1 /*
2 * Copyright (c) 2018, 2024, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/vmSymbols.hpp"
27 #include "gc/shared/barrierSetNMethod.hpp"
28 #include "oops/method.inline.hpp"
29 #include "oops/oop.inline.hpp"
30 #include "prims/jvmtiThreadState.inline.hpp"
31 #include "runtime/continuation.hpp"
32 #include "runtime/continuationEntry.inline.hpp"
33 #include "runtime/continuationHelper.inline.hpp"
34 #include "runtime/continuationJavaClasses.inline.hpp"
35 #include "runtime/continuationWrapper.inline.hpp"
36 #include "runtime/interfaceSupport.inline.hpp"
37 #include "runtime/javaThread.inline.hpp"
38 #include "runtime/jniHandles.inline.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 #if INCLUDE_JVMTI
61 class JvmtiUnmountBeginMark : public StackObj {
62 JavaThread* _target;
63 int _preempt_result;
64
65 public:
66 JvmtiUnmountBeginMark(JavaThread* t) :
67 _target(t), _preempt_result(freeze_pinned_native) {
68 assert(!_target->is_in_any_VTMS_transition(), "must be");
69
70 if (JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events()) {
71 JvmtiVTMSTransitionDisabler::start_VTMS_transition(JNIHandles::make_local(_target->vthread()), /* is_mount */ false);
72 } else {
73 _target->set_is_in_VTMS_transition(true);
74 java_lang_Thread::set_is_in_VTMS_transition(_target->vthread(), true);
75 }
76 }
77 ~JvmtiUnmountBeginMark() {
78 assert(!_target->is_suspended(), "must be");
79
80 assert(_target->is_in_VTMS_transition(), "must be");
81 assert(java_lang_Thread::is_in_VTMS_transition(_target->vthread()), "must be");
82
83 // Read it again since for late binding agents the flag could have
84 // been set while blocked in the allocation path during freeze.
85 bool jvmti_present = JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events();
86
87 if (_preempt_result != freeze_ok) {
88 // Undo transition
89 if (jvmti_present) {
90 JvmtiVTMSTransitionDisabler::finish_VTMS_transition(JNIHandles::make_local(_target->vthread()), false);
91 } else {
92 _target->set_is_in_VTMS_transition(false);
93 java_lang_Thread::set_is_in_VTMS_transition(_target->vthread(), false);
94 }
95 } else {
96 if (jvmti_present) {
97 _target->rebind_to_jvmti_thread_state_of(_target->threadObj());
98 _target->set_jvmti_unmount_event_pending(true);
99 }
100 }
101 }
102 void set_preempt_result(int res) { _preempt_result = res; }
103 };
104
105 static bool is_safe_vthread_to_preempt_for_jvmti(JavaThread* target, oop vthread) {
106 assert(!target->has_pending_popframe(), "should be true; no support for vthreads yet");
107 JvmtiThreadState* state = target->jvmti_thread_state();
108 assert(state == nullptr || !state->is_earlyret_pending(), "should be true; no support for vthreads yet");
109
110 if (target->is_in_any_VTMS_transition()) {
111 // We caught target at the end of a mount transition (is_in_VTMS_transition()) or at the
112 // beginning or end of a temporary switch to carrier thread (is_in_tmp_VTMS_transition()).
113 return false;
114 }
115 return true;
116 }
117 #endif
118
119 static bool is_safe_vthread_to_preempt(JavaThread* target, oop vthread) {
120 if (!java_lang_VirtualThread::is_instance(vthread) || // inside transition
121 java_lang_VirtualThread::state(vthread) != java_lang_VirtualThread::RUNNING) { // inside transition
122 return false;
123 }
124 return JVMTI_ONLY(is_safe_vthread_to_preempt_for_jvmti(target, vthread)) NOT_JVMTI(true);
125 }
126
127 typedef int (*FreezeContFnT)(JavaThread*, intptr_t*);
128
129 int Continuation::try_preempt(JavaThread* target, oop continuation, bool set_state_yielding) {
130 assert(target->is_on_monitorenter(), "must be");
131 assert(target->has_last_Java_frame(), "must be");
132 assert(!target->preempting(), "must be");
133 assert(!target->is_suspended() || target->is_disable_suspend(), "must be");
134 assert(!target->has_pending_exception(), "must be");
135 assert(target->last_continuation() != nullptr, "must be");
136 assert(target->last_continuation()->cont_oop(target) == continuation, "must be");
137 assert(!is_continuation_preempted(continuation), "shouldn't be");
138 assert(Continuation::continuation_scope(continuation) == java_lang_VirtualThread::vthread_scope(), "must be");
139
140 if (!VM_Version::supports_cont_preemption()) {
141 return unsupported;
142 }
143
144 if (is_continuation_done(continuation)) {
145 return freeze_not_mounted;
146 }
147
148 // Continuation is mounted and it's not done so check if it's safe to preempt.
149 if (!is_safe_vthread_to_preempt(target, target->vthread())) {
150 return freeze_pinned_native;
151 }
152
153 #if INCLUDE_JVMTI
154 JvmtiUnmountBeginMark jubm(target);
155 #endif
156 target->set_preempting(true);
157 int res = CAST_TO_FN_PTR(FreezeContFnT, freeze_preempt_entry())(target, target->last_Java_sp());
158 log_trace(continuations, preempt)("try_preempt: %d", res);
159 JVMTI_ONLY(jubm.set_preempt_result(res);)
160 if (res != freeze_ok) {
161 target->set_preempting(false);
162 } else if (set_state_yielding) {
163 java_lang_VirtualThread::set_state(target->vthread(), java_lang_VirtualThread::YIELDING);
164 }
165 return res;
166 }
167
168 bool Continuation::is_continuation_preempted(oop cont) {
169 return jdk_internal_vm_Continuation::is_preempted(cont);
170 }
171
172 bool Continuation::is_continuation_done(oop cont) {
173 return jdk_internal_vm_Continuation::done(cont);
174 }
175
176 #ifndef PRODUCT
177 static jlong java_tid(JavaThread* thread) {
178 return java_lang_Thread::thread_id(thread->threadObj());
179 }
180 #endif
181
182 ContinuationEntry* Continuation::get_continuation_entry_for_continuation(JavaThread* thread, oop continuation) {
183 if (thread == nullptr || continuation == nullptr) {
184 return nullptr;
185 }
186
187 for (ContinuationEntry* entry = thread->last_continuation(); entry != nullptr; entry = entry->parent()) {
188 if (continuation == entry->cont_oop(thread)) {
189 return entry;
190 }
191 }
192 return nullptr;
193 }
194
195 static bool is_on_stack(JavaThread* thread, const ContinuationEntry* entry) {
196 if (entry == nullptr) {
197 return false;
198 }
199
200 assert(thread->is_in_full_stack((address)entry), "");
201 return true;
202 // return false if called when transitioning to Java on return from freeze
203 // return !thread->has_last_Java_frame() || thread->last_Java_sp() < cont->entry_sp();
204 }
205
206 bool Continuation::is_continuation_mounted(JavaThread* thread, oop continuation) {
207 return is_on_stack(thread, get_continuation_entry_for_continuation(thread, continuation));
208 }
209
210 // When walking the virtual stack, this method returns true
211 // iff the frame is a thawed continuation frame whose
212 // caller is still frozen on the h-stack.
213 // The continuation object can be extracted from the thread.
214 bool Continuation::is_cont_barrier_frame(const frame& f) {
215 assert(f.is_interpreted_frame() || f.cb() != nullptr, "");
216 if (!Continuations::enabled()) return false;
217 return is_return_barrier_entry(f.is_interpreted_frame() ? ContinuationHelper::InterpretedFrame::return_pc(f)
218 : ContinuationHelper::CompiledFrame::return_pc(f));
219 }
220
221 bool Continuation::is_return_barrier_entry(const address pc) {
222 if (!Continuations::enabled()) return false;
223 return pc == StubRoutines::cont_returnBarrier();
224 }
225
226 bool Continuation::is_continuation_enterSpecial(const frame& f) {
227 if (f.cb() == nullptr || !f.cb()->is_nmethod()) {
228 return false;
229 }
230 Method* m = f.cb()->as_nmethod()->method();
231 return (m != nullptr && m->is_continuation_enter_intrinsic());
232 }
233
234 bool Continuation::is_continuation_entry_frame(const frame& f, const RegisterMap *map) {
235 // we can do this because the entry frame is never inlined
236 Method* m = (map != nullptr && map->in_cont() && f.is_interpreted_frame())
237 ? map->stack_chunk()->interpreter_frame_method(f)
238 : ContinuationHelper::Frame::frame_method(f);
239 return m != nullptr && m->intrinsic_id() == vmIntrinsics::_Continuation_enter;
240 }
241
242 // The parameter `sp` should be the actual sp and not the unextended sp because at
243 // least on PPC64 unextended_sp < sp is possible as interpreted frames are trimmed
244 // to the actual size of the expression stack before calls. The problem there is
245 // that even unextended_sp < entry_sp < sp is possible for an interpreted frame.
