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8292077: G1 nmethod entry barriers don't keep oops alive

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Reviewed-by: tschatzl, stefank, vlivanov
This commit is contained in:
Erik Österlund 2022-08-11 11:45:11 +00:00
parent ad5f628c58
commit 1c0f0f4211
1 changed files with 21 additions and 11 deletions
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32
src/hotspot/share/gc/shared/barrierSetNMethod.cpp
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@ -28,8 +28,10 @@
#include "gc/shared/barrierSet.hpp"
#include "gc/shared/barrierSetAssembler.hpp"
#include "gc/shared/barrierSetNMethod.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "logging/log.hpp"
#include "memory/iterator.hpp"
#include "memory/universe.hpp"
#include "oops/access.inline.hpp"
#include "oops/method.inline.hpp"
#include "runtime/frame.inline.hpp"
@ -38,14 +40,6 @@
#include "runtime/threads.hpp"
#include "utilities/debug.hpp"
class LoadPhantomOopClosure : public OopClosure {
public:
virtual void do_oop(oop* p) {
NativeAccess<ON_PHANTOM_OOP_REF>::oop_load(p);
}
virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
};
int BarrierSetNMethod::disarmed_value() const {
return *disarmed_value_address();
}
@ -67,10 +61,26 @@ bool BarrierSetNMethod::supports_entry_barrier(nmethod* nm) {
}
bool BarrierSetNMethod::nmethod_entry_barrier(nmethod* nm) {
class OopKeepAliveClosure : public OopClosure {
public:
virtual void do_oop(oop* p) {
// Loads on nmethod oops are phantom strength.
//
// Note that we could have used NativeAccess<ON_PHANTOM_OOP_REF>::oop_load(p),
// but that would have *required* us to convert the returned LoadOopProxy to an oop,
// or else keep alive load barrier will never be called. It's the LoadOopProxy-to-oop
// conversion that performs the load barriers. This is too subtle, so we instead
// perform an explicit keep alive call.
oop obj = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(p);
Universe::heap()->keep_alive(obj);
}
virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
};
// 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. This is done
// by the phantom load.
LoadPhantomOopClosure cl;
// SATB GC, then it is important that this code marks them live.
OopKeepAliveClosure cl;
nm->oops_do(&cl);
// CodeCache sweeper support