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