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6722113: CMS: Incorrect overflow handling during precleaning of Reference lists

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When we encounter marking stack overflow during precleaning of Reference lists, we were using the overflow list mechanism, which can cause problems on account of mutating the mark word of the header because of conflicts with mutator accesses and updates of that field. Instead we should use the usual mechanism for overflow handling in concurrent phases, namely dirtying of the card on which the overflowed object lies. Since precleaning effectively does a form of discovered list processing, albeit with discovery enabled, we needed to adjust some code to be correct in the face of interleaved processing and discovery.

Reviewed-by: apetrusenko, jcoomes
This commit is contained in:
Y. Srinivas Ramakrishna 2008-11-20 12:27:41 -08:00
parent 28b2c4aeaf
commit db6bef2c70
5 changed files with 95 additions and 48 deletions
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12
hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/cmsOopClosures.hpp
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@ -325,24 +325,30 @@ class Par_PushOrMarkClosure: public OopClosure {
// For objects in CMS generation, this closure marks
// given objects (transitively) as being reachable/live.
// This is currently used during the (weak) reference object
// processing phase of the CMS final checkpoint step.
// processing phase of the CMS final checkpoint step, as
// well as during the concurrent precleaning of the discovered
// reference lists.
class CMSKeepAliveClosure: public OopClosure {
private:
CMSCollector* _collector;
const MemRegion _span;
CMSMarkStack* _mark_stack;
CMSBitMap* _bit_map;
bool _concurrent_precleaning;
protected:
DO_OOP_WORK_DEFN
public:
CMSKeepAliveClosure(CMSCollector* collector, MemRegion span,
CMSBitMap* bit_map, CMSMarkStack* mark_stack):
CMSBitMap* bit_map, CMSMarkStack* mark_stack,
bool cpc):
_collector(collector),
_span(span),
_bit_map(bit_map),
_mark_stack(mark_stack) {
_mark_stack(mark_stack),
_concurrent_precleaning(cpc) {
assert(!_span.is_empty(), "Empty span could spell trouble");
}
bool concurrent_precleaning() const { return _concurrent_precleaning; }
virtual void do_oop(oop* p);
virtual void do_oop(narrowOop* p);
inline void do_oop_nv(oop* p) { CMSKeepAliveClosure::do_oop_work(p); }