1 /*
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  3  * Copyright (c) 2013, 2021, 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
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 25 
 26 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP
 27 #define SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP
 28 
 29 #include "gc/shared/markBitMap.hpp"
 30 #include "gc/shared/softRefPolicy.hpp"
 31 #include "gc/shared/collectedHeap.hpp"
 32 #include "gc/shenandoah/heuristics/shenandoahSpaceInfo.hpp"
 33 #include "gc/shenandoah/shenandoahAsserts.hpp"
 34 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
 35 #include "gc/shenandoah/shenandoahLock.hpp"
 36 #include "gc/shenandoah/shenandoahEvacOOMHandler.hpp"
 37 #include "gc/shenandoah/shenandoahPadding.hpp"
 38 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
 39 #include "gc/shenandoah/shenandoahUnload.hpp"
 40 #include "memory/metaspace.hpp"
 41 #include "services/memoryManager.hpp"
 42 #include "utilities/globalDefinitions.hpp"
 43 #include "utilities/stack.hpp"
 44 
 45 class ConcurrentGCTimer;
 46 class ObjectIterateScanRootClosure;
 47 class ShenandoahCollectorPolicy;
 48 class ShenandoahControlThread;
 49 class ShenandoahGCSession;
 50 class ShenandoahGCStateResetter;
 51 class ShenandoahHeuristics;
 52 class ShenandoahMarkingContext;
 53 class ShenandoahMode;
 54 class ShenandoahPhaseTimings;
 55 class ShenandoahHeap;
 56 class ShenandoahHeapRegion;
 57 class ShenandoahHeapRegionClosure;
 58 class ShenandoahCollectionSet;
 59 class ShenandoahFreeSet;
 60 class ShenandoahConcurrentMark;
 61 class ShenandoahFullGC;
 62 class ShenandoahMonitoringSupport;
 63 class ShenandoahPacer;
 64 class ShenandoahReferenceProcessor;
 65 class ShenandoahVerifier;
 66 class ShenandoahWorkerThreads;
 67 class VMStructs;
 68 
 69 // Used for buffering per-region liveness data.
 70 // Needed since ShenandoahHeapRegion uses atomics to update liveness.
 71 // The ShenandoahHeap array has max-workers elements, each of which is an array of
 72 // uint16_t * max_regions. The choice of uint16_t is not accidental:
 73 // there is a tradeoff between static/dynamic footprint that translates
 74 // into cache pressure (which is already high during marking), and
 75 // too many atomic updates. uint32_t is too large, uint8_t is too small.
 76 typedef uint16_t ShenandoahLiveData;
 77 #define SHENANDOAH_LIVEDATA_MAX ((ShenandoahLiveData)-1)
 78 
 79 class ShenandoahRegionIterator : public StackObj {
 80 private:
 81   ShenandoahHeap* _heap;
 82 
 83   shenandoah_padding(0);
 84   volatile size_t _index;
 85   shenandoah_padding(1);
 86 
 87   // No implicit copying: iterators should be passed by reference to capture the state
 88   NONCOPYABLE(ShenandoahRegionIterator);
 89 
 90 public:
 91   ShenandoahRegionIterator();
 92   ShenandoahRegionIterator(ShenandoahHeap* heap);
 93 
 94   // Reset iterator to default state
 95   void reset();
 96 
 97   // Returns next region, or null if there are no more regions.
 98   // This is multi-thread-safe.
 99   inline ShenandoahHeapRegion* next();
100 
101   // This is *not* MT safe. However, in the absence of multithreaded access, it
102   // can be used to determine if there is more work to do.
103   bool has_next() const;
104 };
105 
106 class ShenandoahHeapRegionClosure : public StackObj {
107 public:
108   virtual void heap_region_do(ShenandoahHeapRegion* r) = 0;
109   virtual bool is_thread_safe() { return false; }
110 };
111 
112 typedef ShenandoahLock    ShenandoahHeapLock;
113 typedef ShenandoahLocker  ShenandoahHeapLocker;
114 typedef Stack<oop, mtGC>  ShenandoahScanObjectStack;
115 
116 // Shenandoah GC is low-pause concurrent GC that uses Brooks forwarding pointers
117 // to encode forwarding data. See BrooksPointer for details on forwarding data encoding.
118 // See ShenandoahControlThread for GC cycle structure.
119 //
120 class ShenandoahHeap : public CollectedHeap, public ShenandoahSpaceInfo {
121   friend class ShenandoahAsserts;
122   friend class VMStructs;
123   friend class ShenandoahGCSession;
124   friend class ShenandoahGCStateResetter;
125   friend class ShenandoahParallelObjectIterator;
126   friend class ShenandoahSafepoint;
127   // Supported GC
128   friend class ShenandoahConcurrentGC;
129   friend class ShenandoahDegenGC;
130   friend class ShenandoahFullGC;
131   friend class ShenandoahUnload;
132 
133 // ---------- Locks that guard important data structures in Heap
134 //
135 private:
136   ShenandoahHeapLock _lock;
137 
138 public:
139   ShenandoahHeapLock* lock() {
140     return &_lock;
141   }
142 
143 // ---------- Initialization, termination, identification, printing routines
144 //
145 public:
146   static ShenandoahHeap* heap();
147 
148   const char* name()          const override { return "Shenandoah"; }
149   ShenandoahHeap::Name kind() const override { return CollectedHeap::Shenandoah; }
150 
151   ShenandoahHeap(ShenandoahCollectorPolicy* policy);
152   jint initialize() override;
153   void post_initialize() override;
154   void initialize_mode();
155   void initialize_heuristics();
156 
157   void initialize_serviceability() override;
158 
159   void print_on(outputStream* st)              const override;
160   void print_extended_on(outputStream *st)     const override;
161   void print_tracing_info()                    const override;
162   void print_heap_regions_on(outputStream* st) const;
163 
164   void stop() override;
165 
166   void prepare_for_verify() override;
167   void verify(VerifyOption vo) override;
168 
169 // WhiteBox testing support.
170   bool supports_concurrent_gc_breakpoints() const override {
171     return true;
172   }
173 
174 // ---------- Heap counters and metrics
175 //
176 private:
177            size_t _initial_size;
178            size_t _minimum_size;
179   volatile size_t _soft_max_size;
180   shenandoah_padding(0);
181   volatile size_t _used;
182   volatile size_t _committed;
183   volatile size_t _bytes_allocated_since_gc_start;
184   shenandoah_padding(1);
185 
186 public:
187   void increase_used(size_t bytes);
188   void decrease_used(size_t bytes);
189   void set_used(size_t bytes);
190 
191   void increase_committed(size_t bytes);
192   void decrease_committed(size_t bytes);
193   void increase_allocated(size_t bytes);
194 
195   size_t bytes_allocated_since_gc_start() const override;
196   void reset_bytes_allocated_since_gc_start();
197 
198   size_t min_capacity()      const;
199   size_t max_capacity()      const override;
200   size_t soft_max_capacity() const override;
201   size_t initial_capacity()  const;
202   size_t capacity()          const override;
203   size_t used()              const override;
204   size_t committed()         const;
205   size_t available()         const override;
206 
207   void set_soft_max_capacity(size_t v);
208 
209 // ---------- Workers handling
210 //
211 private:
212   uint _max_workers;
213   ShenandoahWorkerThreads* _workers;
214   ShenandoahWorkerThreads* _safepoint_workers;
215 
216 public:
217   uint max_workers();
218   void assert_gc_workers(uint nworker) NOT_DEBUG_RETURN;
219 
220   WorkerThreads* workers() const;
221   WorkerThreads* safepoint_workers() override;
222 
223   void gc_threads_do(ThreadClosure* tcl) const override;
224 
225 // ---------- Heap regions handling machinery
226 //
227 private:
228   MemRegion _heap_region;
229   bool      _heap_region_special;
230   size_t    _num_regions;
231   ShenandoahHeapRegion** _regions;
232   ShenandoahRegionIterator _update_refs_iterator;
233 
234 public:
235 
236   inline HeapWord* base() const { return _heap_region.start(); }
237 
238   inline size_t num_regions() const { return _num_regions; }
239   inline bool is_heap_region_special() { return _heap_region_special; }
240 
241   inline ShenandoahHeapRegion* heap_region_containing(const void* addr) const;
242   inline size_t heap_region_index_containing(const void* addr) const;
243 
244   inline ShenandoahHeapRegion* get_region(size_t region_idx) const;
245 
246   void heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
247   void parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
248 
249 // ---------- GC state machinery
250 //
251 // GC state describes the important parts of collector state, that may be
252 // used to make barrier selection decisions in the native and generated code.
253 // Multiple bits can be set at once.
254 //
255 // Important invariant: when GC state is zero, the heap is stable, and no barriers
256 // are required.
257 //
258 public:
259   enum GCStateBitPos {
260     // Heap has forwarded objects: needs LRB barriers.
261     HAS_FORWARDED_BITPOS   = 0,
262 
263     // Heap is under marking: needs SATB barriers.
264     MARKING_BITPOS    = 1,
265 
266     // Heap is under evacuation: needs LRB barriers. (Set together with HAS_FORWARDED)
267     EVACUATION_BITPOS = 2,
268 
269     // Heap is under updating: needs no additional barriers.
270     UPDATEREFS_BITPOS = 3,
271 
272     // Heap is under weak-reference/roots processing: needs weak-LRB barriers.
273     WEAK_ROOTS_BITPOS  = 4,
274   };
275 
276   enum GCState {
277     STABLE        = 0,
278     HAS_FORWARDED = 1 << HAS_FORWARDED_BITPOS,
279     MARKING       = 1 << MARKING_BITPOS,
280     EVACUATION    = 1 << EVACUATION_BITPOS,
281     UPDATEREFS    = 1 << UPDATEREFS_BITPOS,
282     WEAK_ROOTS    = 1 << WEAK_ROOTS_BITPOS,
283   };
284 
285 private:
286   ShenandoahSharedBitmap _gc_state;
287   ShenandoahSharedFlag   _degenerated_gc_in_progress;
288   ShenandoahSharedFlag   _full_gc_in_progress;
289   ShenandoahSharedFlag   _full_gc_move_in_progress;
290   ShenandoahSharedFlag   _progress_last_gc;
291   ShenandoahSharedFlag   _concurrent_strong_root_in_progress;
292 
293   void set_gc_state_all_threads(char state);
294   void set_gc_state_mask(uint mask, bool value);
295 
296 public:
297   char gc_state() const;
298   static address gc_state_addr();
299 
300   void set_concurrent_mark_in_progress(bool in_progress);
301   void set_evacuation_in_progress(bool in_progress);
302   void set_update_refs_in_progress(bool in_progress);
303   void set_degenerated_gc_in_progress(bool in_progress);
304   void set_full_gc_in_progress(bool in_progress);
305   void set_full_gc_move_in_progress(bool in_progress);
306   void set_has_forwarded_objects(bool cond);
307   void set_concurrent_strong_root_in_progress(bool cond);
308   void set_concurrent_weak_root_in_progress(bool cond);
309 
310   inline bool is_stable() const;
311   inline bool is_idle() const;
312   inline bool is_concurrent_mark_in_progress() const;
313   inline bool is_update_refs_in_progress() const;
314   inline bool is_evacuation_in_progress() const;
315   inline bool is_degenerated_gc_in_progress() const;
316   inline bool is_full_gc_in_progress() const;
317   inline bool is_full_gc_move_in_progress() const;
318   inline bool has_forwarded_objects() const;
319   inline bool is_gc_in_progress_mask(uint mask) const;
320   inline bool is_stw_gc_in_progress() const;
321   inline bool is_concurrent_strong_root_in_progress() const;
322   inline bool is_concurrent_weak_root_in_progress() const;
323 
324 private:
325   enum CancelState {
326     // Normal state. GC has not been cancelled and is open for cancellation.
327     // Worker threads can suspend for safepoint.
328     CANCELLABLE,
329 
330     // GC has been cancelled. Worker threads can not suspend for
331     // safepoint but must finish their work as soon as possible.
