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