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comparison src/share/vm/memory/iterator.hpp @ 935:05f89f00a864

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6798898: CMS: bugs related to class unloading Summary: Override should_remember_klasses() and remember_klass() as needed. Reviewed-by: ysr, jcoomes
author jmasa
date Mon, 24 Aug 2009 10:36:31 -0700
parents 1ee8caae33af
children 8b46c4d82093
comparison
equal deleted inserted replaced
912:308762b2bf14 935:05f89f00a864
52 virtual void do_oop(narrowOop* o) = 0; 52 virtual void do_oop(narrowOop* o) = 0;
53 virtual void do_oop_v(narrowOop* o) { do_oop(o); } 53 virtual void do_oop_v(narrowOop* o) { do_oop(o); }
54 54
55 // In support of post-processing of weak links of KlassKlass objects; 55 // In support of post-processing of weak links of KlassKlass objects;
56 // see KlassKlass::oop_oop_iterate(). 56 // see KlassKlass::oop_oop_iterate().
57 virtual const bool should_remember_klasses() const { return false; } 57
58 virtual const bool should_remember_klasses() const {
59 assert(!must_remember_klasses(), "Should have overriden this method.");
60 return false;
61 }
62
58 virtual void remember_klass(Klass* k) { /* do nothing */ } 63 virtual void remember_klass(Klass* k) { /* do nothing */ }
59 64
60 // If "true", invoke on nmethods (when scanning compiled frames). 65 // If "true", invoke on nmethods (when scanning compiled frames).
61 virtual const bool do_nmethods() const { return false; } 66 virtual const bool do_nmethods() const { return false; }
62 67
72 77
73 // True iff this closure may be safely applied more than once to an oop 78 // True iff this closure may be safely applied more than once to an oop
74 // location without an intervening "major reset" (like the end of a GC). 79 // location without an intervening "major reset" (like the end of a GC).
75 virtual bool idempotent() { return false; } 80 virtual bool idempotent() { return false; }
76 virtual bool apply_to_weak_ref_discovered_field() { return false; } 81 virtual bool apply_to_weak_ref_discovered_field() { return false; }
82
83 #ifdef ASSERT
84 static bool _must_remember_klasses;
85 static bool must_remember_klasses();
86 static void set_must_remember_klasses(bool v);
87 #endif
77 }; 88 };
78 89
79 // ObjectClosure is used for iterating through an object space 90 // ObjectClosure is used for iterating through an object space
80 91
81 class ObjectClosure : public Closure { 92 class ObjectClosure : public Closure {
217 // the passed in value and fail is they don't match. This allows 228 // the passed in value and fail is they don't match. This allows
218 // for verification that sections of the serialized data are of the 229 // for verification that sections of the serialized data are of the
219 // correct length. 230 // correct length.
220 virtual void do_tag(int tag) = 0; 231 virtual void do_tag(int tag) = 0;
221 }; 232 };
233
234 #ifdef ASSERT
235 // This class is used to flag phases of a collection that
236 // can unload classes and which should override the
237 // should_remember_klasses() and remember_klass() of OopClosure.
238 // The _must_remember_klasses is set in the contructor and restored
239 // in the destructor. _must_remember_klasses is checked in assertions
240 // in the OopClosure implementations of should_remember_klasses() and
241 // remember_klass() and the expectation is that the OopClosure
242 // implementation should not be in use if _must_remember_klasses is set.
243 // Instances of RememberKlassesChecker can be place in
244 // marking phases of collections which can do class unloading.
245 // RememberKlassesChecker can be passed "false" to turn off checking.
246 // It is used by CMS when CMS yields to a different collector.
247 class RememberKlassesChecker: StackObj {
248 bool _state;
249 bool _skip;
250 public:
251 RememberKlassesChecker(bool checking_on) : _state(false), _skip(false) {
252 _skip = !(ClassUnloading && !UseConcMarkSweepGC ||
253 CMSClassUnloadingEnabled && UseConcMarkSweepGC);
254 if (_skip) {
255 return;
256 }
257 _state = OopClosure::must_remember_klasses();
258 OopClosure::set_must_remember_klasses(checking_on);
259 }
260 ~RememberKlassesChecker() {
261 if (_skip) {
262 return;
263 }
264 OopClosure::set_must_remember_klasses(_state);
265 }
266 };
267 #endif // ASSERT