73a801bc43
Add indirection for fetching mirror so that GC doesn't have to follow CLD::_klasses Co-authored-by: Rickard Backman <rickard.backman@oracle.com> Reviewed-by: hseigel, thartmann, eosterlund, stefank
438 lines
17 KiB
C++
438 lines
17 KiB
C++
/*
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* Copyright (c) 2012, 2017, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP
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#define SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP
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#include "memory/allocation.hpp"
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#include "memory/memRegion.hpp"
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#include "memory/metaspace.hpp"
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#include "memory/metaspaceCounters.hpp"
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#include "oops/oopHandle.hpp"
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#include "runtime/mutex.hpp"
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#include "trace/traceMacros.hpp"
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#include "utilities/growableArray.hpp"
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#include "utilities/macros.hpp"
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#if INCLUDE_TRACE
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#include "utilities/ticks.hpp"
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#endif
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//
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// A class loader represents a linkset. Conceptually, a linkset identifies
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// the complete transitive closure of resolved links that a dynamic linker can
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// produce.
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//
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// A ClassLoaderData also encapsulates the allocation space, called a metaspace,
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// used by the dynamic linker to allocate the runtime representation of all
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// the types it defines.
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//
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// ClassLoaderData are stored in the runtime representation of classes,
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// and provides iterators for root tracing and other GC operations.
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class ClassLoaderData;
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class JNIMethodBlock;
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class Metadebug;
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class ModuleEntry;
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class PackageEntry;
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class ModuleEntryTable;
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class PackageEntryTable;
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class DictionaryEntry;
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class Dictionary;
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// GC root for walking class loader data created
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class ClassLoaderDataGraph : public AllStatic {
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friend class ClassLoaderData;
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friend class ClassLoaderDataGraphMetaspaceIterator;
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friend class ClassLoaderDataGraphKlassIteratorAtomic;
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friend class ClassLoaderDataGraphKlassIteratorStatic;
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friend class VMStructs;
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private:
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// All CLDs (except the null CLD) can be reached by walking _head->_next->...
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static ClassLoaderData* _head;
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static ClassLoaderData* _unloading;
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// CMS support.
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static ClassLoaderData* _saved_head;
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static ClassLoaderData* _saved_unloading;
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static bool _should_purge;
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// OOM has been seen in metaspace allocation. Used to prevent some
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// allocations until class unloading
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static bool _metaspace_oom;
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static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS);
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static void post_class_unload_events();
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public:
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static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);
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static void purge();
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static void clear_claimed_marks();
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// oops do
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static void oops_do(OopClosure* f, bool must_claim);
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static void keep_alive_oops_do(OopClosure* blk, bool must_claim);
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static void always_strong_oops_do(OopClosure* blk, bool must_claim);
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// cld do
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static void cld_do(CLDClosure* cl);
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static void cld_unloading_do(CLDClosure* cl);
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static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
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static void keep_alive_cld_do(CLDClosure* cl);
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static void always_strong_cld_do(CLDClosure* cl);
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// klass do
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// Walking classes through the ClassLoaderDataGraph include array classes. It also includes
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// classes that are allocated but not loaded, classes that have errors, and scratch classes
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// for redefinition. These classes are removed during the next class unloading.
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// Walking the ClassLoaderDataGraph also includes anonymous classes.
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static void classes_do(KlassClosure* klass_closure);
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static void classes_do(void f(Klass* const));
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static void methods_do(void f(Method*));
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static void modules_do(void f(ModuleEntry*));
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static void modules_unloading_do(void f(ModuleEntry*));
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static void packages_do(void f(PackageEntry*));
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static void packages_unloading_do(void f(PackageEntry*));
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static void loaded_classes_do(KlassClosure* klass_closure);
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static void classes_unloading_do(void f(Klass* const));
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static bool do_unloading(BoolObjectClosure* is_alive, bool clean_previous_versions);
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// dictionary do
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// Iterate over all klasses in dictionary, but
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// just the classes from defining class loaders.
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static void dictionary_classes_do(void f(InstanceKlass*));
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// Added for initialize_itable_for_klass to handle exceptions.
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static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS);
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// Iterate all classes and their class loaders, including initiating class loaders.
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static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*));
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// VM_CounterDecay iteration support
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static InstanceKlass* try_get_next_class();
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static void verify_dictionary();
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static void print_dictionary(outputStream* st);
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static void print_dictionary_statistics(outputStream* st);
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// CMS support.
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static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
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static GrowableArray<ClassLoaderData*>* new_clds();
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static void set_should_purge(bool b) { _should_purge = b; }
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static void purge_if_needed() {
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// Only purge the CLDG for CMS if concurrent sweep is complete.
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if (_should_purge) {
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purge();
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// reset for next time.
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set_should_purge(false);
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}
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}
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static bool has_metaspace_oom() { return _metaspace_oom; }
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static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
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static void dump_on(outputStream * const out) PRODUCT_RETURN;
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static void dump() { dump_on(tty); }
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static void verify();
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static void print_creation(outputStream* out, Handle loader, ClassLoaderData* cld, TRAPS);
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static bool unload_list_contains(const void* x);
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#ifndef PRODUCT
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static bool contains_loader_data(ClassLoaderData* loader_data);
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#endif
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#if INCLUDE_TRACE
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private:
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static Ticks _class_unload_time;
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static void class_unload_event(Klass* const k);
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#endif
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};
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// ClassLoaderData class
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class ClassLoaderData : public CHeapObj<mtClass> {
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friend class VMStructs;
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private:
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class Dependencies VALUE_OBJ_CLASS_SPEC {
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objArrayOop _list_head;
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void locked_add(objArrayHandle last,
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objArrayHandle new_dependency,
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Thread* THREAD);
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public:
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Dependencies() : _list_head(NULL) {}
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Dependencies(TRAPS) : _list_head(NULL) {
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init(CHECK);
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}
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void add(Handle dependency, TRAPS);
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void init(TRAPS);
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void oops_do(OopClosure* f);
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};
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class ChunkedHandleList VALUE_OBJ_CLASS_SPEC {
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struct Chunk : public CHeapObj<mtClass> {
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static const size_t CAPACITY = 32;
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oop _data[CAPACITY];
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volatile juint _size;
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Chunk* _next;
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Chunk(Chunk* c) : _next(c), _size(0) { }
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};
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Chunk* _head;
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void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
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public:
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ChunkedHandleList() : _head(NULL) {}
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~ChunkedHandleList();
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// Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
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// However, multiple threads can execute oops_do concurrently with add.
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oop* add(oop o);
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#ifdef ASSERT
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bool contains(oop* p);
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#endif
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void oops_do(OopClosure* f);
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};
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friend class ClassLoaderDataGraph;
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friend class ClassLoaderDataGraphKlassIteratorAtomic;
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friend class ClassLoaderDataGraphKlassIteratorStatic;
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friend class ClassLoaderDataGraphMetaspaceIterator;
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friend class MetaDataFactory;
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friend class Method;
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static ClassLoaderData * _the_null_class_loader_data;
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oop _class_loader; // oop used to uniquely identify a class loader
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// class loader or a canonical class path
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Dependencies _dependencies; // holds dependencies from this class loader
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// data to others.
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Metaspace * volatile _metaspace; // Meta-space where meta-data defined by the
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// classes in the class loader are allocated.
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Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
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bool _unloading; // true if this class loader goes away
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bool _is_anonymous; // if this CLD is for an anonymous class
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// Remembered sets support for the oops in the class loader data.
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bool _modified_oops; // Card Table Equivalent (YC/CMS support)
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bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
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s2 _keep_alive; // if this CLD is kept alive without a keep_alive_object().
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// Used for anonymous classes and the boot class
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// loader. _keep_alive does not need to be volatile or
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// atomic since there is one unique CLD per anonymous class.
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volatile int _claimed; // true if claimed, for example during GC traces.
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// To avoid applying oop closure more than once.
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// Has to be an int because we cas it.
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ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
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// have the same life cycle of the corresponding ClassLoader.
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Klass* volatile _klasses; // The classes defined by the class loader.
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PackageEntryTable* volatile _packages; // The packages defined by the class loader.
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ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
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ModuleEntry* _unnamed_module; // This class loader's unnamed module.
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Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
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// These method IDs are created for the class loader and set to NULL when the
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// class loader is unloaded. They are rarely freed, only for redefine classes
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// and if they lose a data race in InstanceKlass.
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JNIMethodBlock* _jmethod_ids;
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// Metadata to be deallocated when it's safe at class unloading, when
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// this class loader isn't unloaded itself.
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GrowableArray<Metadata*>* _deallocate_list;
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// Support for walking class loader data objects
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ClassLoaderData* _next; /// Next loader_datas created
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// ReadOnly and ReadWrite metaspaces (static because only on the null
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// class loader for now).
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static Metaspace* _ro_metaspace;
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static Metaspace* _rw_metaspace;
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TRACE_DEFINE_TRACE_ID_FIELD;
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void set_next(ClassLoaderData* next) { _next = next; }
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ClassLoaderData* next() const { return _next; }
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ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
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~ClassLoaderData();
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// GC interface.
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void clear_claimed() { _claimed = 0; }
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bool claimed() const { return _claimed == 1; }
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bool claim();
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// The CLD are not placed in the Heap, so the Card Table or
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// the Mod Union Table can't be used to mark when CLD have modified oops.
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// The CT and MUT bits saves this information for the whole class loader data.
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void clear_modified_oops() { _modified_oops = false; }
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public:
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void record_modified_oops() { _modified_oops = true; }
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bool has_modified_oops() { return _modified_oops; }
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void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
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void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
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bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
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private:
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void unload();
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bool keep_alive() const { return _keep_alive > 0; }
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void classes_do(void f(Klass*));
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void loaded_classes_do(KlassClosure* klass_closure);
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void classes_do(void f(InstanceKlass*));
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void methods_do(void f(Method*));
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void modules_do(void f(ModuleEntry*));
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void packages_do(void f(PackageEntry*));
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// Deallocate free list during class unloading.
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void free_deallocate_list();
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// Allocate out of this class loader data
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MetaWord* allocate(size_t size);
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Dictionary* create_dictionary();
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public:
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bool is_alive(BoolObjectClosure* is_alive_closure) const;
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// Accessors
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Metaspace* metaspace_or_null() const { return _metaspace; }
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static ClassLoaderData* the_null_class_loader_data() {
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return _the_null_class_loader_data;
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}
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Mutex* metaspace_lock() const { return _metaspace_lock; }
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bool is_anonymous() const { return _is_anonymous; }
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static void init_null_class_loader_data() {
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assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
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assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
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// We explicitly initialize the Dependencies object at a later phase in the initialization
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_the_null_class_loader_data = new ClassLoaderData(Handle(), false, Dependencies());
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ClassLoaderDataGraph::_head = _the_null_class_loader_data;
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assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
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}
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bool is_the_null_class_loader_data() const {
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return this == _the_null_class_loader_data;
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}
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bool is_system_class_loader_data() const;
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bool is_platform_class_loader_data() const;
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bool is_builtin_class_loader_data() const;
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// The Metaspace is created lazily so may be NULL. This
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// method will allocate a Metaspace if needed.
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Metaspace* metaspace_non_null();
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oop class_loader() const { return _class_loader; }
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// The object the GC is using to keep this ClassLoaderData alive.
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oop keep_alive_object() const;
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// Returns true if this class loader data is for a loader going away.
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bool is_unloading() const {
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assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
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return _unloading;
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}
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// Used to refcount an anonymous class's CLD in order to
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// indicate their aliveness without a keep_alive_object().
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void inc_keep_alive();
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void dec_keep_alive();
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inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); }
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void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
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void classes_do(KlassClosure* klass_closure);
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Klass* klasses() { return _klasses; }
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JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
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void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
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void print() { print_on(tty); }
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void print_on(outputStream* out) const;
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void print_value() { print_value_on(tty); }
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void print_value_on(outputStream* out) const;
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void dump(outputStream * const out) PRODUCT_RETURN;
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void verify();
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const char* loader_name();
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OopHandle add_handle(Handle h);
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void remove_handle(OopHandle h);
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void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
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void add_class(Klass* k, bool publicize = true);
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void remove_class(Klass* k);
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bool contains_klass(Klass* k);
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void record_dependency(const Klass* to, TRAPS);
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void init_dependencies(TRAPS);
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PackageEntryTable* packages() { return _packages; }
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ModuleEntry* unnamed_module() { return _unnamed_module; }
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ModuleEntryTable* modules();
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bool modules_defined() { return (_modules != NULL); }
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// Loaded class dictionary
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Dictionary* dictionary() const { return _dictionary; }
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void add_to_deallocate_list(Metadata* m);
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static ClassLoaderData* class_loader_data(oop loader);
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static ClassLoaderData* class_loader_data_or_null(oop loader);
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static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
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static void print_loader(ClassLoaderData *loader_data, outputStream *out);
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TRACE_DEFINE_TRACE_ID_METHODS;
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};
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// An iterator that distributes Klasses to parallel worker threads.
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class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
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Klass* volatile _next_klass;
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public:
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ClassLoaderDataGraphKlassIteratorAtomic();
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Klass* next_klass();
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private:
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static Klass* next_klass_in_cldg(Klass* klass);
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};
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class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
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ClassLoaderData* _data;
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public:
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ClassLoaderDataGraphMetaspaceIterator();
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~ClassLoaderDataGraphMetaspaceIterator();
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bool repeat() { return _data != NULL; }
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Metaspace* get_next() {
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assert(_data != NULL, "Should not be NULL in call to the iterator");
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Metaspace* result = _data->metaspace_or_null();
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_data = _data->next();
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// This result might be NULL for class loaders without metaspace
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// yet. It would be nice to return only non-null results but
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// there is no guarantee that there will be a non-null result
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// down the list so the caller is going to have to check.
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return result;
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}
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};
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#endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP
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