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 /*

  * Copyright (c) 2000, 2014, 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

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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/atomic.inline.hpp"

 #include "runtime/fprofiler.hpp"

 #include "runtime/java.hpp"

 #include "services/management.hpp"

 #include "utilities/copy.hpp"

 #include "utilities/workgroup.hpp"

 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC

 SharedHeap* SharedHeap::_sh;

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

 enum SH_process_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_ClassLoaderDataGraph_oops_do,

   SH_PS_jvmti_oops_do,

   SH_PS_CodeCache_oops_do,

   // Leave this one last.

   SH_PS_NumElements

 };

 SharedHeap::SharedHeap(CollectorPolicy* policy_) :

   CollectedHeap(),

   _collector_policy(policy_),

   _rem_set(NULL),

   _strong_roots_scope(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 && (CMSParallelInitialMarkEnabled ||

                               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);

 }

 void SharedHeap::set_par_threads(uint t) {

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

   _n_par_threads = t;

   _process_strong_tasks->set_n_threads(t);

 }

 #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

 SharedHeap::StrongRootsScope* SharedHeap::active_strong_roots_scope() const {

   return _strong_roots_scope;

 }

 void SharedHeap::register_strong_roots_scope(SharedHeap::StrongRootsScope* scope) {

   assert(_strong_roots_scope == NULL, "Should only have one StrongRootsScope active");

   assert(scope != NULL, "Illegal argument");

   _strong_roots_scope = scope;

 }

 void SharedHeap::unregister_strong_roots_scope(SharedHeap::StrongRootsScope* scope) {

   assert(_strong_roots_scope == scope, "Wrong scope unregistered");

   _strong_roots_scope = NULL;

 }

 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* heap, bool activate)

   : MarkScope(activate), _sh(heap), _n_workers_done_with_threads(0)

 {

   if (_active) {

     _sh->register_strong_roots_scope(this);

     _sh->change_strong_roots_parity();

     // Zero the claimed high water mark in the StringTable

     StringTable::clear_parallel_claimed_index();

   }

 }

 SharedHeap::StrongRootsScope::~StrongRootsScope() {

   if (_active) {

     _sh->unregister_strong_roots_scope(this);

   }

 }

 Monitor* SharedHeap::StrongRootsScope::_lock = new Monitor(Mutex::leaf, "StrongRootsScope lock", false);

 void SharedHeap::StrongRootsScope::mark_worker_done_with_threads(uint n_workers) {

   // The Thread work barrier is only needed by G1 Class Unloading.

   // No need to use the barrier if this is single-threaded code.

   if (UseG1GC && ClassUnloadingWithConcurrentMark && n_workers > 0) {

     uint new_value = (uint)Atomic::add(1, &_n_workers_done_with_threads);

     if (new_value == n_workers) {

       // This thread is last. Notify the others.

       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);

       _lock->notify_all();

     }

   }

 }

 void SharedHeap::StrongRootsScope::wait_until_all_workers_done_with_threads(uint n_workers) {

   assert(UseG1GC,                          "Currently only used by G1");

   assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");

   // No need to use the barrier if this is single-threaded code.

   if (n_workers > 0 && (uint)_n_workers_done_with_threads != n_workers) {

     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);

     while ((uint)_n_workers_done_with_threads != n_workers) {

       _lock->wait(Mutex::_no_safepoint_check_flag, 0, false);

     }

   }

 }

 void SharedHeap::process_roots(bool activate_scope,

                                ScanningOption so,

                                OopClosure* strong_roots,

                                OopClosure* weak_roots,

                                CLDClosure* strong_cld_closure,

                                CLDClosure* weak_cld_closure,

                                CodeBlobClosure* code_roots) {

   StrongRootsScope srs(this, activate_scope);

   // General roots.

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

   assert(code_roots != NULL, "code root closure should always be set");

   // _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.

   // Iterating over the CLDG and the Threads are done early to allow G1 to

   // first process the strong CLDs and nmethods and then, after a barrier,

   // let the thread process the weak CLDs and nmethods.

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

     ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);

   }

   // Some CLDs contained in the thread frames should be considered strong.

   // Don't process them if they will be processed during the ClassLoaderDataGraph phase.

   CLDClosure* roots_from_clds_p = (strong_cld_closure != weak_cld_closure) ? strong_cld_closure : NULL;

   // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway

   CodeBlobClosure* roots_from_code_p = (so & SO_AllCodeCache) ? NULL : code_roots;

   Threads::possibly_parallel_oops_do(strong_roots, roots_from_clds_p, roots_from_code_p);

   // This is the point where this worker thread will not find more strong CLDs/nmethods.

   // Report this so G1 can synchronize the strong and weak CLDs/nmethods processing.

   active_strong_roots_scope()->mark_worker_done_with_threads(n_par_threads());

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

     Universe::oops_do(strong_roots);

   }

   // Global (strong) JNI handles

   if (!_process_strong_tasks->is_task_claimed(SH_PS_JNIHandles_oops_do))

     JNIHandles::oops_do(strong_roots);

   if (!_process_strong_tasks-> is_task_claimed(SH_PS_ObjectSynchronizer_oops_do))

     ObjectSynchronizer::oops_do(strong_roots);

   if (!_process_strong_tasks->is_task_claimed(SH_PS_FlatProfiler_oops_do))

     FlatProfiler::oops_do(strong_roots);

   if (!_process_strong_tasks->is_task_claimed(SH_PS_Management_oops_do))

     Management::oops_do(strong_roots);

   if (!_process_strong_tasks->is_task_claimed(SH_PS_jvmti_oops_do))

     JvmtiExport::oops_do(strong_roots);

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

     SystemDictionary::roots_oops_do(strong_roots, weak_roots);

   }

   // All threads execute the following. A specific chunk of buckets

   // from the StringTable are the individual tasks.

   if (weak_roots != NULL) {

     if (CollectedHeap::use_parallel_gc_threads()) {

       StringTable::possibly_parallel_oops_do(weak_roots);

     } else {

       StringTable::oops_do(weak_roots);

     }

   }

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

     if (so & SO_ScavengeCodeCache) {

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

       // We only visit parts of the CodeCache when scavenging.

       CodeCache::scavenge_root_nmethods_do(code_roots);

     }

     if (so & SO_AllCodeCache) {

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

       // CMSCollector uses this to do intermediate-strength collections.

       // We scan the entire code cache, since CodeCache::do_unloading is not called.

       CodeCache::blobs_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, !CodeBlobToOopClosure::FixRelocations));

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

   }

   _process_strong_tasks->all_tasks_completed();

 }

 void SharedHeap::process_all_roots(bool activate_scope,

                                    ScanningOption so,

                                    OopClosure* roots,

                                    CLDClosure* cld_closure,

                                    CodeBlobClosure* code_closure) {

   process_roots(activate_scope, so,

                 roots, roots,

                 cld_closure, cld_closure,

                 code_closure);

 }

 void SharedHeap::process_strong_roots(bool activate_scope,

                                       ScanningOption so,

                                       OopClosure* roots,

                                       CLDClosure* cld_closure,

                                       CodeBlobClosure* code_closure) {

   process_roots(activate_scope, so,

                 roots, NULL,

                 cld_closure, NULL,

                 code_closure);

 }

 class AlwaysTrueClosure: public BoolObjectClosure {

 public:

   bool do_object_b(oop p) { return true; }

 };

 static AlwaysTrueClosure always_true;

 void SharedHeap::process_weak_roots(OopClosure* root_closure) {

   // Global (weak) JNI handles

   JNIHandles::weak_oops_do(&always_true, 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() {

   CollectedHeap::post_initialize();

   ref_processing_init();

 }

 void SharedHeap::ref_processing_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));

 }