Attachment 210221 Details for Bug 120568 – the patch

[patch] the patch

blah.patch (text/plain), 3.71 KB, created by Filip Pizlo on 2013-08-31 17:47:21 PDT

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Creator: Filip Pizlo

Created: 2013-08-31 17:47:21 PDT

Size: 3.71 KB

patch

obsolete

>Index: Source/WTF/ChangeLog
>===================================================================
>--- Source/WTF/ChangeLog	(revision 154934)
>+++ Source/WTF/ChangeLog	(working copy)
>@@ -1,3 +1,18 @@
>+2013-08-31  Filip Pizlo  <fpizlo@apple.com>
>+
>+        DeferredRefCounted should be thread-safe
>+        https://bugs.webkit.org/show_bug.cgi?id=120568
>+
>+        Reviewed by NOBODY (OOPS!).
>+        
>+        This makes the class more general. It also happens that this doesn't hurt
>+        performance for current users of DeferredRefCounted (i.e. ArrayBuffers).
>+
>+        * wtf/DeferrableRefCounted.h:
>+        (WTF::DeferrableRefCountedBase::ref):
>+        (WTF::DeferrableRefCountedBase::derefBase):
>+        (WTF::DeferrableRefCountedBase::setIsDeferredBase):
>+
> 2013-08-30  Oliver Hunt  <oliver@apple.com>
> 
>         Make JSValue bool conversion less dangerous
>Index: Source/WTF/wtf/DeferrableRefCounted.h
>===================================================================
>--- Source/WTF/wtf/DeferrableRefCounted.h	(revision 154933)
>+++ Source/WTF/wtf/DeferrableRefCounted.h	(working copy)
>@@ -27,8 +27,10 @@
> #define DeferrableRefCounted_h
> 
> #include <wtf/Assertions.h>
>+#include <wtf/Atomics.h>
> #include <wtf/FastAllocBase.h>
> #include <wtf/Noncopyable.h>
>+#include <wtf/ThreadingPrimitives.h>
> 
> namespace WTF {
> 
>@@ -38,6 +40,10 @@ namespace WTF {
> // specifically happened - this can be useful either for debugging, or
> // sometimes even for some additional functionality.
> 
>+// Note, this is always thread-safe ref-counted - this works out fine
>+// because the users of this class either have low refCount churn, or
>+// need thread-safe reference counting, or both.
>+
> class DeferrableRefCountedBase {
>     static const unsigned deferredFlag = 1;
>     static const unsigned normalIncrement = 2;
>@@ -45,7 +51,15 @@ class DeferrableRefCountedBase {
> public:
>     void ref()
>     {
>+#if ENABLE(COMPARE_AND_SWAP)
>+        unsigned oldValue;
>+        do
>+            oldValue = m_refCount;
>+        while (!weakCompareAndSwap(&m_refCount, oldValue, oldValue + normalIncrement));
>+#else // ENABLE(COMPARE_AND_SWAP)
>+        MutexLocker locker(m_lock);
>         m_refCount += normalIncrement;
>+#endif // ENABLE(COMPARE_AND_SWAP)
>     }
>     
>     bool hasOneRef() const
>@@ -75,22 +89,55 @@ protected:
>     
>     bool derefBase()
>     {
>+#if ENABLE(COMPARE_AND_SWAP)
>+        unsigned oldValue;
>+        unsigned newValue;
>+        do {
>+            oldValue = m_refCount;
>+            newValue = oldValue - normalIncrement;
>+        } while (!weakCompareAndSwap(&m_refCount, oldValue, newValue));
>+        return !newValue;
>+#else // ENABLE(COMPARE_AND_SWAP)
>+        MutexLocker locker(m_lock);
>         m_refCount -= normalIncrement;
>         return !m_refCount;
>+#endif // ENABLE(COMPARE_AND_SWAP)
>     }
> 
>     bool setIsDeferredBase(bool value)
>     {
>+#if ENABLE(COMPARE_AND_SWAP)
>+        unsigned oldValue;
>+        unsigned newValue;
>+        bool result;
>+        do {
>+            oldValue = m_refCount;
>+            if (value) {
>+                newValue = oldValue | deferredFlag;
>+                result = false;
>+            } else {
>+                newValue = oldValue & ~deferredFlag;
>+                result = !newValue;
>+            }
>+        } while (!weakCompareAndSwap(&m_refCount, oldValue, newValue));
>+        return result;
>+#else // ENABLE(COMPARE_AND_SWAP)
>+        MutexLocker locker(m_lock);
>         if (value) {
>             m_refCount |= deferredFlag;
>             return false;
>         }
>         m_refCount &= ~deferredFlag;
>         return !m_refCount;
>+#endif // ENABLE(COMPARE_AND_SWAP)
>     }
>     
> private:
>     unsigned m_refCount;
>+
>+#if !ENABLE(COMPARE_AND_SWAP)
>+    Mutex m_lock;
>+#endif // !ENABLE(COMPARE_AND_SWAP)
> };
> 
> template<typename T>

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