/*

 * Copyright (c) 2000, 2011, 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.

 *

 */

#include "precompiled.hpp"

#include "classfile/symbolTable.hpp"

#include "classfile/systemDictionary.hpp"

#include "code/codeCache.hpp"

#include "gc_interface/collectedHeap.inline.hpp"

#include "memory/sharedHeap.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/fprofiler.hpp"

#include "runtime/java.hpp"

#include "services/management.hpp"

#include "utilities/copy.hpp"

#include "utilities/workgroup.hpp"

SharedHeap* SharedHeap::_sh;

// The set of potentially parallel tasks in strong root scanning.

enum SH_process_strong_roots_tasks {

  SH_PS_Universe_oops_do,

  SH_PS_JNIHandles_oops_do,

  SH_PS_ObjectSynchronizer_oops_do,

  SH_PS_FlatProfiler_oops_do,

  SH_PS_Management_oops_do,

  SH_PS_SystemDictionary_oops_do,

  SH_PS_jvmti_oops_do,

  SH_PS_StringTable_oops_do,

  SH_PS_CodeCache_oops_do,

  // Leave this one last.

  SH_PS_NumElements

};

SharedHeap::SharedHeap(CollectorPolicy* policy_) :

  CollectedHeap(),

  _collector_policy(policy_),

  _perm_gen(NULL), _rem_set(NULL),

  _strong_roots_parity(0),

  _process_strong_tasks(new SubTasksDone(SH_PS_NumElements)),

  _workers(NULL)

{

  if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {

    vm_exit_during_initialization("Failed necessary allocation.");

  }

  _sh = this;  // ch is static, should be set only once.

  if ((UseParNewGC ||

      (UseConcMarkSweepGC && CMSParallelRemarkEnabled) ||

       UseG1GC) &&

      ParallelGCThreads > 0) {

    _workers = new FlexibleWorkGang("Parallel GC Threads", ParallelGCThreads,

                            /* are_GC_task_threads */true,

                            /* are_ConcurrentGC_threads */false);

    if (_workers == NULL) {

      vm_exit_during_initialization("Failed necessary allocation.");

    } else {

      _workers->initialize_workers();

    }

  }

}

int SharedHeap::n_termination() {

  return _process_strong_tasks->n_threads();

}

void SharedHeap::set_n_termination(int t) {

  _process_strong_tasks->set_n_threads(t);

}

bool SharedHeap::heap_lock_held_for_gc() {

  Thread* t = Thread::current();

  return    Heap_lock->owned_by_self()

         || (   (t->is_GC_task_thread() ||  t->is_VM_thread())

             && _thread_holds_heap_lock_for_gc);

}

  assert(t == 0 || !UseSerialGC, "Cannot have parallel threads");

  _n_par_threads = t;

  _process_strong_tasks->set_n_threads(t);

}

class AssertIsPermClosure: public OopClosure {

public:

  virtual void do_oop(oop* p) {

    assert((*p) == NULL || (*p)->is_perm(), "Referent should be perm.");

  }

  virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }

};

static AssertIsPermClosure assert_is_perm_closure;

#ifdef ASSERT

class AssertNonScavengableClosure: public OopClosure {

public:

  virtual void do_oop(oop* p) {

    assert(!Universe::heap()->is_in_partial_collection(*p),

      "Referent should not be scavengable.");  }

  virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }

};

static AssertNonScavengableClosure assert_is_non_scavengable_closure;

#endif

void SharedHeap::change_strong_roots_parity() {

  // Also set the new collection parity.

  assert(_strong_roots_parity >= 0 && _strong_roots_parity <= 2,

         "Not in range.");

  _strong_roots_parity++;

  if (_strong_roots_parity == 3) _strong_roots_parity = 1;

  assert(_strong_roots_parity >= 1 && _strong_roots_parity <= 2,

         "Not in range.");

}

SharedHeap::StrongRootsScope::StrongRootsScope(SharedHeap* outer, bool activate)

  : MarkScope(activate)

{

  if (_active) {

    outer->change_strong_roots_parity();

  }

}

SharedHeap::StrongRootsScope::~StrongRootsScope() {

  // nothing particular

}

void SharedHeap::process_strong_roots(bool activate_scope,

                                      bool collecting_perm_gen,

                                      ScanningOption so,

                                      OopClosure* roots,

                                      CodeBlobClosure* code_roots,

                                      OopsInGenClosure* perm_blk) {

  StrongRootsScope srs(this, activate_scope);

  // General strong roots.

  assert(_strong_roots_parity != 0, "must have called prologue code");

  // _n_termination for _process_strong_tasks should be set up stream

  // in a method not running in a GC worker.  Otherwise the GC worker

  // could be trying to change the termination condition while the task

  // is executing in another GC worker.

  if (!_process_strong_tasks->is_task_claimed(SH_PS_Universe_oops_do)) {

    Universe::oops_do(roots);

    // Consider perm-gen discovered lists to be strong.

    perm_gen()->ref_processor()->weak_oops_do(roots);

  }

  // Global (strong) JNI handles

  if (!_process_strong_tasks->is_task_claimed(SH_PS_JNIHandles_oops_do))

    JNIHandles::oops_do(roots);

  // All threads execute this; the individual threads are task groups.

  if (ParallelGCThreads > 0) {

    Threads::possibly_parallel_oops_do(roots, code_roots);

  } else {

    Threads::oops_do(roots, code_roots);

  }

  if (!_process_strong_tasks-> is_task_claimed(SH_PS_ObjectSynchronizer_oops_do))

    ObjectSynchronizer::oops_do(roots);

  if (!_process_strong_tasks->is_task_claimed(SH_PS_FlatProfiler_oops_do))

    FlatProfiler::oops_do(roots);

  if (!_process_strong_tasks->is_task_claimed(SH_PS_Management_oops_do))

    Management::oops_do(roots);

  if (!_process_strong_tasks->is_task_claimed(SH_PS_jvmti_oops_do))

    JvmtiExport::oops_do(roots);

  if (!_process_strong_tasks->is_task_claimed(SH_PS_SystemDictionary_oops_do)) {

    if (so & SO_AllClasses) {

      SystemDictionary::oops_do(roots);

    } else if (so & SO_SystemClasses) {

      SystemDictionary::always_strong_oops_do(roots);

    }

  }

  if (!_process_strong_tasks->is_task_claimed(SH_PS_StringTable_oops_do)) {

    if (so & SO_Strings || (!collecting_perm_gen && !JavaObjectsInPerm)) {

      StringTable::oops_do(roots);

    }

    if (JavaObjectsInPerm) {

      // Verify the string table contents are in the perm gen

      NOT_PRODUCT(StringTable::oops_do(&assert_is_perm_closure));

    }

  }

  if (!_process_strong_tasks->is_task_claimed(SH_PS_CodeCache_oops_do)) {

    if (so & SO_CodeCache) {

      // (Currently, CMSCollector uses this to do intermediate-strength collections.)

      assert(collecting_perm_gen, "scanning all of code cache");

      assert(code_roots != NULL, "must supply closure for code cache");

      if (code_roots != NULL) {

        CodeCache::blobs_do(code_roots);

      }

    } else if (so & (SO_SystemClasses|SO_AllClasses)) {

      if (!collecting_perm_gen) {

        // If we are collecting from class statics, but we are not going to

        // visit all of the CodeCache, collect from the non-perm roots if any.

        // This makes the code cache function temporarily as a source of strong

        // roots for oops, until the next major collection.

        //

        // If collecting_perm_gen is true, we require that this phase will call

        // CodeCache::do_unloading.  This will kill off nmethods with expired

        // weak references, such as stale invokedynamic targets.

        CodeCache::scavenge_root_nmethods_do(code_roots);

      }

    }

    // Verify that the code cache contents are not subject to

    // movement by a scavenging collection.

    DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, /*do_marking=*/ false));

    DEBUG_ONLY(CodeCache::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));

  }

  if (!collecting_perm_gen) {

    // All threads perform this; coordination is handled internally.

    rem_set()->younger_refs_iterate(perm_gen(), perm_blk);

  }

  _process_strong_tasks->all_tasks_completed();

}

class AlwaysTrueClosure: public BoolObjectClosure {

public:

  void do_object(oop p) { ShouldNotReachHere(); }

  bool do_object_b(oop p) { return true; }

};

static AlwaysTrueClosure always_true;

class SkipAdjustingSharedStrings: public OopClosure {

  OopClosure* _clo;

public:

  SkipAdjustingSharedStrings(OopClosure* clo) : _clo(clo) {}

  virtual void do_oop(oop* p) {

    oop o = (*p);

    if (!o->is_shared_readwrite()) {

      _clo->do_oop(p);

    }

  }

  virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }

};

// Unmarked shared Strings in the StringTable (which got there due to

// being in the constant pools of as-yet unloaded shared classes) were

// not marked and therefore did not have their mark words preserved.

// These entries are also deliberately not purged from the string

// table during unloading of unmarked strings. If an identity hash

// code was computed for any of these objects, it will not have been

// cleared to zero during the forwarding process or by the

// RecursiveAdjustSharedObjectClosure, and will be confused by the

// adjusting process as a forwarding pointer. We need to skip

// forwarding StringTable entries which contain unmarked shared

// Strings. Actually, since shared strings won't be moving, we can

// just skip adjusting any shared entries in the string table.

void SharedHeap::process_weak_roots(OopClosure* root_closure,

                                    CodeBlobClosure* code_roots,

                                    OopClosure* non_root_closure) {

  // Global (weak) JNI handles

  JNIHandles::weak_oops_do(&always_true, root_closure);

  CodeCache::blobs_do(code_roots);

  if (UseSharedSpaces && !DumpSharedSpaces) {

    SkipAdjustingSharedStrings skip_closure(root_closure);

    StringTable::oops_do(&skip_closure);

  } else {

    StringTable::oops_do(root_closure);

  }

}

void SharedHeap::set_barrier_set(BarrierSet* bs) {

  _barrier_set = bs;

  // Cached barrier set for fast access in oops

  oopDesc::set_bs(bs);

}

void SharedHeap::post_initialize() {

  ref_processing_init();

}

void SharedHeap::ref_processing_init() {

  perm_gen()->ref_processor_init();

}

// Some utilities.

void SharedHeap::print_size_transition(outputStream* out,

                                       size_t bytes_before,

                                       size_t bytes_after,

                                       size_t capacity) {

  out->print(" %d%s->%d%s(%d%s)",

             byte_size_in_proper_unit(bytes_before),

             proper_unit_for_byte_size(bytes_before),

             byte_size_in_proper_unit(bytes_after),

             proper_unit_for_byte_size(bytes_after),

             byte_size_in_proper_unit(capacity),

             proper_unit_for_byte_size(capacity));

}