1 /*
   2  * Copyright (c) 2015, 2017, Red Hat, Inc. and/or its affiliates.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #ifndef SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
  25 #define SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
  26 
  27 #include "classfile/javaClasses.inline.hpp"
  28 #include "gc/g1/suspendibleThreadSet.hpp"
  29 #include "gc/shared/markBitMap.inline.hpp"
  30 #include "gc/shared/threadLocalAllocBuffer.inline.hpp"
  31 #include "gc/shenandoah/brooksPointer.inline.hpp"
  32 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
  33 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
  34 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
  35 #include "gc/shenandoah/shenandoahConnectionMatrix.inline.hpp"
  36 #include "gc/shenandoah/shenandoahHeap.hpp"
  37 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
  38 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
  39 #include "gc/shenandoah/shenandoahStringDedup.hpp"
  40 #include "gc/shenandoah/shenandoahUtils.hpp"
  41 #include "oops/oop.inline.hpp"
  42 #include "runtime/atomic.hpp"
  43 #include "runtime/interfaceSupport.hpp"
  44 #include "runtime/prefetch.hpp"
  45 #include "runtime/prefetch.inline.hpp"
  46 #include "runtime/thread.hpp"
  47 #include "utilities/copy.hpp"
  48 
  49 template <class T>
  50 void ShenandoahUpdateRefsClosure::do_oop_work(T* p) {
  51   T o = oopDesc::load_heap_oop(p);
  52   if (! oopDesc::is_null(o)) {
  53     oop obj = oopDesc::decode_heap_oop_not_null(o);
  54     _heap->update_oop_ref_not_null(p, obj);
  55   }
  56 }
  57 
  58 void ShenandoahUpdateRefsClosure::do_oop(oop* p)       { do_oop_work(p); }
  59 void ShenandoahUpdateRefsClosure::do_oop(narrowOop* p) { do_oop_work(p); }
  60 
  61 /*
  62  * Marks the object. Returns true if the object has not been marked before and has
  63  * been marked by this thread. Returns false if the object has already been marked,
  64  * or if a competing thread succeeded in marking this object.
  65  */
  66 inline bool ShenandoahHeap::mark(oop obj) const {
  67 #ifdef ASSERT
  68   if (! oopDesc::unsafe_equals(obj, oopDesc::bs()->read_barrier(obj))) {
  69     tty->print_cr("heap region containing obj:");
  70     ShenandoahHeapRegion* obj_region = heap_region_containing(obj);
  71     obj_region->print();
  72     tty->print_cr("heap region containing forwardee:");
  73     ShenandoahHeapRegion* forward_region = heap_region_containing(oopDesc::bs()->read_barrier(obj));
  74     forward_region->print();
  75   }
  76 #endif
  77 
  78   assert(oopDesc::unsafe_equals(obj, oopDesc::bs()->read_barrier(obj)), "only mark forwarded copy of objects");
  79   return mark_no_checks(obj);
  80 }
  81 
  82 inline bool ShenandoahHeap::mark_no_checks(oop obj) const {
  83   HeapWord* addr = (HeapWord*) obj;
  84   return (! allocated_after_mark_start(addr)) && _mark_bit_map->parMark(addr);
  85 }
  86 
  87 inline bool ShenandoahHeap::is_marked(oop obj) const {
  88   HeapWord* addr = (HeapWord*) obj;
  89   return allocated_after_mark_start(addr) || _mark_bit_map->isMarked(addr);
  90 }
  91 
  92 inline bool ShenandoahHeap::need_update_refs() const {
  93   return _need_update_refs;
  94 }
  95 
  96 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
  97   uintptr_t region_start = ((uintptr_t) addr);
  98   uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
  99 #ifdef ASSERT
 100   if (index >= num_regions()) {
 101     tty->print_cr("heap region does not contain address, heap base: "PTR_FORMAT \
 102                   ", real bottom of first region: "PTR_FORMAT", num_regions: "SIZE_FORMAT", region_size: "SIZE_FORMAT,
 103                   p2i(base()),
 104                   p2i(_ordered_regions->get(0)->bottom()),
 105                   num_regions(),
 106                   ShenandoahHeapRegion::region_size_bytes());
 107   }
 108 #endif
 109   assert(index < num_regions(), "heap region index must be in range");
