationHelper::return_address_at(retaddr_slot),
2087              "unexpected pc");
2088     }
2089 #endif
2090   }

2210   return rs.sp();
2211 }
2212 
2213 inline bool ThawBase::seen_by_gc() {
2214   return _barriers || _cont.tail()->is_gc_mode();
2215 }
2216 
2217 static inline void relativize_chunk_concurrently(stackChunkOop chunk) {
2218 #if INCLUDE_ZGC || INCLUDE_SHENANDOAHGC
2219   if (UseZGC || UseShenandoahGC) {
2220     chunk->relativize_derived_pointers_concurrently();
2221   }
2222 #endif
2223 }
2224 
2225 template <typename ConfigT>
2226 NOINLINE intptr_t* Thaw<ConfigT>::thaw_slow(stackChunkOop chunk, Continuation::thaw_kind kind) {
2227   Continuation::preempt_kind preempt_kind;
2228   bool retry_fast_path = false;
2229 

2230   _preempted_case = chunk->preempted();
2231   if (_preempted_case) {
2232     ObjectWaiter* waiter = java_lang_VirtualThread::objectWaiter(_thread->vthread());
2233     if (waiter != nullptr) {
2234       // Mounted again after preemption. Resume the pending monitor operation,
2235       // which will be either a monitorenter or Object.wait() call.
2236       ObjectMonitor* mon = waiter->monitor();
2237       preempt_kind = waiter->is_wait() ? Continuation::freeze_on_wait : Continuation::freeze_on_monitorenter;
2238 
2239       bool mon_acquired = mon->resume_operation(_thread, waiter, _cont);
2240       assert(!mon_acquired || mon->has_owner(_thread), "invariant");
2241       if (!mon_acquired) {
2242         // Failed to acquire monitor. Return to enterSpecial to unmount again.

2243         return push_cleanup_continuation();
2244       }

2245       chunk = _cont.tail();  // reload oop in case of safepoint in resume_operation (if posting JVMTI events).

2246     } else {
2247       // Preemption cancelled in moniterenter case. We actually acquired
2248       // the monitor after freezing all frames so nothing to do.
2249       preempt_kind = Continuation::freeze_on_monitorenter;




2250     }

2251     // Call this first to avoid racing with GC threads later when modifying the chunk flags.
2252     relativize_chunk_concurrently(chunk);










2253     chunk->set_preempted(false);
2254     retry_fast_path = true;
2255   } else {
2256     relativize_chunk_concurrently(chunk);
2257   }
2258 
2259   // On first thaw after freeze restore oops to the lockstack if any.
2260   assert(chunk->lockstack_size() == 0 || kind == Continuation::thaw_top, "");
2261   if (kind == Continuation::thaw_top && chunk->lockstack_size() > 0) {
2262     thaw_lockstack(chunk);
2263     retry_fast_path = true;
2264   }
2265 
2266   // Retry the fast path now that we possibly cleared the FLAG_HAS_LOCKSTACK
2267   // and FLAG_PREEMPTED flags from the stackChunk.
2268   if (retry_fast_path && can_thaw_fast(chunk)) {
2269     intptr_t* sp = thaw_fast<true>(chunk);
2270     if (_preempted_case) {
2271       return handle_preempted_continuation(sp, preempt_kind, true /* fast_case */);
2272     }

2316 
2317   intptr_t* sp = caller.sp();
2318 
2319   if (_preempted_case) {
2320     return handle_preempted_continuation(sp, preempt_kind, false /* fast_case */);
2321   }
2322   return sp;
2323 }
2324 
2325 void ThawBase::recurse_thaw(const frame& heap_frame, frame& caller, int num_frames, bool top_on_preempt_case) {
2326   log_develop_debug(continuations)("thaw num_frames: %d", num_frames);
2327   assert(!_cont.is_empty(), "no more frames");
2328   assert(num_frames > 0, "");
2329   assert(!heap_frame.is_empty(), "");
2330 
2331   if (top_on_preempt_case && (heap_frame.is_native_frame() || heap_frame.is_runtime_frame())) {
2332     heap_frame.is_native_frame() ? recurse_thaw_native_frame(heap_frame, caller, 2) : recurse_thaw_stub_frame(heap_frame, caller, 2);
2333   } else if (!heap_frame.is_interpreted_frame()) {
2334     recurse_thaw_compiled_frame(heap_frame, caller, num_frames, false);
2335   } else {
2336     recurse_thaw_interpreted_frame(heap_frame, caller, num_frames);
2337   }
2338 }
2339 
2340 template<typename FKind>
2341 bool ThawBase::recurse_thaw_java_frame(frame& caller, int num_frames) {
2342   assert(num_frames > 0, "");
2343 
2344   DEBUG_ONLY(_frames++;)
2345 
2346   int argsize = _stream.stack_argsize();
2347 
2348   _stream.next(SmallRegisterMap::instance());
2349   assert(_stream.to_frame().is_empty() == _stream.is_done(), "");
2350 
2351   // we never leave a compiled caller of an interpreted frame as the top frame in the chunk
2352   // as it makes detecting that situation and adjusting unextended_sp tricky
2353   if (num_frames == 1 && !_stream.is_done() && FKind::interpreted && _stream.is_compiled()) {
2354     log_develop_trace(continuations)("thawing extra compiled frame to not leave a compiled interpreted-caller at top");
2355     num_frames++;
2356   }
2357 
2358   if (num_frames == 1 || _stream.is_done()) { // end recursion
2359     finalize_thaw(caller, FKind::interpreted ? 0 : argsize);
2360     return true; // bottom
2361   } else { // recurse
2362     recurse_thaw(_stream.to_frame(), caller, num_frames - 1, false /* top_on_preempt_case */);
2363     return false;
2364   }
2365 }
2366 
2367 void ThawBase::finalize_thaw(frame& entry, int argsize) {
2368   stackChunkOop chunk = _cont.tail();

2433 
2434 void ThawBase::clear_bitmap_bits(address start, address end) {
2435   assert(is_aligned(start, wordSize), "should be aligned: " PTR_FORMAT, p2i(start));
2436   assert(is_aligned(end, VMRegImpl::stack_slot_size), "should be aligned: " PTR_FORMAT, p2i(end));
2437 
2438   // we need to clear the bits that correspond to arguments as they reside in the caller frame
2439   // or they will keep objects that are otherwise unreachable alive.
2440 
2441   // Align `end` if UseCompressedOops is not set to avoid UB when calculating the bit index, since
2442   // `end` could be at an odd number of stack slots from `start`, i.e might not be oop aligned.
2443   // If that's the case the bit range corresponding to the last stack slot should not have bits set
2444   // anyways and we assert that before returning.
2445   address effective_end = UseCompressedOops ? end : align_down(end, wordSize);
2446   log_develop_trace(continuations)("clearing bitmap for " INTPTR_FORMAT " - " INTPTR_FORMAT, p2i(start), p2i(effective_end));
2447   stackChunkOop chunk = _cont.tail();
2448   chunk->bitmap().clear_range(chunk->bit_index_for(start), chunk->bit_index_for(effective_end));
2449   assert(effective_end == end || !chunk->bitmap().at(chunk->bit_index_for(effective_end)), "bit should not be set");
2450 }
2451 
2452 intptr_t* ThawBase::handle_preempted_continuation(intptr_t* sp, Continuation::preempt_kind preempt_kind, bool fast_case) {
2453   assert(preempt_kind == Continuation::freeze_on_wait || preempt_kind == Continuation::freeze_on_monitorenter, "");
2454   frame top(sp);
2455   assert(top.pc() == *(address*)(sp - frame::sender_sp_ret_address_offset()), "");


2456 
2457 #if INCLUDE_JVMTI
2458   // Finish the VTMS transition.
2459   assert(_thread->is_in_VTMS_transition(), "must be");
2460   bool is_vthread = Continuation::continuation_scope(_cont.continuation()) == java_lang_VirtualThread::vthread_scope();
2461   if (is_vthread) {
2462     if (JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events()) {
2463       jvmti_mount_end(_thread, _cont, top);
2464     } else {
2465       _thread->set_is_in_VTMS_transition(false);
2466       java_lang_Thread::set_is_in_VTMS_transition(_thread->vthread(), false);
2467     }
2468   }
2469 #endif
2470 
2471   if (fast_case) {
2472     // If we thawed in the slow path the runtime stub/native wrapper frame already
2473     // has the correct fp (see ThawBase::new_stack_frame). On the fast path though,
2474     // we copied the fp patched during freeze, which will now have to be fixed.
2475     assert(top.is_runtime_frame() || top.is_native_frame(), "");
2476     int fsize = top.cb()->frame_size();
2477     patch_pd(top, sp + fsize);
2478   }
2479 
2480   if (preempt_kind == Continuation::freeze_on_wait) {
2481     // Check now if we need to throw IE exception.
2482     if (_thread->pending_interrupted_exception()) {

2483       throw_interrupted_exception(_thread, top);
2484       _thread->set_pending_interrupted_exception(false);
2485     }
2486   } else if (top.is_runtime_frame()) {
2487     // The continuation might now run on a different platform thread than the previous time so
2488     // we need to adjust the current thread saved in the stub frame before restoring registers.
2489     JavaThread** thread_addr = frame::saved_thread_address(top);
2490     if (thread_addr != nullptr) *thread_addr = _thread;































































2491   }
2492   return sp;
2493 }
2494 
2495 void ThawBase::throw_interrupted_exception(JavaThread* current, frame& top) {

2496   ContinuationWrapper::SafepointOp so(current, _cont);
2497   // Since we might safepoint set the anchor so that the stack can be walked.
2498   set_anchor(current, top.sp());
2499   JRT_BLOCK
2500     THROW(vmSymbols::java_lang_InterruptedException());
2501   JRT_BLOCK_END
2502   clear_anchor(current);
2503 }
2504 
2505 NOINLINE void ThawBase::recurse_thaw_interpreted_frame(const frame& hf, frame& caller, int num_frames) {
2506   assert(hf.is_interpreted_frame(), "");
2507 
2508   if (UNLIKELY(seen_by_gc())) {
2509     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance());




2510   }
2511 
2512   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::InterpretedFrame>(caller, num_frames);
2513 
2514   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2515 
2516   _align_size += frame::align_wiggle; // possible added alignment for internal interpreted frame alignment om AArch64
2517 
2518   frame f = new_stack_frame<ContinuationHelper::InterpretedFrame>(hf, caller, is_bottom_frame);
2519 
2520   intptr_t* const stack_frame_top = f.sp() + frame::metadata_words_at_top;
2521   intptr_t* const stack_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(f);
2522   intptr_t* const heap_frame_top = hf.unextended_sp() + frame::metadata_words_at_top;
2523   intptr_t* const heap_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(hf);
2524 
2525   assert(hf.is_heap_frame(), "should be");
2526   assert(!f.is_heap_frame(), "should not be");
2527 
2528   const int fsize = pointer_delta_as_int(heap_frame_bottom, heap_frame_top);
2529   assert((stack_frame_bottom == stack_frame_top + fsize), "");

