Index: Source/wtf/Threading.h |
diff --git a/Source/wtf/Threading.h b/Source/wtf/Threading.h |
index 97d4cb390ae0734e9b214a95207e47713bebe7d3..e89dcb793295befc0b136be712fa72e6a6c9d766 100644 |
--- a/Source/wtf/Threading.h |
+++ b/Source/wtf/Threading.h |
@@ -30,14 +30,25 @@ |
#ifndef Threading_h |
#define Threading_h |
+#include "wtf/Atomics.h" |
+#include "wtf/TypeTraits.h" |
#include "wtf/WTFExport.h" |
#include <stdint.h> |
-// For portability, we do not use thread-safe statics natively supported by some compilers (e.g. gcc). |
-#define AtomicallyInitializedStatic(T, name) \ |
- WTF::lockAtomicallyInitializedStaticMutex(); \ |
- static T name; \ |
- WTF::unlockAtomicallyInitializedStaticMutex(); |
+// For portability, we do not make use of C++11 thread-safe statics, as supported |
+// by some toolchains. Make use of double-checked locking to reduce overhead. |
+#define AtomicallyInitializedStaticReference(T, name, initializer) \ |
Noel Gordon
2015/01/24 01:20:06
To "reduce overhead" relative to what?
sof
2015/01/24 06:20:06
To what's on the left here in the diff? :) Doesn't
Noel Gordon
2015/01/24 12:08:24
Think _we_ understand the motivation :) but other
sof
2015/01/24 12:40:05
Sounds sensible; doesn't the description here expl
|
+ /* Init to nullptr is thread-safe on all implementations. */ \ |
+ static void* name##Pointer = nullptr; \ |
+ if (!WTF::acquireLoad(&name##Pointer)) { \ |
Noel Gordon
2015/01/24 01:20:06
Blink prefers the early return. Any reason not to
sof
2015/01/24 06:20:06
You have to bind the reference, and at the scope t
Noel Gordon
2015/01/24 12:08:24
Yes I see your point, @51 it seems, so ok.
|
+ WTF::lockAtomicallyInitializedStaticMutex(); \ |
+ if (!WTF::acquireLoad(&name##Pointer)) { \ |
+ WTF::RemoveConst<T>::Type* initializerResult = initializer; \ |
+ WTF::releaseStore(&name##Pointer, initializerResult); \ |
+ } \ |
+ WTF::unlockAtomicallyInitializedStaticMutex(); \ |
+ } \ |
+ T& name = *static_cast<T*>(name##Pointer) |
namespace WTF { |