1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/skia/trunk/include/core/SkDynamicAnnotations.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,46 @@
1.4 +/*
1.5 + * Copyright 2014 Google Inc.
1.6 + *
1.7 + * Use of this source code is governed by a BSD-style license that can be
1.8 + * found in the LICENSE file.
1.9 + */
1.10 +
1.11 +#ifndef SkDynamicAnnotations_DEFINED
1.12 +#define SkDynamicAnnotations_DEFINED
1.13 +
1.14 +// This file contains macros used to send out-of-band signals to dynamic instrumentation systems,
1.15 +// namely thread sanitizer. This is a cut-down version of the full dynamic_annotations library with
1.16 +// only the features used by Skia.
1.17 +
1.18 +// We check the same define to know to enable the annotations, but prefix all our macros with SK_.
1.19 +#if DYNAMIC_ANNOTATIONS_ENABLED
1.20 +
1.21 +extern "C" {
1.22 +// TSAN provides these hooks.
1.23 +void AnnotateIgnoreReadsBegin(const char* file, int line);
1.24 +void AnnotateIgnoreReadsEnd(const char* file, int line);
1.25 +} // extern "C"
1.26 +
1.27 +// SK_ANNOTATE_UNPROTECTED_READ can wrap any variable read to tell TSAN to ignore that it appears to
1.28 +// be a racy read. This should be used only when we can make an external guarantee that though this
1.29 +// particular read is racy, it is being used as part of a mechanism which is thread safe. Examples:
1.30 +// - the first check in double-checked locking;
1.31 +// - checking if a ref count is equal to 1.
1.32 +// Note that in both these cases, we must still add terrifyingly subtle memory barriers to provide
1.33 +// that overall thread safety guarantee. Using this macro to shut TSAN up without providing such an
1.34 +// external guarantee is pretty much never correct.
1.35 +template <typename T>
1.36 +inline T SK_ANNOTATE_UNPROTECTED_READ(const volatile T& x) {
1.37 + AnnotateIgnoreReadsBegin(__FILE__, __LINE__);
1.38 + T read = x;
1.39 + AnnotateIgnoreReadsEnd(__FILE__, __LINE__);
1.40 + return read;
1.41 +}
1.42 +
1.43 +#else // !DYNAMIC_ANNOTATIONS_ENABLED
1.44 +
1.45 +#define SK_ANNOTATE_UNPROTECTED_READ(x) (x)
1.46 +
1.47 +#endif
1.48 +
1.49 +#endif//SkDynamicAnnotations_DEFINED
