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6497639: 4/3 Profiling Swing application caused JVM crash

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Make RedefineClasses() interoperate better with class sharing.

Reviewed-by: sspitsyn, jmasa
This commit is contained in:
Daniel D. Daugherty 2008-03-12 18:06:50 -07:00
parent 493ac9ee8f
commit 0f1d30354a
4 changed files with 87 additions and 27 deletions
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55
hotspot/src/share/vm/memory/compactingPermGenGen.cpp
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@ -26,9 +26,27 @@
#include "incls/_compactingPermGenGen.cpp.incl"
// Recursively adjust all pointers in an object and all objects by
// referenced it. Clear marks on objects in order to prevent visiting
// any object twice.
// An ObjectClosure helper: Recursively adjust all pointers in an object
// and all objects by referenced it. Clear marks on objects in order to
// prevent visiting any object twice. This helper is used when the
// RedefineClasses() API has been called.
class AdjustSharedObjectClosure : public ObjectClosure {
public:
void do_object(oop obj) {
if (obj->is_shared_readwrite()) {
if (obj->mark()->is_marked()) {
obj->init_mark(); // Don't revisit this object.
obj->adjust_pointers(); // Adjust this object's references.
}
}
}
};
// An OopClosure helper: Recursively adjust all pointers in an object
// and all objects by referenced it. Clear marks on objects in order
// to prevent visiting any object twice.
class RecursiveAdjustSharedObjectClosure : public OopClosure {
public:
@ -274,15 +292,34 @@ CompactingPermGenGen::CompactingPermGenGen(ReservedSpace rs,
// objects in the space will page in more objects than we need.
// Instead, use the system dictionary as strong roots into the read
// write space.
//
// If a RedefineClasses() call has been made, then we have to iterate
// over the entire shared read-write space in order to find all the
// objects that need to be forwarded. For example, it is possible for
// an nmethod to be found and marked in GC phase-1 only for the nmethod
// to be freed by the time we reach GC phase-3. The underlying method
// is still marked, but we can't (easily) find it in GC phase-3 so we
// blow up in GC phase-4. With RedefineClasses() we want replaced code
// (EMCP or obsolete) to go away (i.e., be collectible) once it is no
// longer being executed by any thread so we keep minimal attachments
// to the replaced code. However, we can't guarantee when those EMCP
// or obsolete methods will be collected so they may still be out there
// even after we've severed our minimal attachments.
void CompactingPermGenGen::pre_adjust_pointers() {
if (spec()->enable_shared_spaces()) {
RecursiveAdjustSharedObjectClosure blk;
Universe::oops_do(&blk);
StringTable::oops_do(&blk);
SystemDictionary::always_strong_classes_do(&blk);
TraversePlaceholdersClosure tpc;
SystemDictionary::placeholders_do(&tpc);
if (JvmtiExport::has_redefined_a_class()) {
// RedefineClasses() requires a brute force approach
AdjustSharedObjectClosure blk;
rw_space()->object_iterate(&blk);
} else {
RecursiveAdjustSharedObjectClosure blk;
Universe::oops_do(&blk);
StringTable::oops_do(&blk);
SystemDictionary::always_strong_classes_do(&blk);
TraversePlaceholdersClosure tpc;
SystemDictionary::placeholders_do(&tpc);
}
}
}