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hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/vmCMSOperations.cpp

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+/*
+ * Copyright 2005-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+# include "incls/_precompiled.incl"
+# include "incls/_vmCMSOperations.cpp.incl"
+
+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);
+
+//////////////////////////////////////////////////////////
+// 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) {
+    HandleMark hm;
+    FreelistLocker x(_collector);
+    MutexLockerEx  y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
+    Universe::heap()->prepare_for_verify();
+    Universe::verify(true);
+  }
+}
+
+void VM_CMS_Operation::verify_after_gc() {
+  if (VerifyAfterGC &&
+      GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
+    HandleMark hm;
+    FreelistLocker x(_collector);
+    MutexLockerEx  y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
+    Universe::verify(true);
+  }
+}
+
+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;
+  }
+  HS_DTRACE_PROBE(hs_private, cms__initmark__begin);
+
+  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);
+
+  VM_CMS_Operation::verify_after_gc();
+  HS_DTRACE_PROBE(hs_private, cms__initmark__end);
+}
+
+//////////////////////////////////////////////////////////
+// Methods in class VM_CMS_Final_Remark_Operation
+//////////////////////////////////////////////////////////
+void VM_CMS_Final_Remark::doit() {
+  if (lost_race()) {
+    // Nothing to do.
+    return;
+  }
+  HS_DTRACE_PROBE(hs_private, cms__remark__begin);
+
+  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);
+
+  VM_CMS_Operation::verify_after_gc();
+  HS_DTRACE_PROBE(hs_private, cms__remark__end);
+}
+
+// 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");
+
+  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);
+  if (gch->total_full_collections() == _full_gc_count_before) {
+    // Disable iCMS until the full collection is done.
+    CMSCollector::disable_icms();
+    // 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);
+  } else {
+    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 (gch->total_full_collections_completed() <= _full_gc_count_before) {
+    // 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.
+  CMSCollector::enable_icms();
+}