1 /*
2 * Copyright (c) 2024, 2026, 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), _patchable_jumps(nullptr), _patchable_jumps_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 (_patchable_jumps != nullptr) {
45 FREE_C_HEAP_ARRAY(_patchable_jumps);
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<ShenandoahPatchableJump> jumps;
58
59 parse(nm, oops, non_immediate_oops, jumps);
60
61 int new_oops_count = oops.length();
62 if (_oops_count != new_oops_count) {
63 if (_oops != nullptr) {
64 FREE_C_HEAP_ARRAY(_oops);
65 _oops = nullptr;
66 }
67 if (new_oops_count > 0) {
68 _oops = NEW_C_HEAP_ARRAY(oop*, new_oops_count, mtGC);
69 }
70 }
71 _oops_count = new_oops_count;
72 for (int c = 0; c < _oops_count; c++) {
73 _oops[c] = oops.at(c);
74 }
75 assert_same_oops();
76
77 int new_jumps_count = jumps.length();
78 if (_patchable_jumps_count != new_jumps_count) {
79 if (_patchable_jumps != nullptr) {
80 FREE_C_HEAP_ARRAY(_patchable_jumps);
81 _patchable_jumps = nullptr;
82 }
83 if (new_jumps_count > 0) {
84 _patchable_jumps = NEW_C_HEAP_ARRAY(ShenandoahPatchableJump, new_jumps_count, mtGC);
85 }
86 }
87 _patchable_jumps_count = new_jumps_count;
88 for (int c = 0; c < _patchable_jumps_count; c++) {
89 _patchable_jumps[c] = jumps.at(c);
90 }
91
92 _has_non_immed_oops = non_immediate_oops;
93 }
94
95 void ShenandoahNMethod::parse(nmethod* nm, GrowableArray<oop*>& oops, bool& has_non_immed_oops, GrowableArray<ShenandoahPatchableJump>& jumps) {
96 has_non_immed_oops = false;
97 address code_begin = nm->code_begin();
98 RelocIterator iter(nm);
99 while (iter.next()) {
100 switch (iter.type()) {
101 case relocInfo::oop_type: {
102 oop_Relocation* r = iter.oop_reloc();
103 if (!r->oop_is_immediate()) {
104 // Non-immediate oop found
105 has_non_immed_oops = true;
106 break;
107 }
108
109 oop value = r->oop_value();
110 if (value != nullptr) {
111 oop* addr = r->oop_addr();
112 shenandoah_assert_correct(addr, value);
113 shenandoah_assert_not_in_cset_except(addr, value, ShenandoahHeap::heap()->cancelled_gc());
114 shenandoah_assert_not_forwarded(addr, value);
115 // Non-null immediate oop found. null oops can safely be
116 // ignored since the method will be re-registered if they
117 // are later patched to be non-null.
118 oops.push(addr);
119 }
120 break;
121 }
122 case relocInfo::patchable_barrier_type: {
123 patchable_barrier_Relocation* r = iter.patchable_barrier_reloc();
124
125 ShenandoahPatchableJump b;
126 b._rel_pc = checked_cast<int32_t>(pointer_delta(r->addr(), code_begin, 1));
127 b._rel_target_pc = r->target_offset();
128 b._gc_state = decode_reloc_gc_state(r->metadata());
129 b._jump_when_state = decode_reloc_jump_when_state(r->metadata());
130 jumps.push(b);
131 break;
132 }
133 default:
134 // We do not care about other relocations.
135 break;
136 }
137 }
138 }
139
140 ShenandoahNMethod* ShenandoahNMethod::for_nmethod(nmethod* nm) {
141 return new ShenandoahNMethod(nm);
142 }
143
144 bool ShenandoahNMethod::handle_oops(nmethod* nm) {
145 ShenandoahNMethod* data = gc_data(nm);
146 assert(data != nullptr, "Sanity");
147 assert(data->lock()->owned_by_self(), "Must hold the lock");
148
149 ShenandoahHeap* const heap = ShenandoahHeap::heap();
150 if ((heap->is_concurrent_weak_root_in_progress() && heap->is_evacuation_in_progress()) ||
151 heap->is_concurrent_strong_root_in_progress()) {
152 heal_nmethod_metadata(data);
153 // Assume healing changed the code.
154 return true;
155 } else if (heap->is_concurrent_mark_in_progress()) {
156 ShenandoahKeepAliveClosure cl;
157 data->oops_do(&cl);
158 } else {
159 // There is possibility that GC is cancelled when it arrives final mark.
160 // In this case, concurrent root phase is skipped and degenerated GC should be
161 // followed, where nmethods are disarmed.
162 }
163
164 // No code modifications happened
165 return false;
166 }
167
168 bool ShenandoahNMethod::handle_jumps(nmethod* nm) {
169 ShenandoahNMethod* data = gc_data(nm);
170 assert(data != nullptr, "Sanity");
171 assert(data->lock()->owned_by_self(), "Must hold the lock");
172
173 char gc_state = ShenandoahHeap::heap()->gc_state();
174 address code_begin = nm->code_begin();
175
176 bool changed = false;
177 for (int c = 0; c < data->_patchable_jumps_count; c++) {
178 ShenandoahPatchableJump& b = data->_patchable_jumps[c];
179 changed |= patch_jump(code_begin + b._rel_pc,
180 code_begin + b._rel_target_pc,
181 ((gc_state & b._gc_state) != 0) == b._jump_when_state);
182 }
183 return changed;
184 }
185
186 // Use precise instruction rewrite code, and only when it recognizes the current insns.
187 //
188 // This patching code is non-atomic, but it runs in two safe contexts:
189 // a) For new nmethods that are not yet executing and not yet live. This covers the paths
190 // for newly compiled methods, nmethods that were just relocated, the nmethods that
191 // were AOT-loaded.
192 // b) For existing methods in the nmethod entry barrier context. The nmethod entry barriers
193 // are armed along with stack watermark machinery activation. Together they guarantee
194 // the nmethod updates are not interleaved with execution, and nmethod would be patched
195 // before allowing to proceed.
196 //
197 // The icache flushing is also handled on both paths.
198 //
199 bool ShenandoahNMethod::patch_jump(address pc, address target_pc, bool should_jump) {
200 bool patched = true;
201 if (should_jump && ShenandoahBarrierSetAssembler::is_patchable_nop(pc)) {
202 ShenandoahBarrierSetAssembler::insert_patchable_jump(pc, target_pc);
203 } else if (!should_jump && ShenandoahBarrierSetAssembler::is_patchable_jump(pc, target_pc)) {
204 ShenandoahBarrierSetAssembler::insert_patchable_nop(pc);
205 } else {
206 patched = false;
207 }
208
209 // Failing to change the jump is catastrophic for correctness,
210 // so prefer to crash hard even in product.
211 if (should_jump) {
212 guarantee(ShenandoahBarrierSetAssembler::is_patchable_jump(pc, target_pc),
213 "Should be jump to the same address");
214 assert(ShenandoahBarrierSetAssembler::parse_jump_address(pc) == target_pc,
215 "Cross-checking, jump should be to the same address");
216 } else {
217 guarantee(ShenandoahBarrierSetAssembler::is_patchable_nop(pc),
218 "Should be patchable nop");
219 }
220 return patched;
221 }
222
223 #ifdef ASSERT
224 void ShenandoahNMethod::assert_correct() {
225 ShenandoahHeap* heap = ShenandoahHeap::heap();
226 for (int c = 0; c < _oops_count; c++) {
227 oop *loc = _oops[c];
228 assert(_nm->code_contains((address) loc) || _nm->oops_contains(loc), "nmethod should contain the oop*");
229 oop o = RawAccess<>::oop_load(loc);
230 shenandoah_assert_correct_except(loc, o, o == nullptr || heap->is_full_gc_move_in_progress());
231 }
232
233 oop* const begin = _nm->oops_begin();
234 oop* const end = _nm->oops_end();
235 for (oop* p = begin; p < end; p++) {
236 if (*p != Universe::non_oop_word()) {
237 oop o = RawAccess<>::oop_load(p);
238 shenandoah_assert_correct_except(p, o, o == nullptr || heap->is_full_gc_move_in_progress());
239 }
240 }
241 }
242
243 class ShenandoahNMethodOopDetector : public OopClosure {
244 private:
245 ResourceMark rm; // For growable array allocation below.
246 GrowableArray<oop*> _oops;
247
248 public:
249 ShenandoahNMethodOopDetector() : _oops(10) {};
250
251 void do_oop(oop* o) {
252 _oops.append(o);
253 }
254 void do_oop(narrowOop* o) {
255 fatal("NMethods should not have compressed oops embedded.");
256 }
257
258 GrowableArray<oop*>* oops() {
259 return &_oops;
260 }
261 };
262
263 void ShenandoahNMethod::assert_same_oops() {
264 ShenandoahNMethodOopDetector detector;
265 nm()->oops_do(&detector);
266
267 GrowableArray<oop*>* oops = detector.oops();
268
269 int count = _oops_count;
270 for (int index = 0; index < _oops_count; index ++) {
271 assert(oops->contains(_oops[index]), "Must contain this oop");
272 }
273
274 for (oop* p = nm()->oops_begin(); p < nm()->oops_end(); p ++) {
275 if (*p == Universe::non_oop_word()) continue;
276 count++;
277 assert(oops->contains(p), "Must contain this oop");
278 }
279
280 if (oops->length() < count) {
281 stringStream debug_stream;
282 debug_stream.print_cr("detected locs: %d", oops->length());
283 for (int i = 0; i < oops->length(); i++) {
284 debug_stream.print_cr("-> " PTR_FORMAT, p2i(oops->at(i)));
285 }
286 debug_stream.print_cr("recorded oops: %d", _oops_count);
287 for (int i = 0; i < _oops_count; i++) {
288 debug_stream.print_cr("-> " PTR_FORMAT, p2i(_oops[i]));
289 }
290 GrowableArray<oop*> check;
291 GrowableArray<ShenandoahPatchableJump> jumps;
292 bool non_immed;
293 parse(nm(), check, non_immed, jumps);
294 debug_stream.print_cr("check oops: %d", check.length());
295 for (int i = 0; i < check.length(); i++) {
296 debug_stream.print_cr("-> " PTR_FORMAT, p2i(check.at(i)));
297 }
298 fatal("Must match #detected: %d, #recorded: %d, #total: %d, begin: " PTR_FORMAT ", end: " PTR_FORMAT "\n%s",
299 oops->length(), _oops_count, count, p2i(nm()->oops_begin()), p2i(nm()->oops_end()), debug_stream.freeze());
300 }
301 }
302 #endif
303
304 ShenandoahNMethodTable::ShenandoahNMethodTable() :
305 _heap(ShenandoahHeap::heap()),
306 _bs_nm(BarrierSet::barrier_set()->barrier_set_nmethod()),
307 _index(0),
308 _itr_cnt(0) {
309 _list = new ShenandoahNMethodList(minSize);
310 }
311
312 ShenandoahNMethodTable::~ShenandoahNMethodTable() {
313 assert(_list != nullptr, "Sanity");
314 _list->release();
315 }
316
317 void ShenandoahNMethodTable::register_nmethod(nmethod* nm) {
318 assert(CodeCache_lock->owned_by_self(), "Must have CodeCache_lock held");
319 assert(_index >= 0 && _index <= _list->size(), "Sanity");
320
321 ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);
322
323 if (data != nullptr) {
324 // Re-registering the existing nmethod. This is the C1 oop patching path.
325 // We expect no patchable jumps here, as only oops can change in C1 case.
326 assert(contain(nm), "Must have been registered");
327 assert(nm == data->nm(), "Must be same nmethod");
328 assert(nm->is_compiled_by_c1(), "Must be compiled by C1");
329 assert(!data->has_patchable_jumps(), "Must not have patchable jumps");
330 // Prevent updating a nmethod while concurrent iteration is in progress.
331 wait_until_concurrent_iteration_done();
332 ShenandoahNMethodLocker data_locker(data->lock());
333 data->update();
334 } else {
335 // New nmethod, not yet executing. We can safely append it to the list,
336 // because concurrent iteration will not touch it. Ditto we do jump
337 // fixups right here, without relying on nmethod entry barrier to be armed
338 // for new nmethods.
339 data = ShenandoahNMethod::for_nmethod(nm);
340 assert(data != nullptr, "Sanity");
341 ShenandoahNMethod::attach_gc_data(nm, data);
342 ShenandoahLocker locker(&_lock);
343 log_register_nmethod(nm);
344 append(data);
345 ShenandoahNMethodLocker data_locker(data->lock());
346 if (ShenandoahNMethod::handle_jumps(nm)) {
347 ICache::invalidate_range(nm->code_begin(), nm->code_size());
348 }
349 ShenandoahNMethod::disarm_nmethod(nm);
350 }
351
352 assert(!data->has_patchable_jumps() || _bs_nm->supports_entry_barrier(nm),
353 "NMethods with patchable jumps require entry barrier support");
354 }
355
356 void ShenandoahNMethodTable::unregister_nmethod(nmethod* nm) {
357 assert_locked_or_safepoint(CodeCache_lock);
358
359 ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);
360 assert(data != nullptr, "Sanity");
361 log_unregister_nmethod(nm);
362 ShenandoahLocker locker(&_lock);
363 assert(contain(nm), "Must have been registered");
364
365 int idx = index_of(nm);
366 assert(idx >= 0 && idx < _index, "Invalid index");
367 ShenandoahNMethod::attach_gc_data(nm, nullptr);
368 remove(idx);
369 }
370
371 bool ShenandoahNMethodTable::contain(nmethod* nm) const {
372 return index_of(nm) != -1;
373 }
374
375 ShenandoahNMethod* ShenandoahNMethodTable::at(int index) const {
376 assert(index >= 0 && index < _index, "Out of bound");
377 return _list->at(index);
378 }
379
380 int ShenandoahNMethodTable::index_of(nmethod* nm) const {
381 for (int index = 0; index < length(); index ++) {
382 if (at(index)->nm() == nm) {
383 return index;
384 }
385 }
386 return -1;
387 }
388
389 void ShenandoahNMethodTable::remove(int idx) {
390 shenandoah_assert_locked_or_safepoint(CodeCache_lock);
391 assert(_index >= 0 && _index <= _list->size(), "Sanity");
392
393 assert(idx >= 0 && idx < _index, "Out of bound");
394 ShenandoahNMethod* snm = _list->at(idx);
395 ShenandoahNMethod* tmp = _list->at(_index - 1);
396 _list->set(idx, tmp);
397 _index --;
398
399 delete snm;
400 }
401
402 void ShenandoahNMethodTable::wait_until_concurrent_iteration_done() {
403 assert(CodeCache_lock->owned_by_self(), "Lock must be held");
404 while (iteration_in_progress()) {
405 CodeCache_lock->wait_without_safepoint_check();
406 }
407 }
408
409 void ShenandoahNMethodTable::append(ShenandoahNMethod* snm) {
410 if (is_full()) {
411 int new_size = 2 * _list->size();
412 // Rebuild table and replace current one
413 rebuild(new_size);
414 }
415
416 _list->set(_index++, snm);
417 assert(_index >= 0 && _index <= _list->size(), "Sanity");
418 }
419
420 void ShenandoahNMethodTable::rebuild(int size) {
421 ShenandoahNMethodList* new_list = new ShenandoahNMethodList(size);
422 new_list->transfer(_list, _index);
423
424 // Release old list
425 _list->release();
426 _list = new_list;
427 }
428
429 ShenandoahNMethodTableSnapshot* ShenandoahNMethodTable::snapshot_for_iteration() {
430 assert(CodeCache_lock->owned_by_self(), "Must have CodeCache_lock held");
431 _itr_cnt++;
432 return new ShenandoahNMethodTableSnapshot(this);
433 }
434
435 void ShenandoahNMethodTable::finish_iteration(ShenandoahNMethodTableSnapshot* snapshot) {
436 assert(CodeCache_lock->owned_by_self(), "Must have CodeCache_lock held");
437 assert(iteration_in_progress(), "Why we here?");
438 assert(snapshot != nullptr, "No snapshot");
439 _itr_cnt--;
440
441 delete snapshot;
442 }
443
444 void ShenandoahNMethodTable::log_register_nmethod(nmethod* nm) {
445 LogTarget(Debug, gc, nmethod) log;
446 if (!log.is_enabled()) {
447 return;
448 }
449
450 ResourceMark rm;
451 log.print("Register NMethod: %s.%s [" PTR_FORMAT "] (%s)",
452 nm->method()->method_holder()->external_name(),
453 nm->method()->name()->as_C_string(),
454 p2i(nm),
455 nm->compiler_name());
456 }
457
458 void ShenandoahNMethodTable::log_unregister_nmethod(nmethod* nm) {
459 LogTarget(Debug, gc, nmethod) log;
460 if (!log.is_enabled()) {
461 return;
462 }
463
464 ResourceMark rm;
465 log.print("Unregister NMethod: %s.%s [" PTR_FORMAT "]",
466 nm->method()->method_holder()->external_name(),
467 nm->method()->name()->as_C_string(),
468 p2i(nm));
469 }
470
471 #ifdef ASSERT
472 void ShenandoahNMethodTable::assert_nmethods_correct() {
473 assert_locked_or_safepoint(CodeCache_lock);
474
475 for (int index = 0; index < length(); index ++) {
476 ShenandoahNMethod* m = _list->at(index);
477 // Concurrent unloading may have dead nmethods to be cleaned by sweeper
478 if (m->is_unregistered()) continue;
479 m->assert_correct();
480 }
481 }
482 #endif
483
484
485 ShenandoahNMethodList::ShenandoahNMethodList(int size) :
486 _size(size), _ref_count(1) {
487 _list = NEW_C_HEAP_ARRAY(ShenandoahNMethod*, size, mtGC);
488 }
489
490 ShenandoahNMethodList::~ShenandoahNMethodList() {
491 assert(_list != nullptr, "Sanity");
492 assert(_ref_count == 0, "Must be");
493 FREE_C_HEAP_ARRAY(_list);
494 }
495
496 void ShenandoahNMethodList::transfer(ShenandoahNMethodList* const list, int limit) {
497 assert(limit <= size(), "Sanity");
498 ShenandoahNMethod** old_list = list->list();
499 for (int index = 0; index < limit; index++) {
500 _list[index] = old_list[index];
501 }
502 }
503
504 ShenandoahNMethodList* ShenandoahNMethodList::acquire() {
505 assert_locked_or_safepoint(CodeCache_lock);
506 _ref_count++;
507 return this;
508 }
509
510 void ShenandoahNMethodList::release() {
511 assert_locked_or_safepoint(CodeCache_lock);
512 _ref_count--;
513 if (_ref_count == 0) {
514 delete this;
515 }
516 }
517
518 ShenandoahNMethodTableSnapshot::ShenandoahNMethodTableSnapshot(ShenandoahNMethodTable* table) :
519 _heap(ShenandoahHeap::heap()), _list(table->_list->acquire()), _limit(table->_index), _claimed(0) {
520 }
521
522 ShenandoahNMethodTableSnapshot::~ShenandoahNMethodTableSnapshot() {
523 _list->release();
524 }
525
526 void ShenandoahNMethodTableSnapshot::parallel_nmethods_do(NMethodClosure *f) {
527 size_t stride = 256; // educated guess
528
529 ShenandoahNMethod** const list = _list->list();
530
531 size_t max = (size_t)_limit;
532 while (_claimed.load_relaxed() < max) {
533 size_t cur = _claimed.fetch_then_add(stride, memory_order_relaxed);
534 size_t start = cur;
535 size_t end = MIN2(cur + stride, max);
536 if (start >= max) break;
537
538 for (size_t idx = start; idx < end; idx++) {
539 ShenandoahNMethod* nmr = list[idx];
540 assert(nmr != nullptr, "Sanity");
541 if (nmr->is_unregistered()) {
542 continue;
543 }
544
545 nmr->assert_correct();
546 f->do_nmethod(nmr->nm());
547 }
548 }
549 }
550
551 void ShenandoahNMethodTableSnapshot::concurrent_nmethods_do(NMethodClosure* cl) {
552 size_t stride = 256; // educated guess
553
554 ShenandoahNMethod** list = _list->list();
555 size_t max = (size_t)_limit;
556 while (_claimed.load_relaxed() < max) {
557 size_t cur = _claimed.fetch_then_add(stride, memory_order_relaxed);
558 size_t start = cur;
559 size_t end = MIN2(cur + stride, max);
560 if (start >= max) break;
561
562 for (size_t idx = start; idx < end; idx++) {
563 ShenandoahNMethod* data = list[idx];
564 assert(data != nullptr, "Should not be null");
565 if (!data->is_unregistered()) {
566 cl->do_nmethod(data->nm());
567 }
568 }
569 }
570 }
571
572 ShenandoahConcurrentNMethodIterator::ShenandoahConcurrentNMethodIterator(ShenandoahNMethodTable* table) :
573 _table(table),
574 _table_snapshot(nullptr),
575 _started_workers(0),
576 _finished_workers(0) {}
577
578 void ShenandoahConcurrentNMethodIterator::nmethods_do(NMethodClosure* cl) {
579 // Cannot safepoint when iteration is running, because this can cause deadlocks
580 // with other threads waiting on iteration to be over.
581 NoSafepointVerifier nsv;
582
583 MutexLocker ml(CodeCache_lock, Mutex::_no_safepoint_check_flag);
584
585 if (_finished_workers > 0) {
586 // Some threads have already finished. We are now in rampdown: we are now
587 // waiting for all currently recorded workers to finish. No new workers
588 // should start.
589 return;
590 }
591
592 // Record a new worker and initialize the snapshot if it is a first visitor.
593 if (_started_workers++ == 0) {
594 _table_snapshot = _table->snapshot_for_iteration();
595 }
596
597 // All set, relinquish the lock and go concurrent.
598 {
599 MutexUnlocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
600 _table_snapshot->concurrent_nmethods_do(cl);
601 }
602
603 // Record completion. Last worker shuts down the iterator and notifies any waiters.
604 uint count = ++_finished_workers;
605 if (count == _started_workers) {
606 _table->finish_iteration(_table_snapshot);
607 CodeCache_lock->notify_all();
608 }
609 }