47 lines
1.7 KiB
C
47 lines
1.7 KiB
C
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/*
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* Copyright 2014 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkDynamicAnnotations_DEFINED
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#define SkDynamicAnnotations_DEFINED
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// This file contains macros used to send out-of-band signals to dynamic instrumentation systems,
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// namely thread sanitizer. This is a cut-down version of the full dynamic_annotations library with
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// only the features used by Skia.
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// We check the same define to know to enable the annotations, but prefix all our macros with SK_.
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#if DYNAMIC_ANNOTATIONS_ENABLED
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extern "C" {
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// TSAN provides these hooks.
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void AnnotateIgnoreReadsBegin(const char* file, int line);
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void AnnotateIgnoreReadsEnd(const char* file, int line);
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} // extern "C"
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// SK_ANNOTATE_UNPROTECTED_READ can wrap any variable read to tell TSAN to ignore that it appears to
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// be a racy read. This should be used only when we can make an external guarantee that though this
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// particular read is racy, it is being used as part of a mechanism which is thread safe. Examples:
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// - the first check in double-checked locking;
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// - checking if a ref count is equal to 1.
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// Note that in both these cases, we must still add terrifyingly subtle memory barriers to provide
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// that overall thread safety guarantee. Using this macro to shut TSAN up without providing such an
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// external guarantee is pretty much never correct.
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template <typename T>
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inline T SK_ANNOTATE_UNPROTECTED_READ(const volatile T& x) {
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AnnotateIgnoreReadsBegin(__FILE__, __LINE__);
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T read = x;
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AnnotateIgnoreReadsEnd(__FILE__, __LINE__);
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return read;
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}
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#else // !DYNAMIC_ANNOTATIONS_ENABLED
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#define SK_ANNOTATE_UNPROTECTED_READ(x) (x)
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#endif
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#endif//SkDynamicAnnotations_DEFINED
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