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6798898: CMS: bugs related to class unloading

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Override should_remember_klasses() and remember_klass() as needed.

Reviewed-by: ysr, jcoomes
This commit is contained in:
Jon Masamitsu 2009-08-24 10:36:31 -07:00
parent ead860c069
commit 20a43bad21
8 changed files with 238 additions and 105 deletions
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48
hotspot/src/share/vm/memory/iterator.hpp
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@ -54,7 +54,12 @@ class OopClosure : public Closure {
// In support of post-processing of weak links of KlassKlass objects;
// see KlassKlass::oop_oop_iterate().
virtual const bool should_remember_klasses() const { return false; }
virtual const bool should_remember_klasses() const {
assert(!must_remember_klasses(), "Should have overriden this method.");
return false;
}
virtual void remember_klass(Klass* k) { /* do nothing */ }
// If "true", invoke on nmethods (when scanning compiled frames).
@ -74,6 +79,12 @@ class OopClosure : public Closure {
// location without an intervening "major reset" (like the end of a GC).
virtual bool idempotent() { return false; }
virtual bool apply_to_weak_ref_discovered_field() { return false; }
#ifdef ASSERT
static bool _must_remember_klasses;
static bool must_remember_klasses();
static void set_must_remember_klasses(bool v);
#endif
};
// ObjectClosure is used for iterating through an object space
@ -219,3 +230,38 @@ public:
// correct length.
virtual void do_tag(int tag) = 0;
};
#ifdef ASSERT
// This class is used to flag phases of a collection that
// can unload classes and which should override the
// should_remember_klasses() and remember_klass() of OopClosure.
// The _must_remember_klasses is set in the contructor and restored
// in the destructor. _must_remember_klasses is checked in assertions
// in the OopClosure implementations of should_remember_klasses() and
// remember_klass() and the expectation is that the OopClosure
// implementation should not be in use if _must_remember_klasses is set.
// Instances of RememberKlassesChecker can be place in
// marking phases of collections which can do class unloading.
// RememberKlassesChecker can be passed "false" to turn off checking.
// It is used by CMS when CMS yields to a different collector.
class RememberKlassesChecker: StackObj {
bool _state;
bool _skip;
public:
RememberKlassesChecker(bool checking_on) : _state(false), _skip(false) {
_skip = !(ClassUnloading && !UseConcMarkSweepGC ||
CMSClassUnloadingEnabled && UseConcMarkSweepGC);
if (_skip) {
return;
}
_state = OopClosure::must_remember_klasses();
OopClosure::set_must_remember_klasses(checking_on);
}
~RememberKlassesChecker() {
if (_skip) {
return;
}
OopClosure::set_must_remember_klasses(_state);
}
};
#endif // ASSERT