1 /*
2 * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
3 * Copyright Amazon.com Inc. or its affiliates. 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 #include "gc/shared/barrierSetNMethod.hpp"
27 #include "gc/shenandoah/shenandoahBarrierSetAssembler.hpp"
28 #include "gc/shenandoah/shenandoahBarrierSetNMethod.hpp"
29 #include "gc/shenandoah/shenandoahBarrierSetStackChunk.hpp"
30 #include "gc/shenandoah/shenandoahCardTable.hpp"
31 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
32 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
33 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
34 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
35 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
36 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
37 #include "gc/shenandoah/shenandoahStackWatermark.hpp"
38 #include "memory/iterator.inline.hpp"
39 #include "oops/compressedOops.inline.hpp"
40 #ifdef COMPILER1
41 #include "gc/shenandoah/c1/shenandoahBarrierSetC1.hpp"
42 #endif
43 #ifdef COMPILER2
44 #include "gc/shenandoah/c2/shenandoahBarrierSetC2.hpp"
45 #endif
46
47 class ShenandoahBarrierSetC1;
48 class ShenandoahBarrierSetC2;
49
50 ShenandoahBarrierSet::ShenandoahBarrierSet(ShenandoahHeap* heap, MemRegion heap_region) :
51 BarrierSet(make_barrier_set_assembler<ShenandoahBarrierSetAssembler>(),
52 make_barrier_set_c1<ShenandoahBarrierSetC1>(),
53 make_barrier_set_c2<ShenandoahBarrierSetC2>(),
54 new ShenandoahBarrierSetNMethod(heap),
55 new ShenandoahBarrierSetStackChunk(),
56 BarrierSet::FakeRtti(BarrierSet::ShenandoahBarrierSet)),
57 _heap(heap),
58 _card_table(nullptr),
59 _satb_mark_queue_buffer_allocator("SATB Buffer Allocator", ShenandoahSATBBufferSize),
60 _satb_mark_queue_set(&_satb_mark_queue_buffer_allocator)
61 {
62 if (ShenandoahCardBarrier) {
63 _card_table = new ShenandoahCardTable(heap_region);
64 _card_table->initialize();
65 }
66 }
67
68 ShenandoahBarrierSetAssembler* ShenandoahBarrierSet::assembler() {
69 BarrierSetAssembler* const bsa = BarrierSet::barrier_set()->barrier_set_assembler();
70 return reinterpret_cast<ShenandoahBarrierSetAssembler*>(bsa);
71 }
72
73 void ShenandoahBarrierSet::print_on(outputStream* st) const {
74 st->print("ShenandoahBarrierSet");
75 }
76
77 bool ShenandoahBarrierSet::need_load_reference_barrier(DecoratorSet decorators, BasicType type) {
78 if (!ShenandoahLoadRefBarrier) return false;
79 return is_reference_type(type);
80 }
81
82 bool ShenandoahBarrierSet::need_keep_alive_barrier(DecoratorSet decorators, BasicType type) {
83 if (!ShenandoahSATBBarrier) return false;
84 if (!is_reference_type(type)) return false;
85 bool keep_alive = (decorators & AS_NO_KEEPALIVE) == 0;
86 bool unknown = (decorators & ON_UNKNOWN_OOP_REF) != 0;
87 bool on_weak_ref = (decorators & (ON_WEAK_OOP_REF | ON_PHANTOM_OOP_REF)) != 0;
88 return (on_weak_ref || unknown) && keep_alive;
89 }
90
91 bool ShenandoahBarrierSet::need_satb_barrier(DecoratorSet decorators, BasicType type) {
92 if (!ShenandoahSATBBarrier) return false;
93 if (!is_reference_type(type)) return false;
94 bool as_normal = (decorators & AS_NORMAL) != 0;
95 bool dest_uninitialized = (decorators & IS_DEST_UNINITIALIZED) != 0;
96 return as_normal && !dest_uninitialized;
97 }
98
99 bool ShenandoahBarrierSet::need_card_barrier(DecoratorSet decorators, BasicType type) {
100 if (!ShenandoahCardBarrier) return false;
101 if (!is_reference_type(type)) return false;
102 return is_heap_access(decorators);
103 }
104
105 void ShenandoahBarrierSet::on_slowpath_allocation_exit(JavaThread* thread, oop new_obj) {
106 #ifdef COMPILER2
107 if (ReduceInitialCardMarks && ShenandoahCardBarrier && !ShenandoahHeap::heap()->is_in_young(new_obj)) {
108 log_debug(gc)("Newly allocated object (" PTR_FORMAT ") is not in the young generation", p2i(new_obj));
109 // This can happen when an object is newly allocated, but we come to a safepoint before returning
110 // the object. If the safepoint runs a degenerated cycle that is upgraded to a full GC, this object
111 // will have survived two GC cycles. If the tenuring age is very low (1), this object may be promoted.
112 // In this case, we have an allocated object, but it has received no stores yet. If card marking barriers
113 // have been elided, we could end up with an object in old holding pointers to young that won't be in
114 // the remembered set. The solution here is conservative, but this problem should be rare, and it will
115 // correct itself on subsequent cycles when the remembered set is updated.
116 ShenandoahGenerationalHeap::heap()->old_generation()->card_scan()->mark_range_as_dirty(
117 cast_from_oop<HeapWord*>(new_obj), new_obj->size()
118 );
119 }
120 #endif // COMPILER2
121 }
122
123 void ShenandoahBarrierSet::on_thread_create(Thread* thread) {
124 // Create thread local data
125 ShenandoahThreadLocalData::create(thread);
126 }
127
128 void ShenandoahBarrierSet::on_thread_destroy(Thread* thread) {
129 // Destroy thread local data
130 ShenandoahThreadLocalData::destroy(thread);
131 }
132
133 void ShenandoahBarrierSet::on_thread_attach(Thread *thread) {
134 assert(!thread->is_Java_thread() || !SafepointSynchronize::is_at_safepoint(),
135 "We should not be at a safepoint");
136 SATBMarkQueue& queue = ShenandoahThreadLocalData::satb_mark_queue(thread);
137 assert(!queue.is_active(), "SATB queue should not be active");
138 assert(queue.buffer() == nullptr, "SATB queue should not have a buffer");
139 assert(queue.index() == 0, "SATB queue index should be zero");
140 queue.set_active(_satb_mark_queue_set.is_active());
141
142 if (ShenandoahCardBarrier) {
143 // Every thread always have a pointer to the _current_ _write_ version of the card table.
144 // The JIT'ed code will use this address (+card entry offset) to mark the card as dirty.
145 ShenandoahThreadLocalData::set_card_table(thread, _card_table->write_byte_map_base());
146 }
147 ShenandoahThreadLocalData::set_gc_state(thread, _heap->gc_state());
148
149 if (thread->is_Java_thread()) {
150 ShenandoahThreadLocalData::initialize_gclab(thread);
151
152 BarrierSetNMethod* bs_nm = barrier_set_nmethod();
153 thread->set_nmethod_disarmed_guard_value(bs_nm->disarmed_guard_value());
154
155 JavaThread* const jt = JavaThread::cast(thread);
156 StackWatermark* const watermark = new ShenandoahStackWatermark(jt);
157 StackWatermarkSet::add_watermark(jt, watermark);
158 }
159 }
160
161 void ShenandoahBarrierSet::on_thread_detach(Thread *thread) {
162 SATBMarkQueue& queue = ShenandoahThreadLocalData::satb_mark_queue(thread);
163 _satb_mark_queue_set.flush_queue(queue);
164 if (thread->is_Java_thread()) {
165 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
166 if (gclab != nullptr) {
167 gclab->retire();
168 }
169
170 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
171 if (shenandoah_plab != nullptr) {
172 shenandoah_plab->retire();
173 }
174
175 // SATB protocol requires to keep alive reachable oops from roots at the beginning of GC
176 if (_heap->is_concurrent_mark_in_progress()) {
177 ShenandoahKeepAliveClosure oops;
178 StackWatermarkSet::finish_processing(JavaThread::cast(thread), &oops, StackWatermarkKind::gc);
179 } else if (_heap->is_concurrent_weak_root_in_progress() && _heap->is_evacuation_in_progress()) {
180 ShenandoahContextEvacuateUpdateRootsClosure oops;
181 StackWatermarkSet::finish_processing(JavaThread::cast(thread), &oops, StackWatermarkKind::gc);
182 } else {
183 ShenandoahNoOpClosure oops;
184 StackWatermarkSet::finish_processing(JavaThread::cast(thread), &oops, StackWatermarkKind::gc);
185 }
186
187 _heap->flush_region_pin_cache(JavaThread::cast(thread));
188 }
189 }
190
191 void ShenandoahBarrierSet::keepalive_barrier_slow(oop obj, Filter filter) {
192 if (!ShenandoahSATBBarrier) {
193 return;
194 }
195 assert(obj != nullptr, "Filtered by caller");
196 assert(_heap->is_concurrent_mark_in_progress(), "Filtered by caller");
197
198 // Filter marked objects before hitting the SATB queues. The same predicate would
199 // be used by SATBMQ::filter to eliminate already marked objects downstream, but
200 // filtering here helps to avoid wasteful SATB queueing work to begin with.
201 if (((filter & FILTER_MARKED) != 0) && !_heap->requires_marking(obj)) {
202 return;
203 }
204
205 shenandoah_assert_correct(nullptr, obj);
206 assert(_satb_mark_queue_set.is_active(), "only get here when SATB active");
207
208 SATBMarkQueue& queue = ShenandoahThreadLocalData::satb_mark_queue(Thread::current());
209 _satb_mark_queue_set.enqueue_known_active(queue, obj);
210 }
211
212 template <typename T>
213 oop ShenandoahBarrierSet::load_reference_barrier_slow(oop obj, T* load_addr) {
214 if (!ShenandoahLoadRefBarrier) {
215 return obj;
216 }
217 assert(_heap->has_forwarded_objects(), "Filtered by caller");
218 assert(_heap->in_collection_set(obj), "Filtered by caller");
219 oop fwd = ShenandoahForwarding::get_forwardee(obj);
220 if (obj == fwd && _heap->is_evacuation_in_progress()) {
221 Thread* t = Thread::current();
222 fwd = _heap->evacuate_object(obj, t);
223 }
224 if (load_addr != nullptr && fwd != obj) {
225 // Since we are here and we know the load address, update the reference.
226 ShenandoahHeap::atomic_update_oop(fwd, load_addr, obj);
227 }
228 return fwd;
229 }
230
231 template oop ShenandoahBarrierSet::load_reference_barrier_slow(oop obj, oop* load_addr);
232 template oop ShenandoahBarrierSet::load_reference_barrier_slow(oop obj, narrowOop* load_addr);
233
234 void ShenandoahBarrierSet::card_barrier_array_slow(HeapWord* start, size_t count) {
235 assert(ShenandoahCardBarrier, "Filtered by caller");
236
237 HeapWord* end = (HeapWord*)((char*) start + (count * heapOopSize));
238 // In the case of compressed oops, start and end may potentially be misaligned;
239 // so we need to conservatively align the first downward (this is not
240 // strictly necessary for current uses, but a case of good hygiene and,
241 // if you will, aesthetics) and the second upward (this is essential for
242 // current uses) to a HeapWord boundary, so we mark all cards overlapping
243 // this write.
244 HeapWord* aligned_start = align_down(start, HeapWordSize);
245 HeapWord* aligned_end = align_up (end, HeapWordSize);
246 // If compressed oops were not being used, these should already be aligned
247 assert(UseCompressedOops || (aligned_start == start && aligned_end == end),
248 "Expected heap word alignment of start and end");
249 _heap->old_generation()->card_scan()->mark_range_as_dirty(aligned_start, (aligned_end - aligned_start));
250 }
251
252 // Clone barrier support
253 template <bool EVAC>
254 class ShenandoahUpdateEvacForCloneOopClosure : public BasicOopIterateClosure {
255 private:
256 ShenandoahHeap* const _heap;
257 const ShenandoahCollectionSet* const _cset;
258 Thread* const _thread;
259
260 template <typename T>
261 inline void do_oop_work(T* p) {
262 T o = RawAccess<>::oop_load(p);
263 if (!CompressedOops::is_null(o)) {
264 oop obj = CompressedOops::decode_not_null(o);
265 if (_cset->is_in(obj)) {
266 oop fwd = ShenandoahForwarding::get_forwardee(obj);
267 if (EVAC && obj == fwd) {
268 fwd = _heap->evacuate_object(obj, _thread);
269 }
270 shenandoah_assert_forwarded_except(p, obj, _heap->cancelled_gc());
271 ShenandoahHeap::atomic_update_oop(fwd, p, o);
272 obj = fwd;
273 }
274 }
275 }
276
277 public:
278 ShenandoahUpdateEvacForCloneOopClosure() :
279 _heap(ShenandoahHeap::heap()),
280 _cset(_heap->collection_set()),
281 _thread(Thread::current()) {}
282
283 virtual void do_oop(oop* p) { do_oop_work(p); }
284 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
285 };
286
287 void ShenandoahBarrierSet::clone_evacuation(oop obj) {
288 if (!ShenandoahCloneBarrier) {
289 return;
290 }
291 if (!need_bulk_update(cast_from_oop<HeapWord*>(obj))) {
292 return;
293 }
294
295 ShenandoahUpdateEvacForCloneOopClosure<true> cl;
296 obj->oop_iterate(&cl);
297 }
298
299 void ShenandoahBarrierSet::clone_update(oop obj) {
300 if (!ShenandoahCloneBarrier) {
301 return;
302 }
303 if (!need_bulk_update(cast_from_oop<HeapWord*>(obj))) {
304 return;
305 }
306
307 ShenandoahUpdateEvacForCloneOopClosure<false> cl;
308 obj->oop_iterate(&cl);
309 }
310
311 template <bool IS_GENERATIONAL, typename T>
312 bool ShenandoahBarrierSet::is_above_tams(const ShenandoahMarkingContext* ctx, T* dst) const {
313 // TAMS for an old region is unreliable during a young-only mark, so overwritten pointers in old dst arrays must
314 // be enqueued to preserve old->young referents copied in and overwritten after init mark. See JDK-8373116.
315 return ctx->allocated_after_mark_start(reinterpret_cast<HeapWord*>(dst))
316 && !(IS_GENERATIONAL
317 && _heap->heap_region_containing(dst)->is_old()
318 && _heap->is_concurrent_young_mark_in_progress());
319 }
320
321 inline bool ShenandoahBarrierSet::need_bulk_update(HeapWord* ary) const {
322 return ary < _heap->heap_region_containing(ary)->get_update_watermark();
323 }
324
325 template <bool IS_GENERATIONAL, typename T>
326 void ShenandoahBarrierSet::arraycopy_marking(T* dst, size_t count) {
327 assert(_heap->is_concurrent_mark_in_progress(), "only during marking");
328 if (!ShenandoahSATBBarrier) {
329 return;
330 }
331
332 const ShenandoahMarkingContext* ctx = _heap->marking_context();
333 // Everything allocated above TAMS is alive and doesn't need the barrier to keep it that way
334 if (is_above_tams<IS_GENERATIONAL>(ctx, dst)) {
335 return;
336 }
337
338 assert(!_heap->has_forwarded_objects() || _heap->is_concurrent_old_mark_in_progress(), "Forwarded object status is sane");
339 Thread* thread = Thread::current();
340 SATBMarkQueue& queue = ShenandoahThreadLocalData::satb_mark_queue(thread);
341 T* end = dst + count;
342 for (T* elem_ptr = dst; elem_ptr < end; ++elem_ptr) {
343 T o = RawAccess<>::oop_load(elem_ptr);
344 if (!CompressedOops::is_null(o)) {
345 oop obj = CompressedOops::decode_not_null(o);
346 if (!ctx->is_marked_strong(obj)) {
347 _satb_mark_queue_set.enqueue_known_active(queue, obj);
348 }
349 }
350 }
351 }
352
353 template void ShenandoahBarrierSet::arraycopy_marking<false, oop>(oop* dst, size_t count);
354 template void ShenandoahBarrierSet::arraycopy_marking<false, narrowOop>(narrowOop* dst, size_t count);
355 template void ShenandoahBarrierSet::arraycopy_marking<true, oop>(oop* dst, size_t count);
356 template void ShenandoahBarrierSet::arraycopy_marking<true, narrowOop>(narrowOop* dst, size_t count);
357
358 template <typename T>
359 void ShenandoahBarrierSet::arraycopy_evacuation(T* src, size_t count) {
360 assert(_heap->is_evacuation_in_progress(), "only during evacuation");
361 if (!need_bulk_update(reinterpret_cast<HeapWord*>(src))) {
362 return;
363 }
364
365 assert(_heap->has_forwarded_objects(), "Forwarded object status is sane");
366 Thread* thread = Thread::current();
367 const ShenandoahCollectionSet* const cset = _heap->collection_set();
368 T* end = src + count;
369 for (T* elem_ptr = src; elem_ptr < end; ++elem_ptr) {
370 T o = RawAccess<>::oop_load(elem_ptr);
371 if (!CompressedOops::is_null(o)) {
372 oop obj = CompressedOops::decode_not_null(o);
373 if (cset->is_in(obj)) {
374 oop fwd = ShenandoahForwarding::get_forwardee(obj);
375 if (obj == fwd) {
376 fwd = _heap->evacuate_object(obj, thread);
377 }
378 shenandoah_assert_forwarded_except(elem_ptr, obj, _heap->cancelled_gc());
379 ShenandoahHeap::atomic_update_oop(fwd, elem_ptr, o);
380 }
381 }
382 }
383 }
384
385 template void ShenandoahBarrierSet::arraycopy_evacuation<oop>(oop* src, size_t count);
386 template void ShenandoahBarrierSet::arraycopy_evacuation<narrowOop>(narrowOop* src, size_t count);
387
388 template <typename T>
389 void ShenandoahBarrierSet::arraycopy_update(T* src, size_t count) {
390 assert(_heap->is_update_refs_in_progress(), "only during update-refs");
391 if (!need_bulk_update(reinterpret_cast<HeapWord*>(src))) {
392 return;
393 }
394
395 assert(_heap->has_forwarded_objects(), "Forwarded object status is sane");
396 const ShenandoahCollectionSet* const cset = _heap->collection_set();
397 T* end = src + count;
398 for (T* elem_ptr = src; elem_ptr < end; ++elem_ptr) {
399 T o = RawAccess<>::oop_load(elem_ptr);
400 if (!CompressedOops::is_null(o)) {
401 oop obj = CompressedOops::decode_not_null(o);
402 if (cset->is_in(obj)) {
403 oop fwd = ShenandoahForwarding::get_forwardee(obj);
404 shenandoah_assert_forwarded_except(elem_ptr, obj, _heap->cancelled_gc());
405 ShenandoahHeap::atomic_update_oop(fwd, elem_ptr, o);
406 }
407 }
408 }
409 }
410
411 template void ShenandoahBarrierSet::arraycopy_update<oop>(oop* src, size_t count);
412 template void ShenandoahBarrierSet::arraycopy_update<narrowOop>(narrowOop* src, size_t count);