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 /*

  * Copyright (c) 2005, 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

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"

 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"

 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"

 #include "gc_implementation/shared/gcTimer.hpp"

 #include "gc_implementation/shared/gcTraceTime.hpp"

 #include "gc_implementation/shared/isGCActiveMark.hpp"

 #include "memory/gcLocker.inline.hpp"

 #include "runtime/interfaceSupport.hpp"

 #include "runtime/os.hpp"

 #include "utilities/dtrace.hpp"

 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC

 #ifndef USDT2

 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__begin);

 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__end);

 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__begin);

 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__end);

 #endif /* !USDT2 */

 //////////////////////////////////////////////////////////

 // Methods in abstract class VM_CMS_Operation

 //////////////////////////////////////////////////////////

 void VM_CMS_Operation::acquire_pending_list_lock() {

   // The caller may block while communicating

   // with the SLT thread in order to acquire/release the PLL.

   ConcurrentMarkSweepThread::slt()->

     manipulatePLL(SurrogateLockerThread::acquirePLL);

 }

 void VM_CMS_Operation::release_and_notify_pending_list_lock() {

   // The caller may block while communicating

   // with the SLT thread in order to acquire/release the PLL.

   ConcurrentMarkSweepThread::slt()->

     manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);

 }

 void VM_CMS_Operation::verify_before_gc() {

   if (VerifyBeforeGC &&

       GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {

     GCTraceTime tm("Verify Before", false, false, _collector->_gc_timer_cm);

     HandleMark hm;

     FreelistLocker x(_collector);

     MutexLockerEx  y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);

     Universe::heap()->prepare_for_verify();

     Universe::verify();

   }

 }

 void VM_CMS_Operation::verify_after_gc() {

   if (VerifyAfterGC &&

       GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {

     GCTraceTime tm("Verify After", false, false, _collector->_gc_timer_cm);

     HandleMark hm;

     FreelistLocker x(_collector);

     MutexLockerEx  y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);

     Universe::verify();

   }

 }

 bool VM_CMS_Operation::lost_race() const {

   if (CMSCollector::abstract_state() == CMSCollector::Idling) {

     // We lost a race to a foreground collection

     // -- there's nothing to do

     return true;

   }

   assert(CMSCollector::abstract_state() == legal_state(),

          "Inconsistent collector state?");

   return false;

 }

 bool VM_CMS_Operation::doit_prologue() {

   assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");

   assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");

   assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),

          "Possible deadlock");

   if (needs_pll()) {

     acquire_pending_list_lock();

   }

   // Get the Heap_lock after the pending_list_lock.

   Heap_lock->lock();

   if (lost_race()) {

     assert(_prologue_succeeded == false, "Initialized in c'tor");

     Heap_lock->unlock();

     if (needs_pll()) {

       release_and_notify_pending_list_lock();

     }

   } else {

     _prologue_succeeded = true;

   }

   return _prologue_succeeded;

 }

 void VM_CMS_Operation::doit_epilogue() {

   assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");

   assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");

   assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),

          "Possible deadlock");

   // Release the Heap_lock first.

   Heap_lock->unlock();

   if (needs_pll()) {

     release_and_notify_pending_list_lock();

   }

 }

 //////////////////////////////////////////////////////////

 // Methods in class VM_CMS_Initial_Mark

 //////////////////////////////////////////////////////////

 void VM_CMS_Initial_Mark::doit() {

   if (lost_race()) {

     // Nothing to do.

     return;

   }

 #ifndef USDT2

   HS_DTRACE_PROBE(hs_private, cms__initmark__begin);

 #else /* USDT2 */

   HS_PRIVATE_CMS_INITMARK_BEGIN(

                                 );

 #endif /* USDT2 */

   _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark");

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);

   VM_CMS_Operation::verify_before_gc();

   IsGCActiveMark x; // stop-world GC active

   _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause());

   VM_CMS_Operation::verify_after_gc();

   _collector->_gc_timer_cm->register_gc_pause_end();

 #ifndef USDT2

   HS_DTRACE_PROBE(hs_private, cms__initmark__end);

 #else /* USDT2 */

   HS_PRIVATE_CMS_INITMARK_END(

                                 );

 #endif /* USDT2 */

 }

 //////////////////////////////////////////////////////////

 // Methods in class VM_CMS_Final_Remark_Operation

 //////////////////////////////////////////////////////////

 void VM_CMS_Final_Remark::doit() {

   if (lost_race()) {

     // Nothing to do.

     return;

   }

 #ifndef USDT2

   HS_DTRACE_PROBE(hs_private, cms__remark__begin);

 #else /* USDT2 */

   HS_PRIVATE_CMS_REMARK_BEGIN(

                                 );

 #endif /* USDT2 */

   _collector->_gc_timer_cm->register_gc_pause_start("Final Mark");