 110   return index;
 111 }
 112 
 113 inline ShenandoahHeapRegion* ShenandoahHeap::heap_region_containing(const void* addr) const {
 114   size_t index = heap_region_index_containing(addr);
 115   ShenandoahHeapRegion* result = _ordered_regions->get(index);
 116 #ifdef ASSERT
 117   if (!(addr >= result->bottom() && addr < result->end())) {
 118     tty->print_cr("heap region does not contain address, heap base: "PTR_FORMAT \
 119                   ", real bottom of first region: "PTR_FORMAT", num_regions: "SIZE_FORMAT,
 120                   p2i(base()),
 121                   p2i(_ordered_regions->get(0)->bottom()),
 122                   num_regions());
 123   }
 124 #endif
 125   assert(addr >= result->bottom() && addr < result->end(), "address must be in found region");
 126   return result;
 127 }
 128 
 129 template <class T>
 130 inline oop ShenandoahHeap::update_oop_ref_not_null(T* p, oop obj) {
 131   if (in_collection_set(obj)) {
 132     oop forw = ShenandoahBarrierSet::resolve_oop_static_not_null(obj);
 133     assert(! oopDesc::unsafe_equals(forw, obj) || is_full_gc_in_progress() || cancelled_concgc(), "expect forwarded object");
 134     obj = forw;
 135     oopDesc::encode_store_heap_oop(p, obj);
 136   }
 137 #ifdef ASSERT
 138   else {
 139     assert(oopDesc::unsafe_equals(obj, ShenandoahBarrierSet::resolve_oop_static_not_null(obj)), "expect not forwarded");
 140   }
 141 #endif
 142   return obj;
 143 }
 144 
 145 template <class T>
 146 inline oop ShenandoahHeap::maybe_update_oop_ref(T* p) {
 147   T o = oopDesc::load_heap_oop(p);
 148   if (! oopDesc::is_null(o)) {
 149     oop obj = oopDesc::decode_heap_oop_not_null(o);
 150     return maybe_update_oop_ref_not_null(p, obj);
 151   } else {
 152     return NULL;
 153   }
 154 }
 155 
 156 inline oop ShenandoahHeap::atomic_compare_exchange_oop(oop n, oop* addr, oop c) {
 157   return (oop) Atomic::cmpxchg_ptr(n, addr, c);
 158 }
 159 
 160 inline oop ShenandoahHeap::atomic_compare_exchange_oop(oop n, narrowOop* addr, oop c) {
 161   narrowOop cmp = oopDesc::encode_heap_oop(c);
 162   narrowOop val = oopDesc::encode_heap_oop(n);
 163   return oopDesc::decode_heap_oop((narrowOop) Atomic::cmpxchg(val, addr, cmp));
 164 }
 165 
 166 template <class T>
 167 inline oop ShenandoahHeap::maybe_update_oop_ref_not_null(T* p, oop heap_oop) {
 168 
 169   assert((! is_in(p)) || (! in_collection_set(p))
 170          || is_full_gc_in_progress(),
 171          "never update refs in from-space, unless evacuation has been cancelled");
 172 
 173 #ifdef ASSERT
 174   if (! is_in(heap_oop)) {
 175     print_heap_regions_on(tty);
 176     tty->print_cr("object not in heap: "PTR_FORMAT", referenced by: "PTR_FORMAT, p2i((HeapWord*) heap_oop), p2i(p));
 177     assert(is_in(heap_oop), "object must be in heap");
 178   }
 179 #endif
 180   assert(is_in(heap_oop), "only ever call this on objects in the heap");
 181   if (in_collection_set(heap_oop)) {
 182     oop forwarded_oop = ShenandoahBarrierSet::resolve_oop_static_not_null(heap_oop); // read brooks ptr
 183     if (oopDesc::unsafe_equals(forwarded_oop, heap_oop)) {
 184       // E.g. during evacuation.
 185       return forwarded_oop;
 186     }
 187 
 188     assert(! oopDesc::unsafe_equals(forwarded_oop, heap_oop) || is_full_gc_in_progress(), "expect forwarded object");
 189 
 190     log_develop_trace(gc)("Updating old ref: "PTR_FORMAT" pointing to "PTR_FORMAT" to new ref: "PTR_FORMAT,
 191                           p2i(p), p2i(heap_oop), p2i(forwarded_oop));
 192 
 193     assert(oopDesc::is_oop(forwarded_oop), "oop required");
 194     assert(is_in(forwarded_oop), "forwardee must be in heap");
 195     assert(oopDesc::bs()->is_safe(forwarded_oop), "forwardee must not be in collection set");
 196     // If this fails, another thread wrote to p before us, it will be logged in SATB and the
 197     // reference be updated later.
