1 /*
   2  * Copyright (c) 2005, 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/classLoader.hpp"
  27 #include "classfile/javaClasses.hpp"
  28 #include "gc_implementation/shared/vmGCOperations.hpp"
  29 #include "memory/gcLocker.inline.hpp"
  30 #include "memory/genCollectedHeap.hpp"
  31 #include "memory/oopFactory.hpp"
  32 #include "oops/instanceKlass.hpp"
  33 #include "oops/instanceRefKlass.hpp"
  34 #include "runtime/handles.inline.hpp"
  35 #include "runtime/init.hpp"
  36 #include "runtime/interfaceSupport.hpp"
  37 #include "utilities/dtrace.hpp"
  38 #include "utilities/preserveException.hpp"
  39 #ifndef SERIALGC
  40 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  41 #endif
  42 
  43 HS_DTRACE_PROBE_DECL1(hotspot, gc__begin, bool);
  44 HS_DTRACE_PROBE_DECL(hotspot, gc__end);
  45 
  46 // The same dtrace probe can't be inserted in two different files, so we
  47 // have to call it here, so it's only in one file.  Can't create new probes
  48 // for the other file anymore.   The dtrace probes have to remain stable.
  49 void VM_GC_Operation::notify_gc_begin(bool full) {
  50   HS_DTRACE_PROBE1(hotspot, gc__begin, full);
  51   HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
  52 }
  53 
  54 void VM_GC_Operation::notify_gc_end() {
  55   HS_DTRACE_PROBE(hotspot, gc__end);
  56   HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
  57 }
  58 
  59 void VM_GC_Operation::acquire_pending_list_lock() {
  60   // we may enter this with pending exception set
  61   instanceRefKlass::acquire_pending_list_lock(&_pending_list_basic_lock);
  62 }
  63 
  64 
  65 void VM_GC_Operation::release_and_notify_pending_list_lock() {
  66 
  67   instanceRefKlass::release_and_notify_pending_list_lock(&_pending_list_basic_lock);
  68 }
  69 
  70 // Allocations may fail in several threads at about the same time,
  71 // resulting in multiple gc requests.  We only want to do one of them.
  72 // In case a GC locker is active and the need for a GC is already signalled,
  73 // we want to skip this GC attempt altogether, without doing a futile
  74 // safepoint operation.
  75 bool VM_GC_Operation::skip_operation() const {
  76   bool skip = (_gc_count_before != Universe::heap()->total_collections());
  77   if (_full && skip) {
  78     skip = (_full_gc_count_before != Universe::heap()->total_full_collections());
  79   }
  80   if (!skip && GC_locker::is_active_and_needs_gc()) {
  81     skip = Universe::heap()->is_maximal_no_gc();
  82     assert(!(skip && (_gc_cause == GCCause::_gc_locker)),
  83            "GC_locker cannot be active when initiating GC");
  84   }
  85   return skip;
  86 }
  87 
  88 bool VM_GC_Operation::doit_prologue() {
  89   assert(Thread::current()->is_Java_thread(), "just checking");
  90   assert(((_gc_cause != GCCause::_no_gc) &&
  91           (_gc_cause != GCCause::_no_cause_specified)), "Illegal GCCause");
  92 
  93   acquire_pending_list_lock();
  94   // If the GC count has changed someone beat us to the collection
  95   // Get the Heap_lock after the pending_list_lock.
  96   Heap_lock->lock();
  97 
  98   // Check invocations
  99   if (skip_operation()) {
 100     // skip collection
 101     Heap_lock->unlock();
 102     release_and_notify_pending_list_lock();
 103     _prologue_succeeded = false;
 104   } else {
 105     _prologue_succeeded = true;
 106     SharedHeap* sh = SharedHeap::heap();
 107     if (sh != NULL) sh->_thread_holds_heap_lock_for_gc = true;
 108   }
 109   return _prologue_succeeded;
 110 }
 111 
 112 
 113 void VM_GC_Operation::doit_epilogue() {
 114   assert(Thread::current()->is_Java_thread(), "just checking");
 115   // Release the Heap_lock first.