2534 
2535   // Make sure the relativized locals is already set.
2536   assert(f.interpreter_frame_local_at(0) == stack_frame_bottom - 1, "invalid frame bottom");
2537 
2538   derelativize_interpreted_frame_metadata(hf, f);
2539   patch(f, caller, is_bottom_frame);
2540 
2541   assert(f.is_interpreted_frame_valid(_cont.thread()), "invalid thawed frame");
2542   assert(stack_frame_bottom <= ContinuationHelper::Frame::frame_top(caller), "");
2543 
2544   CONT_JFR_ONLY(_jfr_info.record_interpreted_frame();)
2545 
2546   maybe_set_fastpath(f.sp());
2547 
2548   Method* m = hf.interpreter_frame_method();
2549   assert(!m->is_native() || !is_bottom_frame, "should be top frame of thaw_top case; missing caller frame");
2550   const int locals = m->max_locals();
2551 
2552   if (!is_bottom_frame) {
2553     // can only fix caller once this frame is thawed (due to callee saved regs)
2554     _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance());
2555   } else if (_cont.tail()->has_bitmap() && locals > 0) {
2556     assert(hf.is_heap_frame(), "should be");
2557     address start = (address)(heap_frame_bottom - locals);
2558     address end = (address)heap_frame_bottom;
2559     clear_bitmap_bits(start, end);
2560   }
2561 
2562   DEBUG_ONLY(after_thaw_java_frame(f, is_bottom_frame);)
2563   caller = f;
2564 }
2565 
2566 void ThawBase::recurse_thaw_compiled_frame(const frame& hf, frame& caller, int num_frames, bool stub_caller) {
2567   assert(hf.is_compiled_frame(), "");
2568   assert(_preempted_case || !stub_caller, "stub caller not at preemption");
2569 
2570   if (!stub_caller && UNLIKELY(seen_by_gc())) { // recurse_thaw_stub_frame already invoked our barriers with a full regmap
2571     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance());
2572   }
2573 
2574   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::CompiledFrame>(caller, num_frames);
2575 
2576   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2577 
2578   assert(caller.sp() == caller.unextended_sp(), "");
2579 
2580   if ((!is_bottom_frame && caller.is_interpreted_frame()) || (is_bottom_frame && Interpreter::contains(_cont.tail()->pc()))) {
2581     _align_size += frame::align_wiggle; // we add one whether or not we've aligned because we add it in recurse_freeze_compiled_frame
2582   }
2583 
2584   // new_stack_frame must construct the resulting frame using hf.pc() rather than hf.raw_pc() because the frame is not
2585   // yet laid out in the stack, and so the original_pc is not stored in it.
2586   // As a result, f.is_deoptimized_frame() is always false and we must test hf to know if the frame is deoptimized.
2587   frame f = new_stack_frame<ContinuationHelper::CompiledFrame>(hf, caller, is_bottom_frame);
2588   intptr_t* const stack_frame_top = f.sp();
2589   intptr_t* const heap_frame_top = hf.unextended_sp();
2590 
2591   const int added_argsize = (is_bottom_frame || caller.is_interpreted_frame()) ? hf.compiled_frame_stack_argsize() : 0;

2610   assert(!f.is_deoptimized_frame(), "");
2611   if (hf.is_deoptimized_frame()) {
2612     maybe_set_fastpath(f.sp());
2613   } else if (_thread->is_interp_only_mode()
2614               || (stub_caller && f.cb()->as_nmethod()->is_marked_for_deoptimization())) {
2615     // The caller of the safepoint stub when the continuation is preempted is not at a call instruction, and so
2616     // cannot rely on nmethod patching for deopt.
2617     assert(_thread->is_interp_only_mode() || stub_caller, "expected a stub-caller");
2618 
2619     log_develop_trace(continuations)("Deoptimizing thawed frame");
2620     DEBUG_ONLY(ContinuationHelper::Frame::patch_pc(f, nullptr));
2621 
2622     f.deoptimize(nullptr); // the null thread simply avoids the assertion in deoptimize which we're not set up for
2623     assert(f.is_deoptimized_frame(), "");
2624     assert(ContinuationHelper::Frame::is_deopt_return(f.raw_pc(), f), "");
2625     maybe_set_fastpath(f.sp());
2626   }
2627 
2628   if (!is_bottom_frame) {
2629     // can only fix caller once this frame is thawed (due to callee saved regs); this happens on the stack
2630     _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance());
2631   } else if (_cont.tail()->has_bitmap() && added_argsize > 0) {
2632     address start = (address)(heap_frame_top + ContinuationHelper::CompiledFrame::size(hf) + frame::metadata_words_at_top);
2633     int stack_args_slots = f.cb()->as_nmethod()->num_stack_arg_slots(false /* rounded */);
2634     int argsize_in_bytes = stack_args_slots * VMRegImpl::stack_slot_size;
2635     clear_bitmap_bits(start, start + argsize_in_bytes);
2636   }
2637 
2638   DEBUG_ONLY(after_thaw_java_frame(f, is_bottom_frame);)
2639   caller = f;
2640 }
2641 
2642 void ThawBase::recurse_thaw_stub_frame(const frame& hf, frame& caller, int num_frames) {
2643   DEBUG_ONLY(_frames++;)
2644 
2645   if (UNLIKELY(seen_by_gc())) {
2646     // Process the stub's caller here since we might need the full map.
2647     RegisterMap map(nullptr,
2648                     RegisterMap::UpdateMap::include,
2649                     RegisterMap::ProcessFrames::skip,
2650                     RegisterMap::WalkContinuation::skip);
2651     map.set_include_argument_oops(false);
2652     _stream.next(&map);
2653     assert(!_stream.is_done(), "");
2654     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, &map);
2655   } else {
2656     _stream.next(SmallRegisterMap::instance());
2657     assert(!_stream.is_done(), "");
2658   }
2659 
2660   recurse_thaw_compiled_frame(_stream.to_frame(), caller, num_frames, true);
2661 
2662   assert(caller.is_compiled_frame(), "");
2663   assert(caller.sp() == caller.unextended_sp(), "");
2664 
2665   DEBUG_ONLY(before_thaw_java_frame(hf, caller, false /*is_bottom_frame*/, num_frames);)
2666 
2667   frame f = new_stack_frame<ContinuationHelper::StubFrame>(hf, caller, false);
2668   intptr_t* stack_frame_top = f.sp();
2669   intptr_t* heap_frame_top = hf.sp();
2670   int fsize = ContinuationHelper::StubFrame::size(hf);
2671 
2672   copy_from_chunk(heap_frame_top - frame::metadata_words, stack_frame_top - frame::metadata_words,
2673                   fsize + frame::metadata_words);
2674 
2675   patch(f, caller, false /*is_bottom_frame*/);
2676 
2677   // can only fix caller once this frame is thawed (due to callee saved regs)
2678   RegisterMap map(nullptr,
2679                   RegisterMap::UpdateMap::include,
2680                   RegisterMap::ProcessFrames::skip,
2681                   RegisterMap::WalkContinuation::skip);
2682   map.set_include_argument_oops(false);
2683   f.oop_map()->update_register_map(&f, &map);
2684   ContinuationHelper::update_register_map_with_callee(caller, &map);
2685   _cont.tail()->fix_thawed_frame(caller, &map);
2686 
2687   DEBUG_ONLY(after_thaw_java_frame(f, false /*is_bottom_frame*/);)
2688   caller = f;
2689 }
2690 
2691 void ThawBase::recurse_thaw_native_frame(const frame& hf, frame& caller, int num_frames) {
2692   assert(hf.is_native_frame(), "");
2693   assert(_preempted_case && hf.cb()->as_nmethod()->method()->is_object_wait0(), "");
2694 
2695   if (UNLIKELY(seen_by_gc())) { // recurse_thaw_stub_frame already invoked our barriers with a full regmap
2696     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance());
2697   }
2698 
2699   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::NativeFrame>(caller, num_frames);
2700   assert(!is_bottom_frame, "");
2701 
2702   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2703 
2704   assert(caller.sp() == caller.unextended_sp(), "");
2705 
2706   if (caller.is_interpreted_frame()) {
2707     _align_size += frame::align_wiggle; // we add one whether or not we've aligned because we add it in recurse_freeze_native_frame
2708   }
2709 
2710   // new_stack_frame must construct the resulting frame using hf.pc() rather than hf.raw_pc() because the frame is not
2711   // yet laid out in the stack, and so the original_pc is not stored in it.
2712   // As a result, f.is_deoptimized_frame() is always false and we must test hf to know if the frame is deoptimized.
2713   frame f = new_stack_frame<ContinuationHelper::NativeFrame>(hf, caller, false /* bottom */);
2714   intptr_t* const stack_frame_top = f.sp();
2715   intptr_t* const heap_frame_top = hf.unextended_sp();
2716 
2717   int fsize = ContinuationHelper::NativeFrame::size(hf);
2718   assert(fsize <= (int)(caller.unextended_sp() - f.unextended_sp()), "");
2719 
2720   intptr_t* from = heap_frame_top - frame::metadata_words_at_bottom;
2721   intptr_t* to   = stack_frame_top - frame::metadata_words_at_bottom;
2722   int sz = fsize + frame::metadata_words_at_bottom;
2723 
2724   copy_from_chunk(from, to, sz); // copying good oops because we invoked barriers above
2725 
2726   patch(f, caller, false /* bottom */);
2727 
2728   // f.is_deoptimized_frame() is always false and we must test hf.is_deoptimized_frame() (see comment above)
2729   assert(!f.is_deoptimized_frame(), "");
2730   assert(!hf.is_deoptimized_frame(), "");
2731   assert(!f.cb()->as_nmethod()->is_marked_for_deoptimization(), "");
2732 
2733   // can only fix caller once this frame is thawed (due to callee saved regs); this happens on the stack
2734   _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance());
2735 
2736   DEBUG_ONLY(after_thaw_java_frame(f, false /* bottom */);)
2737   caller = f;
2738 }
2739 
2740 void ThawBase::finish_thaw(frame& f) {
2741   stackChunkOop chunk = _cont.tail();
2742 
2743   if (chunk->is_empty()) {
2744     // Only remove chunk from list if it can't be reused for another freeze
2745     if (seen_by_gc()) {
2746       _cont.set_tail(chunk->parent());
2747     } else {
2748       chunk->set_has_mixed_frames(false);
2749     }
2750     chunk->set_max_thawing_size(0);
2751   } else {
2752     chunk->set_max_thawing_size(chunk->max_thawing_size() - _align_size);
2753   }
2754   assert(chunk->is_empty() == (chunk->max_thawing_size() == 0), "");
2755 
2756   if (!is_aligned(f.sp(), frame::frame_alignment)) {
2757     assert(f.is_interpreted_frame(), "");
2758     f.set_sp(align_down(f.sp(), frame::frame_alignment));
2759   }
2760   push_return_frame(f);
2761   chunk->fix_thawed_frame(f, SmallRegisterMap::instance()); // can only fix caller after push_return_frame (due to callee saved regs)





2762 
2763   assert(_cont.is_empty() == _cont.last_frame().is_empty(), "");
2764 
2765   log_develop_trace(continuations)("thawed %d frames", _frames);
2766 
2767   LogTarget(Trace, continuations) lt;
2768   if (lt.develop_is_enabled()) {
2769     LogStream ls(lt);
2770     ls.print_cr("top hframe after (thaw):");
2771     _cont.last_frame().print_value_on(&ls);
2772   }
2773 }
2774 
2775 void ThawBase::push_return_frame(frame& f) { // see generate_cont_thaw
2776   assert(!f.is_compiled_frame() || f.is_deoptimized_frame() == f.cb()->as_nmethod()->is_deopt_pc(f.raw_pc()), "");
2777   assert(!f.is_compiled_frame() || f.is_deoptimized_frame() == (f.pc() != f.raw_pc()), "");
2778 
2779   LogTarget(Trace, continuations) lt;
2780   if (lt.develop_is_enabled()) {
2781     LogStream ls(lt);

2803 
2804   ContinuationEntry* entry = thread->last_continuation();
2805   assert(entry != nullptr, "");
2806   oop oopCont = entry->cont_oop(thread);
2807 
2808   assert(!jdk_internal_vm_Continuation::done(oopCont), "");
2809   assert(oopCont == get_continuation(thread), "");
2810   verify_continuation(oopCont);
2811 
2812   assert(entry->is_virtual_thread() == (entry->scope(thread) == java_lang_VirtualThread::vthread_scope()), "");
2813 
2814   ContinuationWrapper cont(thread, oopCont);
2815   log_develop_debug(continuations)("THAW #" INTPTR_FORMAT " " INTPTR_FORMAT, cont.hash(), p2i((oopDesc*)oopCont));
2816 
2817 #ifdef ASSERT
2818   set_anchor_to_entry(thread, cont.entry());
2819   log_frames(thread);
2820   clear_anchor(thread);
2821 #endif
2822 
2823   DEBUG_ONLY(bool preempted = cont.tail()->preempted();)
2824   Thaw<ConfigT> thw(thread, cont);
2825   intptr_t* const sp = thw.thaw(kind);
2826   assert(is_aligned(sp, frame::frame_alignment), "");
2827   DEBUG_ONLY(log_frames_after_thaw(thread, cont, sp, preempted);)
2828 
2829   CONT_JFR_ONLY(thw.jfr_info().post_jfr_event(&event, cont.continuation(), thread);)
2830 
2831   verify_continuation(cont.continuation());
2832   log_develop_debug(continuations)("=== End of thaw #" INTPTR_FORMAT, cont.hash());
2833 
2834   return sp;
2835 }
2836 
2837 #ifdef ASSERT
2838 static void do_deopt_after_thaw(JavaThread* thread) {
2839   int i = 0;
2840   StackFrameStream fst(thread, true, false);
2841   fst.register_map()->set_include_argument_oops(false);
2842   ContinuationHelper::update_register_map_with_callee(*fst.current(), fst.register_map());
2843   for (; !fst.is_done(); fst.next()) {
2844     if (fst.current()->cb()->is_nmethod()) {
2845       nmethod* nm = fst.current()->cb()->as_nmethod();
2846       if (!nm->method()->is_continuation_native_intrinsic()) {
2847         nm->make_deoptimized();

2904       if (!fr.is_interpreted_frame()) {
2905         st->print_cr("size: %d argsize: %d",
2906                      ContinuationHelper::NonInterpretedUnknownFrame::size(fr),
2907                      ContinuationHelper::NonInterpretedUnknownFrame::stack_argsize(fr));
2908       }
2909       VMReg reg = fst.register_map()->find_register_spilled_here(cl.p(), fst.current()->sp());
2910       if (reg != nullptr) {
2911         st->print_cr("Reg %s %d", reg->name(), reg->is_stack() ? (int)reg->reg2stack() : -99);
2912       }
2913       cl.reset();
2914       DEBUG_ONLY(thread->print_frame_layout();)
2915       if (chunk != nullptr) {
2916         chunk->print_on(true, st);
2917       }
2918       return false;
2919     }
2920   }
2921   return true;
2922 }
2923 
2924 static void log_frames(JavaThread* thread) {
2925   const static int show_entry_callers = 3;
2926   LogTarget(Trace, continuations) lt;
2927   if (!lt.develop_is_enabled()) {
2928     return;
2929   }
2930   LogStream ls(lt);
2931 
2932   ls.print_cr("------- frames --------- for thread " INTPTR_FORMAT, p2i(thread));
2933   if (!thread->has_last_Java_frame()) {
2934     ls.print_cr("NO ANCHOR!");
2935   }
2936 
2937   RegisterMap map(thread,
2938                   RegisterMap::UpdateMap::include,
2939                   RegisterMap::ProcessFrames::include,
2940                   RegisterMap::WalkContinuation::skip);
2941   map.set_include_argument_oops(false);
2942 
2943   if (false) {
2944     for (frame f = thread->last_frame(); !f.is_entry_frame(); f = f.sender(&map)) {
2945       f.print_on(&ls);
2946     }
2947   } else {

2949     ResetNoHandleMark rnhm;
2950     ResourceMark rm;
2951     HandleMark hm(Thread::current());
2952     FrameValues values;
2953 
2954     int i = 0;
2955     int post_entry = -1;
2956     for (frame f = thread->last_frame(); !f.is_first_frame(); f = f.sender(&map), i++) {
2957       f.describe(values, i, &map, i == 0);
2958       if (post_entry >= 0 || Continuation::is_continuation_enterSpecial(f))
2959         post_entry++;
2960       if (post_entry >= show_entry_callers)
2961         break;
2962     }
2963     values.print_on(thread, &ls);
2964   }
2965 
2966   ls.print_cr("======= end frames =========");
2967 }
2968 
2969 static void log_frames_after_thaw(JavaThread* thread, ContinuationWrapper& cont, intptr_t* sp, bool preempted) {
2970   intptr_t* sp0 = sp;
2971   address pc0 = *(address*)(sp - frame::sender_sp_ret_address_offset());
2972 
2973   if (preempted && sp0 == cont.entrySP()) {


2974     // Still preempted (monitor not acquired) so no frames were thawed.
2975     assert(cont.tail()->preempted(), "");
2976     set_anchor(thread, cont.entrySP(), cont.entryPC());

2977   } else {
2978     set_anchor(thread, sp0);
2979   }
2980 
2981   log_frames(thread);
2982   if (LoomVerifyAfterThaw) {
2983     assert(do_verify_after_thaw(thread, cont.tail(), tty), "");
2984   }
2985   assert(ContinuationEntry::assert_entry_frame_laid_out(thread), "");
2986   clear_anchor(thread);
2987 
2988   LogTarget(Trace, continuations) lt;
2989   if (lt.develop_is_enabled()) {
2990     LogStream ls(lt);
2991     ls.print_cr("Jumping to frame (thaw):");
2992     frame(sp).print_value_on(&ls);
2993   }
2994 }
2995 #endif // ASSERT
2996 
2997 #include CPU_HEADER_INLINE(continuationFreezeThaw)
2998 
2999 #ifdef ASSERT
3000 static void print_frame_layout(const frame& f, bool callee_complete, outputStream* st) {
3001   ResourceMark rm;
3002   FrameValues values;
3003   assert(f.get_cb() != nullptr, "");
3004   RegisterMap map(f.is_heap_frame() ?
3005                     nullptr :

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

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

1085     log_develop_trace(continuations)("Reusing chunk mixed: %d empty: %d", chunk->has_mixed_frames(), chunk->is_empty());
1086     if (chunk->is_empty()) {
1087       int sp = chunk->stack_size() - argsize_md;
1088       chunk->set_sp(sp);
1089       chunk->set_bottom(sp);
1090       _freeze_size += overlap;
1091       assert(chunk->max_thawing_size() == 0, "");
1092     } DEBUG_ONLY(else empty_chunk = false;)
1093   }
1094   assert(!chunk->is_gc_mode(), "");
1095   assert(!chunk->has_bitmap(), "");
1096   chunk->set_has_mixed_frames(true);
1097 
1098   assert(chunk->requires_barriers() == _barriers, "");
1099   assert(!_barriers || chunk->is_empty(), "");
1100 
1101   assert(!chunk->is_empty() || StackChunkFrameStream<ChunkFrames::Mixed>(chunk).is_done(), "");
1102   assert(!chunk->is_empty() || StackChunkFrameStream<ChunkFrames::Mixed>(chunk).to_frame().is_empty(), "");
1103 
1104   if (_preempt) {
1105     frame top_frame = _thread->last_frame();
1106     if (top_frame.is_interpreted_frame()) {
1107       // Some platforms do not save the last_sp in the top interpreter frame on VM calls.
1108       // We need it so that on resume we can restore the sp to the right place, since
1109       // thawing might add an alignment word to the expression stack (see finish_thaw()).
1110       // We do it now that we know freezing will be successful.
1111       prepare_freeze_interpreted_top_frame(top_frame);
1112     }
1113 
1114     // Do this now so should_process_args_at_top() is set before calling finish_freeze
1115     // in case we might need to apply GC barriers to frames in this stackChunk.
1116     if (_thread->at_preemptable_init()) {
1117       assert(top_frame.is_interpreted_frame(), "only InterpreterRuntime::_new/resolve_from_cache allowed");
1118       chunk->set_at_klass_init(true);
1119       methodHandle m(_thread, top_frame.interpreter_frame_method());
1120       Bytecode_invoke call = Bytecode_invoke_check(m, top_frame.interpreter_frame_bci());
1121       assert(!call.is_valid() || call.is_invokestatic(), "only invokestatic allowed");
1122       if (call.is_invokestatic() && call.size_of_parameters() > 0) {
1123         assert(top_frame.interpreter_frame_expression_stack_size() > 0, "should have parameters in exp stack");
1124         chunk->set_has_args_at_top(true);
1125       }
1126     }
1127   }
1128 
1129   // We unwind frames after the last safepoint so that the GC will have found the oops in the frames, but before
1130   // writing into the chunk. This is so that an asynchronous stack walk (not at a safepoint) that suspends us here
1131   // will either see no continuation or a consistent chunk.
1132   unwind_frames();
1133 
1134   chunk->set_max_thawing_size(chunk->max_thawing_size() + _freeze_size - _monitors_in_lockstack - frame::metadata_words);
1135 
1136   if (lt.develop_is_enabled()) {
1137     LogStream ls(lt);
1138     ls.print_cr("top chunk:");
1139     chunk->print_on(&ls);
1140   }
1141 
1142   if (_monitors_in_lockstack > 0) {
1143     freeze_lockstack(chunk);
1144   }
1145 