332     CANCELLED
333   };
334 
335   ShenandoahSharedEnumFlag<CancelState> _cancelled_gc;
336   bool try_cancel_gc();
337 
338 public:
339   static address cancelled_gc_addr();
340 
341   inline bool cancelled_gc() const;
342   inline bool check_cancelled_gc_and_yield(bool sts_active = true);
343 
344   inline void clear_cancelled_gc();
345 
346   void cancel_gc(GCCause::Cause cause);
347 
348 public:
349   // Elastic heap support
350   void entry_uncommit(double shrink_before, size_t shrink_until);
351   void op_uncommit(double shrink_before, size_t shrink_until);
352 
353 private:
354   // GC support
355   // Reset bitmap, prepare regions for new GC cycle
356   void prepare_gc();
357   void prepare_regions_and_collection_set(bool concurrent);
358   // Evacuation
359   void prepare_evacuation(bool concurrent);
360   void evacuate_collection_set(bool concurrent);
361   // Concurrent root processing
362   void prepare_concurrent_roots();
363   void finish_concurrent_roots();
364   // Concurrent class unloading support
365   void do_class_unloading();
366   // Reference updating
367   void prepare_update_heap_references(bool concurrent);
368   void update_heap_references(bool concurrent);
369   // Final update region states
370   void update_heap_region_states(bool concurrent);
371   void rebuild_free_set(bool concurrent);
372 
373   void rendezvous_threads();
374   void recycle_trash();
375 public:
376   void notify_gc_progress()    { _progress_last_gc.set();   }
377   void notify_gc_no_progress() { _progress_last_gc.unset(); }
378 
379 //
380 // Mark support
381 private:
382   ShenandoahControlThread*   _control_thread;
383   ShenandoahCollectorPolicy* _shenandoah_policy;
384   ShenandoahMode*            _gc_mode;
385   ShenandoahHeuristics*      _heuristics;
386   ShenandoahFreeSet*         _free_set;
387   ShenandoahPacer*           _pacer;
388   ShenandoahVerifier*        _verifier;
389 
390   ShenandoahPhaseTimings*    _phase_timings;
391 
392   ShenandoahControlThread*   control_thread()          { return _control_thread;    }
393 
394 public:
395   ShenandoahCollectorPolicy* shenandoah_policy() const { return _shenandoah_policy; }
396   ShenandoahMode*            mode()              const { return _gc_mode;           }
397   ShenandoahHeuristics*      heuristics()        const { return _heuristics;        }
398   ShenandoahFreeSet*         free_set()          const { return _free_set;          }
399   ShenandoahPacer*           pacer()             const { return _pacer;             }
400 
401   ShenandoahPhaseTimings*    phase_timings()     const { return _phase_timings;     }
402 
403   ShenandoahVerifier*        verifier();
404 
405 // ---------- VM subsystem bindings
406 //
407 private:
408   ShenandoahMonitoringSupport* _monitoring_support;
409   MemoryPool*                  _memory_pool;
410   GCMemoryManager              _stw_memory_manager;
411   GCMemoryManager              _cycle_memory_manager;
412   ConcurrentGCTimer*           _gc_timer;
413   SoftRefPolicy                _soft_ref_policy;
414 
415   // For exporting to SA
416   int                          _log_min_obj_alignment_in_bytes;
417 public:
418   ShenandoahMonitoringSupport* monitoring_support()          { return _monitoring_support;    }
419   GCMemoryManager* cycle_memory_manager()                    { return &_cycle_memory_manager; }
420   GCMemoryManager* stw_memory_manager()                      { return &_stw_memory_manager;   }
421   SoftRefPolicy* soft_ref_policy()                  override { return &_soft_ref_policy;      }
422 
423   GrowableArray<GCMemoryManager*> memory_managers() override;
424   GrowableArray<MemoryPool*> memory_pools() override;
425   MemoryUsage memory_usage() override;
426   GCTracer* tracer();
427   ConcurrentGCTimer* gc_timer() const;
428 
429 // ---------- Reference processing
430 //
431 private:
432   ShenandoahReferenceProcessor* const _ref_processor;
433 
434 public:
435   ShenandoahReferenceProcessor* ref_processor() { return _ref_processor; }
436 
437 // ---------- Class Unloading
438 //
439 private:
440   ShenandoahSharedFlag _unload_classes;
441   ShenandoahUnload     _unloader;
442 
443 public:
444   void set_unload_classes(bool uc);
445   bool unload_classes() const;
446 
447   // Perform STW class unloading and weak root cleaning
448   void parallel_cleaning(bool full_gc);
449 
450 private:
451   void stw_unload_classes(bool full_gc);
452   void stw_process_weak_roots(bool full_gc);
453   void stw_weak_refs(bool full_gc);
454 
455   // Heap iteration support
456   void scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops);
457   bool prepare_aux_bitmap_for_iteration();
458   void reclaim_aux_bitmap_for_iteration();
459 
460 // ---------- Generic interface hooks
461 // Minor things that super-interface expects us to implement to play nice with
462 // the rest of runtime. Some of the things here are not required to be implemented,
463 // and can be stubbed out.
464 //
465 public:
466   bool is_maximal_no_gc() const override shenandoah_not_implemented_return(false);
467 
468   bool is_in(const void* p) const override;
469 
470   bool requires_barriers(stackChunkOop obj) const override;
471 
472   MemRegion reserved_region() const { return _reserved; }
473   bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
474 
475   void collect(GCCause::Cause cause) override;
476   void do_full_collection(bool clear_all_soft_refs) override;
477 
478   // Used for parsing heap during error printing
479   HeapWord* block_start(const void* addr) const;
480   bool block_is_obj(const HeapWord* addr) const;
481   bool print_location(outputStream* st, void* addr) const override;
482 
483   // Used for native heap walkers: heap dumpers, mostly
484   void object_iterate(ObjectClosure* cl) override;
485   // Parallel heap iteration support
486   ParallelObjectIteratorImpl* parallel_object_iterator(uint workers) override;
487 
488   // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
489   void keep_alive(oop obj) override;
490 
491 // ---------- Safepoint interface hooks
492 //
493 public:
494   void safepoint_synchronize_begin() override;
495   void safepoint_synchronize_end() override;
496 
497 // ---------- Code roots handling hooks
498 //
499 public:
500   void register_nmethod(nmethod* nm) override;
501   void unregister_nmethod(nmethod* nm) override;
502   void verify_nmethod(nmethod* nm) override {}
503 
504 // ---------- Pinning hooks
505 //
506 public:
507   // Shenandoah supports per-object (per-region) pinning
508   void pin_object(JavaThread* thread, oop obj) override;
509   void unpin_object(JavaThread* thread, oop obj) override;
510 
511   void sync_pinned_region_status();
512   void assert_pinned_region_status() NOT_DEBUG_RETURN;
513 
514 // ---------- Concurrent Stack Processing support
515 //
516 public:
517   bool uses_stack_watermark_barrier() const override { return true; }
518 
519 // ---------- Allocation support
520 //
521 private:
522   HeapWord* allocate_memory_under_lock(ShenandoahAllocRequest& request, bool& in_new_region);
523   inline HeapWord* allocate_from_gclab(Thread* thread, size_t size);
524   HeapWord* allocate_from_gclab_slow(Thread* thread, size_t size);
525   HeapWord* allocate_new_gclab(size_t min_size, size_t word_size, size_t* actual_size);
526 
527 public:
528   HeapWord* allocate_memory(ShenandoahAllocRequest& request);
529   HeapWord* mem_allocate(size_t size, bool* what) override;
530   MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
531                                                size_t size,
532                                                Metaspace::MetadataType mdtype) override;
533 
534   void notify_mutator_alloc_words(size_t words, bool waste);
535 
536   HeapWord* allocate_new_tlab(size_t min_size, size_t requested_size, size_t* actual_size) override;
537   size_t tlab_capacity(Thread *thr) const override;
538   size_t unsafe_max_tlab_alloc(Thread *thread) const override;
539   size_t max_tlab_size() const override;
540   size_t tlab_used(Thread* ignored) const override;
541 
542   void ensure_parsability(bool retire_labs) override;
543 
544   void labs_make_parsable();
545   void tlabs_retire(bool resize);
546   void gclabs_retire(bool resize);
547 
548 // ---------- Marking support
549 //
550 private:
551   ShenandoahMarkingContext* _marking_context;
552   MemRegion  _bitmap_region;
553   MemRegion  _aux_bitmap_region;
554   MarkBitMap _verification_bit_map;
555   MarkBitMap _aux_bit_map;
556 
557   size_t _bitmap_size;
558   size_t _bitmap_regions_per_slice;
559   size_t _bitmap_bytes_per_slice;
560 
