src/share/vm/gc_implementation/g1/g1RemSet.inline.hpp

Tue, 16 Nov 2010 14:07:33 -0800

author
johnc
date
Tue, 16 Nov 2010 14:07:33 -0800
changeset 2302
878b57474103
parent 2216
c32059ef4dc0
child 2314
f95d63e2154a
permissions
-rw-r--r--

6978187: G1: assert(ParallelGCThreads> 1 || n_yielded() == _hrrs->occupied()) strikes again
Summary: An evacuation failure while copying the roots caused an object, A, to be forwarded to itself. During the subsequent RSet updating a reference to A was processed causing the reference to be added to the RSet of A's heap region. As a result of adding to the remembered set we ran into the issue described in 6930581 - the sparse table expanded and the RSet scanning code walked the cards in one instance of RHashTable (_cur) while the occupied() counts the cards in the expanded table (_next).
Reviewed-by: tonyp, iveresov

     1 /*
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     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
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     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  *
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    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
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    22  *
    23  */
    25 inline size_t G1RemSet::n_workers() {
    26   if (_g1->workers() != NULL) {
    27     return _g1->workers()->total_workers();
    28   } else {
    29     return 1;
    30   }
    31 }
    33 template <class T>
    34 inline void G1RemSet::write_ref(HeapRegion* from, T* p) {
    35   par_write_ref(from, p, 0);
    36 }
    38 template <class T>
    39 inline void G1RemSet::par_write_ref(HeapRegion* from, T* p, int tid) {
    40   oop obj = oopDesc::load_decode_heap_oop(p);
    41 #ifdef ASSERT
    42   // can't do because of races
    43   // assert(obj == NULL || obj->is_oop(), "expected an oop");
    45   // Do the safe subset of is_oop
    46   if (obj != NULL) {
    47 #ifdef CHECK_UNHANDLED_OOPS
    48     oopDesc* o = obj.obj();
    49 #else
    50     oopDesc* o = obj;
    51 #endif // CHECK_UNHANDLED_OOPS
    52     assert((intptr_t)o % MinObjAlignmentInBytes == 0, "not oop aligned");
    53     assert(Universe::heap()->is_in_reserved(obj), "must be in heap");
    54   }
    55 #endif // ASSERT
    57   assert(from == NULL || from->is_in_reserved(p), "p is not in from");
    59   HeapRegion* to = _g1->heap_region_containing(obj);
    60   if (to != NULL && from != to) {
    61 #if G1_REM_SET_LOGGING
    62     gclog_or_tty->print_cr("Adding " PTR_FORMAT " (" PTR_FORMAT ") to RS"
    63                            " for region [" PTR_FORMAT ", " PTR_FORMAT ")",
    64                            p, obj,
    65                            to->bottom(), to->end());
    66 #endif
    67     assert(to->rem_set() != NULL, "Need per-region 'into' remsets.");
    68     to->rem_set()->add_reference(p, tid);
    69   }
    70 }
    72 template <class T>
    73 inline void UpdateRSOopClosure::do_oop_work(T* p) {
    74   assert(_from != NULL, "from region must be non-NULL");
    75   _rs->par_write_ref(_from, p, _worker_i);
    76 }
    78 template <class T>
    79 inline void UpdateRSetImmediate::do_oop_work(T* p) {
    80   assert(_from->is_in_reserved(p), "paranoia");
    81   T heap_oop = oopDesc::load_heap_oop(p);
    82   if (!oopDesc::is_null(heap_oop) && !_from->is_survivor()) {
    83     _g1_rem_set->par_write_ref(_from, p, 0);
    84   }
    85 }
    87 template <class T>
    88 inline void UpdateRSOrPushRefOopClosure::do_oop_work(T* p) {
    89   oop obj = oopDesc::load_decode_heap_oop(p);
    90 #ifdef ASSERT
    91   // can't do because of races
    92   // assert(obj == NULL || obj->is_oop(), "expected an oop");
    94   // Do the safe subset of is_oop
    95   if (obj != NULL) {
    96 #ifdef CHECK_UNHANDLED_OOPS
    97     oopDesc* o = obj.obj();
    98 #else
    99     oopDesc* o = obj;
   100 #endif // CHECK_UNHANDLED_OOPS
   101     assert((intptr_t)o % MinObjAlignmentInBytes == 0, "not oop aligned");
   102     assert(Universe::heap()->is_in_reserved(obj), "must be in heap");
   103   }
   104 #endif // ASSERT
   106   assert(_from != NULL, "from region must be non-NULL");
   108   HeapRegion* to = _g1->heap_region_containing(obj);
   109   if (to != NULL && _from != to) {
   110     // The _record_refs_into_cset flag is true during the RSet
   111     // updating part of an evacuation pause. It is false at all
   112     // other times:
   113     //  * rebuilding the rembered sets after a full GC
   114     //  * during concurrent refinement.
   115     //  * updating the remembered sets of regions in the collection
   116     //    set in the event of an evacuation failure (when deferred
   117     //    updates are enabled).
   119     if (_record_refs_into_cset && to->in_collection_set()) {
   120       // We are recording references that point into the collection
   121       // set and this particular reference does exactly that...
   122       // If the referenced object has already been forwarded
   123       // to itself, we are handling an evacuation failure and
   124       // we have already visited/tried to copy this object
   125       // there is no need to retry.
   126       if (!self_forwarded(obj)) {
   127         assert(_push_ref_cl != NULL, "should not be null");
   128         // Push the reference in the refs queue of the G1ParScanThreadState
   129         // instance for this worker thread.
   130         _push_ref_cl->do_oop(p);
   131       }
   133       // Deferred updates to the CSet are either discarded (in the normal case),
   134       // or processed (if an evacuation failure occurs) at the end
   135       // of the collection.
   136       // See G1RemSet::cleanup_after_oops_into_collection_set_do().
   137     } else {
   138       // We either don't care about pushing references that point into the
   139       // collection set (i.e. we're not during an evacuation pause) _or_
   140       // the reference doesn't point into the collection set. Either way
   141       // we add the reference directly to the RSet of the region containing
   142       // the referenced object.
   143       _g1_rem_set->par_write_ref(_from, p, _worker_i);
   144     }
   145   }
   146 }

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