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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/163820">163820</a></dd>
<dt>Author</dt> <dd>mark.lam@apple.com</dd>
<dt>Date</dt> <dd>2014-02-10 14:27:10 -0800 (Mon, 10 Feb 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>Change JSLock::dropAllLocks() and friends to use lock() and unlock().
<https://webkit.org/b/128451>
Reviewed by Geoffrey Garen.
Currently, JSLock's dropAllLocks(), dropAllLocksUnconditionally(), and
grabAllLocks() implement locking / unlocking by duplicating the code from
lock() and unlock(). Instead, they should just call lock() and unlock().
* runtime/JSLock.cpp:
(JSC::JSLock::lock):
(JSC::JSLock::unlock):
- Modified lock() and unlock() into a version that takes an entry count
to lock / unlock. The previous lock() and unlock() now calls these
new versions with an entry count of 1.
(JSC::JSLock::dropAllLocks):
(JSC::JSLock::dropAllLocksUnconditionally):
(JSC::JSLock::grabAllLocks):
- Delegate to unlock() and lock() instead of duplicating the lock / unlock
code.
- There a some differences with calling lock() instead of duplicating its
code in grabAllLock() i.e. lock() does the following additional work:
1. lock() does a re-entry check that is not needed by grabAllLocks().
However, this is effectively a no-op since we never own the JSLock
before calling grabAllLocks().
2. set VM stackPointerAtVMEntry.
3. update VM stackLimit and reservedZoneSize.
4. set VM lastStackTop.
These 3 steps are just busy work which are also effective no-ops
because immediately after lock() returns, grabAllLocks() will write
over those values with their saved versions in the threadData.
* runtime/JSLock.h:</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeJSLockcpp">trunk/Source/JavaScriptCore/runtime/JSLock.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeJSLockh">trunk/Source/JavaScriptCore/runtime/JSLock.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (163819 => 163820)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog        2014-02-10 22:24:32 UTC (rev 163819)
+++ trunk/Source/JavaScriptCore/ChangeLog        2014-02-10 22:27:10 UTC (rev 163820)
</span><span class="lines">@@ -1,3 +1,42 @@
</span><ins>+2014-02-10 Mark Lam <mark.lam@apple.com>
+
+ Change JSLock::dropAllLocks() and friends to use lock() and unlock().
+ <https://webkit.org/b/128451>
+
+ Reviewed by Geoffrey Garen.
+
+ Currently, JSLock's dropAllLocks(), dropAllLocksUnconditionally(), and
+ grabAllLocks() implement locking / unlocking by duplicating the code from
+ lock() and unlock(). Instead, they should just call lock() and unlock().
+
+ * runtime/JSLock.cpp:
+ (JSC::JSLock::lock):
+ (JSC::JSLock::unlock):
+ - Modified lock() and unlock() into a version that takes an entry count
+ to lock / unlock. The previous lock() and unlock() now calls these
+ new versions with an entry count of 1.
+
+ (JSC::JSLock::dropAllLocks):
+ (JSC::JSLock::dropAllLocksUnconditionally):
+ (JSC::JSLock::grabAllLocks):
+ - Delegate to unlock() and lock() instead of duplicating the lock / unlock
+ code.
+ - There a some differences with calling lock() instead of duplicating its
+ code in grabAllLock() i.e. lock() does the following additional work:
+
+ 1. lock() does a re-entry check that is not needed by grabAllLocks().
+ However, this is effectively a no-op since we never own the JSLock
+ before calling grabAllLocks().
+
+ 2. set VM stackPointerAtVMEntry.
+ 3. update VM stackLimit and reservedZoneSize.
+ 4. set VM lastStackTop.
+ These 3 steps are just busy work which are also effective no-ops
+ because immediately after lock() returns, grabAllLocks() will write
+ over those values with their saved versions in the threadData.
+
+ * runtime/JSLock.h:
+
</ins><span class="cx"> 2014-02-10 Anders Carlsson <andersca@apple.com>
</span><span class="cx">
</span><span class="cx"> Try to fix the Windows build.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeJSLockcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/JSLock.cpp (163819 => 163820)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/JSLock.cpp        2014-02-10 22:24:32 UTC (rev 163819)
+++ trunk/Source/JavaScriptCore/runtime/JSLock.cpp        2014-02-10 22:27:10 UTC (rev 163820)
</span><span class="lines">@@ -100,9 +100,15 @@
</span><span class="cx">
</span><span class="cx"> void JSLock::lock()
</span><span class="cx"> {
</span><ins>+ lock(1);
+}
+
+void JSLock::lock(intptr_t lockCount)
+{
+ ASSERT(lockCount > 0);
</ins><span class="cx"> ThreadIdentifier currentThread = WTF::currentThread();
</span><span class="cx"> if (currentThreadIsHoldingLock()) {
</span><del>- m_lockCount++;
</del><ins>+ m_lockCount += lockCount;
</ins><span class="cx"> return;
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -110,7 +116,7 @@
</span><span class="cx">
</span><span class="cx"> setOwnerThread(currentThread);
</span><span class="cx"> ASSERT(!m_lockCount);
</span><del>- m_lockCount = 1;
</del><ins>+ m_lockCount = lockCount;
</ins><span class="cx">
</span><span class="cx"> WTFThreadData& threadData = wtfThreadData();
</span><span class="cx">
</span><span class="lines">@@ -125,9 +131,15 @@
</span><span class="cx">
</span><span class="cx"> void JSLock::unlock()
</span><span class="cx"> {
</span><ins>+ unlock(1);
+}
+
+void JSLock::unlock(intptr_t unlockCount)
+{
</ins><span class="cx"> RELEASE_ASSERT(currentThreadIsHoldingLock());
</span><ins>+ ASSERT(m_lockCount >= unlockCount);
</ins><span class="cx">
</span><del>- m_lockCount--;
</del><ins>+ m_lockCount -= unlockCount;
</ins><span class="cx">
</span><span class="cx"> if (!m_lockCount) {
</span><span class="cx"> if (m_vm) {
</span><span class="lines">@@ -218,13 +230,8 @@
</span><span class="cx"> ++m_lockDropDepth;
</span><span class="cx">
</span><span class="cx"> unsigned droppedLockCount = m_lockCount;
</span><del>- m_lockCount = 0;
- if (m_vm) {
- m_vm->stackPointerAtVMEntry = nullptr;
- m_vm->updateStackLimitWithReservedZoneSize(wtfThreadData().savedReservedZoneSize());
- }
- setOwnerThread(0);
- m_lock.unlock();
</del><ins>+ unlock(droppedLockCount);
+
</ins><span class="cx"> return droppedLockCount;
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -244,13 +251,8 @@
</span><span class="cx"> ++m_lockDropDepth;
</span><span class="cx">
</span><span class="cx"> unsigned droppedLockCount = m_lockCount;
</span><del>- m_lockCount = 0;
- if (m_vm) {
- m_vm->stackPointerAtVMEntry = nullptr;
- m_vm->updateStackLimitWithReservedZoneSize(wtfThreadData().savedReservedZoneSize());
- }
- setOwnerThread(0);
- m_lock.unlock();
</del><ins>+ unlock(droppedLockCount);
+
</ins><span class="cx"> return droppedLockCount;
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -261,12 +263,8 @@
</span><span class="cx"> return;
</span><span class="cx">
</span><span class="cx"> ASSERT(!currentThreadIsHoldingLock());
</span><ins>+ lock(droppedLockCount);
</ins><span class="cx">
</span><del>- m_lock.lock();
-
- setOwnerThread(WTF::currentThread());
- ASSERT(!m_lockCount);
- m_lockCount = droppedLockCount;
</del><span class="cx"> --m_lockDropDepth;
</span><span class="cx">
</span><span class="cx"> WTFThreadData& threadData = wtfThreadData();
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeJSLockh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/JSLock.h (163819 => 163820)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/JSLock.h        2014-02-10 22:24:32 UTC (rev 163819)
+++ trunk/Source/JavaScriptCore/runtime/JSLock.h        2014-02-10 22:27:10 UTC (rev 163820)
</span><span class="lines">@@ -112,6 +112,8 @@
</span><span class="cx"> };
</span><span class="cx">
</span><span class="cx"> private:
</span><ins>+ void lock(intptr_t lockCount);
+ void unlock(intptr_t unlockCount);
</ins><span class="cx"> void setOwnerThread(ThreadIdentifier owner) { m_ownerThread = owner; }
</span><span class="cx">
</span><span class="cx"> unsigned dropAllLocks();
</span></span></pre>
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