246 static inline bool is_sp_in_continuation(const ContinuationEntry* entry, intptr_t* const sp) {
247 // entry_sp() returns the unextended_sp which is always greater or equal to the actual sp
248 return entry->entry_sp() > sp;
249 }
250
251 bool Continuation::is_frame_in_continuation(const ContinuationEntry* entry, const frame& f) {
252 return is_sp_in_continuation(entry, f.sp());
253 }
254
255 ContinuationEntry* Continuation::get_continuation_entry_for_sp(JavaThread* thread, intptr_t* const sp) {
256 assert(thread != nullptr, "");
257 ContinuationEntry* entry = thread->last_continuation();
258 while (entry != nullptr && !is_sp_in_continuation(entry, sp)) {
259 entry = entry->parent();
260 }
261 return entry;
262 }
263
264 ContinuationEntry* Continuation::get_continuation_entry_for_entry_frame(JavaThread* thread, const frame& f) {
265 assert(is_continuation_enterSpecial(f), "");
266 ContinuationEntry* entry = (ContinuationEntry*)f.unextended_sp();
267 assert(entry == get_continuation_entry_for_sp(thread, f.sp()-2), "mismatched entry");
268 return entry;
269 }
270
271 bool Continuation::is_frame_in_continuation(JavaThread* thread, const frame& f) {
272 return f.is_heap_frame() || (get_continuation_entry_for_sp(thread, f.sp()) != nullptr);
273 }
274
275 static frame continuation_top_frame(const ContinuationWrapper& cont, RegisterMap* map) {
276 stackChunkOop chunk = cont.last_nonempty_chunk();
277 map->set_stack_chunk(chunk);
278 return chunk != nullptr ? chunk->top_frame(map) : frame();
279 }
280
281 bool Continuation::has_last_Java_frame(oop continuation, frame* frame, RegisterMap* map) {
282 ContinuationWrapper cont(continuation);
283 if (!cont.is_empty()) {
284 *frame = continuation_top_frame(cont, map);
285 return true;
286 } else {
287 return false;
288 }
289 }
290
291 frame Continuation::last_frame(oop continuation, RegisterMap *map) {
292 assert(map != nullptr, "a map must be given");
293 return continuation_top_frame(ContinuationWrapper(continuation), map);
294 }
295
296 frame Continuation::top_frame(const frame& callee, RegisterMap* map) {
297 assert(map != nullptr, "");
298 ContinuationEntry* ce = get_continuation_entry_for_sp(map->thread(), callee.sp());
299 assert(ce != nullptr, "");
300 oop continuation = ce->cont_oop(map->thread());
301 ContinuationWrapper cont(continuation);
302 return continuation_top_frame(cont, map);
303 }
304
305 javaVFrame* Continuation::last_java_vframe(Handle continuation, RegisterMap *map) {
306 assert(map != nullptr, "a map must be given");
307 if (!ContinuationWrapper(continuation()).is_empty()) {
308 frame f = last_frame(continuation(), map);
309 for (vframe* vf = vframe::new_vframe(&f, map, nullptr); vf; vf = vf->sender()) {
310 if (vf->is_java_frame()) {
311 return javaVFrame::cast(vf);
312 }
313 }
314 }
315 return nullptr;
316 }
317
318 frame Continuation::continuation_parent_frame(RegisterMap* map) {
319 assert(map->in_cont(), "");
320 ContinuationWrapper cont(map);
321 assert(map->thread() != nullptr || !cont.is_mounted(), "");
322
323 log_develop_trace(continuations)("continuation_parent_frame");
324 if (map->update_map()) {
325 // we need to register the link address for the entry frame
326 if (cont.entry() != nullptr) {
327 cont.entry()->update_register_map(map);
328 } else {
329 map->clear();
330 }
331 }
332
333 if (!cont.is_mounted()) { // When we're walking an unmounted continuation and reached the end
334 oop parent = jdk_internal_vm_Continuation::parent(cont.continuation());
