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 (!is_vthread_safe_to_preempt(current, current->vthread())) {
150 return freeze_pinned_native;
151 }
152
153 JVMTI_ONLY(JvmtiUnmountBeginMark jubm(current);)
154 JVMTI_ONLY(if (jubm.failed()) return freeze_pinned_native;)
155 freeze_result res = CAST_TO_FN_PTR(FreezeContFnT, freeze_preempt_entry())(current, current->last_Java_sp());
156 log_trace(continuations, preempt)("try_preempt: %d", res);
157 JVMTI_ONLY(jubm.set_result(res);)
158
159 if (current->has_pending_exception()) {
160 assert(res == freeze_exception, "expecting an exception result from freeze");
161 // We don't want to throw exceptions, especially when returning
162 // from monitorenter since the compiler does not expect one. We
163 // just ignore the exception and pin the vthread to the carrier.
164 current->clear_pending_exception();
165 }
166 return res;
167 }
168
169 #ifndef PRODUCT
170 static jlong java_tid(JavaThread* thread) {
171 return java_lang_Thread::thread_id(thread->threadObj());
172 }
173 #endif
174
175 ContinuationEntry* Continuation::get_continuation_entry_for_continuation(JavaThread* thread, oop continuation) {
176 if (thread == nullptr || continuation == nullptr) {
177 return nullptr;
178 }
179
180 for (ContinuationEntry* entry = thread->last_continuation(); entry != nullptr; entry = entry->parent()) {
181 if (continuation == entry->cont_oop(thread)) {
182 return entry;
183 }
184 }
185 return nullptr;
186 }
187
188 static bool is_on_stack(JavaThread* thread, const ContinuationEntry* entry) {
189 if (entry == nullptr) {
190 return false;
191 }
192
193 assert(thread->is_in_full_stack((address)entry), "");
194 return true;
195 // return false if called when transitioning to Java on return from freeze
196 // return !thread->has_last_Java_frame() || thread->last_Java_sp() < cont->entry_sp();
197 }
198
199 bool Continuation::is_continuation_mounted(JavaThread* thread, oop continuation) {
200 return is_on_stack(thread, get_continuation_entry_for_continuation(thread, continuation));
201 }
202
203 // When walking the virtual stack, this method returns true
204 // iff the frame is a thawed continuation frame whose
205 // caller is still frozen on the h-stack.
206 // The continuation object can be extracted from the thread.
207 bool Continuation::is_cont_barrier_frame(const frame& f) {
208 assert(f.is_interpreted_frame() || f.cb() != nullptr, "");
209 if (!Continuations::enabled()) return false;
210 return is_return_barrier_entry(f.is_interpreted_frame() ? ContinuationHelper::InterpretedFrame::return_pc(f)
211 : ContinuationHelper::CompiledFrame::return_pc(f));
212 }
213
214 bool Continuation::is_return_barrier_entry(const address pc) {
215 if (!Continuations::enabled()) return false;
216 return pc == StubRoutines::cont_returnBarrier();
217 }
218
219 bool Continuation::is_continuation_enterSpecial(const frame& f) {
220 if (f.cb() == nullptr || !f.cb()->is_nmethod()) {
221 return false;
222 }
223 Method* m = f.cb()->as_nmethod()->method();
224 return (m != nullptr && m->is_continuation_enter_intrinsic());
225 }
226
227 bool Continuation::is_continuation_entry_frame(const frame& f, const RegisterMap *map) {
228 // we can do this because the entry frame is never inlined
229 Method* m = (map != nullptr && map->in_cont() && f.is_interpreted_frame())
230 ? map->stack_chunk()->interpreter_frame_method(f)
231 : ContinuationHelper::Frame::frame_method(f);
232 return m != nullptr && m->intrinsic_id() == vmIntrinsics::_Continuation_enter;
233 }
234
235 // The parameter `sp` should be the actual sp and not the unextended sp because at
236 // least on PPC64 unextended_sp < sp is possible as interpreted frames are trimmed
237 // to the actual size of the expression stack before calls. The problem there is
238 // that even unextended_sp < entry_sp < sp is possible for an interpreted frame.
