1 /*
2 * Copyright (c) 2024, 2025, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2019, 2022, Red Hat, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26
27 #include "gc/shenandoah/shenandoahBarrierSetAssembler.hpp"
28 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
29 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
30 #include "gc/shenandoah/shenandoahNMethod.inline.hpp"
31 #include "memory/resourceArea.hpp"
32 #include "runtime/continuation.hpp"
33 #include "runtime/safepointVerifiers.hpp"
34
35 ShenandoahNMethod::ShenandoahNMethod(nmethod* nm, GrowableArray<oop*>& oops, bool non_immediate_oops, GrowableArray<ShenandoahNMethodBarrier>& barriers) :
36 _nm(nm), _oops(nullptr), _oops_count(0), _barriers(nullptr), _barriers_count(0), _unregistered(false), _lock(), _ic_lock() {
37
38 if (!oops.is_empty()) {
39 _oops_count = oops.length();
40 _oops = NEW_C_HEAP_ARRAY(oop*, _oops_count, mtGC);
41 for (int c = 0; c < _oops_count; c++) {
42 _oops[c] = oops.at(c);
43 }
44 }
45 _has_non_immed_oops = non_immediate_oops;
46
47 assert_same_oops();
48
49 if (!barriers.is_empty()) {
50 _barriers_count = barriers.length();
51 _barriers = NEW_C_HEAP_ARRAY(ShenandoahNMethodBarrier, _barriers_count, mtGC);
52 for (int c = 0; c < _barriers_count; c++) {
53 _barriers[c] = barriers.at(c);
54 }
55 }
56 }
57
58 ShenandoahNMethod::~ShenandoahNMethod() {
59 if (_oops != nullptr) {
60 FREE_C_HEAP_ARRAY(oop*, _oops);
61 }
62 if (_barriers != nullptr) {
63 FREE_C_HEAP_ARRAY(ShenandoahNMethodBarrier, _barriers);
64 }
65 }
66
67 void ShenandoahNMethod::update() {
68 ResourceMark rm;
69 bool non_immediate_oops = false;
70 GrowableArray<oop*> oops;
71 GrowableArray<ShenandoahNMethodBarrier> barriers;
72
73 parse(nm(), oops, non_immediate_oops, barriers);
74 if (oops.length() != _oops_count) {
75 if (_oops != nullptr) {
76 FREE_C_HEAP_ARRAY(oop*, _oops);
77 _oops = nullptr;
78 }
79
80 _oops_count = oops.length();
81 if (_oops_count > 0) {
82 _oops = NEW_C_HEAP_ARRAY(oop*, _oops_count, mtGC);
83 }
84 }
85
86 for (int index = 0; index < _oops_count; index ++) {
87 _oops[index] = oops.at(index);
88 }
89 _has_non_immed_oops = non_immediate_oops;
90
91 assert_same_oops();
92 }
93
94 void ShenandoahNMethod::parse(nmethod* nm, GrowableArray<oop*>& oops, bool& has_non_immed_oops, GrowableArray<ShenandoahNMethodBarrier>& barriers) {
95 has_non_immed_oops = false;
96 RelocIterator iter(nm);
97 while (iter.next()) {
98 switch (iter.type()) {
99 case relocInfo::oop_type: {
100 oop_Relocation* r = iter.oop_reloc();
101 if (!r->oop_is_immediate()) {
102 // Non-immediate oop found
103 has_non_immed_oops = true;
104 break;
105 }
106
107 oop value = r->oop_value();
108 if (value != nullptr) {
109 oop* addr = r->oop_addr();
110 shenandoah_assert_correct(addr, value);
111 shenandoah_assert_not_in_cset_except(addr, value, ShenandoahHeap::heap()->cancelled_gc());
112 shenandoah_assert_not_forwarded(addr, value);
113 // Non-null immediate oop found. null oops can safely be
114 // ignored since the method will be re-registered if they
115 // are later patched to be non-null.
116 oops.push(addr);
117 }
118 break;
119 }
120 #ifdef COMPILER2
121 case relocInfo::barrier_type: {
122 assert(ShenandoahGCStateCheckHotpatch, "Who emits these?");
123 barrier_Relocation* r = iter.barrier_reloc();
124
125 ShenandoahNMethodBarrier b;
126 b._pc = r->addr();
127 b._stub_addr = ShenandoahBarrierSetAssembler::parse_stub_address(b._pc);
128 // TODO: Can technically figure out which GC state we care about in this reloc.
