1 /*
   2  * Copyright (c) 2015, 2019, 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 #ifndef SHARE_GC_Z_ZFORWARDING_INLINE_HPP
  25 #define SHARE_GC_Z_ZFORWARDING_INLINE_HPP
  26 
  27 #include "gc/z/zAttachedArray.inline.hpp"
  28 #include "gc/z/zForwarding.hpp"
  29 #include "gc/z/zGlobals.hpp"
  30 #include "gc/z/zHash.inline.hpp"
  31 #include "gc/z/zHeap.hpp"
  32 #include "gc/z/zVirtualMemory.inline.hpp"
  33 #include "runtime/atomic.hpp"
  34 #include "utilities/debug.hpp"
  35 
  36 inline uintptr_t ZForwarding::start() const {
  37   return _virtual.start();
  38 }
  39 
  40 inline size_t ZForwarding::size() const {
  41   return _virtual.size();
  42 }
  43 
  44 inline size_t ZForwarding::object_alignment_shift() const {
  45   return _object_alignment_shift;
  46 }
  47 
  48 inline ZPage* ZForwarding::page() const {
  49   return _page;
  50 }
  51 
  52 inline bool ZForwarding::is_pinned() const {
  53   return Atomic::load(&_pinned);
  54 }
  55 
  56 inline void ZForwarding::set_pinned() {
  57   Atomic::store(true, &_pinned);
  58 }
  59 
  60 inline bool ZForwarding::inc_refcount() {
  61   uint32_t refcount = Atomic::load(&_refcount);
  62 
  63   while (refcount > 0) {
  64     const uint32_t old_refcount = refcount;
  65     const uint32_t new_refcount = old_refcount + 1;
  66     const uint32_t prev_refcount = Atomic::cmpxchg(new_refcount, &_refcount, old_refcount);
  67     if (prev_refcount == old_refcount) {
  68       return true;
  69     }
  70 
  71     refcount = prev_refcount;
  72   }
  73 
  74   return false;
  75 }
  76 
  77 inline bool ZForwarding::dec_refcount() {
  78   assert(_refcount > 0, "Invalid state");
  79   return Atomic::sub(1u, &_refcount) == 0u;
  80 }
  81 
  82 inline bool ZForwarding::retain_page() {
  83   return inc_refcount();
  84 }
  85 
  86 inline void ZForwarding::release_page() {
  87   if (dec_refcount()) {
  88     ZHeap::heap()->free_page(_page, true /* reclaimed */);
  89     _page = NULL;
  90   }
  91 }
  92 
  93 inline ZForwardingEntry* ZForwarding::entries() const {
  94   return _entries(this);
  95 }
  96 
  97 inline ZForwardingEntry ZForwarding::at(ZForwardingCursor* cursor) const {
  98   return Atomic::load(entries() + *cursor);
  99 }
 100 
 101 inline ZForwardingEntry ZForwarding::first(uintptr_t from_index, ZForwardingCursor* cursor) const {
 102   const size_t mask = _entries.length() - 1;
 103   const size_t hash = ZHash::uint32_to_uint32((uint32_t)from_index);
 104   *cursor = hash & mask;
 105   return at(cursor);
 106 }
 107 
 108 inline ZForwardingEntry ZForwarding::next(ZForwardingCursor* cursor) const {
 109   const size_t mask = _entries.length() - 1;
 110   *cursor = (*cursor + 1) & mask;
 111   return at(cursor);
 112 }
 113 
 114 inline ZForwardingEntry ZForwarding::find(uintptr_t from_index) const {
 115   ZForwardingCursor dummy;
 116   return find(from_index, &dummy);
 117 }
 118 
 119 inline ZForwardingEntry ZForwarding::find(uintptr_t from_index, ZForwardingCursor* cursor) const {
 120   // Reading entries in the table races with the atomic CAS done for
 121   // insertion into the table. This is safe because each entry is at
 122   // most updated once (from zero to something else).
 123   ZForwardingEntry entry = first(from_index, cursor);
 124   while (entry.populated()) {
 125     if (entry.from_index() == from_index) {
 126       // Match found, return matching entry
 127       return entry;
 128     }
 129 
 130     entry = next(cursor);
 131   }
 132 
 133   // Match not found, return empty entry
 134   return entry;
 135 }
 136 
 137 inline uintptr_t ZForwarding::insert(uintptr_t from_index, uintptr_t to_offset, ZForwardingCursor* cursor) {
 138   const ZForwardingEntry new_entry(from_index, to_offset);
 139   const ZForwardingEntry old_entry; // Empty
 140 
 141   for (;;) {
 142     const ZForwardingEntry prev_entry = Atomic::cmpxchg(new_entry, entries() + *cursor, old_entry);
 143     if (!prev_entry.populated()) {
 144       // Success
 145       return to_offset;
 146     }
 147 
 148     // Find next empty or matching entry
 149     ZForwardingEntry entry = at(cursor);
 150     while (entry.populated()) {
 151       if (entry.from_index() == from_index) {
 152         // Match found, return already inserted address
 153         return entry.to_offset();
 154       }
 155 
 156       entry = next(cursor);
 157     }
 158   }
 159 }
 160 
 161 #endif // SHARE_GC_Z_ZFORWARDING_INLINE_HPP
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