 198     oop result = atomic_compare_exchange_oop(forwarded_oop, p, heap_oop);
 199 
 200     if (oopDesc::unsafe_equals(result, heap_oop)) { // CAS successful.
 201       return forwarded_oop;
 202     } else {
 203       // Note: we used to assert the following here. This doesn't work because sometimes, during
 204       // marking/updating-refs, it can happen that a Java thread beats us with an arraycopy,
 205       // which first copies the array, which potentially contains from-space refs, and only afterwards
 206       // updates all from-space refs to to-space refs, which leaves a short window where the new array
 207       // elements can be from-space.
 208       // assert(oopDesc::is_null(result) ||
 209       //        oopDesc::unsafe_equals(result, ShenandoahBarrierSet::resolve_oop_static_not_null(result)),
 210       //       "expect not forwarded");
 211       return NULL;
 212     }
 213   } else {
 214     assert(oopDesc::unsafe_equals(heap_oop, ShenandoahBarrierSet::resolve_oop_static_not_null(heap_oop)),
 215            "expect not forwarded");
 216     return heap_oop;
 217   }
 218 }
 219 
 220 inline bool ShenandoahHeap::cancelled_concgc() const {
 221   return OrderAccess::load_acquire((jbyte*) &_cancelled_concgc) == CANCELLED;
 222 }
 223 
 224 inline bool ShenandoahHeap::check_cancelled_concgc_and_yield(bool sts_active) {
 225   if (! (sts_active && ShenandoahSuspendibleWorkers)) {
 226     return cancelled_concgc();
 227   }
 228   jbyte prev = Atomic::cmpxchg((jbyte)NOT_CANCELLED, &_cancelled_concgc, (jbyte)CANCELLABLE);
 229   if (prev == CANCELLABLE || prev == NOT_CANCELLED) {
 230 
 231     if (SuspendibleThreadSet::should_yield()) {
 232       SuspendibleThreadSet::yield();
 233     }
 234 
 235     // Back to CANCELLABLE. The thread that poked NOT_CANCELLED first gets
 236     // to restore to CANCELLABLE.
 237     if (prev == CANCELLABLE) {
 238       OrderAccess::release_store_fence(&_cancelled_concgc, CANCELLABLE);
 239     }
 240     return false;
 241   } else {
 242     return true;
 243   }
 244 }
 245 
 246 inline bool ShenandoahHeap::try_cancel_concgc() {
 247   while (true) {
 248     jbyte prev = Atomic::cmpxchg((jbyte)CANCELLED, &_cancelled_concgc, (jbyte)CANCELLABLE);
 249     if (prev == CANCELLABLE) return true;
 250     else if (prev == CANCELLED) return false;
 251     assert(ShenandoahSuspendibleWorkers, "should not get here when not using suspendible workers");
 252     assert(prev == NOT_CANCELLED, "must be NOT_CANCELLED");
 253     {
 254       // We need to provide a safepoint here, otherwise we might
 255       // spin forever if a SP is pending.
 256       ThreadBlockInVM sp(JavaThread::current());
 257       SpinPause();
 258     }
 259   }
 260 }
 261 
 262 inline void ShenandoahHeap::clear_cancelled_concgc() {
 263   OrderAccess::release_store_fence(&_cancelled_concgc, CANCELLABLE);
 264 }
 265 
 266 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
 267   if (UseTLAB) {
 268     if (!thread->gclab().is_initialized()) {
 269       assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
 270              "Performance: thread should have GCLAB: %s", thread->name());
 271       // No GCLABs in this thread, fallback to shared allocation
 272       return NULL;
 273     }
 274     HeapWord* obj = thread->gclab().allocate(size);
 275     if (obj != NULL) {
 276       return obj;
 277     }
 278     // Otherwise...
