gfx/skia/trunk/include/core/SkDynamicAnnotations.h@b8a032363ba2 (annotated)
gfx/skia/trunk/include/core/SkDynamicAnnotations.h
Thu, 22 Jan 2015 13:21:57 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Thu, 22 Jan 2015 13:21:57 +0100
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
- permissions
- -rw-r--r--
Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6
| michael@0 | 1 | /* |
| michael@0 | 2 | * Copyright 2014 Google Inc. |
| michael@0 | 3 | * |
| michael@0 | 4 | * Use of this source code is governed by a BSD-style license that can be |
| michael@0 | 5 | * found in the LICENSE file. |
| michael@0 | 6 | */ |
| michael@0 | 7 | |
| michael@0 | 8 | #ifndef SkDynamicAnnotations_DEFINED |
| michael@0 | 9 | #define SkDynamicAnnotations_DEFINED |
| michael@0 | 10 | |
| michael@0 | 11 | // This file contains macros used to send out-of-band signals to dynamic instrumentation systems, |
| michael@0 | 12 | // namely thread sanitizer. This is a cut-down version of the full dynamic_annotations library with |
| michael@0 | 13 | // only the features used by Skia. |
| michael@0 | 14 | |
| michael@0 | 15 | // We check the same define to know to enable the annotations, but prefix all our macros with SK_. |
| michael@0 | 16 | #if DYNAMIC_ANNOTATIONS_ENABLED |
| michael@0 | 17 | |
| michael@0 | 18 | extern "C" { |
| michael@0 | 19 | // TSAN provides these hooks. |
| michael@0 | 20 | void AnnotateIgnoreReadsBegin(const char* file, int line); |
| michael@0 | 21 | void AnnotateIgnoreReadsEnd(const char* file, int line); |
| michael@0 | 22 | } // extern "C" |
| michael@0 | 23 | |
| michael@0 | 24 | // SK_ANNOTATE_UNPROTECTED_READ can wrap any variable read to tell TSAN to ignore that it appears to |
| michael@0 | 25 | // be a racy read. This should be used only when we can make an external guarantee that though this |
| michael@0 | 26 | // particular read is racy, it is being used as part of a mechanism which is thread safe. Examples: |
| michael@0 | 27 | // - the first check in double-checked locking; |
| michael@0 | 28 | // - checking if a ref count is equal to 1. |
| michael@0 | 29 | // Note that in both these cases, we must still add terrifyingly subtle memory barriers to provide |
| michael@0 | 30 | // that overall thread safety guarantee. Using this macro to shut TSAN up without providing such an |
| michael@0 | 31 | // external guarantee is pretty much never correct. |
| michael@0 | 32 | template <typename T> |
| michael@0 | 33 | inline T SK_ANNOTATE_UNPROTECTED_READ(const volatile T& x) { |
| michael@0 | 34 | AnnotateIgnoreReadsBegin(__FILE__, __LINE__); |
| michael@0 | 35 | T read = x; |
| michael@0 | 36 | AnnotateIgnoreReadsEnd(__FILE__, __LINE__); |
| michael@0 | 37 | return read; |
| michael@0 | 38 | } |
| michael@0 | 39 | |
| michael@0 | 40 | #else // !DYNAMIC_ANNOTATIONS_ENABLED |
| michael@0 | 41 | |
| michael@0 | 42 | #define SK_ANNOTATE_UNPROTECTED_READ(x) (x) |
| michael@0 | 43 | |
| michael@0 | 44 | #endif |
| michael@0 | 45 | |
| michael@0 | 46 | #endif//SkDynamicAnnotations_DEFINED |