1617       // Some GCs could put direct allocations in old gen for slow-path
1618       // allocations; need to explicitly check if that was the case.
1619       _barriers = chunk->requires_barriers();
1620     }
1621   }
1622 
1623   if (_barriers) {
1624     log_develop_trace(continuations)("allocation requires barriers");
1625   }
1626 
1627   assert(chunk->parent() == nullptr || chunk->parent()->is_stackChunk(), "");
1628 
1629   return chunk;
1630 }
1631 
1632 void FreezeBase::throw_stack_overflow_on_humongous_chunk() {
1633   ContinuationWrapper::SafepointOp so(_thread, _cont); // could also call _cont.done() instead
1634   Exceptions::_throw_msg(_thread, __FILE__, __LINE__, vmSymbols::java_lang_StackOverflowError(), "Humongous stack chunk");
1635 }
1636 
1637 class AnchorMark : public StackObj {
1638   JavaThread* _current;
1639   frame& _top_frame;
1640   intptr_t* _last_sp_from_frame;
1641   bool _is_interpreted;
1642 
1643  public:
1644   AnchorMark(JavaThread* current, frame& f) : _current(current), _top_frame(f), _is_interpreted(false) {
1645     intptr_t* sp = anchor_mark_set_pd();
1646     set_anchor(_current, sp);
1647   }
1648   ~AnchorMark() {
1649     clear_anchor(_current);
1650     anchor_mark_clear_pd();
1651   }
1652   inline intptr_t* anchor_mark_set_pd();
1653   inline void anchor_mark_clear_pd();
1654 };
1655 
1656 #if INCLUDE_JVMTI
1657 static int num_java_frames(ContinuationWrapper& cont) {
1658   ResourceMark rm; // used for scope traversal in num_java_frames(nmethod*, address)
1659   int count = 0;
1660   for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
1661     count += chunk->num_java_frames();
1662   }
1663   return count;
1664 }
1665 
1666 static void invalidate_jvmti_stack(JavaThread* thread) {
1667   JvmtiThreadState *state = thread->jvmti_thread_state();
1668   if (state != nullptr) {
1669     state->invalidate_cur_stack_depth();
1670   }
1671 }
1672 
1673 static void jvmti_yield_cleanup(JavaThread* thread, ContinuationWrapper& cont) {
1674   if (JvmtiExport::has_frame_pops(thread)) {
1675     int num_frames = num_java_frames(cont);
1676 
1677     ContinuationWrapper::SafepointOp so(Thread::current(), cont);
1678     JvmtiExport::continuation_yield_cleanup(JavaThread::current(), num_frames);
1679   }
1680   invalidate_jvmti_stack(thread);
1681 }
1682 
1683 static void jvmti_mount_end(JavaThread* current, ContinuationWrapper& cont, frame top, Continuation::preempt_kind pk) {
1684   assert(current->vthread() != nullptr, "must be");
1685 
1686   HandleMarkCleaner hm(current);  // Cleanup vth and so._conth Handles
1687   Handle vth(current, current->vthread());

1688   ContinuationWrapper::SafepointOp so(current, cont);
1689 
1690   AnchorMark am(current, top);  // Set anchor so that the stack is walkable.

1691 
1692   JRT_BLOCK
1693     JvmtiVTMSTransitionDisabler::VTMS_vthread_mount((jthread)vth.raw_value(), false);
1694 
1695     if (current->pending_contended_entered_event()) {
1696       // No monitor JVMTI events for ObjectLocker case.
1697       if (pk != Continuation::object_locker) {
1698         JvmtiExport::post_monitor_contended_entered(current, current->contended_entered_monitor());
1699       }
1700       current->set_contended_entered_monitor(nullptr);
1701     }
1702   JRT_BLOCK_END


1703 }
1704 #endif // INCLUDE_JVMTI
1705 
1706 #ifdef ASSERT
1707 // There are no interpreted frames if we're not called from the interpreter and we haven't ancountered an i2c
1708 // adapter or called Deoptimization::unpack_frames. As for native frames, upcalls from JNI also go through the
1709 // interpreter (see JavaCalls::call_helper), while the UpcallLinker explicitly sets cont_fastpath.
1710 bool FreezeBase::check_valid_fast_path() {
1711   ContinuationEntry* ce = _thread->last_continuation();
1712   RegisterMap map(_thread,
1713                   RegisterMap::UpdateMap::skip,
1714                   RegisterMap::ProcessFrames::skip,
1715                   RegisterMap::WalkContinuation::skip);
1716   map.set_include_argument_oops(false);
1717   bool is_top_frame = true;
1718   for (frame f = freeze_start_frame(); Continuation::is_frame_in_continuation(ce, f); f = f.sender(&map), is_top_frame = false) {
1719     if (!((f.is_compiled_frame() && !f.is_deoptimized_frame()) || (is_top_frame && (f.is_runtime_frame() || f.is_native_frame())))) {
1720       return false;
1721     }
1722   }
1723   return true;
1724 }
1725 
1726 static void verify_frame_kind(const frame& top, Continuation::preempt_kind preempt_kind, Method** m_ptr, const char** code_name_ptr, int* bci_ptr) {
1727   Method* m;
1728   const char* code_name;
1729   int bci;
1730   if (preempt_kind == Continuation::monitorenter) {
1731     assert(top.is_interpreted_frame() || top.is_runtime_frame(), "");
1732     bool at_sync_method;
1733     if (top.is_interpreted_frame()) {
1734       m = top.interpreter_frame_method();
1735       assert(!m->is_native() || m->is_synchronized(), "invalid method %s", m->external_name());
1736       address bcp = top.interpreter_frame_bcp();
1737       assert(bcp != 0 || m->is_native(), "");
1738       at_sync_method = m->is_synchronized() && (bcp == 0 || bcp == m->code_base());
1739       // bcp is advanced on monitorenter before making the VM call, adjust for that.
1740       bool at_sync_bytecode = bcp > m->code_base() && Bytecode(m, bcp - 1).code() == Bytecodes::Code::_monitorenter;
1741       assert(at_sync_method || at_sync_bytecode, "");
1742       bci = at_sync_method ? -1 : top.interpreter_frame_bci();
1743     } else {
1744       JavaThread* current = JavaThread::current();
1745       ResourceMark rm(current);
1746       CodeBlob* cb = top.cb();
1747       RegisterMap reg_map(current,
1748                   RegisterMap::UpdateMap::skip,
1749                   RegisterMap::ProcessFrames::skip,
1750                   RegisterMap::WalkContinuation::skip);
1751       frame fr = top.sender(&reg_map);
1752       vframe*  vf  = vframe::new_vframe(&fr, &reg_map, current);
1753       compiledVFrame* cvf = compiledVFrame::cast(vf);
1754       m = cvf->method();
1755       bci = cvf->scope()->bci();
1756       at_sync_method = bci == SynchronizationEntryBCI;
1757       assert(!at_sync_method || m->is_synchronized(), "bci is %d but method %s is not synchronized", bci, m->external_name());
1758       bool is_c1_monitorenter = false, is_c2_monitorenter = false;
1759       COMPILER1_PRESENT(is_c1_monitorenter = cb == Runtime1::blob_for(StubId::c1_monitorenter_id) ||
1760                                              cb == Runtime1::blob_for(StubId::c1_monitorenter_nofpu_id);)
1761       COMPILER2_PRESENT(is_c2_monitorenter = cb == CodeCache::find_blob(OptoRuntime::complete_monitor_locking_Java());)
1762       assert(is_c1_monitorenter || is_c2_monitorenter, "wrong runtime stub frame");
1763     }
1764     code_name = at_sync_method ? "synchronized method" : "monitorenter";
1765   } else if (preempt_kind == Continuation::object_wait) {
1766     assert(top.is_interpreted_frame() || top.is_native_frame(), "");
1767     m  = top.is_interpreted_frame() ? top.interpreter_frame_method() : top.cb()->as_nmethod()->method();
1768     assert(m->is_object_wait0(), "");
1769     bci = 0;
1770     code_name = "";
1771   } else {
1772     assert(preempt_kind == Continuation::object_locker, "invalid preempt kind");
1773     assert(top.is_interpreted_frame(), "");
1774     m = top.interpreter_frame_method();
1775     Bytecode current_bytecode = Bytecode(m, top.interpreter_frame_bcp());
1776     Bytecodes::Code code = current_bytecode.code();
1777     assert(code == Bytecodes::Code::_new || code == Bytecodes::Code::_invokestatic ||
1778            (code == Bytecodes::Code::_getstatic || code == Bytecodes::Code::_putstatic), "invalid bytecode");
1779     bci = top.interpreter_frame_bci();
1780     code_name = Bytecodes::name(current_bytecode.code());
1781   }
1782   assert(bci >= 0 || m->is_synchronized(), "invalid bci:%d at method %s", bci, m->external_name());
1783 
1784   if (m_ptr != nullptr) {
1785     *m_ptr = m;
1786     *code_name_ptr = code_name;
1787     *bci_ptr = bci;
1788   }
1789 }
1790 
1791 static void log_preempt_after_freeze(ContinuationWrapper& cont) {
1792   JavaThread* current = cont.thread();
1793   int64_t tid = current->monitor_owner_id();
1794 
1795   StackChunkFrameStream<ChunkFrames::Mixed> sfs(cont.tail());
1796   frame top_frame = sfs.to_frame();
1797   bool at_init = current->at_preemptable_init();
1798   bool at_enter = current->current_pending_monitor() != nullptr;
1799   bool at_wait = current->current_waiting_monitor() != nullptr;
1800   assert((at_enter && !at_wait) || (!at_enter && at_wait), "");
1801   Continuation::preempt_kind pk = at_init ? Continuation::object_locker : at_enter ? Continuation::monitorenter : Continuation::object_wait;
1802 
1803   Method* m = nullptr;
1804   const char* code_name = nullptr;
1805   int bci = InvalidFrameStateBci;
1806   verify_frame_kind(top_frame, pk, &m, &code_name, &bci);
1807   assert(m != nullptr && code_name != nullptr && bci != InvalidFrameStateBci, "should be set");
1808 
1809   ResourceMark rm(current);
1810   if (bci < 0) {
1811     log_trace(continuations, preempt)("Preempted " INT64_FORMAT " while synchronizing on %smethod %s", tid, m->is_native() ? "native " : "", m->external_name());
1812   } else if (m->is_object_wait0()) {
1813     log_trace(continuations, preempt)("Preempted " INT64_FORMAT " at native method %s", tid, m->external_name());
1814   } else {
1815     Klass* k = current->preempt_init_klass();
1816     assert(k != nullptr || !at_init, "");
1817     log_trace(continuations, preempt)("Preempted " INT64_FORMAT " at %s(bci:%d) in method %s %s%s", tid, code_name, bci,
1818             m->external_name(), at_init ? "trying to initialize klass " : "", at_init ? k->external_name() : "");
1819   }
1820 }
1821 #endif // ASSERT
1822 
1823 static inline freeze_result freeze_epilog(ContinuationWrapper& cont) {
1824   verify_continuation(cont.continuation());
1825   assert(!cont.is_empty(), "");
1826 
1827   log_develop_debug(continuations)("=== End of freeze cont ### #" INTPTR_FORMAT, cont.hash());
1828   return freeze_ok;
1829 }
1830 
1831 static freeze_result freeze_epilog(JavaThread* thread, ContinuationWrapper& cont, freeze_result res) {
1832   if (UNLIKELY(res != freeze_ok)) {
1833     JFR_ONLY(thread->set_last_freeze_fail_result(res);)
1834     verify_continuation(cont.continuation());
1835     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
1836     return res;
1837   }
1838 
1839   JVMTI_ONLY(jvmti_yield_cleanup(thread, cont)); // can safepoint
1840   return freeze_epilog(cont);
1841 }
1842 
1843 static freeze_result preempt_epilog(ContinuationWrapper& cont, freeze_result res, frame& old_last_frame) {
1844   if (UNLIKELY(res != freeze_ok)) {
1845     verify_continuation(cont.continuation());
1846     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
1847     return res;
1848   }
1849 
1850   // Set up things so that on return to Java we jump to preempt stub.
1851   patch_return_pc_with_preempt_stub(old_last_frame);
1852   cont.tail()->set_preempted(true);
1853   DEBUG_ONLY(log_preempt_after_freeze(cont);)
1854   return freeze_epilog(cont);
1855 }
1856 
1857 template<typename ConfigT, bool preempt>
1858 static inline freeze_result freeze_internal(JavaThread* current, intptr_t* const sp) {
1859   assert(!current->has_pending_exception(), "");
1860 
1861 #ifdef ASSERT
1862   log_trace(continuations)("~~~~ freeze sp: " INTPTR_FORMAT "JavaThread: " INTPTR_FORMAT, p2i(current->last_continuation()->entry_sp()), p2i(current));
1863   log_frames(current);
1864 #endif
1865 
1866   CONT_JFR_ONLY(EventContinuationFreeze event;)
1867 
1868   ContinuationEntry* entry = current->last_continuation();
1869 
1870   oop oopCont = entry->cont_oop(current);
1871   assert(oopCont == current->last_continuation()->cont_oop(current), "");
1872   assert(ContinuationEntry::assert_entry_frame_laid_out(current), "");
1873 