 279     return allocate_from_gclab_slow(thread, size);
 280   } else {
 281     return NULL;
 282   }
 283 }
 284 
 285 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread, bool& evacuated) {
 286   evacuated = false;
 287 
 288   size_t size_no_fwdptr = (size_t) p->size();
 289   size_t size_with_fwdptr = size_no_fwdptr + BrooksPointer::word_size();
 290 
 291   assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
 292 
 293   bool alloc_from_gclab = true;
 294   HeapWord* filler = allocate_from_gclab(thread, size_with_fwdptr);
 295   if (filler == NULL) {
 296     filler = allocate_memory(size_with_fwdptr, _alloc_shared_gc);
 297     alloc_from_gclab = false;
 298   }
 299 
 300 #ifdef ASSERT
 301   // Checking that current Java thread does not hold Threads_lock when we get here.
 302   // If that ever be the case, we'd deadlock in oom_during_evacuation.
 303   if ((! Thread::current()->is_GC_task_thread()) && (! Thread::current()->is_ConcurrentGC_thread())) {
 304     assert(! Threads_lock->owned_by_self()
 305            || SafepointSynchronize::is_at_safepoint(), "must not hold Threads_lock here");
 306   }
 307 #endif
 308 
 309   if (filler == NULL) {
 310     oom_during_evacuation();
 311     // If this is a Java thread, it should have waited
 312     // until all GC threads are done, and then we
 313     // return the forwardee.
 314     oop resolved = ShenandoahBarrierSet::resolve_oop_static(p);
 315     return resolved;
 316   }
 317 
 318   // Copy the object and initialize its forwarding ptr:
 319   HeapWord* copy = filler + BrooksPointer::word_size();
 320   oop copy_val = oop(copy);
 321 
 322   Copy::aligned_disjoint_words((HeapWord*) p, copy, size_no_fwdptr);
 323   BrooksPointer::initialize(oop(copy));
 324 
 325   log_develop_trace(gc, compaction)("Copy object: " PTR_FORMAT " -> " PTR_FORMAT,
 326                                     p2i(p), p2i(copy));
 327 
 328   // String dedup support
 329   bool need_str_dedup = false;
 330   if (ShenandoahStringDedup::is_enabled()
 331     && java_lang_String::is_instance_inlined(copy_val)) {
 332     // We need to increase age before CAS to avoid race condition.
 333     // Once new copy is published, other threads may set hash code,
 334     // or perform locking, etc. which will race age bits manipulation.
 335     copy_val->incr_age();
 336 
 337     need_str_dedup = ShenandoahStringDedup::is_candidate(copy_val);
 338   }
 339 
 340   // Try to install the new forwarding pointer.
 341   oop result = BrooksPointer::try_update_forwardee(p, copy_val);
 342 
 343   if (oopDesc::unsafe_equals(result, p)) {
 344     // Successfully evacuated. Our copy is now the public one!
 345     evacuated = true;
 346     log_develop_trace(gc, compaction)("Copy object: " PTR_FORMAT " -> " PTR_FORMAT " succeeded",
 347                                       p2i(p), p2i(copy));
 348 
 349     // Only dedup evacuated string
 350     if (need_str_dedup) {
 351       // Shenandoah evacuates objects inside and outside of safepoints.
 352       // But string dedup protocol requires deduplication outside of safepoints,
 353       // so we need to queue candidates during safepoints.
 354       if (SafepointSynchronize::is_at_safepoint()) {
 355         assert(thread->is_Worker_thread(), "Must be a worker thread during a safepoint");
 356         // Use worker thread id instead of worker_id to avoid passing down worker_id.
 357         // This may cause imbalance among the queues, but it is okay, since deduplication is
 358         // single threaded.
 359         ShenandoahStringDedup::enqueue_from_safepoint(copy_val, thread->as_Worker_thread()->id());
 360       } else {
 361         ShenandoahStringDedup::deduplicate(copy_val);
 362       }
 363     }
 364 
 365 #ifdef ASSERT
 366     assert(oopDesc::is_oop(copy_val), "expect oop");
 367     assert(p->klass() == copy_val->klass(), "Should have the same class p: "PTR_FORMAT", copy: "PTR_FORMAT,
 368                                               p2i(p), p2i(copy));
 369 #endif
 370     return copy_val;
 371   }  else {
 372     // Failed to evacuate. We need to deal with the object that is left behind. Since this
 373     // new allocation is certainly after TAMS, it will be considered live in the next cycle.
 374     // But if it happens to contain references to evacuated regions, those references would
 375     // not get updated for this stale copy during this cycle, and we will crash while scanning
 376     // it the next cycle.