239 static inline bool is_sp_in_continuation(const ContinuationEntry* entry, intptr_t* const sp) {
240 // entry_sp() returns the unextended_sp which is always greater or equal to the actual sp
241 return entry->entry_sp() > sp;
242 }
243
244 bool Continuation::is_frame_in_continuation(const ContinuationEntry* entry, const frame& f) {
245 return is_sp_in_continuation(entry, f.sp());
246 }
247
248 ContinuationEntry* Continuation::get_continuation_entry_for_sp(JavaThread* thread, intptr_t* const sp) {
249 assert(thread != nullptr, "");
250 ContinuationEntry* entry = thread->last_continuation();
251 while (entry != nullptr && !is_sp_in_continuation(entry, sp)) {
252 entry = entry->parent();
253 }
254 return entry;
255 }
256
257 ContinuationEntry* Continuation::get_continuation_entry_for_entry_frame(JavaThread* thread, const frame& f) {
258 assert(is_continuation_enterSpecial(f), "");
259 ContinuationEntry* entry = (ContinuationEntry*)f.unextended_sp();
260 assert(entry == get_continuation_entry_for_sp(thread, f.sp()-2), "mismatched entry");
261 return entry;
262 }
263
264 bool Continuation::is_frame_in_continuation(JavaThread* thread, const frame& f) {
265 return f.is_heap_frame() || (get_continuation_entry_for_sp(thread, f.sp()) != nullptr);
266 }
267
268 static frame continuation_top_frame(const ContinuationWrapper& cont, RegisterMap* map) {
269 stackChunkOop chunk = cont.last_nonempty_chunk();
270 map->set_stack_chunk(chunk);
271 return chunk != nullptr ? chunk->top_frame(map) : frame();
272 }
273
274 bool Continuation::has_last_Java_frame(oop continuation, frame* frame, RegisterMap* map) {
275 ContinuationWrapper cont(continuation);
276 if (!cont.is_empty()) {
277 *frame = continuation_top_frame(cont, map);
278 return true;
279 } else {
280 return false;
281 }
282 }
283
284 frame Continuation::last_frame(oop continuation, RegisterMap *map) {
285 assert(map != nullptr, "a map must be given");
286 return continuation_top_frame(ContinuationWrapper(continuation), map);
287 }
288
289 frame Continuation::top_frame(const frame& callee, RegisterMap* map) {
290 assert(map != nullptr, "");
291 ContinuationEntry* ce = get_continuation_entry_for_sp(map->thread(), callee.sp());
292 assert(ce != nullptr, "");
293 oop continuation = ce->cont_oop(map->thread());
294 ContinuationWrapper cont(continuation);
295 return continuation_top_frame(cont, map);
296 }
297
298 javaVFrame* Continuation::last_java_vframe(Handle continuation, RegisterMap *map) {
299 assert(map != nullptr, "a map must be given");
300 if (!ContinuationWrapper(continuation()).is_empty()) {
301 frame f = last_frame(continuation(), map);
302 for (vframe* vf = vframe::new_vframe(&f, map, nullptr); vf; vf = vf->sender()) {
303 if (vf->is_java_frame()) {
304 return javaVFrame::cast(vf);
305 }
306 }
307 }
308 return nullptr;
309 }
310
311 frame Continuation::continuation_parent_frame(RegisterMap* map) {
312 assert(map->in_cont(), "");
313 ContinuationWrapper cont(map);
314 assert(map->thread() != nullptr || !cont.is_mounted(), "");
315
316 log_develop_trace(continuations)("continuation_parent_frame");
317 if (map->update_map()) {
318 // we need to register the link address for the entry frame
319 if (cont.entry() != nullptr) {
320 cont.entry()->update_register_map(map);
321 } else {
322 map->clear();
323 }
324 }
325
326 if (!cont.is_mounted()) { // When we're walking an unmounted continuation and reached the end
