view src/share/vm/classfile/classLoaderData.hpp @ 6972:bd7a7ce2e264

6830717: replay of compilations would help with debugging Summary: When java process crashed in compiler thread, repeat the compilation process will help finding root cause. This is done with using SA dump application class data and replay data from core dump, then use debug version of jvm to recompile the problematic java method. Reviewed-by: kvn, twisti, sspitsyn Contributed-by: yumin.qi@oracle.com
author minqi
date Mon, 12 Nov 2012 14:03:53 -0800
parents e861d44e0c9c
children 90273fc0a981
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/*
 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP
#define SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP

#include "memory/allocation.hpp"
#include "memory/memRegion.hpp"
#include "memory/metaspace.hpp"
#include "memory/metaspaceCounters.hpp"
#include "runtime/mutex.hpp"
#include "utilities/growableArray.hpp"

//
// A class loader represents a linkset. Conceptually, a linkset identifies
// the complete transitive closure of resolved links that a dynamic linker can
// produce.
//
// A ClassLoaderData also encapsulates the allocation space, called a metaspace,
// used by the dynamic linker to allocate the runtime representation of all
// the types it defines.
//
// ClassLoaderData are stored in the runtime representation of classes and the
// system dictionary, are roots of garbage collection, and provides iterators
// for root tracing and other GC operations.

class ClassLoaderData;
class JNIMethodBlock;
class JNIHandleBlock;
class Metadebug;
// GC root for walking class loader data created

class ClassLoaderDataGraph : public AllStatic {
  friend class ClassLoaderData;
  friend class ClassLoaderDataGraphMetaspaceIterator;
  friend class VMStructs;
 private:
  // All CLDs (except the null CLD) can be reached by walking _head->_next->...
  static ClassLoaderData* _head;
  static ClassLoaderData* _unloading;
  // CMS support.
  static ClassLoaderData* _saved_head;

  static ClassLoaderData* add(ClassLoaderData** loader_data_addr, Handle class_loader);
 public:
  static ClassLoaderData* find_or_create(Handle class_loader);
  static void purge();
  static void clear_claimed_marks();
  static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
  static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
  static void classes_do(KlassClosure* klass_closure);
  static bool do_unloading(BoolObjectClosure* is_alive);

  // CMS support.
  static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
  static GrowableArray<ClassLoaderData*>* new_clds();

  static void dump_on(outputStream * const out) PRODUCT_RETURN;
  static void dump() { dump_on(tty); }
  static void verify();

#ifndef PRODUCT
  // expensive test for pointer in metaspace for debugging
  static bool contains(address x);
  static bool contains_loader_data(ClassLoaderData* loader_data);
#endif
};

// ClassLoaderData class

class ClassLoaderData : public CHeapObj<mtClass> {
  friend class VMStructs;
 private:
  friend class ClassLoaderDataGraph;
  friend class ClassLoaderDataGraphMetaspaceIterator;
  friend class MetaDataFactory;
  friend class Method;

  static ClassLoaderData * _the_null_class_loader_data;

  oop _class_loader;       // oop used to uniquely identify a class loader
                           // class loader or a canonical class path
  Metaspace * _metaspace;  // Meta-space where meta-data defined by the
                           // classes in the class loader are allocated.
  Mutex* _metaspace_lock;  // Locks the metaspace for allocations and setup.
  bool _unloading;         // true if this class loader goes away
  volatile int _claimed;   // true if claimed, for example during GC traces.
                           // To avoid applying oop closure more than once.
                           // Has to be an int because we cas it.
  Klass* _klasses;         // The classes defined by the class loader.

  JNIHandleBlock* _handles; // Handles to constant pool arrays

  // These method IDs are created for the class loader and set to NULL when the
  // class loader is unloaded.  They are rarely freed, only for redefine classes
  // and if they lose a data race in InstanceKlass.
  JNIMethodBlock*                  _jmethod_ids;

  // Metadata to be deallocated when it's safe at class unloading, when
  // this class loader isn't unloaded itself.
  GrowableArray<Metadata*>*      _deallocate_list;

  // Support for walking class loader data objects
  ClassLoaderData* _next; /// Next loader_datas created

  // ReadOnly and ReadWrite metaspaces (static because only on the null
  // class loader for now).
  static Metaspace* _ro_metaspace;
  static Metaspace* _rw_metaspace;

  bool has_dependency(ClassLoaderData* cld);
  void add_dependency(ClassLoaderData* to_loader_data, TRAPS);

  void set_next(ClassLoaderData* next) { _next = next; }
  ClassLoaderData* next() const        { return _next; }

  ClassLoaderData(Handle h_class_loader);
  ~ClassLoaderData();

  void set_metaspace(Metaspace* m) { _metaspace = m; }

  JNIHandleBlock* handles() const;
  void set_handles(JNIHandleBlock* handles);

  Mutex* metaspace_lock() const { return _metaspace_lock; }

  // GC interface.
  void clear_claimed()          { _claimed = 0; }
  bool claimed() const          { return _claimed == 1; }
  bool claim();

  void mark_for_unload()        { _unloading = true; }

  void classes_do(void f(InstanceKlass*));

  // Deallocate free list during class unloading.
  void free_deallocate_list();

  // Allocate out of this class loader data
  MetaWord* allocate(size_t size);

 public:
  // Accessors
  Metaspace* metaspace_or_null() const     { return _metaspace; }

  static ClassLoaderData* the_null_class_loader_data() {
    return _the_null_class_loader_data;
  }

  static void init_null_class_loader_data() {
    assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
    assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
    _the_null_class_loader_data = new ClassLoaderData((oop)NULL);
    ClassLoaderDataGraph::_head = _the_null_class_loader_data;
    assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
    if (DumpSharedSpaces) {
      _the_null_class_loader_data->initialize_shared_metaspaces();
    }
  }

  bool is_the_null_class_loader_data() const {
    return this == _the_null_class_loader_data;
  }

  // The Metaspace is created lazily so may be NULL.  This
  // method will allocate a Metaspace if needed.
  Metaspace* metaspace_non_null();

  oop class_loader() const      { return _class_loader; }

  // Returns true if this class loader data is for a loader going away.
  bool is_unloading() const     {
    assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
    return _unloading;
  }

  unsigned int identity_hash() {
    return _class_loader == NULL ? 0 : _class_loader->identity_hash();
  }

  // Used when tracing from klasses.
  void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);

  void classes_do(KlassClosure* klass_closure);

  JNIMethodBlock* jmethod_ids() const              { return _jmethod_ids; }
  void set_jmethod_ids(JNIMethodBlock* new_block)  { _jmethod_ids = new_block; }

  void print_value() { print_value_on(tty); }
  void print_value_on(outputStream* out) const PRODUCT_RETURN;
  void dump(outputStream * const out) PRODUCT_RETURN;
  void verify();

  jobject add_handle(Handle h);
  void add_class(Klass* k);
  void remove_class(Klass* k);
  void record_dependency(Klass* to, TRAPS);

  void add_to_deallocate_list(Metadata* m);

  static ClassLoaderData* class_loader_data(oop loader);
  static void print_loader(ClassLoaderData *loader_data, outputStream *out);

  // CDS support
  Metaspace* ro_metaspace();
  Metaspace* rw_metaspace();
  void initialize_shared_metaspaces();
};

class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
  ClassLoaderData* _data;
 public:
  ClassLoaderDataGraphMetaspaceIterator();
  ~ClassLoaderDataGraphMetaspaceIterator();
  bool repeat() { return _data != NULL; }
  Metaspace* get_next() {
    assert(_data != NULL, "Should not be NULL in call to the iterator");
    Metaspace* result = _data->metaspace_or_null();
    _data = _data->next();
    // This result might be NULL for class loaders without metaspace
    // yet.  It would be nice to return only non-null results but
    // there is no guarantee that there will be a non-null result
    // down the list so the caller is going to have to check.
    return result;
  }
};
#endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP