| /* |
| * 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); |
| } // 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; |
| } |
| |
| #else // !DYNAMIC_ANNOTATIONS_ENABLED |
| |
| #define SK_ANNOTATE_UNPROTECTED_READ(x) (x) |
| |
| #endif |
| |
| #endif//SkDynamicAnnotations_DEFINED |