561   size_t _pretouch_heap_page_size;
562   size_t _pretouch_bitmap_page_size;
563 
564   bool _bitmap_region_special;
565   bool _aux_bitmap_region_special;
566 
567   ShenandoahLiveData** _liveness_cache;
568 
569 public:
570   inline ShenandoahMarkingContext* complete_marking_context() const;
571   inline ShenandoahMarkingContext* marking_context() const;
572   inline void mark_complete_marking_context();
573   inline void mark_incomplete_marking_context();
574 
575   template<class T>
576   inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl);
577 
578   template<class T>
579   inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
580 
581   template<class T>
582   inline void marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
583 
584   void reset_mark_bitmap();
585 
586   // SATB barriers hooks
587   inline bool requires_marking(const void* entry) const;
588 
589   // Support for bitmap uncommits
590   bool commit_bitmap_slice(ShenandoahHeapRegion *r);
591   bool uncommit_bitmap_slice(ShenandoahHeapRegion *r);
592   bool is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self = false);
593 
594   // Liveness caching support
595   ShenandoahLiveData* get_liveness_cache(uint worker_id);
596   void flush_liveness_cache(uint worker_id);
597 
598   size_t pretouch_heap_page_size() { return _pretouch_heap_page_size; }
599 
600 // ---------- Evacuation support
601 //
602 private:
603   ShenandoahCollectionSet* _collection_set;
604   ShenandoahEvacOOMHandler _oom_evac_handler;
605 
606 public:
607   static address in_cset_fast_test_addr();
608 
609   ShenandoahCollectionSet* collection_set() const { return _collection_set; }
610 
611   // Checks if object is in the collection set.
612   inline bool in_collection_set(oop obj) const;
613 
614   // Checks if location is in the collection set. Can be interior pointer, not the oop itself.
615   inline bool in_collection_set_loc(void* loc) const;
616 
617   // Evacuates object src. Returns the evacuated object, either evacuated
618   // by this thread, or by some other thread.
619   inline oop evacuate_object(oop src, Thread* thread);
620 
621   // Call before/after evacuation.
622   inline void enter_evacuation(Thread* t);
623   inline void leave_evacuation(Thread* t);
624 
625 // ---------- Helper functions
626 //
627 public:
628   template <class T>
629   inline void conc_update_with_forwarded(T* p);
630 
631   template <class T>
632   inline void update_with_forwarded(T* p);
633 
634   static inline void atomic_update_oop(oop update,       oop* addr,       oop compare);
635   static inline void atomic_update_oop(oop update, narrowOop* addr,       oop compare);
636   static inline void atomic_update_oop(oop update, narrowOop* addr, narrowOop compare);
637 
638   static inline bool atomic_update_oop_check(oop update,       oop* addr,       oop compare);
639   static inline bool atomic_update_oop_check(oop update, narrowOop* addr,       oop compare);
640   static inline bool atomic_update_oop_check(oop update, narrowOop* addr, narrowOop compare);
641 
642   static inline void atomic_clear_oop(      oop* addr,       oop compare);
643   static inline void atomic_clear_oop(narrowOop* addr,       oop compare);
644   static inline void atomic_clear_oop(narrowOop* addr, narrowOop compare);
645 
646   void trash_humongous_region_at(ShenandoahHeapRegion *r);
647 
648 private:
649   void trash_cset_regions();
650 
651 // ---------- Testing helpers functions
652 //
653 private:
654   ShenandoahSharedFlag _inject_alloc_failure;
655 
656   void try_inject_alloc_failure();
657   bool should_inject_alloc_failure();
658 };
659 
660 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP