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8058209: Race in G1 card scanning could allow scanning of memory covered by PLABs

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Read _top before _gc_time_stamp in saved_mark_word() with LoadLoad order to ensure we get a consistent view

Reviewed-by: brutisso, dcubed, dholmes, stefank
This commit is contained in:
Mikael Gerdin 2014-11-14 14:23:25 +01:00
parent 95704b233c
commit 4feb7b4dab
1 changed files with 6 additions and 3 deletions
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9
hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp
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@ -1004,10 +1004,13 @@ HeapWord* G1OffsetTableContigSpace::cross_threshold(HeapWord* start,
HeapWord* G1OffsetTableContigSpace::saved_mark_word() const {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
assert( _gc_time_stamp <= g1h->get_gc_time_stamp(), "invariant" );
if (_gc_time_stamp < g1h->get_gc_time_stamp())
return top();
else
HeapWord* local_top = top();
OrderAccess::loadload();
if (_gc_time_stamp < g1h->get_gc_time_stamp()) {
return local_top;
} else {
return Space::saved_mark_word();
}
}
void G1OffsetTableContigSpace::record_top_and_timestamp() {