1 /*
  2  * Copyright (c) 2017, 2021, Red Hat, Inc. 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 "gc/shared/tlab_globals.hpp"
 27 #include "gc/shenandoah/shenandoahAsserts.hpp"
 28 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
 29 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
 30 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
 31 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
 32 #include "gc/shenandoah/shenandoahRootProcessor.hpp"
 33 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
 34 #include "gc/shenandoah/shenandoahUtils.hpp"
 35 #include "gc/shenandoah/shenandoahVerifier.hpp"
 36 #include "memory/allocation.hpp"
 37 #include "memory/iterator.inline.hpp"
 38 #include "memory/resourceArea.hpp"
 39 #include "oops/compressedOops.inline.hpp"
 40 #include "runtime/atomic.hpp"
 41 #include "runtime/orderAccess.hpp"
 42 #include "runtime/threads.hpp"
 43 #include "utilities/align.hpp"
 44 
 45 // Avoid name collision on verify_oop (defined in macroAssembler_arm.hpp)
 46 #ifdef verify_oop
 47 #undef verify_oop
 48 #endif
 49 
 50 static bool is_instance_ref_klass(Klass* k) {
 51   return k->is_instance_klass() && InstanceKlass::cast(k)->reference_type() != REF_NONE;
 52 }
 53 
 54 class ShenandoahIgnoreReferenceDiscoverer : public ReferenceDiscoverer {
 55 public:
 56   virtual bool discover_reference(oop obj, ReferenceType type) {
 57     return true;
 58   }
 59 };
 60 
 61 class ShenandoahVerifyOopClosure : public BasicOopIterateClosure {
 62 private:
 63   const char* _phase;
 64   ShenandoahVerifier::VerifyOptions _options;
 65   ShenandoahVerifierStack* _stack;
 66   ShenandoahHeap* _heap;
 67   MarkBitMap* _map;
 68   ShenandoahLivenessData* _ld;
 69   void* _interior_loc;
 70   oop _loc;
 71 
 72 public:
 73   ShenandoahVerifyOopClosure(ShenandoahVerifierStack* stack, MarkBitMap* map, ShenandoahLivenessData* ld,
 74                              const char* phase, ShenandoahVerifier::VerifyOptions options) :
 75     _phase(phase),
 76     _options(options),
 77     _stack(stack),
 78     _heap(ShenandoahHeap::heap()),
 79     _map(map),
 80     _ld(ld),
 81     _interior_loc(NULL),
 82     _loc(NULL) {
 83     if (options._verify_marked == ShenandoahVerifier::_verify_marked_complete_except_references ||
 84         options._verify_marked == ShenandoahVerifier::_verify_marked_disable) {
 85       set_ref_discoverer_internal(new ShenandoahIgnoreReferenceDiscoverer());
 86     }
 87   }
 88 
 89 private:
 90   void check(ShenandoahAsserts::SafeLevel level, oop obj, bool test, const char* label) {
 91     if (!test) {
 92       ShenandoahAsserts::print_failure(level, obj, _interior_loc, _loc, _phase, label, __FILE__, __LINE__);
 93     }
 94   }
 95 
 96   template <class T>
 97   void do_oop_work(T* p) {
 98     T o = RawAccess<>::oop_load(p);
 99     if (!CompressedOops::is_null(o)) {
100       oop obj = CompressedOops::decode_not_null(o);
101       if (is_instance_ref_klass(obj->klass())) {
102         obj = ShenandoahForwarding::get_forwardee(obj);
103       }
104       // Single threaded verification can use faster non-atomic stack and bitmap
105       // methods.
106       //
107       // For performance reasons, only fully verify non-marked field values.
108       // We are here when the host object for *p is already marked.
109 
110       if (_map->par_mark(obj)) {
111         verify_oop_at(p, obj);
112         _stack->push(ShenandoahVerifierTask(obj));
113       }
114     }
115   }
116 
117   void verify_oop(oop obj) {
118     // Perform consistency checks with gradually decreasing safety level. This guarantees
119     // that failure report would not try to touch something that was not yet verified to be
120     // safe to process.
121 
122     check(ShenandoahAsserts::_safe_unknown, obj, _heap->is_in(obj),
123               "oop must be in heap");
124     check(ShenandoahAsserts::_safe_unknown, obj, is_object_aligned(obj),
125               "oop must be aligned");
126 
127     ShenandoahHeapRegion *obj_reg = _heap->heap_region_containing(obj);
128     Klass* obj_klass = obj->klass_or_null();
129 
130     // Verify that obj is not in dead space:
131     {
132       // Do this before touching obj->size()
133       check(ShenandoahAsserts::_safe_unknown, obj, obj_klass != NULL,
134              "Object klass pointer should not be NULL");
135       check(ShenandoahAsserts::_safe_unknown, obj, Metaspace::contains(obj_klass),
136              "Object klass pointer must go to metaspace");
137 
138       HeapWord *obj_addr = cast_from_oop<HeapWord*>(obj);
139       check(ShenandoahAsserts::_safe_unknown, obj, obj_addr < obj_reg->top(),
140              "Object start should be within the region");
141 
142       if (!obj_reg->is_humongous()) {
143         check(ShenandoahAsserts::_safe_unknown, obj, (obj_addr + obj->size()) <= obj_reg->top(),
144                "Object end should be within the region");
145       } else {
146         size_t humongous_start = obj_reg->index();
147         size_t humongous_end = humongous_start + (obj->size() >> ShenandoahHeapRegion::region_size_words_shift());
148         for (size_t idx = humongous_start + 1; idx < humongous_end; idx++) {
149           check(ShenandoahAsserts::_safe_unknown, obj, _heap->get_region(idx)->is_humongous_continuation(),
150                  "Humongous object is in continuation that fits it");
151         }
152       }
153 
154       // ------------ obj is safe at this point --------------
155 
156       check(ShenandoahAsserts::_safe_oop, obj, obj_reg->is_active(),
157             "Object should be in active region");
158 
159       switch (_options._verify_liveness) {
160         case ShenandoahVerifier::_verify_liveness_disable:
161           // skip
162           break;
163         case ShenandoahVerifier::_verify_liveness_complete:
164           Atomic::add(&_ld[obj_reg->index()], (uint) obj->size(), memory_order_relaxed);
165           // fallthrough for fast failure for un-live regions:
166         case ShenandoahVerifier::_verify_liveness_conservative:
167           check(ShenandoahAsserts::_safe_oop, obj, obj_reg->has_live(),
168                    "Object must belong to region with live data");
169           break;
170         default:
171           assert(false, "Unhandled liveness verification");
172       }
173     }
174 
175     oop fwd = ShenandoahForwarding::get_forwardee_raw_unchecked(obj);
176 
177     ShenandoahHeapRegion* fwd_reg = NULL;
178 
179     if (obj != fwd) {
180       check(ShenandoahAsserts::_safe_oop, obj, _heap->is_in(fwd),
181              "Forwardee must be in heap");
182       check(ShenandoahAsserts::_safe_oop, obj, !CompressedOops::is_null(fwd),
183              "Forwardee is set");
184       check(ShenandoahAsserts::_safe_oop, obj, is_object_aligned(fwd),
185              "Forwardee must be aligned");
186 
187       // Do this before touching fwd->size()
188       Klass* fwd_klass = fwd->klass_or_null();
189       check(ShenandoahAsserts::_safe_oop, obj, fwd_klass != NULL,
190              "Forwardee klass pointer should not be NULL");
191       check(ShenandoahAsserts::_safe_oop, obj, Metaspace::contains(fwd_klass),
192              "Forwardee klass pointer must go to metaspace");
193       check(ShenandoahAsserts::_safe_oop, obj, obj_klass == fwd_klass,
194              "Forwardee klass pointer must go to metaspace");
195 
196       fwd_reg = _heap->heap_region_containing(fwd);
197 
198       // Verify that forwardee is not in the dead space:
199       check(ShenandoahAsserts::_safe_oop, obj, !fwd_reg->is_humongous(),
200              "Should have no humongous forwardees");
201 
202       HeapWord *fwd_addr = cast_from_oop<HeapWord *>(fwd);
203       check(ShenandoahAsserts::_safe_oop, obj, fwd_addr < fwd_reg->top(),
204              "Forwardee start should be within the region");
205       check(ShenandoahAsserts::_safe_oop, obj, (fwd_addr + fwd->size()) <= fwd_reg->top(),
206              "Forwardee end should be within the region");
207 
208       oop fwd2 = ShenandoahForwarding::get_forwardee_raw_unchecked(fwd);
209       check(ShenandoahAsserts::_safe_oop, obj, (fwd == fwd2),
210              "Double forwarding");
211     } else {
212       fwd_reg = obj_reg;
213     }
214 
215     // ------------ obj and fwd are safe at this point --------------
216 
217     switch (_options._verify_marked) {
218       case ShenandoahVerifier::_verify_marked_disable:
219         // skip
220         break;
221       case ShenandoahVerifier::_verify_marked_incomplete:
222         check(ShenandoahAsserts::_safe_all, obj, _heap->marking_context()->is_marked(obj),
223                "Must be marked in incomplete bitmap");
224         break;
225       case ShenandoahVerifier::_verify_marked_complete:
226         check(ShenandoahAsserts::_safe_all, obj, _heap->complete_marking_context()->is_marked(obj),
227                "Must be marked in complete bitmap");
228         break;
229       case ShenandoahVerifier::_verify_marked_complete_except_references:
230         check(ShenandoahAsserts::_safe_all, obj, _heap->complete_marking_context()->is_marked(obj),
231               "Must be marked in complete bitmap, except j.l.r.Reference referents");
232         break;
233       default:
234         assert(false, "Unhandled mark verification");
235     }
236 
237     switch (_options._verify_forwarded) {
238       case ShenandoahVerifier::_verify_forwarded_disable:
239         // skip
240         break;
241       case ShenandoahVerifier::_verify_forwarded_none: {
242         check(ShenandoahAsserts::_safe_all, obj, (obj == fwd),
243                "Should not be forwarded");
244         break;
245       }
246       case ShenandoahVerifier::_verify_forwarded_allow: {
247         if (obj != fwd) {
248           check(ShenandoahAsserts::_safe_all, obj, obj_reg != fwd_reg,
249                  "Forwardee should be in another region");
250         }
251         break;
252       }
253       default:
254         assert(false, "Unhandled forwarding verification");
255     }
256 
257     switch (_options._verify_cset) {
258       case ShenandoahVerifier::_verify_cset_disable:
259         // skip
260         break;
261       case ShenandoahVerifier::_verify_cset_none:
262         check(ShenandoahAsserts::_safe_all, obj, !_heap->in_collection_set(obj),
263                "Should not have references to collection set");
264         break;
265       case ShenandoahVerifier::_verify_cset_forwarded:
266         if (_heap->in_collection_set(obj)) {
267           check(ShenandoahAsserts::_safe_all, obj, (obj != fwd),
268                  "Object in collection set, should have forwardee");
269         }
270         break;
271       default:
272         assert(false, "Unhandled cset verification");
273     }
274 
275   }
276 
277 public:
278   /**
279    * Verify object with known interior reference.
280    * @param p interior reference where the object is referenced from; can be off-heap
281    * @param obj verified object
282    */
283   template <class T>
284   void verify_oop_at(T* p, oop obj) {
285     _interior_loc = p;
286     verify_oop(obj);
287     _interior_loc = NULL;
288   }
289 
290   /**
291    * Verify object without known interior reference.
292    * Useful when picking up the object at known offset in heap,
293    * but without knowing what objects reference it.
294    * @param obj verified object
295    */
296   void verify_oop_standalone(oop obj) {
297     _interior_loc = NULL;
298     verify_oop(obj);
299     _interior_loc = NULL;
300   }
301 
302   /**
303    * Verify oop fields from this object.
304    * @param obj host object for verified fields
305    */
306   void verify_oops_from(oop obj) {
307     _loc = obj;
308     obj->oop_iterate(this);
309     _loc = NULL;
310   }
311 
312   virtual void do_oop(oop* p) { do_oop_work(p); }
313   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
314 };
315 
316 class ShenandoahCalculateRegionStatsClosure : public ShenandoahHeapRegionClosure {
317 private:
318   size_t _used, _committed, _garbage;
319 public:
320   ShenandoahCalculateRegionStatsClosure() : _used(0), _committed(0), _garbage(0) {};
321 
322   void heap_region_do(ShenandoahHeapRegion* r) {
323     _used += r->used();
324     _garbage += r->garbage();
325     _committed += r->is_committed() ? ShenandoahHeapRegion::region_size_bytes() : 0;
326   }
327 
328   size_t used() { return _used; }
329   size_t committed() { return _committed; }
330   size_t garbage() { return _garbage; }
331 };
332 
333 class ShenandoahVerifyHeapRegionClosure : public ShenandoahHeapRegionClosure {
334 private:
335   ShenandoahHeap* _heap;
336   const char* _phase;
337   ShenandoahVerifier::VerifyRegions _regions;
338 public:
339   ShenandoahVerifyHeapRegionClosure(const char* phase, ShenandoahVerifier::VerifyRegions regions) :
340     _heap(ShenandoahHeap::heap()),
341     _phase(phase),
342     _regions(regions) {};
343 
344   void print_failure(ShenandoahHeapRegion* r, const char* label) {
345     ResourceMark rm;
346 
347     ShenandoahMessageBuffer msg("Shenandoah verification failed; %s: %s\n\n", _phase, label);
348 
349     stringStream ss;
350     r->print_on(&ss);
351     msg.append("%s", ss.as_string());
352 
353     report_vm_error(__FILE__, __LINE__, msg.buffer());
354   }
355 
356   void verify(ShenandoahHeapRegion* r, bool test, const char* msg) {
357     if (!test) {
358       print_failure(r, msg);
359     }
360   }
361 
362   void heap_region_do(ShenandoahHeapRegion* r) {
363     switch (_regions) {
364       case ShenandoahVerifier::_verify_regions_disable:
365         break;
366       case ShenandoahVerifier::_verify_regions_notrash:
367         verify(r, !r->is_trash(),
368                "Should not have trash regions");
369         break;
370       case ShenandoahVerifier::_verify_regions_nocset:
371         verify(r, !r->is_cset(),
372                "Should not have cset regions");
373         break;
374       case ShenandoahVerifier::_verify_regions_notrash_nocset:
375         verify(r, !r->is_trash(),
376                "Should not have trash regions");
377         verify(r, !r->is_cset(),
378                "Should not have cset regions");
379         break;
380       default:
381         ShouldNotReachHere();
382     }
383 
384     verify(r, r->capacity() == ShenandoahHeapRegion::region_size_bytes(),
385            "Capacity should match region size");
386 
387     verify(r, r->bottom() <= r->top(),
388            "Region top should not be less than bottom");
389 
390     verify(r, r->bottom() <= _heap->marking_context()->top_at_mark_start(r),
391            "Region TAMS should not be less than bottom");
392 
393     verify(r, _heap->marking_context()->top_at_mark_start(r) <= r->top(),
394            "Complete TAMS should not be larger than top");
395 
396     verify(r, r->get_live_data_bytes() <= r->capacity(),
397            "Live data cannot be larger than capacity");
398 
399     verify(r, r->garbage() <= r->capacity(),
400            "Garbage cannot be larger than capacity");
401 
402     verify(r, r->used() <= r->capacity(),
403            "Used cannot be larger than capacity");
404 
405     verify(r, r->get_shared_allocs() <= r->capacity(),
406            "Shared alloc count should not be larger than capacity");
407 
408     verify(r, r->get_tlab_allocs() <= r->capacity(),
409            "TLAB alloc count should not be larger than capacity");
410 
411     verify(r, r->get_gclab_allocs() <= r->capacity(),
412            "GCLAB alloc count should not be larger than capacity");
413 
414     verify(r, r->get_shared_allocs() + r->get_tlab_allocs() + r->get_gclab_allocs() == r->used(),
415            "Accurate accounting: shared + TLAB + GCLAB = used");
416 
417     verify(r, !r->is_empty() || !r->has_live(),
418            "Empty regions should not have live data");
419 
420     verify(r, r->is_cset() == _heap->collection_set()->is_in(r),
421            "Transitional: region flags and collection set agree");
422   }
423 };
424 
425 class ShenandoahVerifierReachableTask : public WorkerTask {
426 private:
427   const char* _label;
428   ShenandoahVerifier::VerifyOptions _options;
429   ShenandoahHeap* _heap;
430   ShenandoahLivenessData* _ld;
431   MarkBitMap* _bitmap;
432   volatile size_t _processed;
433 
434 public:
435   ShenandoahVerifierReachableTask(MarkBitMap* bitmap,
436                                   ShenandoahLivenessData* ld,
437                                   const char* label,
438                                   ShenandoahVerifier::VerifyOptions options) :
439     WorkerTask("Shenandoah Verifier Reachable Objects"),
440     _label(label),
441     _options(options),
442     _heap(ShenandoahHeap::heap()),
443     _ld(ld),
444     _bitmap(bitmap),
445     _processed(0) {};
446 
447   size_t processed() {
448     return _processed;
449   }
450 
451   virtual void work(uint worker_id) {
452     ResourceMark rm;
453     ShenandoahVerifierStack stack;
454 
455     // On level 2, we need to only check the roots once.
456     // On level 3, we want to check the roots, and seed the local stack.
457     // It is a lesser evil to accept multiple root scans at level 3, because
458     // extended parallelism would buy us out.
459     if (((ShenandoahVerifyLevel == 2) && (worker_id == 0))
460         || (ShenandoahVerifyLevel >= 3)) {
461         ShenandoahVerifyOopClosure cl(&stack, _bitmap, _ld,
462                                       ShenandoahMessageBuffer("%s, Roots", _label),
463                                       _options);
464         if (_heap->unload_classes()) {
465           ShenandoahRootVerifier::strong_roots_do(&cl);
466         } else {
467           ShenandoahRootVerifier::roots_do(&cl);
468         }
469     }
470 
471     size_t processed = 0;
472 
473     if (ShenandoahVerifyLevel >= 3) {
474       ShenandoahVerifyOopClosure cl(&stack, _bitmap, _ld,
475                                     ShenandoahMessageBuffer("%s, Reachable", _label),
476                                     _options);
477       while (!stack.is_empty()) {
478         processed++;
479         ShenandoahVerifierTask task = stack.pop();
480         cl.verify_oops_from(task.obj());
481       }
482     }
483 
484     Atomic::add(&_processed, processed, memory_order_relaxed);
485   }
486 };
487 
488 class ShenandoahVerifierMarkedRegionTask : public WorkerTask {
489 private:
490   const char* _label;
491   ShenandoahVerifier::VerifyOptions _options;
492   ShenandoahHeap *_heap;
493   MarkBitMap* _bitmap;
494   ShenandoahLivenessData* _ld;
495   volatile size_t _claimed;
496   volatile size_t _processed;
497 
498 public:
499   ShenandoahVerifierMarkedRegionTask(MarkBitMap* bitmap,
500                                      ShenandoahLivenessData* ld,
501                                      const char* label,
502                                      ShenandoahVerifier::VerifyOptions options) :
503           WorkerTask("Shenandoah Verifier Marked Objects"),
504           _label(label),
505           _options(options),
506           _heap(ShenandoahHeap::heap()),
507           _bitmap(bitmap),
508           _ld(ld),
509           _claimed(0),
510           _processed(0) {};
511 
512   size_t processed() {
513     return Atomic::load(&_processed);
514   }
515 
516   virtual void work(uint worker_id) {
517     ShenandoahVerifierStack stack;
518     ShenandoahVerifyOopClosure cl(&stack, _bitmap, _ld,
519                                   ShenandoahMessageBuffer("%s, Marked", _label),
520                                   _options);
521 
522     while (true) {
523       size_t v = Atomic::fetch_and_add(&_claimed, 1u, memory_order_relaxed);
524       if (v < _heap->num_regions()) {
525         ShenandoahHeapRegion* r = _heap->get_region(v);
526         if (!r->is_humongous() && !r->is_trash()) {
527           work_regular(r, stack, cl);