 116   SharedHeap* sh = SharedHeap::heap();
 117   if (sh != NULL) sh->_thread_holds_heap_lock_for_gc = false;
 118   Heap_lock->unlock();
 119   release_and_notify_pending_list_lock();
 120 }
 121 
 122 bool VM_GC_HeapInspection::doit_prologue() {
 123   if (Universe::heap()->supports_heap_inspection()) {
 124     return VM_GC_Operation::doit_prologue();
 125   } else {
 126     return false;
 127   }
 128 }
 129 
 130 bool VM_GC_HeapInspection::skip_operation() const {
 131   assert(Universe::heap()->supports_heap_inspection(), "huh?");
 132   return false;
 133 }
 134 
 135 void VM_GC_HeapInspection::doit() {
 136   HandleMark hm;
 137   CollectedHeap* ch = Universe::heap();
 138   ch->ensure_parsability(false); // must happen, even if collection does
 139                                  // not happen (e.g. due to GC_locker)
 140   if (_full_gc) {
 141     // The collection attempt below would be skipped anyway if
 142     // the gc locker is held. The following dump may then be a tad
 143     // misleading to someone expecting only live objects to show
 144     // up in the dump (see CR 6944195). Just issue a suitable warning
 145     // in that case and do not attempt to do a collection.
 146     // The latter is a subtle point, because even a failed attempt
 147     // to GC will, in fact, induce one in the future, which we
 148     // probably want to avoid in this case because the GC that we may
 149     // be about to attempt holds value for us only
 150     // if it happens now and not if it happens in the eventual
 151     // future.
 152     if (GC_locker::is_active()) {
 153       warning("GC locker is held; pre-dump GC was skipped");
 154     } else {
 155       ch->collect_as_vm_thread(GCCause::_heap_inspection);
 156     }
 157   }
 158   HeapInspection::heap_inspection(_out, _need_prologue /* need_prologue */);
 159 }
 160 
 161 
 162 void VM_GenCollectForAllocation::doit() {
 163   SvcGCMarker sgcm(SvcGCMarker::MINOR);
 164 
 165   GenCollectedHeap* gch = GenCollectedHeap::heap();
 166   GCCauseSetter gccs(gch, _gc_cause);
 167   _res = gch->satisfy_failed_allocation(_size, _tlab);
 168   assert(gch->is_in_reserved_or_null(_res), "result not in heap");
 169 
 170   if (_res == NULL && GC_locker::is_active_and_needs_gc()) {
 171     set_gc_locked();
 172   }
 173 }
 174 
 175 void VM_GenCollectFull::doit() {
 176   SvcGCMarker sgcm(SvcGCMarker::FULL);
 177 
 178   GenCollectedHeap* gch = GenCollectedHeap::heap();
 179   GCCauseSetter gccs(gch, _gc_cause);
 180   gch->do_full_collection(gch->must_clear_all_soft_refs(), _max_level);
 181 }
 182 
 183 void VM_GenCollectForPermanentAllocation::doit() {
 184   SvcGCMarker sgcm(SvcGCMarker::FULL);
 185 
 186   SharedHeap* heap = (SharedHeap*)Universe::heap();
 187   GCCauseSetter gccs(heap, _gc_cause);
 188   switch (heap->kind()) {
 189     case (CollectedHeap::GenCollectedHeap): {
 190       GenCollectedHeap* gch = (GenCollectedHeap*)heap;
 191       gch->do_full_collection(gch->must_clear_all_soft_refs(),
 192                               gch->n_gens() - 1);
 193       break;
 194     }
 195 #ifndef SERIALGC
 196     case (CollectedHeap::G1CollectedHeap): {
 197       G1CollectedHeap* g1h = (G1CollectedHeap*)heap;
 198       g1h->do_full_collection(_gc_cause == GCCause::_last_ditch_collection);
 199       break;
 200     }
 201 #endif // SERIALGC
 202     default:
 203       ShouldNotReachHere();
 204   }
 205   _res = heap->perm_gen()->allocate(_size, false);
 206   assert(heap->is_in_reserved_or_null(_res), "result not in heap");
 207   if (_res == NULL && GC_locker::is_active_and_needs_gc()) {
 208     set_gc_locked();
 209   }
 210 }