1 /*
2 * Copyright (c) 2018, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "classfile/vmSymbols.hpp"
26 #include "gc/shared/barrierSetNMethod.hpp"
27 #include "oops/method.inline.hpp"
28 #include "oops/oop.inline.hpp"
29 #include "prims/jvmtiThreadState.inline.hpp"
30 #include "runtime/continuation.hpp"
31 #include "runtime/continuationEntry.inline.hpp"
32 #include "runtime/continuationHelper.inline.hpp"
33 #include "runtime/continuationJavaClasses.inline.hpp"
34 #include "runtime/continuationWrapper.inline.hpp"
35 #include "runtime/interfaceSupport.inline.hpp"
36 #include "runtime/javaThread.inline.hpp"
37 #include "runtime/jniHandles.inline.hpp"
38 #include "runtime/osThread.hpp"
39 #include "runtime/vframe.inline.hpp"
40 #include "runtime/vframe_hp.hpp"
41
42 // defined in continuationFreezeThaw.cpp
43 extern "C" jint JNICALL CONT_isPinned0(JNIEnv* env, jobject cont_scope);
44
45 JVM_ENTRY(void, CONT_pin(JNIEnv* env, jclass cls)) {
46 if (!Continuation::pin(JavaThread::thread_from_jni_environment(env))) {
47 THROW_MSG(vmSymbols::java_lang_IllegalStateException(), "pin overflow");
48 }
49 }
50 JVM_END
51
52 JVM_ENTRY(void, CONT_unpin(JNIEnv* env, jclass cls)) {
53 if (!Continuation::unpin(JavaThread::thread_from_jni_environment(env))) {
54 THROW_MSG(vmSymbols::java_lang_IllegalStateException(), "pin underflow");
55 }
56 }
57 JVM_END
58
59 #if INCLUDE_JVMTI
60 class JvmtiUnmountBeginMark : public StackObj {
61 Handle _vthread;
62 JavaThread* _current;
63 freeze_result _result;
64 bool _failed;
65
66 public:
67 JvmtiUnmountBeginMark(JavaThread* t) :
68 _vthread(t, t->vthread()), _current(t), _result(freeze_pinned_native), _failed(false) {
69 assert(!_current->is_in_VTMS_transition(), "must be");
70
71 if (JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events()) {
72 JvmtiVTMSTransitionDisabler::VTMS_vthread_unmount((jthread)_vthread.raw_value(), true);
73
74 // Don't preempt if there is a pending popframe or earlyret operation. This can
75 // be installed in start_VTMS_transition() so we need to check it here.
76 if (JvmtiExport::can_pop_frame() || JvmtiExport::can_force_early_return()) {
77 JvmtiThreadState* state = _current->jvmti_thread_state();
78 if (_current->has_pending_popframe() || (state != nullptr && state->is_earlyret_pending())) {
79 _failed = true;
80 }
81 }
82
83 // Don't preempt in case there is an async exception installed since
84 // we would incorrectly throw it during the unmount logic in the carrier.
85 if (_current->has_async_exception_condition()) {
86 _failed = true;
87 }
88 } else {
89 _current->set_is_in_VTMS_transition(true);
90 java_lang_Thread::set_is_in_VTMS_transition(_vthread(), true);
91 }
92 }
93 ~JvmtiUnmountBeginMark() {
94 assert(!_current->is_suspended(), "must be");
95
96 assert(_current->is_in_VTMS_transition(), "must be");
97 assert(java_lang_Thread::is_in_VTMS_transition(_vthread()), "must be");
98
99 // Read it again since for late binding agents the flag could have
100 // been set while blocked in the allocation path during freeze.
101 bool jvmti_present = JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events();
102
103 if (_result != freeze_ok) {
104 // Undo transition
105 if (jvmti_present) {
106 JvmtiVTMSTransitionDisabler::VTMS_vthread_mount((jthread)_vthread.raw_value(), false);
107 } else {
108 _current->set_is_in_VTMS_transition(false);
109 java_lang_Thread::set_is_in_VTMS_transition(_vthread(), false);
110 }
111 }
112 }
113 void set_result(freeze_result res) { _result = res; }
114 bool failed() { return _failed; }
115 };
116
117 static bool is_vthread_safe_to_preempt_for_jvmti(JavaThread* current) {
118 if (current->is_in_VTMS_transition()) {
119 // We are at the end of a mount transition.
120 return false;
121 }
122 return true;
123 }
124 #endif // INCLUDE_JVMTI
125
126 static bool is_vthread_safe_to_preempt(JavaThread* current, oop vthread) {
127 assert(java_lang_VirtualThread::is_instance(vthread), "");
128 if (java_lang_VirtualThread::state(vthread) != java_lang_VirtualThread::RUNNING) { // inside transition
129 return false;
130 }
131 return JVMTI_ONLY(is_vthread_safe_to_preempt_for_jvmti(current)) NOT_JVMTI(true);
132 }
133
134 typedef freeze_result (*FreezeContFnT)(JavaThread*, intptr_t*);
135
136 static void verify_preempt_preconditions(JavaThread* current, oop continuation) {
137 assert(current == JavaThread::current(), "no support for external preemption");
138 assert(current->has_last_Java_frame(), "");
139 assert(!current->preempting(), "");
140 assert(current->last_continuation() != nullptr, "");
141 assert(current->last_continuation()->cont_oop(current) == continuation, "");
142 assert(Continuation::continuation_scope(continuation) == java_lang_VirtualThread::vthread_scope(), "");
143 assert(!current->has_pending_exception(), "");
144 }
145
146 freeze_result Continuation::try_preempt(JavaThread* current, oop continuation) {
147 verify_preempt_preconditions(current, continuation);
148
149 if (LockingMode == LM_LEGACY) {
150 return freeze_unsupported;
151 }
152
153 if (!is_vthread_safe_to_preempt(current, current->vthread())) {
154 return freeze_pinned_native;
155 }
156
157 JVMTI_ONLY(JvmtiUnmountBeginMark jubm(current);)
158 JVMTI_ONLY(if (jubm.failed()) return freeze_pinned_native;)
159 freeze_result res = CAST_TO_FN_PTR(FreezeContFnT, freeze_preempt_entry())(current, current->last_Java_sp());
160 log_trace(continuations, preempt)("try_preempt: %d", res);
161 JVMTI_ONLY(jubm.set_result(res);)
162
163 if (current->has_pending_exception()) {
164 assert(res == freeze_exception, "expecting an exception result from freeze");
165 // We don't want to throw exceptions, especially when returning
166 // from monitorenter since the compiler does not expect one. We
167 // just ignore the exception and pin the vthread to the carrier.
168 current->clear_pending_exception();
169 }
170 return res;
171 }
172
173 ContinuationEntry* Continuation::get_continuation_entry_for_continuation(JavaThread* thread, oop continuation) {
174 if (thread == nullptr || continuation == nullptr) {
175 return nullptr;
176 }
177
178 for (ContinuationEntry* entry = thread->last_continuation(); entry != nullptr; entry = entry->parent()) {
179 if (continuation == entry->cont_oop(thread)) {
180 return entry;
181 }
182 }
183 return nullptr;
184 }
185
186 static bool is_on_stack(JavaThread* thread, const ContinuationEntry* entry) {
187 if (entry == nullptr) {
188 return false;
189 }
190
191 assert(thread->is_in_full_stack((address)entry), "");
192 return true;
193 // return false if called when transitioning to Java on return from freeze
194 // return !thread->has_last_Java_frame() || thread->last_Java_sp() < cont->entry_sp();
195 }
196
197 bool Continuation::is_continuation_mounted(JavaThread* thread, oop continuation) {
198 return is_on_stack(thread, get_continuation_entry_for_continuation(thread, continuation));
199 }
200
201 // When walking the virtual stack, this method returns true
202 // iff the frame is a thawed continuation frame whose
203 // caller is still frozen on the h-stack.
204 // The continuation object can be extracted from the thread.
205 bool Continuation::is_cont_barrier_frame(const frame& f) {
206 assert(f.is_interpreted_frame() || f.cb() != nullptr, "");
207 if (!Continuations::enabled()) return false;
208 return is_return_barrier_entry(f.is_interpreted_frame() ? ContinuationHelper::InterpretedFrame::return_pc(f)
209 : ContinuationHelper::CompiledFrame::return_pc(f));
210 }
211
212 bool Continuation::is_return_barrier_entry(const address pc) {
213 if (!Continuations::enabled()) return false;
214 return pc == StubRoutines::cont_returnBarrier();
215 }
216
217 bool Continuation::is_continuation_enterSpecial(const frame& f) {
218 if (f.cb() == nullptr || !f.cb()->is_nmethod()) {
219 return false;
220 }
221 Method* m = f.cb()->as_nmethod()->method();
222 return (m != nullptr && m->is_continuation_enter_intrinsic());
223 }
224
225 bool Continuation::is_continuation_entry_frame(const frame& f, const RegisterMap *map) {
226 // we can do this because the entry frame is never inlined
227 Method* m = (map != nullptr && map->in_cont() && f.is_interpreted_frame())
228 ? map->stack_chunk()->interpreter_frame_method(f)
229 : ContinuationHelper::Frame::frame_method(f);
230 return m != nullptr && m->intrinsic_id() == vmIntrinsics::_Continuation_enter;
231 }
232
233 // The parameter `sp` should be the actual sp and not the unextended sp because at
234 // least on PPC64 unextended_sp < sp is possible as interpreted frames are trimmed
235 // to the actual size of the expression stack before calls. The problem there is
236 // that even unextended_sp < entry_sp < sp is possible for an interpreted frame.
237 static inline bool is_sp_in_continuation(const ContinuationEntry* entry, intptr_t* const sp) {
238 // entry_sp() returns the unextended_sp which is always greater or equal to the actual sp
239 return entry->entry_sp() > sp;
240 }
241
242 bool Continuation::is_frame_in_continuation(const ContinuationEntry* entry, const frame& f) {
243 return is_sp_in_continuation(entry, f.sp());
244 }
245
246 ContinuationEntry* Continuation::get_continuation_entry_for_sp(JavaThread* thread, intptr_t* const sp) {
247 assert(thread != nullptr, "");
248 ContinuationEntry* entry = thread->last_continuation();
249 while (entry != nullptr && !is_sp_in_continuation(entry, sp)) {
250 entry = entry->parent();
251 }
252 return entry;
253 }
254
255 ContinuationEntry* Continuation::get_continuation_entry_for_entry_frame(JavaThread* thread, const frame& f) {
256 assert(is_continuation_enterSpecial(f), "");
257 ContinuationEntry* entry = (ContinuationEntry*)f.unextended_sp();
258 assert(entry == get_continuation_entry_for_sp(thread, f.sp()-2), "mismatched entry");
259 return entry;
260 }
261
262 bool Continuation::is_frame_in_continuation(JavaThread* thread, const frame& f) {
263 return f.is_heap_frame() || (get_continuation_entry_for_sp(thread, f.sp()) != nullptr);
264 }
265
266 static frame continuation_top_frame(const ContinuationWrapper& cont, RegisterMap* map) {
267 stackChunkOop chunk = cont.last_nonempty_chunk();
268 map->set_stack_chunk(chunk);
269 return chunk != nullptr ? chunk->top_frame(map) : frame();
270 }
271
272 bool Continuation::has_last_Java_frame(oop continuation, frame* frame, RegisterMap* map) {
273 ContinuationWrapper cont(continuation);
274 if (!cont.is_empty()) {
275 *frame = continuation_top_frame(cont, map);
276 return true;
277 } else {
278 return false;
279 }
280 }
281
282 frame Continuation::last_frame(oop continuation, RegisterMap *map) {
283 assert(map != nullptr, "a map must be given");
284 return continuation_top_frame(ContinuationWrapper(continuation), map);
285 }
286
287 frame Continuation::top_frame(const frame& callee, RegisterMap* map) {
288 assert(map != nullptr, "");
289 ContinuationEntry* ce = get_continuation_entry_for_sp(map->thread(), callee.sp());
290 assert(ce != nullptr, "");
291 oop continuation = ce->cont_oop(map->thread());
292 ContinuationWrapper cont(continuation);
293 return continuation_top_frame(cont, map);
294 }
295
296 javaVFrame* Continuation::last_java_vframe(Handle continuation, RegisterMap *map) {
297 assert(map != nullptr, "a map must be given");
298 if (!ContinuationWrapper(continuation()).is_empty()) {
299 frame f = last_frame(continuation(), map);
300 for (vframe* vf = vframe::new_vframe(&f, map, nullptr); vf; vf = vf->sender()) {
301 if (vf->is_java_frame()) {
302 return javaVFrame::cast(vf);
303 }
304 }
305 }
306 return nullptr;
307 }
308
309 frame Continuation::continuation_parent_frame(RegisterMap* map) {
310 assert(map->in_cont(), "");
311 ContinuationWrapper cont(map);
312 assert(map->thread() != nullptr || !cont.is_mounted(), "");
313
314 log_develop_trace(continuations)("continuation_parent_frame");
315 if (map->update_map()) {
316 // we need to register the link address for the entry frame
317 if (cont.entry() != nullptr) {
318 cont.entry()->update_register_map(map);
319 } else {
320 map->clear();
321 }
322 }
323
324 if (!cont.is_mounted()) { // When we're walking an unmounted continuation and reached the end
325 oop parent = jdk_internal_vm_Continuation::parent(cont.continuation());
326 stackChunkOop chunk = parent != nullptr ? ContinuationWrapper(parent).last_nonempty_chunk() : nullptr;
327 if (chunk != nullptr) {
328 return chunk->top_frame(map);
329 }
330
331 map->set_stack_chunk(nullptr);
332 return frame();
333 }
334
335 map->set_stack_chunk(nullptr);
336
337 #if (defined(X86) || defined(AARCH64) || defined(RISCV64) || defined(PPC64)) && !defined(ZERO)
338 frame sender(cont.entrySP(), cont.entryFP(), cont.entryPC());
339 #else
340 frame sender = frame();
341 Unimplemented();
342 #endif
343
344 return sender;
345 }
346
347 oop Continuation::continuation_scope(oop continuation) {
348 return continuation != nullptr ? jdk_internal_vm_Continuation::scope(continuation) : nullptr;
349 }
350
351 bool Continuation::is_scope_bottom(oop cont_scope, const frame& f, const RegisterMap* map) {
352 if (cont_scope == nullptr || !is_continuation_entry_frame(f, map)) {
353 return false;
354 }
355
356 oop continuation;
357 if (map->in_cont()) {
358 continuation = map->cont();
359 } else {
360 ContinuationEntry* ce = get_continuation_entry_for_sp(map->thread(), f.sp());
361 if (ce == nullptr) {
362 return false;
363 }
364 continuation = ce->cont_oop(map->thread());
365 }
366 if (continuation == nullptr) {
367 return false;
368 }
369
370 oop sc = continuation_scope(continuation);
371 assert(sc != nullptr, "");
372 return sc == cont_scope;
373 }
374
375 bool Continuation::is_in_usable_stack(address addr, const RegisterMap* map) {
376 ContinuationWrapper cont(map);
377 stackChunkOop chunk = cont.find_chunk_by_address(addr);
378 return chunk != nullptr ? chunk->is_usable_in_chunk(addr) : false;
379 }
380
381 bool Continuation::pin(JavaThread* current) {
382 ContinuationEntry* ce = current->last_continuation();
383 if (ce == nullptr) {
384 return true; // no continuation mounted
385 }
386 return ce->pin();
387 }
388
389 bool Continuation::unpin(JavaThread* current) {
390 ContinuationEntry* ce = current->last_continuation();
391 if (ce == nullptr) {
392 return true; // no continuation mounted
393 }
394 return ce->unpin();
395 }
396
397 frame Continuation::continuation_bottom_sender(JavaThread* thread, const frame& callee, intptr_t* sender_sp) {
398 assert (thread != nullptr, "");
399 ContinuationEntry* ce = get_continuation_entry_for_sp(thread, callee.sp());
400 assert(ce != nullptr, "callee.sp(): " INTPTR_FORMAT, p2i(callee.sp()));
401
402 log_develop_debug(continuations)("continuation_bottom_sender: [%d] callee: " INTPTR_FORMAT " sender_sp: " INTPTR_FORMAT,
403 thread->osthread()->thread_id(), p2i(callee.sp()), p2i(sender_sp));
404
405 frame entry = ce->to_frame();
406 if (callee.is_interpreted_frame()) {
407 entry.set_sp(sender_sp); // sp != unextended_sp
408 }
409 return entry;
410 }
411
412 address Continuation::get_top_return_pc_post_barrier(JavaThread* thread, address pc) {
413 ContinuationEntry* ce;
414 if (thread != nullptr && is_return_barrier_entry(pc) && (ce = thread->last_continuation()) != nullptr) {
415 return ce->entry_pc();
416 }
417 return pc;
418 }
419
420 void Continuation::set_cont_fastpath_thread_state(JavaThread* thread) {
421 assert(thread != nullptr, "");
422 bool fast = !thread->is_interp_only_mode();
423 thread->set_cont_fastpath_thread_state(fast);
424 }
425
426 void Continuation::notify_deopt(JavaThread* thread, intptr_t* sp) {
427 ContinuationEntry* entry = thread->last_continuation();
428
429 if (entry == nullptr) {
430 return;
431 }
432
433 if (is_sp_in_continuation(entry, sp)) {
434 thread->push_cont_fastpath(sp);
435 return;
436 }
437
438 ContinuationEntry* prev;
439 do {
440 prev = entry;
441 entry = entry->parent();
442 } while (entry != nullptr && !is_sp_in_continuation(entry, sp));
443
444 if (entry == nullptr) {
445 return;
446 }
447 assert(is_sp_in_continuation(entry, sp), "");
448 if (sp > prev->parent_cont_fastpath()) {
449 prev->set_parent_cont_fastpath(sp);
450 }
451 }
452
453 #ifndef PRODUCT
454 void Continuation::describe(FrameValues &values) {
455 JavaThread* thread = JavaThread::active();
456 if (thread != nullptr) {
457 for (ContinuationEntry* ce = thread->last_continuation(); ce != nullptr; ce = ce->parent()) {
458 intptr_t* bottom = ce->entry_sp();
459 if (bottom != nullptr) {
460 values.describe(-1, bottom, "continuation entry");
461 }
462 }
463 }
464 }
465 #endif
466
467 #ifdef ASSERT
468 void Continuation::debug_verify_continuation(oop contOop) {
469 if (!VerifyContinuations) {
470 return;
471 }
472 assert(contOop != nullptr, "");
473 assert(oopDesc::is_oop(contOop), "");
474 ContinuationWrapper cont(contOop);
475
476 assert(oopDesc::is_oop_or_null(cont.tail()), "");
477 assert(cont.chunk_invariant(), "");
478
479 bool nonempty_chunk = false;
480 size_t max_size = 0;
481 int num_chunks = 0;
482 int num_frames = 0;
483 int num_interpreted_frames = 0;
484 int num_oops = 0;
485
486 for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
487 log_develop_trace(continuations)("debug_verify_continuation chunk %d", num_chunks);
488 chunk->verify(&max_size, &num_oops, &num_frames, &num_interpreted_frames);
489 if (!chunk->is_empty()) {
490 nonempty_chunk = true;
491 }
492 num_chunks++;
493 }
494
495 const bool is_empty = cont.is_empty();
496 assert(!nonempty_chunk || !is_empty, "");
497 assert(is_empty == (!nonempty_chunk && cont.last_frame().is_empty()), "");
498 }
499
500 void Continuation::print(oop continuation) { print_on(tty, continuation); }
501
502 void Continuation::print_on(outputStream* st, oop continuation) {
503 ContinuationWrapper cont(continuation);
504
505 st->print_cr("CONTINUATION: " PTR_FORMAT " done: %d",
506 continuation->identity_hash(), jdk_internal_vm_Continuation::done(continuation));
507 st->print_cr("CHUNKS:");
508 for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
509 st->print("* ");
510 chunk->print_on(true, st);
511 }
512 }
513 #endif // ASSERT
514
515
516 void continuations_init() { Continuations::init(); }
517
518 void Continuations::init() {
519 Continuation::init();
520 }
521
522 bool Continuations::enabled() {
523 return VMContinuations;
524 }
525
526 #define CC (char*) /*cast a literal from (const char*)*/
527 #define FN_PTR(f) CAST_FROM_FN_PTR(void*, &f)
528
529 static JNINativeMethod CONT_methods[] = {
530 {CC"pin", CC"()V", FN_PTR(CONT_pin)},
531 {CC"unpin", CC"()V", FN_PTR(CONT_unpin)},
532 {CC"isPinned0", CC"(Ljdk/internal/vm/ContinuationScope;)I", FN_PTR(CONT_isPinned0)},
533 };
534
535 void CONT_RegisterNativeMethods(JNIEnv *env, jclass cls) {
536 JavaThread* thread = JavaThread::current();
537 ThreadToNativeFromVM trans(thread);
538 int status = env->RegisterNatives(cls, CONT_methods, sizeof(CONT_methods)/sizeof(JNINativeMethod));
539 guarantee(status == JNI_OK, "register jdk.internal.vm.Continuation natives");
540 guarantee(!env->ExceptionCheck(), "register jdk.internal.vm.Continuation natives");
541 }