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8302462: [REDO] 8297487: G1 Remark: no need to keep alive oop constants of nmethods on stack

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Reviewed-by: tschatzl, ayang
This commit is contained in:
Richard Reingruber 2023-02-20 06:47:57 +00:00
parent 7abe26935a
commit 2009dc2b73
2 changed files with 3 additions and 14 deletions
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15
src/hotspot/share/gc/g1/g1ConcurrentMark.cpp
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@ -1777,27 +1777,14 @@ public:
class G1RemarkThreadsClosure : public ThreadClosure {
G1SATBMarkQueueSet& _qset;
G1CMOopClosure _cm_cl;
MarkingCodeBlobClosure _code_cl;
public:
G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) :
_qset(G1BarrierSet::satb_mark_queue_set()),
_cm_cl(g1h, task),
_code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations, true /* keepalive nmethods */) {}
_qset(G1BarrierSet::satb_mark_queue_set()) {}
void do_thread(Thread* thread) {
// Transfer any partial buffer to the qset for completed buffer processing.
_qset.flush_queue(G1ThreadLocalData::satb_mark_queue(thread));
if (thread->is_Java_thread()) {
// In theory it should not be necessary to explicitly walk the nmethods to find roots for concurrent marking
// however the liveness of oops reachable from nmethods have very complex lifecycles:
// * Alive if on the stack of an executing method
// * Weakly reachable otherwise
// Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
// live by the SATB invariant but other oops recorded in nmethods may behave differently.
JavaThread::cast(thread)->nmethods_do(&_code_cl);
}
}
};

2
src/hotspot/share/gc/shared/barrierSetNMethod.cpp
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@ -99,6 +99,8 @@ bool BarrierSetNMethod::nmethod_entry_barrier(nmethod* nm) {
// If the nmethod is the only thing pointing to the oops, and we are using a
// SATB GC, then it is important that this code marks them live.
// Also, with concurrent GC, it is possible that frames in continuation stack
// chunks are not visited if they are allocated after concurrent GC started.
OopKeepAliveClosure cl;
nm->oops_do(&cl);