129 // b._gc_state_fast_bit = r->format();
130 barriers.push(b);
131 break;
132 }
133 #endif
134 default:
135 // We do not care about other relocations.
136 break;
137 }
138 }
139 }
140
141 ShenandoahNMethod* ShenandoahNMethod::for_nmethod(nmethod* nm) {
142 ResourceMark rm;
143 bool non_immediate_oops = false;
144 GrowableArray<oop*> oops;
145 GrowableArray<ShenandoahNMethodBarrier> barriers;
146
147 parse(nm, oops, non_immediate_oops, barriers);
148 return new ShenandoahNMethod(nm, oops, non_immediate_oops, barriers);
149 }
150
151 void ShenandoahNMethod::heal_nmethod(nmethod* nm) {
152 ShenandoahNMethod* data = gc_data(nm);
153 assert(data != nullptr, "Sanity");
154 assert(data->lock()->owned_by_self(), "Must hold the lock");
155
156 ShenandoahHeap* const heap = ShenandoahHeap::heap();
157 if (heap->is_concurrent_weak_root_in_progress() ||
158 heap->is_concurrent_strong_root_in_progress()) {
159 ShenandoahEvacOOMScope evac_scope;
160 heal_nmethod_metadata(data);
161 } else if (heap->is_concurrent_mark_in_progress()) {
162 ShenandoahKeepAliveClosure cl;
163 data->oops_do(&cl);
164 } else {
165 // There is possibility that GC is cancelled when it arrives final mark.
166 // In this case, concurrent root phase is skipped and degenerated GC should be
167 // followed, where nmethods are disarmed.
168 }
169 }
170
171 void ShenandoahNMethod::update_barriers() {
172 #ifdef COMPILER2
173 if (!ShenandoahGCStateCheckHotpatch) {
174 return;
175 }
176
177 ShenandoahHeap* heap = ShenandoahHeap::heap();
178
179 for (int c = 0; c < _barriers_count; c++) {
180 address pc = _barriers[c]._pc;
181 address stub_addr = _barriers[c]._stub_addr;
182 if (heap->is_idle()) {
183 ShenandoahBarrierSetAssembler::patch_branch_to_nop(pc);
184 } else {
185 ShenandoahBarrierSetAssembler::patch_nop_to_branch(pc, stub_addr);
186 }
187 }
188 #endif
189 }
190
191 #ifdef ASSERT
192 void ShenandoahNMethod::assert_correct() {
193 ShenandoahHeap* heap = ShenandoahHeap::heap();
194 for (int c = 0; c < _oops_count; c++) {
195 oop *loc = _oops[c];
196 assert(_nm->code_contains((address) loc) || _nm->oops_contains(loc), "nmethod should contain the oop*");
197 oop o = RawAccess<>::oop_load(loc);
198 shenandoah_assert_correct_except(loc, o, o == nullptr || heap->is_full_gc_move_in_progress());
199 }
200
201 oop* const begin = _nm->oops_begin();
202 oop* const end = _nm->oops_end();
203 for (oop* p = begin; p < end; p++) {
204 if (*p != Universe::non_oop_word()) {
205 oop o = RawAccess<>::oop_load(p);
206 shenandoah_assert_correct_except(p, o, o == nullptr || heap->is_full_gc_move_in_progress());
207 }
208 }
209 }
210
211 class ShenandoahNMethodOopDetector : public OopClosure {
212 private:
213 ResourceMark rm; // For growable array allocation below.
214 GrowableArray<oop*> _oops;
215
216 public:
217 ShenandoahNMethodOopDetector() : _oops(10) {};
218
219 void do_oop(oop* o) {
220 _oops.append(o);
221 }
222 void do_oop(narrowOop* o) {
223 fatal("NMethods should not have compressed oops embedded.");
224 }
225
226 GrowableArray<oop*>* oops() {
227 return &_oops;
228 }
229 };
230
231 void ShenandoahNMethod::assert_same_oops() {
232 ShenandoahNMethodOopDetector detector;
233 nm()->oops_do(&detector);
234
235 GrowableArray<oop*>* oops = detector.oops();
236
237 int count = _oops_count;
238 for (int index = 0; index < _oops_count; index ++) {
239 assert(oops->contains(_oops[index]), "Must contain this oop");
240 }
241
242 for (oop* p = nm()->oops_begin(); p < nm()->oops_end(); p ++) {
243 if (*p == Universe::non_oop_word()) continue;
244 count++;
245 assert(oops->contains(p), "Must contain this oop");
246 }
247
248 if (oops->length() < count) {
249 stringStream debug_stream;
250 debug_stream.print_cr("detected locs: %d", oops->length());
251 for (int i = 0; i < oops->length(); i++) {
252 debug_stream.print_cr("-> " PTR_FORMAT, p2i(oops->at(i)));
253 }
254 debug_stream.print_cr("recorded oops: %d", _oops_count);
255 for (int i = 0; i < _oops_count; i++) {
256 debug_stream.print_cr("-> " PTR_FORMAT, p2i(_oops[i]));
257 }
258 GrowableArray<oop*> check;
259 GrowableArray<ShenandoahNMethodBarrier> barriers;
260 bool non_immed;
261 parse(nm(), check, non_immed, barriers);
262 debug_stream.print_cr("check oops: %d", check.length());
263 for (int i = 0; i < check.length(); i++) {
264 debug_stream.print_cr("-> " PTR_FORMAT, p2i(check.at(i)));
265 }
266 fatal("Must match #detected: %d, #recorded: %d, #total: %d, begin: " PTR_FORMAT ", end: " PTR_FORMAT "\n%s",
267 oops->length(), _oops_count, count, p2i(nm()->oops_begin()), p2i(nm()->oops_end()), debug_stream.freeze());
268 }
269 }
270 #endif
271
272 ShenandoahNMethodTable::ShenandoahNMethodTable() :
273 _heap(ShenandoahHeap::heap()),
274 _index(0),
275 _itr_cnt(0) {
276 _list = new ShenandoahNMethodList(minSize);
277 }
278
279 ShenandoahNMethodTable::~ShenandoahNMethodTable() {
280 assert(_list != nullptr, "Sanity");
281 _list->release();
282 }
283
284 void ShenandoahNMethodTable::register_nmethod(nmethod* nm) {
285 assert(CodeCache_lock->owned_by_self(), "Must have CodeCache_lock held");
286 assert(_index >= 0 && _index <= _list->size(), "Sanity");
287
288 ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);
289
290 if (data != nullptr) {
291 assert(contain(nm), "Must have been registered");
292 assert(nm == data->nm(), "Must be same nmethod");
293 // Prevent updating a nmethod while concurrent iteration is in progress.
294 wait_until_concurrent_iteration_done();
295 ShenandoahNMethodLocker data_locker(data->lock());
296 data->update();
297 data->update_barriers();
298 } else {
299 // For a new nmethod, we can safely append it to the list, because
300 // concurrent iteration will not touch it.
301 data = ShenandoahNMethod::for_nmethod(nm);
302 assert(data != nullptr, "Sanity");
303 ShenandoahNMethod::attach_gc_data(nm, data);
304 ShenandoahLocker locker(&_lock);
305 log_register_nmethod(nm);
306 append(data);
307 data->update_barriers();
308 }
309 // Disarm new nmethod
310 ShenandoahNMethod::disarm_nmethod(nm);
311 }
312
313 void ShenandoahNMethodTable::unregister_nmethod(nmethod* nm) {
314 assert_locked_or_safepoint(CodeCache_lock);
315
316 ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);
317 assert(data != nullptr, "Sanity");
318 log_unregister_nmethod(nm);
319 ShenandoahLocker locker(&_lock);
320 assert(contain(nm), "Must have been registered");
321
322 int idx = index_of(nm);
323 assert(idx >= 0 && idx < _index, "Invalid index");
324 ShenandoahNMethod::attach_gc_data(nm, nullptr);
325 remove(idx);
326 }
327
328 bool ShenandoahNMethodTable::contain(nmethod* nm) const {
329 return index_of(nm) != -1;
330 }
331
332 ShenandoahNMethod* ShenandoahNMethodTable::at(int index) const {
333 assert(index >= 0 && index < _index, "Out of bound");
334 return _list->at(index);
335 }
336
337 int ShenandoahNMethodTable::index_of(nmethod* nm) const {
338 for (int index = 0; index < length(); index ++) {
339 if (at(index)->nm() == nm) {
340 return index;
341 }
342 }
343 return -1;
344 }
345
346 void ShenandoahNMethodTable::remove(int idx) {
347 shenandoah_assert_locked_or_safepoint(CodeCache_lock);
348 assert(_index >= 0 && _index <= _list->size(), "Sanity");
349
350 assert(idx >= 0 && idx < _index, "Out of bound");
351 ShenandoahNMethod* snm = _list->at(idx);
352 ShenandoahNMethod* tmp = _list->at(_index - 1);
353 _list->set(idx, tmp);
354 _index --;
355
356 delete snm;
357 }
358
359 void ShenandoahNMethodTable::wait_until_concurrent_iteration_done() {
360 assert(CodeCache_lock->owned_by_self(), "Lock must be held");
361 while (iteration_in_progress()) {
362 CodeCache_lock->wait_without_safepoint_check();
363 }
364 }
365
366 void ShenandoahNMethodTable::append(ShenandoahNMethod* snm) {
367 if (is_full()) {
368 int new_size = 2 * _list->size();
369 // Rebuild table and replace current one
370 rebuild(new_size);
371 }
372
373 _list->set(_index++, snm);
374 assert(_index >= 0 && _index <= _list->size(), "Sanity");
375 }
376
377 void ShenandoahNMethodTable::rebuild(int size) {
378 ShenandoahNMethodList* new_list = new ShenandoahNMethodList(size);
379 new_list->transfer(_list, _index);
380
381 // Release old list
382 _list->release();
383 _list = new_list;
384 }
385
386 ShenandoahNMethodTableSnapshot* ShenandoahNMethodTable::snapshot_for_iteration() {
387 assert(CodeCache_lock->owned_by_self(), "Must have CodeCache_lock held");
388 _itr_cnt++;
389 return new ShenandoahNMethodTableSnapshot(this);
390 }
391
392 void ShenandoahNMethodTable::finish_iteration(ShenandoahNMethodTableSnapshot* snapshot) {
393 assert(CodeCache_lock->owned_by_self(), "Must have CodeCache_lock held");
394 assert(iteration_in_progress(), "Why we here?");
395 assert(snapshot != nullptr, "No snapshot");
396 _itr_cnt--;
397
398 delete snapshot;
399 }
400
401 void ShenandoahNMethodTable::log_register_nmethod(nmethod* nm) {
402 LogTarget(Debug, gc, nmethod) log;
403 if (!log.is_enabled()) {
404 return;
405 }
406
407 ResourceMark rm;
408 log.print("Register NMethod: %s.%s [" PTR_FORMAT "] (%s)",
409 nm->method()->method_holder()->external_name(),
410 nm->method()->name()->as_C_string(),
411 p2i(nm),
412 nm->compiler_name());
413 }
414
415 void ShenandoahNMethodTable::log_unregister_nmethod(nmethod* nm) {
416 LogTarget(Debug, gc, nmethod) log;
417 if (!log.is_enabled()) {
418 return;
419 }
420
421 ResourceMark rm;
422 log.print("Unregister NMethod: %s.%s [" PTR_FORMAT "]",
423 nm->method()->method_holder()->external_name(),
424 nm->method()->name()->as_C_string(),
425 p2i(nm));
426 }
427
428 #ifdef ASSERT
429 void ShenandoahNMethodTable::assert_nmethods_correct() {
430 assert_locked_or_safepoint(CodeCache_lock);
431
432 for (int index = 0; index < length(); index ++) {
433 ShenandoahNMethod* m = _list->at(index);
434 // Concurrent unloading may have dead nmethods to be cleaned by sweeper
435 if (m->is_unregistered()) continue;
436 m->assert_correct();
437 }
438 }
439 #endif
440
441
442 ShenandoahNMethodList::ShenandoahNMethodList(int size) :
443 _size(size), _ref_count(1) {
444 _list = NEW_C_HEAP_ARRAY(ShenandoahNMethod*, size, mtGC);
445 }
446
447 ShenandoahNMethodList::~ShenandoahNMethodList() {
448 assert(_list != nullptr, "Sanity");
449 assert(_ref_count == 0, "Must be");
450 FREE_C_HEAP_ARRAY(ShenandoahNMethod*, _list);
451 }
452
453 void ShenandoahNMethodList::transfer(ShenandoahNMethodList* const list, int limit) {
454 assert(limit <= size(), "Sanity");
455 ShenandoahNMethod** old_list = list->list();
456 for (int index = 0; index < limit; index++) {
457 _list[index] = old_list[index];
458 }
459 }
460
461 ShenandoahNMethodList* ShenandoahNMethodList::acquire() {
462 assert_locked_or_safepoint(CodeCache_lock);
463 _ref_count++;
464 return this;
465 }
466
467 void ShenandoahNMethodList::release() {
468 assert_locked_or_safepoint(CodeCache_lock);
469 _ref_count--;
470 if (_ref_count == 0) {
471 delete this;
472 }
473 }
474
475 ShenandoahNMethodTableSnapshot::ShenandoahNMethodTableSnapshot(ShenandoahNMethodTable* table) :
476 _heap(ShenandoahHeap::heap()), _list(table->_list->acquire()), _limit(table->_index), _claimed(0) {
477 }
478
479 ShenandoahNMethodTableSnapshot::~ShenandoahNMethodTableSnapshot() {
480 _list->release();
481 }
482
483 void ShenandoahNMethodTableSnapshot::parallel_nmethods_do(NMethodClosure *f) {
484 size_t stride = 256; // educated guess
485
486 ShenandoahNMethod** const list = _list->list();
487
488 size_t max = (size_t)_limit;
489 while (_claimed.load_relaxed() < max) {
490 size_t cur = _claimed.fetch_then_add(stride, memory_order_relaxed);
491 size_t start = cur;
492 size_t end = MIN2(cur + stride, max);
493 if (start >= max) break;
494
495 for (size_t idx = start; idx < end; idx++) {
496 ShenandoahNMethod* nmr = list[idx];
497 assert(nmr != nullptr, "Sanity");
498 if (nmr->is_unregistered()) {
499 continue;
500 }
501
502 nmr->assert_correct();
503 f->do_nmethod(nmr->nm());
504 }
505 }
506 }
507
508 void ShenandoahNMethodTableSnapshot::concurrent_nmethods_do(NMethodClosure* cl) {
509 size_t stride = 256; // educated guess
510
511 ShenandoahNMethod** list = _list->list();
512 size_t max = (size_t)_limit;
513 while (_claimed.load_relaxed() < max) {
514 size_t cur = _claimed.fetch_then_add(stride, memory_order_relaxed);
515 size_t start = cur;
516 size_t end = MIN2(cur + stride, max);
517 if (start >= max) break;
518
519 for (size_t idx = start; idx < end; idx++) {
520 ShenandoahNMethod* data = list[idx];
521 assert(data != nullptr, "Should not be null");
522 if (!data->is_unregistered()) {
523 cl->do_nmethod(data->nm());
524 }
525 }
526 }
527 }
528
529 ShenandoahConcurrentNMethodIterator::ShenandoahConcurrentNMethodIterator(ShenandoahNMethodTable* table) :
530 _table(table),
531 _table_snapshot(nullptr),
532 _started_workers(0),
533 _finished_workers(0) {}
534
535 void ShenandoahConcurrentNMethodIterator::nmethods_do(NMethodClosure* cl) {
536 // Cannot safepoint when iteration is running, because this can cause deadlocks
537 // with other threads waiting on iteration to be over.
538 NoSafepointVerifier nsv;
539
540 MutexLocker ml(CodeCache_lock, Mutex::_no_safepoint_check_flag);
541
542 if (_finished_workers > 0) {
543 // Some threads have already finished. We are now in rampdown: we are now
544 // waiting for all currently recorded workers to finish. No new workers
545 // should start.
546 return;
547 }
548
549 // Record a new worker and initialize the snapshot if it is a first visitor.
550 if (_started_workers++ == 0) {
551 _table_snapshot = _table->snapshot_for_iteration();
552 }
553
554 // All set, relinquish the lock and go concurrent.
555 {
556 MutexUnlocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
557 _table_snapshot->concurrent_nmethods_do(cl);
558 }
559
560 // Record completion. Last worker shuts down the iterator and notifies any waiters.
561 uint count = ++_finished_workers;
562 if (count == _started_workers) {
563 _table->finish_iteration(_table_snapshot);
564 CodeCache_lock->notify_all();
565 }
566 }