1.1 --- a/src/share/vm/memory/compactingPermGenGen.cpp Fri Feb 29 20:03:58 2008 -0800
1.2 +++ b/src/share/vm/memory/compactingPermGenGen.cpp Wed Mar 12 18:06:50 2008 -0700
1.3 @@ -26,9 +26,27 @@
1.4 #include "incls/_compactingPermGenGen.cpp.incl"
1.5
1.6
1.7 -// Recursively adjust all pointers in an object and all objects by
1.8 -// referenced it. Clear marks on objects in order to prevent visiting
1.9 -// any object twice.
1.10 +// An ObjectClosure helper: Recursively adjust all pointers in an object
1.11 +// and all objects by referenced it. Clear marks on objects in order to
1.12 +// prevent visiting any object twice. This helper is used when the
1.13 +// RedefineClasses() API has been called.
1.14 +
1.15 +class AdjustSharedObjectClosure : public ObjectClosure {
1.16 +public:
1.17 + void do_object(oop obj) {
1.18 + if (obj->is_shared_readwrite()) {
1.19 + if (obj->mark()->is_marked()) {
1.20 + obj->init_mark(); // Don't revisit this object.
1.21 + obj->adjust_pointers(); // Adjust this object's references.
1.22 + }
1.23 + }
1.24 + }
1.25 +};
1.26 +
1.27 +
1.28 +// An OopClosure helper: Recursively adjust all pointers in an object
1.29 +// and all objects by referenced it. Clear marks on objects in order
1.30 +// to prevent visiting any object twice.
1.31
1.32 class RecursiveAdjustSharedObjectClosure : public OopClosure {
1.33 public:
1.34 @@ -274,15 +292,34 @@
1.35 // objects in the space will page in more objects than we need.
1.36 // Instead, use the system dictionary as strong roots into the read
1.37 // write space.
1.38 +//
1.39 +// If a RedefineClasses() call has been made, then we have to iterate
1.40 +// over the entire shared read-write space in order to find all the
1.41 +// objects that need to be forwarded. For example, it is possible for
1.42 +// an nmethod to be found and marked in GC phase-1 only for the nmethod
1.43 +// to be freed by the time we reach GC phase-3. The underlying method
1.44 +// is still marked, but we can't (easily) find it in GC phase-3 so we
1.45 +// blow up in GC phase-4. With RedefineClasses() we want replaced code
1.46 +// (EMCP or obsolete) to go away (i.e., be collectible) once it is no
1.47 +// longer being executed by any thread so we keep minimal attachments
1.48 +// to the replaced code. However, we can't guarantee when those EMCP
1.49 +// or obsolete methods will be collected so they may still be out there
1.50 +// even after we've severed our minimal attachments.
1.51
1.52 void CompactingPermGenGen::pre_adjust_pointers() {
1.53 if (spec()->enable_shared_spaces()) {
1.54 - RecursiveAdjustSharedObjectClosure blk;
1.55 - Universe::oops_do(&blk);
1.56 - StringTable::oops_do(&blk);
1.57 - SystemDictionary::always_strong_classes_do(&blk);
1.58 - TraversePlaceholdersClosure tpc;
1.59 - SystemDictionary::placeholders_do(&tpc);
1.60 + if (JvmtiExport::has_redefined_a_class()) {
1.61 + // RedefineClasses() requires a brute force approach
1.62 + AdjustSharedObjectClosure blk;
1.63 + rw_space()->object_iterate(&blk);
1.64 + } else {
1.65 + RecursiveAdjustSharedObjectClosure blk;
1.66 + Universe::oops_do(&blk);
1.67 + StringTable::oops_do(&blk);
1.68 + SystemDictionary::always_strong_classes_do(&blk);
1.69 + TraversePlaceholdersClosure tpc;
1.70 + SystemDictionary::placeholders_do(&tpc);
1.71 + }
1.72 }
1.73 }
1.74