2029   // 300 is an estimate for stack size taken for this native code, in addition to StackShadowPages
2030   // for the Java frames in the check below.
2031   if (!stack_overflow_check(thread, size + 300, bottom)) {
2032     return 0;
2033   }
2034 
2035   log_develop_trace(continuations)("prepare_thaw bottom: " INTPTR_FORMAT " top: " INTPTR_FORMAT " size: %d",
2036                               p2i(bottom), p2i(bottom - size), size);
2037   return size;
2038 }
2039 
2040 class ThawBase : public StackObj {
2041 protected:
2042   JavaThread* _thread;
2043   ContinuationWrapper& _cont;
2044   CONT_JFR_ONLY(FreezeThawJfrInfo _jfr_info;)
2045 
2046   intptr_t* _fastpath;
2047   bool _barriers;
2048   bool _preempted_case;
2049   bool _process_args_at_top;
2050   intptr_t* _top_unextended_sp_before_thaw;
2051   int _align_size;
2052   DEBUG_ONLY(intptr_t* _top_stack_address);
2053 
2054   // Only used for preemption on ObjectLocker
2055   ObjectMonitor* _monitor;
2056 
2057   StackChunkFrameStream<ChunkFrames::Mixed> _stream;
2058 
2059   NOT_PRODUCT(int _frames;)
2060 
2061 protected:
2062   ThawBase(JavaThread* thread, ContinuationWrapper& cont) :
2063       _thread(thread), _cont(cont),
2064       _fastpath(nullptr) {
2065     DEBUG_ONLY(_top_unextended_sp_before_thaw = nullptr;)
2066     assert (cont.tail() != nullptr, "no last chunk");
2067     DEBUG_ONLY(_top_stack_address = _cont.entrySP() - thaw_size(cont.tail());)
2068   }
2069 
2070   void clear_chunk(stackChunkOop chunk);
2071   template<bool check_stub>
2072   int remove_top_compiled_frame_from_chunk(stackChunkOop chunk, int &argsize);
2073   void copy_from_chunk(intptr_t* from, intptr_t* to, int size);
2074 
2075   void thaw_lockstack(stackChunkOop chunk);
2076 
2077   // fast path
2078   inline void prefetch_chunk_pd(void* start, int size_words);
2079   void patch_return(intptr_t* sp, bool is_last);
2080 
2081   intptr_t* handle_preempted_continuation(intptr_t* sp, Continuation::preempt_kind preempt_kind, bool fast_case);
2082   inline intptr_t* push_cleanup_continuation();
2083   inline intptr_t* push_preempt_adapter();
2084   intptr_t* redo_vmcall(JavaThread* current, frame& top);
2085   void throw_interrupted_exception(JavaThread* current, frame& top);
2086 
2087   void recurse_thaw(const frame& heap_frame, frame& caller, int num_frames, bool top_on_preempt_case);
2088   void finish_thaw(frame& f);
2089 
2090 private:
2091   template<typename FKind> bool recurse_thaw_java_frame(frame& caller, int num_frames);
2092   void finalize_thaw(frame& entry, int argsize);
2093 
2094   inline bool seen_by_gc();
2095 
2096   inline void before_thaw_java_frame(const frame& hf, const frame& caller, bool bottom, int num_frame);
2097   inline void after_thaw_java_frame(const frame& f, bool bottom);
2098   inline void patch(frame& f, const frame& caller, bool bottom);
2099   void clear_bitmap_bits(address start, address end);
2100 
2101   NOINLINE void recurse_thaw_interpreted_frame(const frame& hf, frame& caller, int num_frames, bool is_top);
2102   void recurse_thaw_compiled_frame(const frame& hf, frame& caller, int num_frames, bool stub_caller);
2103   void recurse_thaw_stub_frame(const frame& hf, frame& caller, int num_frames);
2104   void recurse_thaw_native_frame(const frame& hf, frame& caller, int num_frames);
2105 
2106   void push_return_frame(frame& f);
2107   inline frame new_entry_frame();
2108   template<typename FKind> frame new_stack_frame(const frame& hf, frame& caller, bool bottom);
2109   inline void patch_pd(frame& f, const frame& sender);
2110   inline void patch_pd(frame& f, intptr_t* caller_sp);
2111   inline intptr_t* align(const frame& hf, intptr_t* frame_sp, frame& caller, bool bottom);
2112 
2113   void maybe_set_fastpath(intptr_t* sp) { if (sp > _fastpath) _fastpath = sp; }
2114 
2115   static inline void derelativize_interpreted_frame_metadata(const frame& hf, const frame& f);
2116 
2117  public:
2118   CONT_JFR_ONLY(FreezeThawJfrInfo& jfr_info() { return _jfr_info; })
2119 };
2120 
2121 template <typename ConfigT>

2181   chunk->set_sp(chunk->bottom());
2182   chunk->set_max_thawing_size(0);
2183 }
2184 
2185 template<bool check_stub>
2186 int ThawBase::remove_top_compiled_frame_from_chunk(stackChunkOop chunk, int &argsize) {
2187   bool empty = false;
2188   StackChunkFrameStream<ChunkFrames::CompiledOnly> f(chunk);
2189   DEBUG_ONLY(intptr_t* const chunk_sp = chunk->start_address() + chunk->sp();)
2190   assert(chunk_sp == f.sp(), "");
2191   assert(chunk_sp == f.unextended_sp(), "");
2192 
2193   int frame_size = f.cb()->frame_size();
2194   argsize = f.stack_argsize();
2195 
2196   assert(!f.is_stub() || check_stub, "");
2197   if (check_stub && f.is_stub()) {
2198     // If we don't thaw the top compiled frame too, after restoring the saved
2199     // registers back in Java, we would hit the return barrier to thaw one more
2200     // frame effectively overwriting the restored registers during that call.
2201     f.next(SmallRegisterMap::instance_no_args(), true /* stop */);
2202     assert(!f.is_done(), "");
2203 
2204     f.get_cb();
2205     assert(f.is_compiled(), "");
2206     frame_size += f.cb()->frame_size();
2207     argsize = f.stack_argsize();
2208 
2209     if (f.cb()->as_nmethod()->is_marked_for_deoptimization()) {
2210       // The caller of the runtime stub when the continuation is preempted is not at a
2211       // Java call instruction, and so cannot rely on nmethod patching for deopt.
2212       log_develop_trace(continuations)("Deoptimizing runtime stub caller");
2213       f.to_frame().deoptimize(nullptr); // the null thread simply avoids the assertion in deoptimize which we're not set up for
2214     }
2215   }
2216 
2217   f.next(SmallRegisterMap::instance_no_args(), true /* stop */);
2218   empty = f.is_done();
2219   assert(!empty || argsize == chunk->argsize(), "");
2220 
2221   if (empty) {
2222     clear_chunk(chunk);
2223   } else {
2224     chunk->set_sp(chunk->sp() + frame_size);
2225     chunk->set_max_thawing_size(chunk->max_thawing_size() - frame_size);
2226     // We set chunk->pc to the return pc into the next frame
2227     chunk->set_pc(f.pc());
2228 #ifdef ASSERT
2229     {
2230       intptr_t* retaddr_slot = (chunk_sp
2231                                 + frame_size
2232                                 - frame::sender_sp_ret_address_offset());
2233       assert(f.pc() == ContinuationHelper::return_address_at(retaddr_slot),
2234              "unexpected pc");
2235     }
2236 #endif
2237   }

2357   return rs.sp();
2358 }
2359 
2360 inline bool ThawBase::seen_by_gc() {
2361   return _barriers || _cont.tail()->is_gc_mode();
2362 }
2363 
2364 static inline void relativize_chunk_concurrently(stackChunkOop chunk) {
2365 #if INCLUDE_ZGC || INCLUDE_SHENANDOAHGC
2366   if (UseZGC || UseShenandoahGC) {
2367     chunk->relativize_derived_pointers_concurrently();
2368   }
2369 #endif
2370 }
2371 
2372 template <typename ConfigT>
2373 NOINLINE intptr_t* Thaw<ConfigT>::thaw_slow(stackChunkOop chunk, Continuation::thaw_kind kind) {
2374   Continuation::preempt_kind preempt_kind;
2375   bool retry_fast_path = false;
2376 
2377   _process_args_at_top = false;
2378   _preempted_case = chunk->preempted();
2379   if (_preempted_case) {
2380     ObjectWaiter* waiter = java_lang_VirtualThread::objectWaiter(_thread->vthread());
2381     if (waiter != nullptr) {
2382       // Mounted again after preemption. Resume the pending monitor operation,
2383       // which will be either a monitorenter or Object.wait() call.
2384       ObjectMonitor* mon = waiter->monitor();
2385       preempt_kind = waiter->is_wait() ? Continuation::object_wait : Continuation::monitorenter;
2386 
2387       bool mon_acquired = mon->resume_operation(_thread, waiter, _cont);
2388       assert(!mon_acquired || mon->has_owner(_thread), "invariant");
2389       if (!mon_acquired) {
2390         // Failed to acquire monitor. Return to enterSpecial to unmount again.
2391         log_develop_trace(continuations, preempt)("Failed to acquire monitor, unmounting again");
2392         return push_cleanup_continuation();
2393       }
2394       _monitor = mon;        // remember monitor since we might need it on handle_preempted_continuation()
2395       chunk = _cont.tail();  // reload oop in case of safepoint in resume_operation (if posting JVMTI events).
2396       JVMTI_ONLY(assert(_thread->contended_entered_monitor() == nullptr || _thread->contended_entered_monitor() == _monitor, ""));
2397     } else {
2398       // Preemption cancelled on moniterenter or ObjectLocker case. We
2399       // actually acquired the monitor after freezing all frames so no
2400       // need to call resume_operation. If this is the ObjectLocker case
2401       // we released the monitor already at ~ObjectLocker, so here we set
2402       // _monitor to nullptr to indicate there is no need to release it later.
2403       preempt_kind = Continuation::monitorenter;
2404       _monitor = nullptr;
2405     }
2406 
2407     // Call this first to avoid racing with GC threads later when modifying the chunk flags.
2408     relativize_chunk_concurrently(chunk);
2409 
2410     if (chunk->at_klass_init()) {
2411       preempt_kind = Continuation::object_locker;
2412       chunk->set_at_klass_init(false);
2413       _process_args_at_top = chunk->has_args_at_top();
2414       if (_process_args_at_top) {
2415         // Only needed for the top frame which will be thawed.
2416         chunk->set_has_args_at_top(false);
2417       }
2418     }
2419     chunk->set_preempted(false);
2420     retry_fast_path = true;
2421   } else {
2422     relativize_chunk_concurrently(chunk);
2423   }
2424 
2425   // On first thaw after freeze restore oops to the lockstack if any.
2426   assert(chunk->lockstack_size() == 0 || kind == Continuation::thaw_top, "");
2427   if (kind == Continuation::thaw_top && chunk->lockstack_size() > 0) {
2428     thaw_lockstack(chunk);
2429     retry_fast_path = true;
2430   }
2431 
2432   // Retry the fast path now that we possibly cleared the FLAG_HAS_LOCKSTACK
2433   // and FLAG_PREEMPTED flags from the stackChunk.
2434   if (retry_fast_path && can_thaw_fast(chunk)) {
2435     intptr_t* sp = thaw_fast<true>(chunk);
2436     if (_preempted_case) {
2437       return handle_preempted_continuation(sp, preempt_kind, true /* fast_case */);
2438     }

2482 
2483   intptr_t* sp = caller.sp();
2484 
2485   if (_preempted_case) {
2486     return handle_preempted_continuation(sp, preempt_kind, false /* fast_case */);
2487   }
2488   return sp;
2489 }
2490 
2491 void ThawBase::recurse_thaw(const frame& heap_frame, frame& caller, int num_frames, bool top_on_preempt_case) {
2492   log_develop_debug(continuations)("thaw num_frames: %d", num_frames);
2493   assert(!_cont.is_empty(), "no more frames");
2494   assert(num_frames > 0, "");
2495   assert(!heap_frame.is_empty(), "");
2496 
2497   if (top_on_preempt_case && (heap_frame.is_native_frame() || heap_frame.is_runtime_frame())) {
2498     heap_frame.is_native_frame() ? recurse_thaw_native_frame(heap_frame, caller, 2) : recurse_thaw_stub_frame(heap_frame, caller, 2);
2499   } else if (!heap_frame.is_interpreted_frame()) {
2500     recurse_thaw_compiled_frame(heap_frame, caller, num_frames, false);
2501   } else {
2502     recurse_thaw_interpreted_frame(heap_frame, caller, num_frames, top_on_preempt_case);
2503   }
2504 }
2505 
2506 template<typename FKind>
2507 bool ThawBase::recurse_thaw_java_frame(frame& caller, int num_frames) {
2508   assert(num_frames > 0, "");
2509 
2510   DEBUG_ONLY(_frames++;)
2511 
2512   int argsize = _stream.stack_argsize();
2513 
2514   _stream.next(SmallRegisterMap::instance_no_args());
2515   assert(_stream.to_frame().is_empty() == _stream.is_done(), "");
2516 
2517   // we never leave a compiled caller of an interpreted frame as the top frame in the chunk
2518   // as it makes detecting that situation and adjusting unextended_sp tricky
2519   if (num_frames == 1 && !_stream.is_done() && FKind::interpreted && _stream.is_compiled()) {
2520     log_develop_trace(continuations)("thawing extra compiled frame to not leave a compiled interpreted-caller at top");
2521     num_frames++;
2522   }
2523 
2524   if (num_frames == 1 || _stream.is_done()) { // end recursion
2525     finalize_thaw(caller, FKind::interpreted ? 0 : argsize);
2526     return true; // bottom
2527   } else { // recurse
2528     recurse_thaw(_stream.to_frame(), caller, num_frames - 1, false /* top_on_preempt_case */);
2529     return false;
2530   }
2531 }
2532 
2533 void ThawBase::finalize_thaw(frame& entry, int argsize) {
2534   stackChunkOop chunk = _cont.tail();

2599 
2600 void ThawBase::clear_bitmap_bits(address start, address end) {
2601   assert(is_aligned(start, wordSize), "should be aligned: " PTR_FORMAT, p2i(start));
2602   assert(is_aligned(end, VMRegImpl::stack_slot_size), "should be aligned: " PTR_FORMAT, p2i(end));
2603 
2604   // we need to clear the bits that correspond to arguments as they reside in the caller frame
2605   // or they will keep objects that are otherwise unreachable alive.
2606 
2607   // Align `end` if UseCompressedOops is not set to avoid UB when calculating the bit index, since
2608   // `end` could be at an odd number of stack slots from `start`, i.e might not be oop aligned.
2609   // If that's the case the bit range corresponding to the last stack slot should not have bits set
2610   // anyways and we assert that before returning.
2611   address effective_end = UseCompressedOops ? end : align_down(end, wordSize);
2612   log_develop_trace(continuations)("clearing bitmap for " INTPTR_FORMAT " - " INTPTR_FORMAT, p2i(start), p2i(effective_end));
2613   stackChunkOop chunk = _cont.tail();
2614   chunk->bitmap().clear_range(chunk->bit_index_for(start), chunk->bit_index_for(effective_end));
2615   assert(effective_end == end || !chunk->bitmap().at(chunk->bit_index_for(effective_end)), "bit should not be set");
2616 }
2617 
2618 intptr_t* ThawBase::handle_preempted_continuation(intptr_t* sp, Continuation::preempt_kind preempt_kind, bool fast_case) {

2619   frame top(sp);
2620   assert(top.pc() == *(address*)(sp - frame::sender_sp_ret_address_offset()), "");
2621   DEBUG_ONLY(verify_frame_kind(top, preempt_kind);)
2622   NOT_PRODUCT(int64_t tid = _thread->monitor_owner_id();)
2623 
2624 #if INCLUDE_JVMTI
2625   // Finish the VTMS transition.
2626   assert(_thread->is_in_VTMS_transition(), "must be");
2627   bool is_vthread = Continuation::continuation_scope(_cont.continuation()) == java_lang_VirtualThread::vthread_scope();
2628   if (is_vthread) {
2629     if (JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events()) {
2630       jvmti_mount_end(_thread, _cont, top, preempt_kind);
2631     } else {
2632       _thread->set_is_in_VTMS_transition(false);
2633       java_lang_Thread::set_is_in_VTMS_transition(_thread->vthread(), false);
2634     }
2635   }
2636 #endif
2637 
2638   if (fast_case) {
2639     // If we thawed in the slow path the runtime stub/native wrapper frame already
2640     // has the correct fp (see ThawBase::new_stack_frame). On the fast path though,
2641     // we copied the fp patched during freeze, which will now have to be fixed.
2642     assert(top.is_runtime_frame() || top.is_native_frame(), "");
2643     int fsize = top.cb()->frame_size();
2644     patch_pd(top, sp + fsize);
2645   }
2646 
2647   if (preempt_kind == Continuation::object_wait) {
2648     // Check now if we need to throw IE exception.
2649     bool throw_ie = _thread->pending_interrupted_exception();
2650     if (throw_ie) {
2651       throw_interrupted_exception(_thread, top);
2652       _thread->set_pending_interrupted_exception(false);
2653     }
2654     log_develop_trace(continuations, preempt)("Resuming " INT64_FORMAT" after preemption on Object.wait%s", tid, throw_ie ? "(throwing IE)" : "");
2655   } else if (preempt_kind == Continuation::monitorenter) {
2656     if (top.is_runtime_frame()) {
2657       // The continuation might now run on a different platform thread than the previous time so
2658       // we need to adjust the current thread saved in the stub frame before restoring registers.
2659       JavaThread** thread_addr = frame::saved_thread_address(top);
2660       if (thread_addr != nullptr) *thread_addr = _thread;
2661     }
2662     log_develop_trace(continuations, preempt)("Resuming " INT64_FORMAT " after preemption on monitorenter", tid);
2663   } else {
2664     // We need to redo the original call into the VM. First though, we need
2665     // to exit the monitor we just acquired (except on preemption cancelled
2666     // case where it was already released).
2667     assert(preempt_kind == Continuation::object_locker, "");
2668     if (_monitor != nullptr) _monitor->exit(_thread);
2669     sp = redo_vmcall(_thread, top);
2670   }
2671   return sp;
2672 }
2673 
2674 intptr_t* ThawBase::redo_vmcall(JavaThread* current, frame& top) {
2675   assert(!current->preempting(), "");
2676   NOT_PRODUCT(int64_t tid = current->monitor_owner_id();)
2677   intptr_t* sp = top.sp();
2678 
2679   {
2680     HandleMarkCleaner hmc(current);  // Cleanup so._conth Handle
2681     ContinuationWrapper::SafepointOp so(current, _cont);
2682     AnchorMark am(current, top);    // Set the anchor so that the stack is walkable.
2683 
2684     Method* m = top.interpreter_frame_method();
2685     Bytecode current_bytecode = Bytecode(m, top.interpreter_frame_bcp());
2686     Bytecodes::Code code = current_bytecode.code();
2687     log_develop_trace(continuations, preempt)("Redoing InterpreterRuntime::%s for " INT64_FORMAT, code == Bytecodes::Code::_new ? "_new" : "resolve_from_cache", tid);
2688 
2689     // These InterpreterRuntime entry points use JRT_ENTRY which uses a HandleMarkCleaner.
2690     // Create a HandeMark to avoid destroying so._conth.
2691     HandleMark hm(current);
2692     DEBUG_ONLY(JavaThread::AtRedoVMCall apvmc(current);)
2693     if (code == Bytecodes::Code::_new) {
2694       InterpreterRuntime::_new(current, m->constants(), current_bytecode.get_index_u2(code));
2695     } else {
2696       InterpreterRuntime::resolve_from_cache(current, code);
2697     }
2698   }
2699 
2700   if (current->preempting()) {
2701     // Preempted again so we just arrange to return to preempt stub to unmount.
2702     sp = push_preempt_adapter();
2703     current->set_preempt_alternate_return(nullptr);
2704     bool cancelled = current->preemption_cancelled();
2705     if (cancelled) {
2706       // Since preemption was cancelled, the thread will call thaw again from the preempt
2707       // stub. These retries could happen several times due to contention on the init_lock,
2708       // so just let the vthread umount to give a chance for other vthreads to run.
2709       current->set_preemption_cancelled(false);
2710       oop vthread = current->vthread();
2711       assert(java_lang_VirtualThread::state(vthread) == java_lang_VirtualThread::RUNNING, "wrong state for vthread");
2712       java_lang_VirtualThread::set_state(vthread, java_lang_VirtualThread::YIELDING);
2713 #if INCLUDE_JVMTI
2714       if (current->contended_entered_monitor() != nullptr) {
2715         current->set_contended_entered_monitor(nullptr);
2716       }
2717 #endif
2718     }
2719     log_develop_trace(continuations, preempt)("Preempted " INT64_FORMAT " again%s", tid, cancelled ? "(preemption cancelled, setting state to YIELDING)" : "");
2720   } else {
2721     log_develop_trace(continuations, preempt)("Call succesful, resuming " INT64_FORMAT, tid);
2722   }
2723   return sp;
2724 }
2725 
2726 void ThawBase::throw_interrupted_exception(JavaThread* current, frame& top) {
2727   HandleMarkCleaner hm(current);  // Cleanup so._conth Handle
2728   ContinuationWrapper::SafepointOp so(current, _cont);
2729   // Since we might safepoint set the anchor so that the stack can be walked.
2730   set_anchor(current, top.sp());
2731   JRT_BLOCK
2732     THROW(vmSymbols::java_lang_InterruptedException());
2733   JRT_BLOCK_END
2734   clear_anchor(current);
2735 }
2736 
2737 NOINLINE void ThawBase::recurse_thaw_interpreted_frame(const frame& hf, frame& caller, int num_frames, bool is_top) {
2738   assert(hf.is_interpreted_frame(), "");
2739 
2740   if (UNLIKELY(seen_by_gc())) {
2741     if (is_top && _process_args_at_top) {
2742       _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance_with_args());  
2743     } else {
2744       _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance_no_args());  
2745     }
2746   }
2747 
2748   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::InterpretedFrame>(caller, num_frames);
2749 
2750   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2751 
2752   _align_size += frame::align_wiggle; // possible added alignment for internal interpreted frame alignment om AArch64
2753 
2754   frame f = new_stack_frame<ContinuationHelper::InterpretedFrame>(hf, caller, is_bottom_frame);
2755 
2756   intptr_t* const stack_frame_top = f.sp() + frame::metadata_words_at_top;
2757   intptr_t* const stack_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(f);
2758   intptr_t* const heap_frame_top = hf.unextended_sp() + frame::metadata_words_at_top;
2759   intptr_t* const heap_frame_bottom = ContinuationHelper::InterpretedFrame::frame_bottom(hf);
2760 
2761   assert(hf.is_heap_frame(), "should be");
2762   assert(!f.is_heap_frame(), "should not be");
2763 
2764   const int fsize = pointer_delta_as_int(heap_frame_bottom, heap_frame_top);
2765   assert((stack_frame_bottom == stack_frame_top + fsize), "");

2770 
2771   // Make sure the relativized locals is already set.
2772   assert(f.interpreter_frame_local_at(0) == stack_frame_bottom - 1, "invalid frame bottom");
2773 
2774   derelativize_interpreted_frame_metadata(hf, f);
2775   patch(f, caller, is_bottom_frame);
2776 
2777   assert(f.is_interpreted_frame_valid(_cont.thread()), "invalid thawed frame");
2778   assert(stack_frame_bottom <= ContinuationHelper::Frame::frame_top(caller), "");
2779 
2780   CONT_JFR_ONLY(_jfr_info.record_interpreted_frame();)
2781 
2782   maybe_set_fastpath(f.sp());
2783 
2784   Method* m = hf.interpreter_frame_method();
2785   assert(!m->is_native() || !is_bottom_frame, "should be top frame of thaw_top case; missing caller frame");
2786   const int locals = m->max_locals();
2787 
2788   if (!is_bottom_frame) {
2789     // can only fix caller once this frame is thawed (due to callee saved regs)
2790     _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance_no_args());
2791   } else if (_cont.tail()->has_bitmap() && locals > 0) {
2792     assert(hf.is_heap_frame(), "should be");
2793     address start = (address)(heap_frame_bottom - locals);
2794     address end = (address)heap_frame_bottom;
2795     clear_bitmap_bits(start, end);
2796   }
2797 
2798   DEBUG_ONLY(after_thaw_java_frame(f, is_bottom_frame);)
2799   caller = f;
2800 }
2801 
2802 void ThawBase::recurse_thaw_compiled_frame(const frame& hf, frame& caller, int num_frames, bool stub_caller) {
2803   assert(hf.is_compiled_frame(), "");
2804   assert(_preempted_case || !stub_caller, "stub caller not at preemption");
2805 
2806   if (!stub_caller && UNLIKELY(seen_by_gc())) { // recurse_thaw_stub_frame already invoked our barriers with a full regmap
2807     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance_no_args());
2808   }
2809 
2810   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::CompiledFrame>(caller, num_frames);
2811 
2812   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2813 
2814   assert(caller.sp() == caller.unextended_sp(), "");
2815 
2816   if ((!is_bottom_frame && caller.is_interpreted_frame()) || (is_bottom_frame && Interpreter::contains(_cont.tail()->pc()))) {
2817     _align_size += frame::align_wiggle; // we add one whether or not we've aligned because we add it in recurse_freeze_compiled_frame
2818   }
2819 
2820   // new_stack_frame must construct the resulting frame using hf.pc() rather than hf.raw_pc() because the frame is not
2821   // yet laid out in the stack, and so the original_pc is not stored in it.
2822   // As a result, f.is_deoptimized_frame() is always false and we must test hf to know if the frame is deoptimized.
2823   frame f = new_stack_frame<ContinuationHelper::CompiledFrame>(hf, caller, is_bottom_frame);
2824   intptr_t* const stack_frame_top = f.sp();
2825   intptr_t* const heap_frame_top = hf.unextended_sp();
2826 
2827   const int added_argsize = (is_bottom_frame || caller.is_interpreted_frame()) ? hf.compiled_frame_stack_argsize() : 0;

2846   assert(!f.is_deoptimized_frame(), "");
2847   if (hf.is_deoptimized_frame()) {
2848     maybe_set_fastpath(f.sp());
2849   } else if (_thread->is_interp_only_mode()
2850               || (stub_caller && f.cb()->as_nmethod()->is_marked_for_deoptimization())) {
2851     // The caller of the safepoint stub when the continuation is preempted is not at a call instruction, and so
2852     // cannot rely on nmethod patching for deopt.
2853     assert(_thread->is_interp_only_mode() || stub_caller, "expected a stub-caller");
2854 
2855     log_develop_trace(continuations)("Deoptimizing thawed frame");
2856     DEBUG_ONLY(ContinuationHelper::Frame::patch_pc(f, nullptr));
2857 
2858     f.deoptimize(nullptr); // the null thread simply avoids the assertion in deoptimize which we're not set up for
2859     assert(f.is_deoptimized_frame(), "");
2860     assert(ContinuationHelper::Frame::is_deopt_return(f.raw_pc(), f), "");
2861     maybe_set_fastpath(f.sp());
2862   }
2863 
2864   if (!is_bottom_frame) {
2865     // can only fix caller once this frame is thawed (due to callee saved regs); this happens on the stack
2866     _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance_no_args());
2867   } else if (_cont.tail()->has_bitmap() && added_argsize > 0) {
2868     address start = (address)(heap_frame_top + ContinuationHelper::CompiledFrame::size(hf) + frame::metadata_words_at_top);
2869     int stack_args_slots = f.cb()->as_nmethod()->num_stack_arg_slots(false /* rounded */);
2870     int argsize_in_bytes = stack_args_slots * VMRegImpl::stack_slot_size;
2871     clear_bitmap_bits(start, start + argsize_in_bytes);
2872   }
2873 
2874   DEBUG_ONLY(after_thaw_java_frame(f, is_bottom_frame);)
2875   caller = f;
2876 }
2877 
2878 void ThawBase::recurse_thaw_stub_frame(const frame& hf, frame& caller, int num_frames) {
2879   DEBUG_ONLY(_frames++;)
2880 
2881   if (UNLIKELY(seen_by_gc())) {
2882     // Process the stub's caller here since we might need the full map.
2883     RegisterMap map(nullptr,
2884                     RegisterMap::UpdateMap::include,
2885                     RegisterMap::ProcessFrames::skip,
2886                     RegisterMap::WalkContinuation::skip);
2887     map.set_include_argument_oops(false);
2888     _stream.next(&map);
2889     assert(!_stream.is_done(), "");
2890     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, &map);
2891   } else {
2892     _stream.next(SmallRegisterMap::instance_no_args());
2893     assert(!_stream.is_done(), "");
2894   }
2895 
2896   recurse_thaw_compiled_frame(_stream.to_frame(), caller, num_frames, true);
2897 
2898   assert(caller.is_compiled_frame(), "");
2899   assert(caller.sp() == caller.unextended_sp(), "");
2900 
2901   DEBUG_ONLY(before_thaw_java_frame(hf, caller, false /*is_bottom_frame*/, num_frames);)
2902 
2903   frame f = new_stack_frame<ContinuationHelper::StubFrame>(hf, caller, false);
2904   intptr_t* stack_frame_top = f.sp();
2905   intptr_t* heap_frame_top = hf.sp();
2906   int fsize = ContinuationHelper::StubFrame::size(hf);
2907 
2908   copy_from_chunk(heap_frame_top - frame::metadata_words, stack_frame_top - frame::metadata_words,
2909                   fsize + frame::metadata_words);
2910 
2911   patch(f, caller, false /*is_bottom_frame*/);
2912 
2913   // can only fix caller once this frame is thawed (due to callee saved regs)
2914   RegisterMap map(nullptr,
2915                   RegisterMap::UpdateMap::include,
2916                   RegisterMap::ProcessFrames::skip,
2917                   RegisterMap::WalkContinuation::skip);
2918   map.set_include_argument_oops(false);
2919   f.oop_map()->update_register_map(&f, &map);
2920   ContinuationHelper::update_register_map_with_callee(caller, &map);
2921   _cont.tail()->fix_thawed_frame(caller, &map);
2922 
2923   DEBUG_ONLY(after_thaw_java_frame(f, false /*is_bottom_frame*/);)
2924   caller = f;
2925 }
2926 
2927 void ThawBase::recurse_thaw_native_frame(const frame& hf, frame& caller, int num_frames) {
2928   assert(hf.is_native_frame(), "");
2929   assert(_preempted_case && hf.cb()->as_nmethod()->method()->is_object_wait0(), "");
2930 
2931   if (UNLIKELY(seen_by_gc())) { // recurse_thaw_stub_frame already invoked our barriers with a full regmap
2932     _cont.tail()->do_barriers<stackChunkOopDesc::BarrierType::Store>(_stream, SmallRegisterMap::instance_no_args());
2933   }
2934 
2935   const bool is_bottom_frame = recurse_thaw_java_frame<ContinuationHelper::NativeFrame>(caller, num_frames);
2936   assert(!is_bottom_frame, "");
2937 
2938   DEBUG_ONLY(before_thaw_java_frame(hf, caller, is_bottom_frame, num_frames);)
2939 
2940   assert(caller.sp() == caller.unextended_sp(), "");
2941 
2942   if (caller.is_interpreted_frame()) {
2943     _align_size += frame::align_wiggle; // we add one whether or not we've aligned because we add it in recurse_freeze_native_frame
2944   }
2945 
2946   // new_stack_frame must construct the resulting frame using hf.pc() rather than hf.raw_pc() because the frame is not
2947   // yet laid out in the stack, and so the original_pc is not stored in it.
2948   // As a result, f.is_deoptimized_frame() is always false and we must test hf to know if the frame is deoptimized.
2949   frame f = new_stack_frame<ContinuationHelper::NativeFrame>(hf, caller, false /* bottom */);
2950   intptr_t* const stack_frame_top = f.sp();
2951   intptr_t* const heap_frame_top = hf.unextended_sp();
2952 
2953   int fsize = ContinuationHelper::NativeFrame::size(hf);
2954   assert(fsize <= (int)(caller.unextended_sp() - f.unextended_sp()), "");
2955 
2956   intptr_t* from = heap_frame_top - frame::metadata_words_at_bottom;
2957   intptr_t* to   = stack_frame_top - frame::metadata_words_at_bottom;
2958   int sz = fsize + frame::metadata_words_at_bottom;
2959 
2960   copy_from_chunk(from, to, sz); // copying good oops because we invoked barriers above
2961 
2962   patch(f, caller, false /* bottom */);
2963 
2964   // f.is_deoptimized_frame() is always false and we must test hf.is_deoptimized_frame() (see comment above)
2965   assert(!f.is_deoptimized_frame(), "");
2966   assert(!hf.is_deoptimized_frame(), "");
2967   assert(!f.cb()->as_nmethod()->is_marked_for_deoptimization(), "");
2968 
2969   // can only fix caller once this frame is thawed (due to callee saved regs); this happens on the stack
2970   _cont.tail()->fix_thawed_frame(caller, SmallRegisterMap::instance_no_args());
2971 
2972   DEBUG_ONLY(after_thaw_java_frame(f, false /* bottom */);)
2973   caller = f;
2974 }
2975 
2976 void ThawBase::finish_thaw(frame& f) {
2977   stackChunkOop chunk = _cont.tail();
2978 
2979   if (chunk->is_empty()) {
2980     // Only remove chunk from list if it can't be reused for another freeze
2981     if (seen_by_gc()) {
2982       _cont.set_tail(chunk->parent());
2983     } else {
2984       chunk->set_has_mixed_frames(false);
2985     }
2986     chunk->set_max_thawing_size(0);
2987   } else {
2988     chunk->set_max_thawing_size(chunk->max_thawing_size() - _align_size);
2989   }
2990   assert(chunk->is_empty() == (chunk->max_thawing_size() == 0), "");
2991 
2992   if (!is_aligned(f.sp(), frame::frame_alignment)) {
2993     assert(f.is_interpreted_frame(), "");
2994     f.set_sp(align_down(f.sp(), frame::frame_alignment));
2995   }
2996   push_return_frame(f);
2997    // can only fix caller after push_return_frame (due to callee saved regs)
2998   if (_process_args_at_top) {
2999     chunk->fix_thawed_frame(f, SmallRegisterMap::instance_with_args());
3000   } else {
3001     chunk->fix_thawed_frame(f, SmallRegisterMap::instance_no_args());  
3002   }
3003 
3004   assert(_cont.is_empty() == _cont.last_frame().is_empty(), "");
3005 
3006   log_develop_trace(continuations)("thawed %d frames", _frames);
3007 
3008   LogTarget(Trace, continuations) lt;
3009   if (lt.develop_is_enabled()) {
3010     LogStream ls(lt);
3011     ls.print_cr("top hframe after (thaw):");
3012     _cont.last_frame().print_value_on(&ls);
3013   }
3014 }
3015 
3016 void ThawBase::push_return_frame(frame& f) { // see generate_cont_thaw
3017   assert(!f.is_compiled_frame() || f.is_deoptimized_frame() == f.cb()->as_nmethod()->is_deopt_pc(f.raw_pc()), "");
3018   assert(!f.is_compiled_frame() || f.is_deoptimized_frame() == (f.pc() != f.raw_pc()), "");
3019 
3020   LogTarget(Trace, continuations) lt;
3021   if (lt.develop_is_enabled()) {
3022     LogStream ls(lt);

3044 
3045   ContinuationEntry* entry = thread->last_continuation();
3046   assert(entry != nullptr, "");
3047   oop oopCont = entry->cont_oop(thread);
3048 
3049   assert(!jdk_internal_vm_Continuation::done(oopCont), "");
3050   assert(oopCont == get_continuation(thread), "");
3051   verify_continuation(oopCont);
3052 
3053   assert(entry->is_virtual_thread() == (entry->scope(thread) == java_lang_VirtualThread::vthread_scope()), "");
3054 
3055   ContinuationWrapper cont(thread, oopCont);
3056   log_develop_debug(continuations)("THAW #" INTPTR_FORMAT " " INTPTR_FORMAT, cont.hash(), p2i((oopDesc*)oopCont));
3057 
3058 #ifdef ASSERT
3059   set_anchor_to_entry(thread, cont.entry());
3060   log_frames(thread);
3061   clear_anchor(thread);
3062 #endif
3063 

3064   Thaw<ConfigT> thw(thread, cont);
3065   intptr_t* const sp = thw.thaw(kind);
3066   assert(is_aligned(sp, frame::frame_alignment), "");
3067   DEBUG_ONLY(log_frames_after_thaw(thread, cont, sp);)
3068 
3069   CONT_JFR_ONLY(thw.jfr_info().post_jfr_event(&event, cont.continuation(), thread);)
3070 
3071   verify_continuation(cont.continuation());
3072   log_develop_debug(continuations)("=== End of thaw #" INTPTR_FORMAT, cont.hash());
3073 
3074   return sp;
3075 }
3076 
3077 #ifdef ASSERT
3078 static void do_deopt_after_thaw(JavaThread* thread) {
3079   int i = 0;
3080   StackFrameStream fst(thread, true, false);
3081   fst.register_map()->set_include_argument_oops(false);
3082   ContinuationHelper::update_register_map_with_callee(*fst.current(), fst.register_map());
3083   for (; !fst.is_done(); fst.next()) {
3084     if (fst.current()->cb()->is_nmethod()) {
3085       nmethod* nm = fst.current()->cb()->as_nmethod();
3086       if (!nm->method()->is_continuation_native_intrinsic()) {
3087         nm->make_deoptimized();

3144       if (!fr.is_interpreted_frame()) {
3145         st->print_cr("size: %d argsize: %d",
3146                      ContinuationHelper::NonInterpretedUnknownFrame::size(fr),
3147                      ContinuationHelper::NonInterpretedUnknownFrame::stack_argsize(fr));
3148       }
3149       VMReg reg = fst.register_map()->find_register_spilled_here(cl.p(), fst.current()->sp());
3150       if (reg != nullptr) {
3151         st->print_cr("Reg %s %d", reg->name(), reg->is_stack() ? (int)reg->reg2stack() : -99);
3152       }
3153       cl.reset();
3154       DEBUG_ONLY(thread->print_frame_layout();)
3155       if (chunk != nullptr) {
3156         chunk->print_on(true, st);
3157       }
3158       return false;
3159     }
3160   }
3161   return true;
3162 }
3163 
3164 static void log_frames(JavaThread* thread, bool dolog) {
3165   const static int show_entry_callers = 3;
3166   LogTarget(Trace, continuations) lt;
3167   if (!lt.develop_is_enabled() || !dolog) {
3168     return;
3169   }
3170   LogStream ls(lt);
3171 
3172   ls.print_cr("------- frames --------- for thread " INTPTR_FORMAT, p2i(thread));
3173   if (!thread->has_last_Java_frame()) {
3174     ls.print_cr("NO ANCHOR!");
3175   }
3176 
3177   RegisterMap map(thread,
3178                   RegisterMap::UpdateMap::include,
3179                   RegisterMap::ProcessFrames::include,
3180                   RegisterMap::WalkContinuation::skip);
3181   map.set_include_argument_oops(false);
3182 
3183   if (false) {
3184     for (frame f = thread->last_frame(); !f.is_entry_frame(); f = f.sender(&map)) {
3185       f.print_on(&ls);
3186     }
3187   } else {

3189     ResetNoHandleMark rnhm;
3190     ResourceMark rm;
3191     HandleMark hm(Thread::current());
3192     FrameValues values;
3193 
3194     int i = 0;
3195     int post_entry = -1;
3196     for (frame f = thread->last_frame(); !f.is_first_frame(); f = f.sender(&map), i++) {
3197       f.describe(values, i, &map, i == 0);
3198       if (post_entry >= 0 || Continuation::is_continuation_enterSpecial(f))
3199         post_entry++;
3200       if (post_entry >= show_entry_callers)
3201         break;
3202     }
3203     values.print_on(thread, &ls);
3204   }
3205 
3206   ls.print_cr("======= end frames =========");
3207 }
3208 
3209 static void log_frames_after_thaw(JavaThread* thread, ContinuationWrapper& cont, intptr_t* sp) {
3210   intptr_t* sp0 = sp;
3211   address pc0 = *(address*)(sp - frame::sender_sp_ret_address_offset());
3212 
3213   bool preempted = false;
3214   stackChunkOop tail = cont.tail();
3215   if (tail != nullptr && tail->preempted()) {
3216     // Still preempted (monitor not acquired) so no frames were thawed.

3217     set_anchor(thread, cont.entrySP(), cont.entryPC());
3218     preempted = true;
3219   } else {
3220     set_anchor(thread, sp0);
3221   }
3222 
3223   log_frames(thread);
3224   if (LoomVerifyAfterThaw) {
3225     assert(do_verify_after_thaw(thread, cont.tail(), tty), "");
3226   }
3227   assert(ContinuationEntry::assert_entry_frame_laid_out(thread, preempted), "");
3228   clear_anchor(thread);
3229 
3230   LogTarget(Trace, continuations) lt;
3231   if (lt.develop_is_enabled()) {
3232     LogStream ls(lt);
3233     ls.print_cr("Jumping to frame (thaw):");
3234     frame(sp).print_value_on(&ls);
3235   }
3236 }
3237 #endif // ASSERT
3238 
3239 #include CPU_HEADER_INLINE(continuationFreezeThaw)
3240 
3241 #ifdef ASSERT
3242 static void print_frame_layout(const frame& f, bool callee_complete, outputStream* st) {
3243   ResourceMark rm;
3244   FrameValues values;
3245   assert(f.get_cb() != nullptr, "");
3246   RegisterMap map(f.is_heap_frame() ?
3247                     nullptr :
< prev index next >