528         } else if (r->is_humongous_start()) {
529           work_humongous(r, stack, cl);
530         }
531       } else {
532         break;
533       }
534     }
535   }
536 
537   virtual void work_humongous(ShenandoahHeapRegion *r, ShenandoahVerifierStack& stack, ShenandoahVerifyOopClosure& cl) {
538     size_t processed = 0;
539     HeapWord* obj = r->bottom();
540     if (_heap->complete_marking_context()->is_marked(cast_to_oop(obj))) {
541       verify_and_follow(obj, stack, cl, &processed);
542     }
543     Atomic::add(&_processed, processed, memory_order_relaxed);
544   }
545 
546   virtual void work_regular(ShenandoahHeapRegion *r, ShenandoahVerifierStack &stack, ShenandoahVerifyOopClosure &cl) {
547     size_t processed = 0;
548     ShenandoahMarkingContext* ctx = _heap->complete_marking_context();
549     HeapWord* tams = ctx->top_at_mark_start(r);
550 
551     // Bitmaps, before TAMS
552     if (tams > r->bottom()) {
553       HeapWord* start = r->bottom();
554       HeapWord* addr = ctx->get_next_marked_addr(start, tams);
555 
556       while (addr < tams) {
557         verify_and_follow(addr, stack, cl, &processed);
558         addr += 1;
559         if (addr < tams) {
560           addr = ctx->get_next_marked_addr(addr, tams);
561         }
562       }
563     }
564 
565     // Size-based, after TAMS
566     {
567       HeapWord* limit = r->top();
568       HeapWord* addr = tams;
569 
570       while (addr < limit) {
571         verify_and_follow(addr, stack, cl, &processed);
572         addr += cast_to_oop(addr)->size();
573       }
574     }
575 
576     Atomic::add(&_processed, processed, memory_order_relaxed);
577   }
578 
579   void verify_and_follow(HeapWord *addr, ShenandoahVerifierStack &stack, ShenandoahVerifyOopClosure &cl, size_t *processed) {
580     if (!_bitmap->par_mark(addr)) return;
581 
582     // Verify the object itself:
583     oop obj = cast_to_oop(addr);
584     cl.verify_oop_standalone(obj);
585 
586     // Verify everything reachable from that object too, hopefully realizing
587     // everything was already marked, and never touching further:
588     if (!is_instance_ref_klass(obj->klass())) {
589       cl.verify_oops_from(obj);
590       (*processed)++;
591     }
592     while (!stack.is_empty()) {
593       ShenandoahVerifierTask task = stack.pop();
594       cl.verify_oops_from(task.obj());
595       (*processed)++;
596     }
597   }
598 };
599 
600 class VerifyThreadGCState : public ThreadClosure {
601 private:
602   const char* const _label;
603          char const _expected;
604 
605 public:
606   VerifyThreadGCState(const char* label, char expected) : _label(label), _expected(expected) {}
607   void do_thread(Thread* t) {
608     char actual = ShenandoahThreadLocalData::gc_state(t);
609     if (actual != _expected) {
610       fatal("%s: Thread %s: expected gc-state %d, actual %d", _label, t->name(), _expected, actual);
611     }
612   }
613 };
614 
615 void ShenandoahVerifier::verify_at_safepoint(const char *label,
616                                              VerifyForwarded forwarded, VerifyMarked marked,
617                                              VerifyCollectionSet cset,
618                                              VerifyLiveness liveness, VerifyRegions regions,
619                                              VerifyGCState gcstate) {
620   guarantee(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "only when nothing else happens");
621   guarantee(ShenandoahVerify, "only when enabled, and bitmap is initialized in ShenandoahHeap::initialize");
622 
623   // Avoid side-effect of changing workers' active thread count, but bypass concurrent/parallel protocol check
624   ShenandoahPushWorkerScope verify_worker_scope(_heap->workers(), _heap->max_workers(), false /*bypass check*/);
625 
626   log_info(gc,start)("Verify %s, Level " INTX_FORMAT, label, ShenandoahVerifyLevel);
627 
628   // GC state checks
629   {
630     char expected = -1;
631     bool enabled;
632     switch (gcstate) {
633       case _verify_gcstate_disable:
634         enabled = false;
635         break;
636       case _verify_gcstate_forwarded:
637         enabled = true;
638         expected = ShenandoahHeap::HAS_FORWARDED;
639         break;
640       case _verify_gcstate_evacuation:
641         enabled = true;
642         expected = ShenandoahHeap::HAS_FORWARDED | ShenandoahHeap::EVACUATION;
643         if (!_heap->is_stw_gc_in_progress()) {
644           // Only concurrent GC sets this.
645           expected |= ShenandoahHeap::WEAK_ROOTS;
646         }
647         break;
648       case _verify_gcstate_stable:
649         enabled = true;
650         expected = ShenandoahHeap::STABLE;
651         break;
652       case _verify_gcstate_stable_weakroots:
653         enabled = true;
654         expected = ShenandoahHeap::STABLE;
655         if (!_heap->is_stw_gc_in_progress()) {
656           // Only concurrent GC sets this.
657           expected |= ShenandoahHeap::WEAK_ROOTS;
658         }
659         break;
660       default:
661         enabled = false;
662         assert(false, "Unhandled gc-state verification");
663     }
664 
665     if (enabled) {
666       char actual = _heap->gc_state();
667       if (actual != expected) {
668         fatal("%s: Global gc-state: expected %d, actual %d", label, expected, actual);
669       }
670 
671       VerifyThreadGCState vtgcs(label, expected);
672       Threads::java_threads_do(&vtgcs);
673     }
674   }
675 
676   // Deactivate barriers temporarily: Verifier wants plain heap accesses
677   ShenandoahGCStateResetter resetter;
678 
679   // Heap size checks
680   {
681     ShenandoahHeapLocker lock(_heap->lock());
682 
683     ShenandoahCalculateRegionStatsClosure cl;
684     _heap->heap_region_iterate(&cl);
685     size_t heap_used = _heap->used();
686     guarantee(cl.used() == heap_used,
687               "%s: heap used size must be consistent: heap-used = " SIZE_FORMAT "%s, regions-used = " SIZE_FORMAT "%s",
688               label,
689               byte_size_in_proper_unit(heap_used), proper_unit_for_byte_size(heap_used),
690               byte_size_in_proper_unit(cl.used()), proper_unit_for_byte_size(cl.used()));
691 
692     size_t heap_committed = _heap->committed();
693     guarantee(cl.committed() == heap_committed,
694               "%s: heap committed size must be consistent: heap-committed = " SIZE_FORMAT "%s, regions-committed = " SIZE_FORMAT "%s",
695               label,
696               byte_size_in_proper_unit(heap_committed), proper_unit_for_byte_size(heap_committed),
697               byte_size_in_proper_unit(cl.committed()), proper_unit_for_byte_size(cl.committed()));
698   }
699 
700   // Internal heap region checks
701   if (ShenandoahVerifyLevel >= 1) {
702     ShenandoahVerifyHeapRegionClosure cl(label, regions);
703     _heap->heap_region_iterate(&cl);
704   }
705 
706   OrderAccess::fence();
707 
708   if (UseTLAB) {
709     _heap->labs_make_parsable();
710   }
711 
712   // Allocate temporary bitmap for storing marking wavefront:
713   _verification_bit_map->clear();
714 
715   // Allocate temporary array for storing liveness data
716   ShenandoahLivenessData* ld = NEW_C_HEAP_ARRAY(ShenandoahLivenessData, _heap->num_regions(), mtGC);
717   Copy::fill_to_bytes((void*)ld, _heap->num_regions()*sizeof(ShenandoahLivenessData), 0);
718 
719   const VerifyOptions& options = ShenandoahVerifier::VerifyOptions(forwarded, marked, cset, liveness, regions, gcstate);
720 
721   // Steps 1-2. Scan root set to get initial reachable set. Finish walking the reachable heap.
722   // This verifies what application can see, since it only cares about reachable objects.
723   size_t count_reachable = 0;
724   if (ShenandoahVerifyLevel >= 2) {
725     ShenandoahVerifierReachableTask task(_verification_bit_map, ld, label, options);
726     _heap->workers()->run_task(&task);
727     count_reachable = task.processed();
728   }
729 
730   // Step 3. Walk marked objects. Marked objects might be unreachable. This verifies what collector,
731   // not the application, can see during the region scans. There is no reason to process the objects
732   // that were already verified, e.g. those marked in verification bitmap. There is interaction with TAMS:
733   // before TAMS, we verify the bitmaps, if available; after TAMS, we walk until the top(). It mimics
734   // what marked_object_iterate is doing, without calling into that optimized (and possibly incorrect)
735   // version
736 
737   size_t count_marked = 0;
738   if (ShenandoahVerifyLevel >= 4 && (marked == _verify_marked_complete || marked == _verify_marked_complete_except_references)) {
739     guarantee(_heap->marking_context()->is_complete(), "Marking context should be complete");
740     ShenandoahVerifierMarkedRegionTask task(_verification_bit_map, ld, label, options);
741     _heap->workers()->run_task(&task);
742     count_marked = task.processed();
743   } else {
744     guarantee(ShenandoahVerifyLevel < 4 || marked == _verify_marked_incomplete || marked == _verify_marked_disable, "Should be");
745   }
746 
747   // Step 4. Verify accumulated liveness data, if needed. Only reliable if verification level includes
748   // marked objects.
749 
750   if (ShenandoahVerifyLevel >= 4 && marked == _verify_marked_complete && liveness == _verify_liveness_complete) {
751     for (size_t i = 0; i < _heap->num_regions(); i++) {
752       ShenandoahHeapRegion* r = _heap->get_region(i);
753 
754       juint verf_live = 0;
755       if (r->is_humongous()) {
756         // For humongous objects, test if start region is marked live, and if so,
757         // all humongous regions in that chain have live data equal to their "used".
758         juint start_live = Atomic::load(&ld[r->humongous_start_region()->index()]);
759         if (start_live > 0) {
760           verf_live = (juint)(r->used() / HeapWordSize);
761         }
762       } else {
763         verf_live = Atomic::load(&ld[r->index()]);
764       }
765 
766       size_t reg_live = r->get_live_data_words();
767       if (reg_live != verf_live) {
768         ResourceMark rm;
769         stringStream ss;
770         r->print_on(&ss);
771         fatal("%s: Live data should match: region-live = " SIZE_FORMAT ", verifier-live = " UINT32_FORMAT "\n%s",
772               label, reg_live, verf_live, ss.as_string());
773       }
774     }
775   }
776 
777   log_info(gc)("Verify %s, Level " INTX_FORMAT " (" SIZE_FORMAT " reachable, " SIZE_FORMAT " marked)",
778                label, ShenandoahVerifyLevel, count_reachable, count_marked);
779 
780   FREE_C_HEAP_ARRAY(ShenandoahLivenessData, ld);
781 }
782 
783 void ShenandoahVerifier::verify_generic(VerifyOption vo) {
784   verify_at_safepoint(
785           "Generic Verification",
786           _verify_forwarded_allow,     // conservatively allow forwarded
787           _verify_marked_disable,      // do not verify marked: lots ot time wasted checking dead allocations
788           _verify_cset_disable,        // cset may be inconsistent
789           _verify_liveness_disable,    // no reliable liveness data
790           _verify_regions_disable,     // no reliable region data
791           _verify_gcstate_disable      // no data about gcstate
792   );
793 }
794 
795 void ShenandoahVerifier::verify_before_concmark() {
796     verify_at_safepoint(
797           "Before Mark",
798           _verify_forwarded_none,      // UR should have fixed up
799           _verify_marked_disable,      // do not verify marked: lots ot time wasted checking dead allocations
800           _verify_cset_none,           // UR should have fixed this
801           _verify_liveness_disable,    // no reliable liveness data
802           _verify_regions_notrash,     // no trash regions
803           _verify_gcstate_stable       // there are no forwarded objects
804   );
805 }
806 
807 void ShenandoahVerifier::verify_after_concmark() {
808   verify_at_safepoint(
809           "After Mark",
810           _verify_forwarded_none,      // no forwarded references
811           _verify_marked_complete_except_references, // bitmaps as precise as we can get, except dangling j.l.r.Refs
812           _verify_cset_none,           // no references to cset anymore
813           _verify_liveness_complete,   // liveness data must be complete here
814           _verify_regions_disable,     // trash regions not yet recycled
815           _verify_gcstate_stable_weakroots  // heap is still stable, weakroots are in progress
816   );
817 }
818 
819 void ShenandoahVerifier::verify_before_evacuation() {
820   verify_at_safepoint(
821           "Before Evacuation",
822           _verify_forwarded_none,                    // no forwarded references
823           _verify_marked_complete_except_references, // walk over marked objects too
824           _verify_cset_disable,                      // non-forwarded references to cset expected
825           _verify_liveness_complete,                 // liveness data must be complete here
826           _verify_regions_disable,                   // trash regions not yet recycled
827           _verify_gcstate_stable_weakroots           // heap is still stable, weakroots are in progress
828   );
829 }
830 
831 void ShenandoahVerifier::verify_during_evacuation() {
832   verify_at_safepoint(
833           "During Evacuation",
834           _verify_forwarded_allow,    // some forwarded references are allowed
835           _verify_marked_disable,     // walk only roots
836           _verify_cset_disable,       // some cset references are not forwarded yet
837           _verify_liveness_disable,   // liveness data might be already stale after pre-evacs
838           _verify_regions_disable,    // trash regions not yet recycled
839           _verify_gcstate_evacuation  // evacuation is in progress
840   );
841 }
842 
843 void ShenandoahVerifier::verify_after_evacuation() {
844   verify_at_safepoint(
845           "After Evacuation",
846           _verify_forwarded_allow,     // objects are still forwarded
847           _verify_marked_complete,     // bitmaps might be stale, but alloc-after-mark should be well
848           _verify_cset_forwarded,      // all cset refs are fully forwarded
849           _verify_liveness_disable,    // no reliable liveness data anymore
850           _verify_regions_notrash,     // trash regions have been recycled already
851           _verify_gcstate_forwarded    // evacuation produced some forwarded objects
852   );
853 }
854 
855 void ShenandoahVerifier::verify_before_updaterefs() {
856   verify_at_safepoint(
857           "Before Updating References",
858           _verify_forwarded_allow,     // forwarded references allowed
859           _verify_marked_complete,     // bitmaps might be stale, but alloc-after-mark should be well
860           _verify_cset_forwarded,      // all cset refs are fully forwarded
861           _verify_liveness_disable,    // no reliable liveness data anymore
862           _verify_regions_notrash,     // trash regions have been recycled already
863           _verify_gcstate_forwarded    // evacuation should have produced some forwarded objects
864   );
865 }
866 
867 void ShenandoahVerifier::verify_after_updaterefs() {
868   verify_at_safepoint(
869           "After Updating References",
870           _verify_forwarded_none,      // no forwarded references
871           _verify_marked_complete,     // bitmaps might be stale, but alloc-after-mark should be well
872           _verify_cset_none,           // no cset references, all updated
873           _verify_liveness_disable,    // no reliable liveness data anymore
874           _verify_regions_nocset,      // no cset regions, trash regions have appeared
875           _verify_gcstate_stable       // update refs had cleaned up forwarded objects
876   );
877 }
878 
879 void ShenandoahVerifier::verify_after_degenerated() {
880   verify_at_safepoint(
881           "After Degenerated GC",
882           _verify_forwarded_none,      // all objects are non-forwarded
883           _verify_marked_complete,     // all objects are marked in complete bitmap
884           _verify_cset_none,           // no cset references
885           _verify_liveness_disable,    // no reliable liveness data anymore
886           _verify_regions_notrash_nocset, // no trash, no cset
887           _verify_gcstate_stable       // degenerated refs had cleaned up forwarded objects
888   );
889 }
890 
891 void ShenandoahVerifier::verify_before_fullgc() {
892   verify_at_safepoint(
893           "Before Full GC",
894           _verify_forwarded_allow,     // can have forwarded objects
895           _verify_marked_disable,      // do not verify marked: lots ot time wasted checking dead allocations
896           _verify_cset_disable,        // cset might be foobared
897           _verify_liveness_disable,    // no reliable liveness data anymore
898           _verify_regions_disable,     // no reliable region data here
899           _verify_gcstate_disable      // no reliable gcstate data
900   );
901 }
902 
903 void ShenandoahVerifier::verify_after_fullgc() {
904   verify_at_safepoint(
905           "After Full GC",
906           _verify_forwarded_none,      // all objects are non-forwarded
907           _verify_marked_complete,     // all objects are marked in complete bitmap
908           _verify_cset_none,           // no cset references
909           _verify_liveness_disable,    // no reliable liveness data anymore
910           _verify_regions_notrash_nocset, // no trash, no cset
911           _verify_gcstate_stable        // full gc cleaned up everything
912   );
913 }
914 
915 class ShenandoahVerifyNoForwared : public OopClosure {
916 private:
917   template <class T>
918   void do_oop_work(T* p) {
919     T o = RawAccess<>::oop_load(p);
920     if (!CompressedOops::is_null(o)) {
921       oop obj = CompressedOops::decode_not_null(o);
922       oop fwd = ShenandoahForwarding::get_forwardee_raw_unchecked(obj);
923       if (obj != fwd) {
924         ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, p, NULL,
925                                          "Verify Roots", "Should not be forwarded", __FILE__, __LINE__);
926       }
927     }
928   }
929 
930 public:
931   void do_oop(narrowOop* p) { do_oop_work(p); }
932   void do_oop(oop* p)       { do_oop_work(p); }
933 };
934 
935 class ShenandoahVerifyInToSpaceClosure : public OopClosure {
936 private:
937   template <class T>
938   void do_oop_work(T* p) {
939     T o = RawAccess<>::oop_load(p);
940     if (!CompressedOops::is_null(o)) {
941       oop obj = CompressedOops::decode_not_null(o);
942       ShenandoahHeap* heap = ShenandoahHeap::heap();
943 
944       if (!heap->marking_context()->is_marked(obj)) {
945         ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, p, NULL,
946                 "Verify Roots In To-Space", "Should be marked", __FILE__, __LINE__);
947       }
948 
949       if (heap->in_collection_set(obj)) {
950         ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, p, NULL,
951                 "Verify Roots In To-Space", "Should not be in collection set", __FILE__, __LINE__);
952       }
953 
954       oop fwd = ShenandoahForwarding::get_forwardee_raw_unchecked(obj);
955       if (obj != fwd) {
956         ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, p, NULL,
957                 "Verify Roots In To-Space", "Should not be forwarded", __FILE__, __LINE__);
958       }
959     }
960   }
961 
962 public:
963   void do_oop(narrowOop* p) { do_oop_work(p); }
964   void do_oop(oop* p)       { do_oop_work(p); }
965 };
966 
967 void ShenandoahVerifier::verify_roots_in_to_space() {
968   ShenandoahVerifyInToSpaceClosure cl;
969   ShenandoahRootVerifier::roots_do(&cl);
970 }
971 
972 void ShenandoahVerifier::verify_roots_no_forwarded() {
973   ShenandoahVerifyNoForwared cl;
974   ShenandoahRootVerifier::roots_do(&cl);
975 }