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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/201180">201180</a></dd>
<dt>Author</dt> <dd>mark.lam@apple.com</dd>
<dt>Date</dt> <dd>2016-05-19 14:02:44 -0700 (Thu, 19 May 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Code that null checks the VM pointer before any use should ref the VM.
https://bugs.webkit.org/show_bug.cgi?id=157864
Reviewed by Filip Pizlo and Keith Miller.
JSLock::willReleaseLock() and HeapTimer::timerDidFire() need to reference the VM
through a RefPtr. Otherwise, there's no guarantee that the VM won't be deleted
after their null checks.
* bytecode/CodeBlock.h:
(JSC::CodeBlock::vm):
(JSC::CodeBlock::setVM): Deleted.
- Not used, and suggests that it can be changed during the lifetime of the
CodeBlock (which should not be).
* heap/HeapTimer.cpp:
(JSC::HeapTimer::timerDidFire):
* runtime/JSLock.cpp:
(JSC::JSLock::willReleaseLock):
- Store the VM pointer in a RefPtr first, and null check the RefPtr instead of
the raw VM pointer. This makes the null check a strong guarantee that the
VM pointer is valid while these functions are using it.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCorebytecodeCodeBlockh">trunk/Source/JavaScriptCore/bytecode/CodeBlock.h</a></li>
<li><a href="#trunkSourceJavaScriptCoreheapHeapTimercpp">trunk/Source/JavaScriptCore/heap/HeapTimer.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeJSLockcpp">trunk/Source/JavaScriptCore/runtime/JSLock.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (201179 => 201180)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2016-05-19 20:40:54 UTC (rev 201179)
+++ trunk/Source/JavaScriptCore/ChangeLog 2016-05-19 21:02:44 UTC (rev 201180)
</span><span class="lines">@@ -1,3 +1,28 @@
</span><ins>+2016-05-19 Mark Lam <mark.lam@apple.com>
+
+ Code that null checks the VM pointer before any use should ref the VM.
+ https://bugs.webkit.org/show_bug.cgi?id=157864
+
+ Reviewed by Filip Pizlo and Keith Miller.
+
+ JSLock::willReleaseLock() and HeapTimer::timerDidFire() need to reference the VM
+ through a RefPtr. Otherwise, there's no guarantee that the VM won't be deleted
+ after their null checks.
+
+ * bytecode/CodeBlock.h:
+ (JSC::CodeBlock::vm):
+ (JSC::CodeBlock::setVM): Deleted.
+ - Not used, and suggests that it can be changed during the lifetime of the
+ CodeBlock (which should not be).
+
+ * heap/HeapTimer.cpp:
+ (JSC::HeapTimer::timerDidFire):
+ * runtime/JSLock.cpp:
+ (JSC::JSLock::willReleaseLock):
+ - Store the VM pointer in a RefPtr first, and null check the RefPtr instead of
+ the raw VM pointer. This makes the null check a strong guarantee that the
+ VM pointer is valid while these functions are using it.
+
</ins><span class="cx"> 2016-05-19 Saam barati <sbarati@apple.com>
</span><span class="cx">
</span><span class="cx"> arrow function lexical environment should reuse the same environment as the function's lexical environment where possible
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorebytecodeCodeBlockh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/bytecode/CodeBlock.h (201179 => 201180)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/bytecode/CodeBlock.h 2016-05-19 20:40:54 UTC (rev 201179)
+++ trunk/Source/JavaScriptCore/bytecode/CodeBlock.h 2016-05-19 21:02:44 UTC (rev 201180)
</span><span class="lines">@@ -340,8 +340,7 @@
</span><span class="cx"> ExecutableBase* ownerExecutable() const { return m_ownerExecutable.get(); }
</span><span class="cx"> ScriptExecutable* ownerScriptExecutable() const { return jsCast<ScriptExecutable*>(m_ownerExecutable.get()); }
</span><span class="cx">
</span><del>- void setVM(VM* vm) { m_vm = vm; }
- VM* vm() { return m_vm; }
</del><ins>+ VM* vm() const { return m_vm; }
</ins><span class="cx">
</span><span class="cx"> void setThisRegister(VirtualRegister thisRegister) { m_thisRegister = thisRegister; }
</span><span class="cx"> VirtualRegister thisRegister() const { return m_thisRegister; }
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreheapHeapTimercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/heap/HeapTimer.cpp (201179 => 201180)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/heap/HeapTimer.cpp 2016-05-19 20:40:54 UTC (rev 201179)
+++ trunk/Source/JavaScriptCore/heap/HeapTimer.cpp 2016-05-19 21:02:44 UTC (rev 201180)
</span><span class="lines">@@ -80,9 +80,9 @@
</span><span class="cx"> JSLock* apiLock = static_cast<JSLock*>(context);
</span><span class="cx"> apiLock->lock();
</span><span class="cx">
</span><del>- VM* vm = apiLock->vm();
- // The VM has been destroyed, so we should just give up.
</del><ins>+ RefPtr<VM> vm = apiLock->vm();
</ins><span class="cx"> if (!vm) {
</span><ins>+ // The VM has been destroyed, so we should just give up.
</ins><span class="cx"> apiLock->unlock();
</span><span class="cx"> return;
</span><span class="cx"> }
</span><span class="lines">@@ -98,7 +98,7 @@
</span><span class="cx"> RELEASE_ASSERT_NOT_REACHED();
</span><span class="cx">
</span><span class="cx"> {
</span><del>- JSLockHolder locker(vm);
</del><ins>+ JSLockHolder locker(vm.get());
</ins><span class="cx"> heapTimer->doWork();
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeJSLockcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/JSLock.cpp (201179 => 201180)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/JSLock.cpp 2016-05-19 20:40:54 UTC (rev 201179)
+++ trunk/Source/JavaScriptCore/runtime/JSLock.cpp 2016-05-19 21:02:44 UTC (rev 201180)
</span><span class="lines">@@ -177,11 +177,12 @@
</span><span class="cx">
</span><span class="cx"> void JSLock::willReleaseLock()
</span><span class="cx"> {
</span><del>- if (m_vm) {
- m_vm->drainMicrotasks();
</del><ins>+ RefPtr<VM> vm = m_vm;
+ if (vm) {
+ vm->drainMicrotasks();
</ins><span class="cx">
</span><del>- m_vm->heap.releaseDelayedReleasedObjects();
- m_vm->setStackPointerAtVMEntry(nullptr);
</del><ins>+ vm->heap.releaseDelayedReleasedObjects();
+ vm->setStackPointerAtVMEntry(nullptr);
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> if (m_entryAtomicStringTable) {
</span></span></pre>
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