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 /*

  * Copyright (c) 2001, 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

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  */

 #include "precompiled.hpp"

 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"

 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"

 #include "gc_implementation/g1/g1CollectorPolicy.hpp"

 #include "gc_implementation/g1/vm_operations_g1.hpp"

 #include "gc_implementation/shared/isGCActiveMark.hpp"

 #include "gc_implementation/g1/vm_operations_g1.hpp"

 #include "runtime/interfaceSupport.hpp"

 VM_G1CollectForAllocation::VM_G1CollectForAllocation(

                                                   unsigned int gc_count_before,

                                                   size_t word_size)

   : VM_G1OperationWithAllocRequest(gc_count_before, word_size,

                                    GCCause::_allocation_failure) {

   guarantee(word_size > 0, "an allocation should always be requested");

 }

 void VM_G1CollectForAllocation::doit() {

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   _result = g1h->satisfy_failed_allocation(_word_size, &_pause_succeeded);

   assert(_result == NULL || _pause_succeeded,

          "if we get back a result, the pause should have succeeded");

 }

 void VM_G1CollectFull::doit() {

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   GCCauseSetter x(g1h, _gc_cause);

   g1h->do_full_collection(false /* clear_all_soft_refs */);

 }

 VM_G1IncCollectionPause::VM_G1IncCollectionPause(

                                       unsigned int   gc_count_before,

                                       size_t         word_size,

                                       bool           should_initiate_conc_mark,

                                       double         target_pause_time_ms,

                                       GCCause::Cause gc_cause)

   : VM_G1OperationWithAllocRequest(gc_count_before, word_size, gc_cause),

     _should_initiate_conc_mark(should_initiate_conc_mark),

     _target_pause_time_ms(target_pause_time_ms),

     _should_retry_gc(false),

     _full_collections_completed_before(0) {

   guarantee(target_pause_time_ms > 0.0,

             err_msg("target_pause_time_ms = %1.6lf should be positive",

                     target_pause_time_ms));

   guarantee(word_size == 0 || gc_cause == GCCause::_g1_inc_collection_pause,

             "we can only request an allocation if the GC cause is for "

             "an incremental GC pause");

   _gc_cause = gc_cause;

 }

 bool VM_G1IncCollectionPause::doit_prologue() {

   bool res = VM_GC_Operation::doit_prologue();

   if (!res) {

     if (_should_initiate_conc_mark) {

       // The prologue can fail for a couple of reasons. The first is that another GC

       // got scheduled and prevented the scheduling of the initial mark GC. The

       // second is that the GC locker may be active and the heap can't be expanded.

       // In both cases we want to retry the GC so that the initial mark pause is

       // actually scheduled. In the second case, however, we should stall until

       // until the GC locker is no longer active and then retry the initial mark GC.

       _should_retry_gc = true;

     }

   }

   return res;

 }

 void VM_G1IncCollectionPause::doit() {

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   assert(!_should_initiate_conc_mark ||

   ((_gc_cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||

    (_gc_cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent) ||

     _gc_cause == GCCause::_g1_humongous_allocation),

          "only a GC locker, a System.gc() or a hum allocation induced GC should start a cycle");

   if (_word_size > 0) {

     // An allocation has been requested. So, try to do that first.

     _result = g1h->attempt_allocation_at_safepoint(_word_size,

                                      false /* expect_null_cur_alloc_region */);

     if (_result != NULL) {

       // If we can successfully allocate before we actually do the

       // pause then we will consider this pause successful.

       _pause_succeeded = true;

       return;

     }

   }

   GCCauseSetter x(g1h, _gc_cause);

   if (_should_initiate_conc_mark) {

     // It's safer to read full_collections_completed() here, given

     // that noone else will be updating it concurrently. Since we'll

     // only need it if we're initiating a marking cycle, no point in

     // setting it earlier.

     _full_collections_completed_before = g1h->full_collections_completed();

     // At this point we are supposed to start a concurrent cycle. We

     // will do so if one is not already in progress.

     bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);

     // The above routine returns true if we were able to force the

     // next GC pause to be an initial mark; it returns false if a

     // marking cycle is already in progress.

     //

     // If a marking cycle is already in progress just return and skip the

     // pause below - if the reason for requesting this initial mark pause

     // was due to a System.gc() then the requesting thread should block in

     // doit_epilogue() until the marking cycle is complete.

     //

     // If this initial mark pause was requested as part of a humongous

     // allocation then we know that the marking cycle must just have

     // been started by another thread (possibly also allocating a humongous

     // object) as there was no active marking cycle when the requesting

     // thread checked before calling collect() in

     // attempt_allocation_humongous(). Retrying the GC, in this case,

     // will cause the requesting thread to spin inside collect() until the

     // just started marking cycle is complete - which may be a while. So

     // we do NOT retry the GC.

     if (!res) {

       assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");

       if (_gc_cause != GCCause::_g1_humongous_allocation) {

         _should_retry_gc = true;

       }

       return;

     }

   }

   _pause_succeeded =

     g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);

   if (_pause_succeeded && _word_size > 0) {

     // An allocation had been requested.

     _result = g1h->attempt_allocation_at_safepoint(_word_size,

                                       true /* expect_null_cur_alloc_region */);

   } else {

     assert(_result == NULL, "invariant");

     if (!_pause_succeeded) {

       // Another possible reason reason for the pause to not be successful

       // is that, again, the GC locker is active (and has become active

       // since the prologue was executed). In this case we should retry

       // the pause after waiting for the GC locker to become inactive.

       _should_retry_gc = true;

     }

   }

 }

 void VM_G1IncCollectionPause::doit_epilogue() {

   VM_GC_Operation::doit_epilogue();

   // If the pause was initiated by a System.gc() and

   // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle

   // that just started (or maybe one that was already in progress) to

   // finish.

   if (_gc_cause == GCCause::_java_lang_system_gc &&

       _should_initiate_conc_mark) {

     assert(ExplicitGCInvokesConcurrent,

            "the only way to be here is if ExplicitGCInvokesConcurrent is set");

     G1CollectedHeap* g1h = G1CollectedHeap::heap();

     // In the doit() method we saved g1h->full_collections_completed()

     // in the _full_collections_completed_before field. We have to

     // wait until we observe that g1h->full_collections_completed()

     // has increased by at least one. This can happen if a) we started

     // a cycle and it completes, b) a cycle already in progress

     // completes, or c) a Full GC happens.

     // If the condition has already been reached, there's no point in

     // actually taking the lock and doing the wait.

     if (g1h->full_collections_completed() <=

                                           _full_collections_completed_before) {

       // The following is largely copied from CMS

       Thread* thr = Thread::current();

       assert(thr->is_Java_thread(), "invariant");

       JavaThread* jt = (JavaThread*)thr;

       ThreadToNativeFromVM native(jt);

       MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);

       while (g1h->full_collections_completed() <=

                                           _full_collections_completed_before) {

         FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);

       }

     }

   }

 }

 void VM_CGC_Operation::acquire_pending_list_lock() {

   assert(_needs_pll, "don't call this otherwise");

   // The caller may block while communicating

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

   ConcurrentMarkThread::slt()->

     manipulatePLL(SurrogateLockerThread::acquirePLL);

 }

 void VM_CGC_Operation::release_and_notify_pending_list_lock() {

   assert(_needs_pll, "don't call this otherwise");

   // The caller may block while communicating

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

   ConcurrentMarkThread::slt()->

     manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);

 }

 void VM_CGC_Operation::doit() {

   gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);

   TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);

   TraceTime t(_printGCMessage, PrintGC, true, gclog_or_tty);

   SharedHeap* sh = SharedHeap::heap();

   // This could go away if CollectedHeap gave access to _gc_is_active...

   if (sh != NULL) {

     IsGCActiveMark x;

     _cl->do_void();

   } else {

     _cl->do_void();

   }

 }

 bool VM_CGC_Operation::doit_prologue() {

   // Note the relative order of the locks must match that in

   // VM_GC_Operation::doit_prologue() or deadlocks can occur

   if (_needs_pll) {

     acquire_pending_list_lock();

   }

   Heap_lock->lock();

   SharedHeap::heap()->_thread_holds_heap_lock_for_gc = true;

   return true;

 }

 void VM_CGC_Operation::doit_epilogue() {

   // Note the relative order of the unlocks must match that in

   // VM_GC_Operation::doit_epilogue()

   SharedHeap::heap()->_thread_holds_heap_lock_for_gc = false;

   Heap_lock->unlock();

   if (_needs_pll) {

     release_and_notify_pending_list_lock();

   }

 }