1 /*
   2  * Copyright (c) 2005, 2014, 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 "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
  27 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  28 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"
  29 #include "gc_implementation/shared/gcTimer.hpp"
  30 #include "gc_implementation/shared/gcTraceTime.hpp"
  31 #include "gc_implementation/shared/isGCActiveMark.hpp"
  32 #include "memory/gcLocker.inline.hpp"
  33 #include "runtime/interfaceSupport.hpp"
  34 #include "runtime/os.hpp"
  35 #include "utilities/dtrace.hpp"
  36 
  37 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  38 
  39 #ifndef USDT2
  40 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__begin);
  41 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__end);
  42 
  43 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__begin);
  44 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__end);
  45 #endif /* !USDT2 */
  46 
  47 //////////////////////////////////////////////////////////
  48 // Methods in abstract class VM_CMS_Operation
  49 //////////////////////////////////////////////////////////
  50 void VM_CMS_Operation::acquire_pending_list_lock() {
  51   // The caller may block while communicating
  52   // with the SLT thread in order to acquire/release the PLL.
  53   SurrogateLockerThread* slt = ConcurrentMarkSweepThread::slt();
  54   if (slt != NULL) {
  55     slt->manipulatePLL(SurrogateLockerThread::acquirePLL);
  56   } else {
  57     SurrogateLockerThread::report_missing_slt();
  58   }
  59 }
  60 
  61 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
  62   // The caller may block while communicating
  63   // with the SLT thread in order to acquire/release the PLL.
  64   ConcurrentMarkSweepThread::slt()->
  65     manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
  66 }
  67 
  68 void VM_CMS_Operation::verify_before_gc() {
  69   if (VerifyBeforeGC &&
  70       GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
  71     GCTraceTime tm("Verify Before", false, false, _collector->_gc_timer_cm, _collector->_gc_tracer_cm->gc_id());
  72     HandleMark hm;
  73     FreelistLocker x(_collector);
  74     MutexLockerEx  y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
  75     Universe::heap()->prepare_for_verify();
  76     Universe::verify();
  77   }
  78 }
  79 
  80 void VM_CMS_Operation::verify_after_gc() {
  81   if (VerifyAfterGC &&
  82       GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
  83     GCTraceTime tm("Verify After", false, false, _collector->_gc_timer_cm, _collector->_gc_tracer_cm->gc_id());
  84     HandleMark hm;
  85     FreelistLocker x(_collector);
  86     MutexLockerEx  y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
  87     Universe::verify();
  88   }
  89 }
  90 
  91 bool VM_CMS_Operation::lost_race() const {
  92   if (CMSCollector::abstract_state() == CMSCollector::Idling) {
  93     // We lost a race to a foreground collection
  94     // -- there's nothing to do
  95     return true;
  96   }
  97   assert(CMSCollector::abstract_state() == legal_state(),
  98          "Inconsistent collector state?");
  99   return false;
 100 }
 101 
 102 bool VM_CMS_Operation::doit_prologue() {
 103   assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
 104   assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
 105   assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
 106          "Possible deadlock");
 107 
 108   if (needs_pll()) {
 109     acquire_pending_list_lock();
 110   }
 111   // Get the Heap_lock after the pending_list_lock.
 112   Heap_lock->lock();
 113   if (lost_race()) {
 114     assert(_prologue_succeeded == false, "Initialized in c'tor");
 115     Heap_lock->unlock();
 116     if (needs_pll()) {
 117       release_and_notify_pending_list_lock();
 118     }
 119   } else {
 120     _prologue_succeeded = true;
 121   }
 122   return _prologue_succeeded;
 123 }
 124 
 125 void VM_CMS_Operation::doit_epilogue() {
 126   assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
 127   assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
 128   assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
 129          "Possible deadlock");
 130 
 131   // Release the Heap_lock first.
 132   Heap_lock->unlock();
 133   if (needs_pll()) {
 134     release_and_notify_pending_list_lock();
 135   }
 136 }
 137 
 138 //////////////////////////////////////////////////////////
 139 // Methods in class VM_CMS_Initial_Mark
 140 //////////////////////////////////////////////////////////
 141 void VM_CMS_Initial_Mark::doit() {
 142   if (lost_race()) {
 143     // Nothing to do.
 144     return;
 145   }
 146 #ifndef USDT2
 147   HS_DTRACE_PROBE(hs_private, cms__initmark__begin);
 148 #else /* USDT2 */
 149   HS_PRIVATE_CMS_INITMARK_BEGIN(
 150                                 );
 151 #endif /* USDT2 */
 152 
 153   _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark");
 154 
 155   GenCollectedHeap* gch = GenCollectedHeap::heap();
 156   GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
 157 
 158   VM_CMS_Operation::verify_before_gc();
 159 
 160   IsGCActiveMark x; // stop-world GC active
 161   _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause());
 162 
 163   VM_CMS_Operation::verify_after_gc();
 164 
 165   _collector->_gc_timer_cm->register_gc_pause_end();
 166 
 167 #ifndef USDT2
 168   HS_DTRACE_PROBE(hs_private, cms__initmark__end);
 169 #else /* USDT2 */
 170   HS_PRIVATE_CMS_INITMARK_END(
 171                                 );
 172 #endif /* USDT2 */
 173 }
 174 
 175 //////////////////////////////////////////////////////////
 176 // Methods in class VM_CMS_Final_Remark_Operation
 177 //////////////////////////////////////////////////////////
 178 void VM_CMS_Final_Remark::doit() {
 179   if (lost_race()) {
 180     // Nothing to do.
