jdk8-mips64-public/hotspot: src/share/vm/memory/genMarkSweep.cpp@2c022e432e10 (annotated)

src/share/vm/memory/genMarkSweep.cpp@2c022e432e10 (annotated)

src/share/vm/memory/genMarkSweep.cpp

Fri, 20 Sep 2013 10:53:28 +0200

author: stefank
date: Fri, 20 Sep 2013 10:53:28 +0200
changeset 5769: 2c022e432e10
parent 5519: bd902affe102
child 6876: 710a3c8b516e
child 6904: 0982ec23da03
permissions: -rw-r--r--

8024974: Incorrect use of GC_locker::is_active()
Summary: SymbolTable and StringTable can make calls to GC_locker::is_active() outside a safepoint. This isn't safe because the GC_locker active state (lock count) is only updated at a safepoint and only remains valid as long as _needs_gc is true. However, outside a safepoint_needs_gc can change to false at any time, which makes it impossible to do a correct call to is_active() in that context. In this case these calls can just be removed since the input argument to basic_add() should never be on the heap and so there's no need to check the GC_locker state. This change also adjusts the assert() in is_active() to makes sure all calls to this function are always done under a safepoint.
Reviewed-by: brutisso, dcubed
Contributed-by: per.liden@oracle.com

 /*
  * Copyright (c) 2001, 2013, 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 "classfile/javaClasses.hpp"
 #include "classfile/symbolTable.hpp"
 #include "classfile/systemDictionary.hpp"
 #include "classfile/vmSymbols.hpp"
 #include "code/codeCache.hpp"
 #include "code/icBuffer.hpp"
 #include "gc_implementation/shared/gcHeapSummary.hpp"
 #include "gc_implementation/shared/gcTimer.hpp"
 #include "gc_implementation/shared/gcTrace.hpp"
 #include "gc_implementation/shared/gcTraceTime.hpp"
 #include "gc_interface/collectedHeap.inline.hpp"
 #include "memory/genCollectedHeap.hpp"
 #include "memory/genMarkSweep.hpp"
 #include "memory/genOopClosures.inline.hpp"
 #include "memory/generation.inline.hpp"
 #include "memory/modRefBarrierSet.hpp"
 #include "memory/referencePolicy.hpp"
 #include "memory/space.hpp"
 #include "oops/instanceRefKlass.hpp"
 #include "oops/oop.inline.hpp"
 #include "prims/jvmtiExport.hpp"
 #include "runtime/fprofiler.hpp"
 #include "runtime/handles.inline.hpp"
 #include "runtime/synchronizer.hpp"
 #include "runtime/thread.inline.hpp"
 #include "runtime/vmThread.hpp"
 #include "utilities/copy.hpp"
 #include "utilities/events.hpp"
 void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp, bool clear_all_softrefs) {
   guarantee(level == 1, "We always collect both old and young.");
   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
   GenCollectedHeap* gch = GenCollectedHeap::heap();
 #ifdef ASSERT
   if (gch->collector_policy()->should_clear_all_soft_refs()) {
     assert(clear_all_softrefs, "Policy should have been checked earlier");
   }
 #endif
   // hook up weak ref data so it can be used during Mark-Sweep
   assert(ref_processor() == NULL, "no stomping");
   assert(rp != NULL, "should be non-NULL");
   _ref_processor = rp;
   rp->setup_policy(clear_all_softrefs);
   GCTraceTime t1(GCCauseString("Full GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL);
   gch->trace_heap_before_gc(_gc_tracer);
   // When collecting the permanent generation Method*s may be moving,
   // so we either have to flush all bcp data or convert it into bci.
   CodeCache::gc_prologue();
   Threads::gc_prologue();
   // Increment the invocation count
   _total_invocations++;
   // Capture heap size before collection for printing.
   size_t gch_prev_used = gch->used();
   // Capture used regions for each generation that will be
   // subject to collection, so that card table adjustments can
   // be made intelligently (see clear / invalidate further below).
   gch->save_used_regions(level);
   allocate_stacks();
   mark_sweep_phase1(level, clear_all_softrefs);
   mark_sweep_phase2();
   // Don't add any more derived pointers during phase3
   COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
   COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
   mark_sweep_phase3(level);
   mark_sweep_phase4();
   restore_marks();
   // Set saved marks for allocation profiler (and other things? -- dld)
   // (Should this be in general part?)
   gch->save_marks();
   deallocate_stacks();
   // If compaction completely evacuated all generations younger than this
   // one, then we can clear the card table.  Otherwise, we must invalidate
   // it (consider all cards dirty).  In the future, we might consider doing
   // compaction within generations only, and doing card-table sliding.
   bool all_empty = true;
   for (int i = 0; all_empty && i < level; i++) {
     Generation* g = gch->get_gen(i);
     all_empty = all_empty && gch->get_gen(i)->used() == 0;
   }
   GenRemSet* rs = gch->rem_set();
   Generation* old_gen = gch->get_gen(level);
   // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
   if (all_empty) {
     // We've evacuated all generations below us.
     rs->clear_into_younger(old_gen);
   } else {
     // Invalidate the cards corresponding to the currently used
     // region and clear those corresponding to the evacuated region.
     rs->invalidate_or_clear(old_gen);
   }
   Threads::gc_epilogue();
   CodeCache::gc_epilogue();
   JvmtiExport::gc_epilogue();
   if (PrintGC && !PrintGCDetails) {
     gch->print_heap_change(gch_prev_used);
   }
   // refs processing: clean slate
   _ref_processor = NULL;
   // Update heap occupancy information which is used as
   // input to soft ref clearing policy at the next gc.
   Universe::update_heap_info_at_gc();
   // Update time of last gc for all generations we collected
   // (which curently is all the generations in the heap).
   // We need to use a monotonically non-deccreasing time in ms
   // or we will see time-warp warnings and os::javaTimeMillis()
   // does not guarantee monotonicity.
   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
   gch->update_time_of_last_gc(now);
   gch->trace_heap_after_gc(_gc_tracer);
 }
 void GenMarkSweep::allocate_stacks() {
   GenCollectedHeap* gch = GenCollectedHeap::heap();
   // Scratch request on behalf of oldest generation; will do no
   // allocation.
   ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
   // $$$ To cut a corner, we'll only use the first scratch block, and then
   // revert to malloc.
   if (scratch != NULL) {
     _preserved_count_max =
       scratch->num_words * HeapWordSize / sizeof(PreservedMark);
   } else {
     _preserved_count_max = 0;
   }
   _preserved_marks = (PreservedMark*)scratch;
   _preserved_count = 0;
 }
 void GenMarkSweep::deallocate_stacks() {
   if (!UseG1GC) {
     GenCollectedHeap* gch = GenCollectedHeap::heap();
     gch->release_scratch();
   }
   _preserved_mark_stack.clear(true);
   _preserved_oop_stack.clear(true);
   _marking_stack.clear();
   _objarray_stack.clear(true);
 }
 void GenMarkSweep::mark_sweep_phase1(int level,
                                   bool clear_all_softrefs) {
   // Recursively traverse all live objects and mark them
   GCTraceTime tm("phase 1", PrintGC && Verbose, true, _gc_timer);
   trace(" 1");
   GenCollectedHeap* gch = GenCollectedHeap::heap();
   // Because follow_root_closure is created statically, cannot
   // use OopsInGenClosure constructor which takes a generation,
   // as the Universe has not been created when the static constructors
   // are run.
   follow_root_closure.set_orig_generation(gch->get_gen(level));
   // Need new claim bits before marking starts.
   ClassLoaderDataGraph::clear_claimed_marks();
   gch->gen_process_strong_roots(level,
                                 false, // Younger gens are not roots.
                                 true,  // activate StrongRootsScope
                                 false, // not scavenging
                                 SharedHeap::SO_SystemClasses,
                                 &follow_root_closure,
                                 true,   // walk code active on stacks
                                 &follow_root_closure,
                                 &follow_klass_closure);
   // Process reference objects found during marking
   {
     ref_processor()->setup_policy(clear_all_softrefs);
     const ReferenceProcessorStats& stats =
       ref_processor()->process_discovered_references(
         &is_alive, &keep_alive, &follow_stack_closure, NULL, _gc_timer);
     gc_tracer()->report_gc_reference_stats(stats);
   }
   // This is the point where the entire marking should have completed.
   assert(_marking_stack.is_empty(), "Marking should have completed");
   // Unload classes and purge the SystemDictionary.
   bool purged_class = SystemDictionary::do_unloading(&is_alive);
   // Unload nmethods.
   CodeCache::do_unloading(&is_alive, purged_class);
   // Prune dead klasses from subklass/sibling/implementor lists.
   Klass::clean_weak_klass_links(&is_alive);
   // Delete entries for dead interned strings.
   StringTable::unlink(&is_alive);
   // Clean up unreferenced symbols in symbol table.
   SymbolTable::unlink();
   gc_tracer()->report_object_count_after_gc(&is_alive);
 }
 void GenMarkSweep::mark_sweep_phase2() {
   // Now all live objects are marked, compute the new object addresses.
   // It is imperative that we traverse perm_gen LAST. If dead space is
   // allowed a range of dead object may get overwritten by a dead int
   // array. If perm_gen is not traversed last a Klass* may get
   // overwritten. This is fine since it is dead, but if the class has dead
   // instances we have to skip them, and in order to find their size we
   // need the Klass*!
   //
   // It is not required that we traverse spaces in the same order in
   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
   // tracking expects us to do so. See comment under phase4.
   GenCollectedHeap* gch = GenCollectedHeap::heap();
   GCTraceTime tm("phase 2", PrintGC && Verbose, true, _gc_timer);
   trace("2");
   gch->prepare_for_compaction();
 }
 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
 public:
   void do_generation(Generation* gen) {
     gen->adjust_pointers();
   }
 };
 void GenMarkSweep::mark_sweep_phase3(int level) {
   GenCollectedHeap* gch = GenCollectedHeap::heap();
   // Adjust the pointers to reflect the new locations
   GCTraceTime tm("phase 3", PrintGC && Verbose, true, _gc_timer);
   trace("3");
   // Need new claim bits for the pointer adjustment tracing.
   ClassLoaderDataGraph::clear_claimed_marks();
   // Because the closure below is created statically, we cannot
   // use OopsInGenClosure constructor which takes a generation,
   // as the Universe has not been created when the static constructors
   // are run.
   adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
   gch->gen_process_strong_roots(level,
                                 false, // Younger gens are not roots.
                                 true,  // activate StrongRootsScope
                                 false, // not scavenging
                                 SharedHeap::SO_AllClasses,
                                 &adjust_pointer_closure,
                                 false, // do not walk code
                                 &adjust_pointer_closure,
                                 &adjust_klass_closure);
   // Now adjust pointers in remaining weak roots.  (All of which should
   // have been cleared if they pointed to non-surviving objects.)
   CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure,
                                                    /*do_marking=*/ false);
   gch->gen_process_weak_roots(&adjust_pointer_closure,
                               &adjust_code_pointer_closure);
   adjust_marks();
   GenAdjustPointersClosure blk;
   gch->generation_iterate(&blk, true);
 }
 class GenCompactClosure: public GenCollectedHeap::GenClosure {
 public:
   void do_generation(Generation* gen) {
     gen->compact();
   }
 };
 void GenMarkSweep::mark_sweep_phase4() {
   // All pointers are now adjusted, move objects accordingly
   // It is imperative that we traverse perm_gen first in phase4. All
   // classes must be allocated earlier than their instances, and traversing
   // perm_gen first makes sure that all Klass*s have moved to their new
   // location before any instance does a dispatch through it's klass!
   // The ValidateMarkSweep live oops tracking expects us to traverse spaces
   // in the same order in phase2, phase3 and phase4. We don't quite do that
   // here (perm_gen first rather than last), so we tell the validate code
   // to use a higher index (saved from phase2) when verifying perm_gen.
   GenCollectedHeap* gch = GenCollectedHeap::heap();
   GCTraceTime tm("phase 4", PrintGC && Verbose, true, _gc_timer);
   trace("4");
   GenCompactClosure blk;
   gch->generation_iterate(&blk, true);
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/memory/genMarkSweep.cpp@2c022e432e10 (annotated)

src/share/vm/memory/genMarkSweep.cpp