335 stackChunkOop chunk = parent != nullptr ? ContinuationWrapper(parent).last_nonempty_chunk() : nullptr;
336 if (chunk != nullptr) {
337 return chunk->top_frame(map);
338 }
339
340 map->set_stack_chunk(nullptr);
341 return frame();
342 }
343
344 map->set_stack_chunk(nullptr);
345
346 #if (defined(X86) || defined(AARCH64) || defined(RISCV64) || defined(PPC64)) && !defined(ZERO)
347 frame sender(cont.entrySP(), cont.entryFP(), cont.entryPC());
348 #else
349 frame sender = frame();
350 Unimplemented();
351 #endif
352
353 return sender;
354 }
355
356 oop Continuation::continuation_scope(oop continuation) {
357 return continuation != nullptr ? jdk_internal_vm_Continuation::scope(continuation) : nullptr;
358 }
359
360 bool Continuation::is_scope_bottom(oop cont_scope, const frame& f, const RegisterMap* map) {
361 if (cont_scope == nullptr || !is_continuation_entry_frame(f, map)) {
362 return false;
363 }
364
365 oop continuation;
366 if (map->in_cont()) {
367 continuation = map->cont();
368 } else {
369 ContinuationEntry* ce = get_continuation_entry_for_sp(map->thread(), f.sp());
370 if (ce == nullptr) {
371 return false;
372 }
373 continuation = ce->cont_oop(map->thread());
374 }
375 if (continuation == nullptr) {
376 return false;
377 }
378
379 oop sc = continuation_scope(continuation);
380 assert(sc != nullptr, "");
381 return sc == cont_scope;
382 }
383
384 bool Continuation::is_in_usable_stack(address addr, const RegisterMap* map) {
385 ContinuationWrapper cont(map);
386 stackChunkOop chunk = cont.find_chunk_by_address(addr);
387 return chunk != nullptr ? chunk->is_usable_in_chunk(addr) : false;
388 }
389
390 bool Continuation::pin(JavaThread* current) {
391 ContinuationEntry* ce = current->last_continuation();
392 if (ce == nullptr) {
393 return true; // no continuation mounted
394 }
395 return ce->pin();
396 }
397
398 bool Continuation::unpin(JavaThread* current) {
399 ContinuationEntry* ce = current->last_continuation();
400 if (ce == nullptr) {
401 return true; // no continuation mounted
402 }
403 return ce->unpin();
404 }
405
406 frame Continuation::continuation_bottom_sender(JavaThread* thread, const frame& callee, intptr_t* sender_sp) {
407 assert (thread != nullptr, "");
408 ContinuationEntry* ce = get_continuation_entry_for_sp(thread, callee.sp());
409 assert(ce != nullptr, "callee.sp(): " INTPTR_FORMAT, p2i(callee.sp()));
410
411 log_develop_debug(continuations)("continuation_bottom_sender: [" JLONG_FORMAT "] [%d] callee: " INTPTR_FORMAT
412 " sender_sp: " INTPTR_FORMAT,
413 java_tid(thread), thread->osthread()->thread_id(), p2i(callee.sp()), p2i(sender_sp));
414
415 frame entry = ce->to_frame();
416 if (callee.is_interpreted_frame()) {
417 entry.set_sp(sender_sp); // sp != unextended_sp
418 }
419 return entry;
420 }
421
422 address Continuation::get_top_return_pc_post_barrier(JavaThread* thread, address pc) {
423 ContinuationEntry* ce;
424 if (thread != nullptr && is_return_barrier_entry(pc) && (ce = thread->last_continuation()) != nullptr) {
425 return ce->entry_pc();
426 }
427 return pc;
428 }
429
430 void Continuation::set_cont_fastpath_thread_state(JavaThread* thread) {
431 assert(thread != nullptr, "");
432 bool fast = !thread->is_interp_only_mode();
433 thread->set_cont_fastpath_thread_state(fast);
434 }
435
436 void Continuation::notify_deopt(JavaThread* thread, intptr_t* sp) {
437 ContinuationEntry* entry = thread->last_continuation();
438
439 if (entry == nullptr) {
440 return;
441 }
442
443 if (is_sp_in_continuation(entry, sp)) {
444 thread->push_cont_fastpath(sp);
445 return;
446 }
447
448 ContinuationEntry* prev;
449 do {
450 prev = entry;
451 entry = entry->parent();
452 } while (entry != nullptr && !is_sp_in_continuation(entry, sp));
453
454 if (entry == nullptr) {
455 return;
456 }
457 assert(is_sp_in_continuation(entry, sp), "");
458 if (sp > prev->parent_cont_fastpath()) {
459 prev->set_parent_cont_fastpath(sp);
460 }
461 }
462
463 #ifndef PRODUCT
464 void Continuation::describe(FrameValues &values) {
465 JavaThread* thread = JavaThread::active();
466 if (thread != nullptr) {
467 for (ContinuationEntry* ce = thread->last_continuation(); ce != nullptr; ce = ce->parent()) {
468 intptr_t* bottom = ce->entry_sp();
469 if (bottom != nullptr) {
470 values.describe(-1, bottom, "continuation entry");
471 }
472 }
473 }
474 }
475 #endif
476
477 #ifdef ASSERT
478 void Continuation::debug_verify_continuation(oop contOop) {
479 if (!VerifyContinuations) {
480 return;
481 }
482 assert(contOop != nullptr, "");
483 assert(oopDesc::is_oop(contOop), "");
484 ContinuationWrapper cont(contOop);
485
486 assert(oopDesc::is_oop_or_null(cont.tail()), "");
487 assert(cont.chunk_invariant(), "");
488
489 bool nonempty_chunk = false;
490 size_t max_size = 0;
491 int num_chunks = 0;
492 int num_frames = 0;
493 int num_interpreted_frames = 0;
494 int num_oops = 0;
495
496 for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
497 log_develop_trace(continuations)("debug_verify_continuation chunk %d", num_chunks);
498 chunk->verify(&max_size, &num_oops, &num_frames, &num_interpreted_frames);
499 if (!chunk->is_empty()) {
500 nonempty_chunk = true;
501 }
502 num_chunks++;
503 }
504
505 const bool is_empty = cont.is_empty();
506 assert(!nonempty_chunk || !is_empty, "");
507 assert(is_empty == (!nonempty_chunk && cont.last_frame().is_empty()), "");
508 }
509
510 void Continuation::print(oop continuation) { print_on(tty, continuation); }
511
512 void Continuation::print_on(outputStream* st, oop continuation) {
513 ContinuationWrapper cont(continuation);
514
515 st->print_cr("CONTINUATION: " PTR_FORMAT " done: %d",
516 continuation->identity_hash(), jdk_internal_vm_Continuation::done(continuation));
517 st->print_cr("CHUNKS:");
518 for (stackChunkOop chunk = cont.tail(); chunk != nullptr; chunk = chunk->parent()) {
519 st->print("* ");
520 chunk->print_on(true, st);
521 }
522 }
523 #endif // ASSERT
524
525
526 void continuations_init() { Continuations::init(); }
527
528 void Continuations::init() {
529 Continuation::init();
530 }
531
532 bool Continuations::enabled() {
533 return VMContinuations;
534 }
535
536 #define CC (char*) /*cast a literal from (const char*)*/
537 #define FN_PTR(f) CAST_FROM_FN_PTR(void*, &f)
538
539 static JNINativeMethod CONT_methods[] = {
540 {CC"pin", CC"()V", FN_PTR(CONT_pin)},
541 {CC"unpin", CC"()V", FN_PTR(CONT_unpin)},
542 {CC"isPinned0", CC"(Ljdk/internal/vm/ContinuationScope;)I", FN_PTR(CONT_isPinned0)},
543 };
544
545 void CONT_RegisterNativeMethods(JNIEnv *env, jclass cls) {
546 JavaThread* thread = JavaThread::current();
547 ThreadToNativeFromVM trans(thread);
548 int status = env->RegisterNatives(cls, CONT_methods, sizeof(CONT_methods)/sizeof(JNINativeMethod));
549 guarantee(status == JNI_OK, "register jdk.internal.vm.Continuation natives");
550 guarantee(!env->ExceptionOccurred(), "register jdk.internal.vm.Continuation natives");
551 }