 181     return;
 182   }
 183 #ifndef USDT2
 184   HS_DTRACE_PROBE(hs_private, cms__remark__begin);
 185 #else /* USDT2 */
 186   HS_PRIVATE_CMS_REMARK_BEGIN(
 187                                 );
 188 #endif /* USDT2 */
 189 
 190   _collector->_gc_timer_cm->register_gc_pause_start("Final Mark");
 191 
 192   GenCollectedHeap* gch = GenCollectedHeap::heap();
 193   GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
 194 
 195   VM_CMS_Operation::verify_before_gc();
 196 
 197   IsGCActiveMark x; // stop-world GC active
 198   _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause());
 199 
 200   VM_CMS_Operation::verify_after_gc();
 201 
 202   _collector->save_heap_summary();
 203   _collector->_gc_timer_cm->register_gc_pause_end();
 204 
 205 #ifndef USDT2
 206   HS_DTRACE_PROBE(hs_private, cms__remark__end);
 207 #else /* USDT2 */
 208   HS_PRIVATE_CMS_REMARK_END(
 209                                 );
 210 #endif /* USDT2 */
 211 }
 212 
 213 // VM operation to invoke a concurrent collection of a
 214 // GenCollectedHeap heap.
 215 void VM_GenCollectFullConcurrent::doit() {
 216   assert(Thread::current()->is_VM_thread(), "Should be VM thread");
 217   assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
 218 
 219   GenCollectedHeap* gch = GenCollectedHeap::heap();
 220   if (_gc_count_before == gch->total_collections()) {
 221     // The "full" of do_full_collection call below "forces"
 222     // a collection; the second arg, 0, below ensures that
 223     // only the young gen is collected. XXX In the future,
 224     // we'll probably need to have something in this interface
 225     // to say do this only if we are sure we will not bail
 226     // out to a full collection in this attempt, but that's
 227     // for the future.
 228     assert(SafepointSynchronize::is_at_safepoint(),
 229       "We can only be executing this arm of if at a safepoint");
 230     GCCauseSetter gccs(gch, _gc_cause);
 231     gch->do_full_collection(gch->must_clear_all_soft_refs(),
 232                             0 /* collect only youngest gen */);
 233   } // Else no need for a foreground young gc
 234   assert((_gc_count_before < gch->total_collections()) ||
 235          (GC_locker::is_active() /* gc may have been skipped */
 236           && (_gc_count_before == gch->total_collections())),
 237          "total_collections() should be monotonically increasing");
 238 
 239   MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 240   assert(_full_gc_count_before <= gch->total_full_collections(), "Error");
 241   if (gch->total_full_collections() == _full_gc_count_before) {
 242     // Disable iCMS until the full collection is done, and
 243     // remember that we did so.
 244     CMSCollector::disable_icms();
 245     _disabled_icms = true;
 246     // In case CMS thread was in icms_wait(), wake it up.
 247     CMSCollector::start_icms();
 248     // Nudge the CMS thread to start a concurrent collection.
 249     CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause);
 250   } else {
 251     assert(_full_gc_count_before < gch->total_full_collections(), "Error");
 252     FullGCCount_lock->notify_all();  // Inform the Java thread its work is done
 253   }
 254 }
 255 
 256 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
 257   Thread* thr = Thread::current();
 258   assert(thr != NULL, "Unexpected tid");
 259   if (!thr->is_Java_thread()) {
 260     assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
 261     GenCollectedHeap* gch = GenCollectedHeap::heap();
 262     if (_gc_count_before != gch->total_collections()) {
 263       // No need to do a young gc, we'll just nudge the CMS thread
 264       // in the doit() method above, to be executed soon.
 265       assert(_gc_count_before < gch->total_collections(),
 266              "total_collections() should be monotnically increasing");
 267       return false;  // no need for foreground young gc
 268     }
 269   }
 270   return true;       // may still need foreground young gc
 271 }
 272 
 273 
 274 void VM_GenCollectFullConcurrent::doit_epilogue() {
 275   Thread* thr = Thread::current();
 276   assert(thr->is_Java_thread(), "just checking");
 277   JavaThread* jt = (JavaThread*)thr;
 278   // Release the Heap_lock first.
 279   Heap_lock->unlock();
 280   release_and_notify_pending_list_lock();
 281 
 282   // It is fine to test whether completed collections has
 283   // exceeded our request count without locking because
 284   // the completion count is monotonically increasing;
 285   // this will break for very long-running apps when the
 286   // count overflows and wraps around. XXX fix me !!!
 287   // e.g. at the rate of 1 full gc per ms, this could
 288   // overflow in about 1000 years.
 289   GenCollectedHeap* gch = GenCollectedHeap::heap();
 290   if (_gc_cause != GCCause::_gc_locker &&
 291       gch->total_full_collections_completed() <= _full_gc_count_before) {
 292     // maybe we should change the condition to test _gc_cause ==
 293     // GCCause::_java_lang_system_gc or GCCause::_dcmd_gc_run,
 294     // instead of _gc_cause != GCCause::_gc_locker
 295     assert(GCCause::is_user_requested_gc(_gc_cause),
 296            "the only way to get here if this was a System.gc()-induced GC");
 297     assert(ExplicitGCInvokesConcurrent, "Error");
 298     // Now, wait for witnessing concurrent gc cycle to complete,
 299     // but do so in native mode, because we want to lock the
 300     // FullGCEvent_lock, which may be needed by the VM thread
 301     // or by the CMS thread, so we do not want to be suspended
 302     // while holding that lock.
 303     ThreadToNativeFromVM native(jt);
 304     MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 305     // Either a concurrent or a stop-world full gc is sufficient
 306     // witness to our request.
 307     while (gch->total_full_collections_completed() <= _full_gc_count_before) {
 308       FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
 309     }
 310   }
 311   // Enable iCMS back if we disabled it earlier.
 312   if (_disabled_icms) {
 313     CMSCollector::enable_icms();
 314   }
 315 }