 377     //
 378     // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
 379     // object will overwrite this stale copy, or the filler object on LAB retirement will
 380     // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
 381     // have to explicitly overwrite the copy with the filler object. With that overwrite,
 382     // we have to keep the fwdptr initialized and pointing to our (stale) copy.
 383     if (alloc_from_gclab) {
 384       thread->gclab().rollback(size_with_fwdptr);
 385     } else {
 386       fill_with_object(copy, size_no_fwdptr);
 387     }
 388     log_develop_trace(gc, compaction)("Copy object: " PTR_FORMAT " -> " PTR_FORMAT " failed, use other: " PTR_FORMAT,
 389                                       p2i(p), p2i(copy), p2i(result));
 390     return result;
 391   }
 392 }
 393 
 394 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
 395   return ! is_marked(oop(entry));
 396 }
 397 
 398 bool ShenandoahHeap::region_in_collection_set(size_t region_index) const {
 399   assert(collection_set() != NULL, "Sanity");
 400   return collection_set()->is_in(region_index);
 401 }
 402 
 403 bool ShenandoahHeap::in_collection_set(ShenandoahHeapRegion* r) const {
 404   return region_in_collection_set(r->region_number());
 405 }
 406 
 407 template <class T>
 408 inline bool ShenandoahHeap::in_collection_set(T p) const {
 409   HeapWord* obj = (HeapWord*) p;
 410   assert(collection_set() != NULL, "Sanity");
 411   assert(is_in(obj), "should be in heap");
 412 
 413   return collection_set()->is_in(obj);
 414 }
 415 
 416 inline bool ShenandoahHeap::concurrent_mark_in_progress() const {
 417   return _concurrent_mark_in_progress != 0;
 418 }
 419 
 420 inline address ShenandoahHeap::concurrent_mark_in_progress_addr() {
 421   return (address) &(ShenandoahHeap::heap()->_concurrent_mark_in_progress);
 422 }
 423 
 424 inline address ShenandoahHeap::update_refs_in_progress_addr() {
 425   return (address) &(ShenandoahHeap::heap()->_update_refs_in_progress);
 426 }
 427 
 428 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
 429   return _evacuation_in_progress != 0;
 430 }
 431 
 432 inline address ShenandoahHeap::evacuation_in_progress_addr() {
 433   return (address) &(ShenandoahHeap::heap()->_evacuation_in_progress);
 434 }
 435 
 436 inline bool ShenandoahHeap::allocated_after_mark_start(HeapWord* addr) const {
 437   uintx index = ((uintx) addr) >> ShenandoahHeapRegion::region_size_bytes_shift();
 438   HeapWord* top_at_mark_start = _top_at_mark_starts[index];
 439   bool alloc_after_mark_start = addr >= top_at_mark_start;
 440   return alloc_after_mark_start;
 441 }
 442 
 443 template<class T>
 444 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
 445   marked_object_iterate(region, cl, region->top());
 446 }
 447 
 448 template<class T>
 449 inline void ShenandoahHeap::marked_object_safe_iterate(ShenandoahHeapRegion* region, T* cl) {
 450   marked_object_iterate(region, cl, region->concurrent_iteration_safe_limit());
 451 }
 452 
 453 template<class T>
 454 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
 455   assert(BrooksPointer::word_offset() < 0, "skip_delta calculation below assumes the forwarding ptr is before obj");
 456 
 457   assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
 458   assert(is_bitmap_valid(), "only try this with complete marking bitmap");
 459 
 460   MarkBitMap* mark_bit_map = _mark_bit_map;
 461   HeapWord* tams = top_at_mark_start(region->bottom());
 462 
 463   size_t skip_bitmap_delta = BrooksPointer::word_size() + 1;
 464   size_t skip_objsize_delta = BrooksPointer::word_size() /* + actual obj.size() below */;
 465   HeapWord* start = region->bottom() + BrooksPointer::word_size();
 466 
 467   HeapWord* end = MIN2(tams + BrooksPointer::word_size(), region->end());
 468   HeapWord* addr = mark_bit_map->getNextMarkedWordAddress(start, end);
 469 
 470   intx dist = ShenandoahMarkScanPrefetch;
 471   if (dist > 0) {
 472     // Batched scan that prefetches the oop data, anticipating the access to
 473     // either header, oop field, or forwarding pointer. Not that we cannot
 474     // touch anything in oop, while it still being prefetched to get enough
 475     // time for prefetch to work. This is why we try to scan the bitmap linearly,
 476     // disregarding the object size. However, since we know forwarding pointer
 477     // preceeds the object, we can skip over it. Once we cannot trust the bitmap,
 478     // there is no point for prefetching the oop contents, as oop->size() will
 479     // touch it prematurely.
 480 
 481     // No variable-length arrays in standard C++, have enough slots to fit
 482     // the prefetch distance.
 483     static const int SLOT_COUNT = 256;
 484     guarantee(dist <= SLOT_COUNT, "adjust slot count");
 485     oop slots[SLOT_COUNT];
 486 
 487     bool aborting = false;
 488     int avail;
 489     do {
 490       avail = 0;
 491       for (int c = 0; (c < dist) && (addr < limit); c++) {
 492         Prefetch::read(addr, BrooksPointer::byte_offset());
 493         oop obj = oop(addr);
 494         slots[avail++] = obj;
 495         if (addr < tams) {
 496           addr += skip_bitmap_delta;
 497           addr = mark_bit_map->getNextMarkedWordAddress(addr, end);
 498         } else {
 499           // cannot trust mark bitmap anymore, finish the current stride,
 500           // and switch to accurate traversal
 501           addr += obj->size() + skip_objsize_delta;
 502           aborting = true;
 503         }
 504       }
 505 
 506       for (int c = 0; c < avail; c++) {
 507         do_marked_object(mark_bit_map, cl, slots[c]);
 508       }
 509     } while (avail > 0 && !aborting);
 510 
 511     // accurate traversal
 512     while (addr < limit) {
 513       oop obj = oop(addr);
 514       int size = obj->size();
 515       do_marked_object(mark_bit_map, cl, obj);
 516       addr += size + skip_objsize_delta;
 517     }
 518   } else {
 519     while (addr < limit) {
 520       oop obj = oop(addr);
 521       int size = obj->size();
 522       do_marked_object(mark_bit_map, cl, obj);
 523       addr += size + skip_objsize_delta;
 524       if (addr < tams) {
 525         addr = mark_bit_map->getNextMarkedWordAddress(addr, end);
 526       }
 527     }
 528   }
 529 }
 530 
 531 template<class T>
 532 inline void ShenandoahHeap::do_marked_object(MarkBitMap* bitmap, T* cl, oop obj) {
 533   assert(!oopDesc::is_null(obj), "sanity");
 534   assert(oopDesc::is_oop(obj), "sanity");
 535   assert(is_in(obj), "sanity");
 536   assert(bitmap == _mark_bit_map, "only iterate completed mark bitmap");
 537   assert(is_marked(obj), "object expected to be marked");
 538   cl->do_object(obj);
 539 }
 540 
 541 template <class T>
 542 class ShenandoahObjectToOopClosure : public ObjectClosure {
 543   T* _cl;
 544 public:
 545   ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
 546 
 547   void do_object(oop obj) {
 548     obj->oop_iterate(_cl);
 549   }
 550 };
 551 
 552 template <class T>
 553 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
 554   T* _cl;
 555   MemRegion _bounds;
 556 public:
 557   ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
 558     _cl(cl), _bounds(bottom, top) {}
 559 
 560   void do_object(oop obj) {
 561     obj->oop_iterate(_cl, _bounds);
 562   }
 563 };
 564 
 565 template<class T>
 566 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
 567   if (region->is_humongous()) {
 568     HeapWord* bottom = region->bottom();
 569     if (top > bottom) {
 570       region = region->humongous_start_region();
 571       ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
 572       marked_object_iterate(region, &objs);
 573     }
 574   } else {
 575     ShenandoahObjectToOopClosure<T> objs(cl);
 576     marked_object_iterate(region, &objs, top);
 577   }
 578 }
 579 
 580 template<class T>
 581 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl) {
 582   marked_object_oop_iterate(region, cl, region->top());
 583 }
 584 
 585 template<class T>
 586 inline void ShenandoahHeap::marked_object_oop_safe_iterate(ShenandoahHeapRegion* region, T* cl) {
 587   marked_object_oop_iterate(region, cl, region->concurrent_iteration_safe_limit());
 588 }
 589 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP