1 /*
   2  * Copyright (c) 2015, 2018, 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/g1/g1OopClosures.inline.hpp"
  27 #include "gc/g1/g1RootClosures.hpp"
  28 #include "gc/g1/g1SharedClosures.hpp"
  29 
  30 // Closures used for standard G1 evacuation.
  31 class G1EvacuationClosures : public G1EvacuationRootClosures {
  32   G1SharedClosures<G1MarkNone> _closures;
  33 
  34 public:
  35   G1EvacuationClosures(G1CollectedHeap* g1h,
  36                        G1ParScanThreadState* pss,
  37                        bool in_young_gc) :
  38       _closures(g1h, pss, in_young_gc, /* cld_claim */ ClassLoaderData::_claim_none) {}
  39 
  40   OopClosure* weak_oops()   { return &_closures._oops; }
  41   OopClosure* strong_oops() { return &_closures._oops; }
  42 
  43   CLDClosure* weak_clds()             { return &_closures._clds; }
  44   CLDClosure* strong_clds()           { return &_closures._clds; }
  45   CLDClosure* second_pass_weak_clds() { return NULL; }
  46 
  47   CodeBlobClosure* strong_codeblobs()      { return &_closures._codeblobs; }
  48   CodeBlobClosure* weak_codeblobs()        { return &_closures._codeblobs; }
  49 
  50   bool trace_metadata()         { return false; }
  51 };
  52 
  53 // Closures used during initial mark.
  54 // The treatment of "weak" roots is selectable through the template parameter,
  55 // this is usually used to control unloading of classes and interned strings.
  56 template <G1Mark MarkWeak>
  57 class G1InitialMarkClosures : public G1EvacuationRootClosures {
  58   G1SharedClosures<G1MarkFromRoot> _strong;
  59   G1SharedClosures<MarkWeak>       _weak;
  60 
  61   // Filter method to help with returning the appropriate closures
  62   // depending on the class template parameter.
  63   template <G1Mark Mark, typename T>
  64   T* null_if(T* t) {
  65     if (Mark == MarkWeak) {
  66       return NULL;
  67     }
  68     return t;
  69   }
  70 
  71 public:
  72   G1InitialMarkClosures(G1CollectedHeap* g1h,
  73                         G1ParScanThreadState* pss) :
  74       _strong(g1h, pss, /* process_only_dirty_klasses */ false, /* cld_claim */ ClassLoaderData::_claim_strong),
  75       _weak(g1h, pss,   /* process_only_dirty_klasses */ false, /* cld_claim */ ClassLoaderData::_claim_strong) {}
  76 
  77   OopClosure* weak_oops()   { return &_weak._oops; }
  78   OopClosure* strong_oops() { return &_strong._oops; }
  79 
  80   // If MarkWeak is G1MarkPromotedFromRoot then the weak CLDs must be processed in a second pass.
  81   CLDClosure* weak_clds()             { return null_if<G1MarkPromotedFromRoot>(&_weak._clds); }
  82   CLDClosure* strong_clds()           { return &_strong._clds; }
  83 
  84   // If MarkWeak is G1MarkFromRoot then all CLDs are processed by the weak and strong variants
  85   // return a NULL closure for the following specialized versions in that case.
  86   CLDClosure* second_pass_weak_clds() { return null_if<G1MarkFromRoot>(&_weak._clds); }
  87 
  88   CodeBlobClosure* strong_codeblobs()      { return &_strong._codeblobs; }
  89   CodeBlobClosure* weak_codeblobs()        { return &_weak._codeblobs; }
  90 
  91   // If we are not marking all weak roots then we are tracing
  92   // which metadata is alive.
  93   bool trace_metadata()         { return MarkWeak == G1MarkPromotedFromRoot; }
  94 };
  95 
  96 G1EvacuationRootClosures* G1EvacuationRootClosures::create_root_closures(G1ParScanThreadState* pss, G1CollectedHeap* g1h) {
  97   G1EvacuationRootClosures* res = NULL;
  98   if (g1h->collector_state()->in_initial_mark_gc()) {
  99     if (ClassUnloadingWithConcurrentMark) {
 100       res = new G1InitialMarkClosures<G1MarkPromotedFromRoot>(g1h, pss);
 101     } else {
 102       res = new G1InitialMarkClosures<G1MarkFromRoot>(g1h, pss);
 103     }
 104   } else {
 105     res = new G1EvacuationClosures(g1h, pss, g1h->collector_state()->in_young_only_phase());
 106   }
 107   return res;
 108 }