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   GCCauseSetter gccs(gch, GCCause::_cms_final_remark);

   VM_CMS_Operation::verify_before_gc();

   IsGCActiveMark x; // stop-world GC active

   _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause());

   VM_CMS_Operation::verify_after_gc();

   _collector->save_heap_summary();

   _collector->_gc_timer_cm->register_gc_pause_end();

 #ifndef USDT2

   HS_DTRACE_PROBE(hs_private, cms__remark__end);

 #else /* USDT2 */

   HS_PRIVATE_CMS_REMARK_END(

                                 );

 #endif /* USDT2 */

 }

 // VM operation to invoke a concurrent collection of a

 // GenCollectedHeap heap.

 void VM_GenCollectFullConcurrent::doit() {

   assert(Thread::current()->is_VM_thread(), "Should be VM thread");

   assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   if (_gc_count_before == gch->total_collections()) {

     // The "full" of do_full_collection call below "forces"

     // a collection; the second arg, 0, below ensures that

     // only the young gen is collected. XXX In the future,

     // we'll probably need to have something in this interface

     // to say do this only if we are sure we will not bail

     // out to a full collection in this attempt, but that's

     // for the future.

     assert(SafepointSynchronize::is_at_safepoint(),

       "We can only be executing this arm of if at a safepoint");

     GCCauseSetter gccs(gch, _gc_cause);

     gch->do_full_collection(gch->must_clear_all_soft_refs(),

                             0 /* collect only youngest gen */);

   } // Else no need for a foreground young gc

   assert((_gc_count_before < gch->total_collections()) ||

          (GC_locker::is_active() /* gc may have been skipped */

           && (_gc_count_before == gch->total_collections())),

          "total_collections() should be monotonically increasing");

   MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);

   assert(_full_gc_count_before <= gch->total_full_collections(), "Error");

   if (gch->total_full_collections() == _full_gc_count_before) {

     // Disable iCMS until the full collection is done, and

     // remember that we did so.

     CMSCollector::disable_icms();

     _disabled_icms = true;

     // In case CMS thread was in icms_wait(), wake it up.

     CMSCollector::start_icms();

     // Nudge the CMS thread to start a concurrent collection.

     CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause);

   } else {

     assert(_full_gc_count_before < gch->total_full_collections(), "Error");

     FullGCCount_lock->notify_all();  // Inform the Java thread its work is done

   }

 }

 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {

   Thread* thr = Thread::current();

   assert(thr != NULL, "Unexpected tid");

   if (!thr->is_Java_thread()) {

     assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");

     GenCollectedHeap* gch = GenCollectedHeap::heap();

     if (_gc_count_before != gch->total_collections()) {

       // No need to do a young gc, we'll just nudge the CMS thread

       // in the doit() method above, to be executed soon.

       assert(_gc_count_before < gch->total_collections(),

              "total_collections() should be monotnically increasing");

       return false;  // no need for foreground young gc

     }

   }

   return true;       // may still need foreground young gc

 }

 void VM_GenCollectFullConcurrent::doit_epilogue() {

   Thread* thr = Thread::current();

   assert(thr->is_Java_thread(), "just checking");

   JavaThread* jt = (JavaThread*)thr;

   // Release the Heap_lock first.

   Heap_lock->unlock();

   release_and_notify_pending_list_lock();

   // It is fine to test whether completed collections has

   // exceeded our request count without locking because

   // the completion count is monotonically increasing;

   // this will break for very long-running apps when the

   // count overflows and wraps around. XXX fix me !!!

   // e.g. at the rate of 1 full gc per ms, this could

   // overflow in about 1000 years.

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   if (_gc_cause != GCCause::_gc_locker &&

       gch->total_full_collections_completed() <= _full_gc_count_before) {

     // maybe we should change the condition to test _gc_cause ==

     // GCCause::_java_lang_system_gc, instead of

     // _gc_cause != GCCause::_gc_locker

     assert(_gc_cause == GCCause::_java_lang_system_gc,

            "the only way to get here if this was a System.gc()-induced GC");

     assert(ExplicitGCInvokesConcurrent, "Error");

     // Now, wait for witnessing concurrent gc cycle to complete,

     // but do so in native mode, because we want to lock the

     // FullGCEvent_lock, which may be needed by the VM thread

     // or by the CMS thread, so we do not want to be suspended

     // while holding that lock.

     ThreadToNativeFromVM native(jt);

     MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);

     // Either a concurrent or a stop-world full gc is sufficient

     // witness to our request.

     while (gch->total_full_collections_completed() <= _full_gc_count_before) {

       FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);

     }

   }

   // Enable iCMS back if we disabled it earlier.

   if (_disabled_icms) {

     CMSCollector::enable_icms();

   }

 }