heap/HandleHeap.cpp

   1 /*
   2  * Copyright (C) 2011 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  23  * THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "HandleHeap.h"
  28
  29 #include "JSObject.h"
  30
  31 namespace JSC {
  32
  33 WeakHandleOwner::~WeakHandleOwner()
  34 {
  35 }
  36
  37 bool WeakHandleOwner::isReachableFromOpaqueRoots(Handle<Unknown>, void*, SlotVisitor&)
  38 {
  39     return false;
  40 }
  41
  42 void WeakHandleOwner::finalize(Handle<Unknown>, void*)
  43 {
  44 }
  45
  46 HandleHeap::HandleHeap(JSGlobalData* globalData)
  47     : m_globalData(globalData)
  48     , m_nextToFinalize(0)
  49 {
  50     grow();
  51 }
  52
  53 void HandleHeap::grow()
  54 {
  55     Node* block = m_blockStack.grow();
  56     for (int i = m_blockStack.blockLength - 1; i >= 0; --i) {
  57         Node* node = &block[i];
  58         new (node) Node(this);
  59         m_freeList.push(node);
  60     }
  61 }
  62
  63 void HandleHeap::markStrongHandles(HeapRootVisitor& heapRootMarker)
  64 {
  65     Node* end = m_strongList.end();
  66     for (Node* node = m_strongList.begin(); node != end; node = node->next())
  67         heapRootMarker.mark(node->slot());
  68 }
  69
  70 void HandleHeap::markWeakHandles(HeapRootVisitor& heapRootVisitor)
  71 {
  72     SlotVisitor& visitor = heapRootVisitor.visitor();
  73
  74     Node* end = m_weakList.end();
  75     for (Node* node = m_weakList.begin(); node != end; node = node->next()) {
  76         ASSERT(isValidWeakNode(node));
  77         JSCell* cell = node->slot()->asCell();
  78         if (Heap::isMarked(cell))
  79             continue;
  80
  81         WeakHandleOwner* weakOwner = node->weakOwner();
  82         if (!weakOwner)
  83             continue;
  84
  85         if (!weakOwner->isReachableFromOpaqueRoots(Handle<Unknown>::wrapSlot(node->slot()), node->weakOwnerContext(), visitor))
  86             continue;
  87
  88         heapRootVisitor.mark(node->slot());
  89     }
  90 }
  91
  92 void HandleHeap::finalizeWeakHandles()
  93 {
  94     Node* end = m_weakList.end();
  95     for (Node* node = m_weakList.begin(); node != end; node = m_nextToFinalize) {
  96         m_nextToFinalize = node->next();
  97
  98         ASSERT(isValidWeakNode(node));
  99         JSCell* cell = node->slot()->asCell();
 100         if (Heap::isMarked(cell))
 101             continue;
 102
 103         if (WeakHandleOwner* weakOwner = node->weakOwner()) {
 104             weakOwner->finalize(Handle<Unknown>::wrapSlot(node->slot()), node->weakOwnerContext());
 105             if (m_nextToFinalize != node->next()) // Owner deallocated node.
 106                 continue;
 107         }
 108
 109         *node->slot() = JSValue();
 110         SentinelLinkedList<Node>::remove(node);
 111         m_immediateList.push(node);
 112     }
 113
 114     m_nextToFinalize = 0;
 115 }
 116
 117 void HandleHeap::writeBarrier(HandleSlot slot, const JSValue& value)
 118 {
 119     ASSERT(!m_nextToFinalize); // Forbid assignment to handles during the finalization phase, since it would violate many GC invariants.
 120
 121     if (!value == !*slot && slot->isCell() == value.isCell())
 122         return;
 123
 124     Node* node = toNode(slot);
 125     SentinelLinkedList<Node>::remove(node);
 126     if (!value || !value.isCell()) {
 127         m_immediateList.push(node);
 128         return;
 129     }
 130
 131     if (node->isWeak()) {
 132         m_weakList.push(node);
 133         return;
 134     }
 135
 136     m_strongList.push(node);
 137 }
 138
 139 unsigned HandleHeap::protectedGlobalObjectCount()
 140 {
 141     unsigned count = 0;
 142     Node* end = m_strongList.end();
 143     for (Node* node = m_strongList.begin(); node != end; node = node->next()) {
 144         JSValue value = *node->slot();
 145         if (value.isObject() && asObject(value.asCell())->isGlobalObject())
 146             count++;
 147     }
 148     return count;
 149 }
 150
 151 #if !ASSERT_DISABLED
 152 bool HandleHeap::isValidWeakNode(Node* node)
 153 {
 154     if (!node->isWeak())
 155         return false;
 156
 157     JSValue value = *node->slot();
 158     if (!value || !value.isCell())
 159         return false;
 160
 161     JSCell* cell = value.asCell();
 162     if (!cell || !cell->structure())
 163         return false;
 164
 165 #if ENABLE(JSC_ZOMBIES)
 166     if (cell->isZombie())
 167         return false;
 168 #endif
 169
 170     return true;
 171 }
 172 #endif
 173
 174 } // namespace JSC