Add SkRacy

include/core/SkDynamicAnnotations.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkDynamicAnnotations_DEFINED
 #define SkDynamicAnnotations_DEFINED
 
 // This file contains macros used to send out-of-band signals to dynamic instrumentation systems,
 // namely thread sanitizer.  This is a cut-down version of the full dynamic_annotations library with
 // only the features used by Skia.
 
 // We check the same define to know to enable the annotations, but prefix all our macros with SK_.
 #if DYNAMIC_ANNOTATIONS_ENABLED
 
 extern "C" {
 // TSAN provides these hooks.
 void AnnotateIgnoreReadsBegin(const char* file, int line);
 void AnnotateIgnoreReadsEnd(const char* file, int line);
+void AnnotateBenignRaceSized(const char* file, int line,
+                             const void* addr, long size, const char* desc);
 }  // extern "C"
 
 // SK_ANNOTATE_UNPROTECTED_READ can wrap any variable read to tell TSAN to ignore that it appears to
 // be a racy read.  This should be used only when we can make an external guarantee that though this
 // particular read is racy, it is being used as part of a mechanism which is thread safe.  Examples:
 //   - the first check in double-checked locking;
 //   - checking if a ref count is equal to 1.
 // Note that in both these cases, we must still add terrifyingly subtle memory barriers to provide
 // that overall thread safety guarantee.  Using this macro to shut TSAN up without providing such an
 // external guarantee is pretty much never correct.
 template <typename T>
 inline T SK_ANNOTATE_UNPROTECTED_READ(const volatile T& x) {
     AnnotateIgnoreReadsBegin(__FILE__, __LINE__);
     T read = x;
     AnnotateIgnoreReadsEnd(__FILE__, __LINE__);
     return read;
 }
 
+// Ignore racy reads and racy writes to this pointer, indefinitely.
+// If at all possible, use the more precise SK_ANNOTATE_UNPROTECTED_READ.
+template <typename T>
+void SK_ANNOTATE_BENIGN_RACE(T* ptr) {
+    AnnotateBenignRaceSized(__FILE__, __LINE__, ptr, sizeof(*ptr), "SK_ANNOTATE_BENIGN_RACE");
+}
+
 #else  // !DYNAMIC_ANNOTATIONS_ENABLED
 
 #define SK_ANNOTATE_UNPROTECTED_READ(x) (x)
+#define SK_ANNOTATE_BENIGN_RACE(ptr)
 
 #endif
 
+// Can be used to wrap values that are intentionally racy, usually small mutable cached values, e.g.
+//   - SkMatrix type mask
+//   - SkPathRef bounds
+//   - SkPixelRef genIDs
+template <typename T>
+class SkRacy {

[reed1, 2014/07/08 19:08:54]

nit: SkTRacy

[mtklein, 2014/07/08 19:14:22]

Done.

+public:
+    SkRacy() { SK_ANNOTATE_BENIGN_RACE(&fVal); }
+
+    operator const T&() const {
+        return fVal;
+    }
+
+    SkRacy& operator=(const T& val) {
+        fVal = val;
+        return *this;
+    }
+
+    const T* get() const { return &fVal; }
+          T* get()       { return &fVal; }
+
+    const T* operator->() const { return &fVal; }
+          T* operator->()       { return &fVal; }
+
+private:
+    T fVal;
+};
+
 #endif//SkDynamicAnnotations_DEFINED