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 /*

  * 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.

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  */

 #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)),

   _n_par_threads(0),

   _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();

     }

   }

 }

 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);

 }

 void SharedHeap::set_par_threads(int t) {

   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");

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

     Universe::oops_do(roots);

     ReferenceProcessor::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));

 }