327 oop parent = jdk_internal_vm_Continuation::parent(cont.continuation());
328 stackChunkOop chunk = parent != nullptr ? ContinuationWrapper(parent).last_nonempty_chunk() : nullptr;
329 if (chunk != nullptr) {
330 return chunk->top_frame(map);
331 }
332
333 map->set_stack_chunk(nullptr);
334 return frame();
335 }
336
337 map->set_stack_chunk(nullptr);
338
339 #if (defined(X86) || defined(AARCH64) || defined(RISCV64) || defined(PPC64)) && !defined(ZERO)
340 frame sender(cont.entrySP(), cont.entryFP(), cont.entryPC());
341 #else
342 frame sender = frame();
343 Unimplemented();
344 #endif
345
346 return sender;
347 }
348
349 oop Continuation::continuation_scope(oop continuation) {
350 return continuation != nullptr ? jdk_internal_vm_Continuation::scope(continuation) : nullptr;
351 }
352
353 bool Continuation::is_scope_bottom(oop cont_scope, const frame& f, const RegisterMap* map) {
354 if (cont_scope == nullptr || !is_continuation_entry_frame(f, map)) {
355 return false;
356 }
357
358 oop continuation;
359 if (map->in_cont()) {
360 continuation = map->cont();
361 } else {
362 ContinuationEntry* ce = get_continuation_entry_for_sp(map->thread(), f.sp());
363 if (ce == nullptr) {
364 return false;
365 }
366 continuation = ce->cont_oop(map->thread());
367 }
368 if (continuation == nullptr) {
369 return false;
370 }
371
372 oop sc = continuation_scope(continuation);
373 assert(sc != nullptr, "");
374 return sc == cont_scope;
375 }
376
377 bool Continuation::is_in_usable_stack(address addr, const RegisterMap* map) {
378 ContinuationWrapper cont(map);
379 stackChunkOop chunk = cont.find_chunk_by_address(addr);
380 return chunk != nullptr ? chunk->is_usable_in_chunk(addr) : false;
381 }
382
383 bool Continuation::pin(JavaThread* current) {
384 ContinuationEntry* ce = current->last_continuation();
385 if (ce == nullptr) {
386 return true; // no continuation mounted
387 }
388 return ce->pin();
389 }
390
391 bool Continuation::unpin(JavaThread* current) {
392 ContinuationEntry* ce = current->last_continuation();
393 if (ce == nullptr) {
394 return true; // no continuation mounted
395 }
396 return ce->unpin();
397 }
398
399 frame Continuation::continuation_bottom_sender(JavaThread* thread, const frame& callee, intptr_t* sender_sp) {
400 assert (thread != nullptr, "");
401 ContinuationEntry* ce = get_continuation_entry_for_sp(thread, callee.sp());
402 assert(ce != nullptr, "callee.sp(): " INTPTR_FORMAT, p2i(callee.sp()));
403
404 log_develop_debug(continuations)("continuation_bottom_sender: [" JLONG_FORMAT "] [%d] callee: " INTPTR_FORMAT
405 " sender_sp: " INTPTR_FORMAT,
406 java_tid(thread), thread->osthread()->thread_id(), p2i(callee.sp()), p2i(sender_sp));
407
408 frame entry = ce->to_frame();
409 if (callee.is_interpreted_frame()) {
410 entry.set_sp(sender_sp); // sp != unextended_sp
411 }
412 return entry;
413 }
414
415 address Continuation::get_top_return_pc_post_barrier(JavaThread* thread, address pc) {
416 ContinuationEntry* ce;
417 if (thread != nullptr && is_return_barrier_entry(pc) && (ce = thread->last_continuation()) != nullptr) {
418 return ce->entry_pc();
419 }
420 return pc;
421 }
422
423 void Continuation::set_cont_fastpath_thread_state(JavaThread* thread) {
424 assert(thread != nullptr, "");
425 bool fast = !thread->is_interp_only_mode();
426 thread->set_cont_fastpath_thread_state(fast);
427 }
428
429 void Continuation::notify_deopt(JavaThread* thread, intptr_t* sp) {
430 ContinuationEntry* entry = thread->last_continuation();
431
432 if (entry == nullptr) {
433 return;
434 }
435
436 if (is_sp_in_continuation(entry, sp)) {
437 thread->push_cont_fastpath(sp);
438 return;
439 }
440
441 ContinuationEntry* prev;
442 do {
443 prev = entry;
444 entry = entry->parent();
445 } while (entry != nullptr && !is_sp_in_continuation(entry, sp));
446
447 if (entry == nullptr) {
448 return;
449 }
450 assert(is_sp_in_continuation(entry, sp), "");
451 if (sp > prev->parent_cont_fastpath()) {
452 prev->set_parent_cont_fastpath(sp);
453 }
454 }
455
456 #ifndef PRODUCT
457 void Continuation::describe(FrameValues &values) {
458 JavaThread* thread = JavaThread::active();
459 if (thread != nullptr) {
460 for (ContinuationEntry* ce = thread->last_continuation(); ce != nullptr; ce = ce->parent()) {
461 intptr_t* bottom = ce->entry_sp();
462 if (bottom != nullptr) {
463 values.describe(-1, bottom, "continuation entry");
464 }
465 }
466 }
467 }
468 #endif
469
470 #ifdef ASSERT
471 void Continuation::debug_verify_continuation(oop contOop) {
472 if (!VerifyContinuations) {
473 return;
474 }
475 assert(contOop != nullptr, "");
476 assert(oopDesc::is_oop(contOop), "");
477 ContinuationWrapper cont(contOop);
478
479 assert(oopDesc::is_oop_or_null(cont.tail()), "");
480 assert(cont.chunk_invariant(), "");
481
482 bool nonempty_chunk = false;
483 size_t max_size = 0;
484 int num_chunks = 0;
485 int num_frames = 0;
486 int num_interpreted_frames = 0;
487 int num_oops = 0;
488
489 for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
490 log_develop_trace(continuations)("debug_verify_continuation chunk %d", num_chunks);
491 chunk->verify(&max_size, &num_oops, &num_frames, &num_interpreted_frames);
492 if (!chunk->is_empty()) {
493 nonempty_chunk = true;
494 }
495 num_chunks++;
496 }
497
498 const bool is_empty = cont.is_empty();
499 assert(!nonempty_chunk || !is_empty, "");
500 assert(is_empty == (!nonempty_chunk && cont.last_frame().is_empty()), "");
501 }
502
503 void Continuation::print(oop continuation) { print_on(tty, continuation); }
504
505 void Continuation::print_on(outputStream* st, oop continuation) {
506 ContinuationWrapper cont(continuation);
507
508 st->print_cr("CONTINUATION: " PTR_FORMAT " done: %d",
509 continuation->identity_hash(), jdk_internal_vm_Continuation::done(continuation));
510 st->print_cr("CHUNKS:");
511 for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
512 st->print("* ");
513 chunk->print_on(true, st);
514 }
515 }
516 #endif // ASSERT
517
518
519 void continuations_init() { Continuations::init(); }
520
521 void Continuations::init() {
522 Continuation::init();
523 }
524
525 bool Continuations::enabled() {
526 return VMContinuations;
527 }
528
529 #define CC (char*) /*cast a literal from (const char*)*/
530 #define FN_PTR(f) CAST_FROM_FN_PTR(void*, &f)
531
532 static JNINativeMethod CONT_methods[] = {
533 {CC"pin", CC"()V", FN_PTR(CONT_pin)},
534 {CC"unpin", CC"()V", FN_PTR(CONT_unpin)},
535 {CC"isPinned0", CC"(Ljdk/internal/vm/ContinuationScope;)I", FN_PTR(CONT_isPinned0)},
536 };
537
538 void CONT_RegisterNativeMethods(JNIEnv *env, jclass cls) {
539 JavaThread* thread = JavaThread::current();
540 ThreadToNativeFromVM trans(thread);
541 int status = env->RegisterNatives(cls, CONT_methods, sizeof(CONT_methods)/sizeof(JNINativeMethod));
542 guarantee(status == JNI_OK, "register jdk.internal.vm.Continuation natives");
543 guarantee(!env->ExceptionCheck(), "register jdk.internal.vm.Continuation natives");
544 }