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Side by Side Diff: include/core/SkDynamicAnnotations.h

Issue 377693005: Revert of Add SkRacy (Closed) Base URL: https://skia.googlesource.com/skia.git@master
Patch Set: Created 6 years, 5 months ago
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1 /* 1 /*
2 * Copyright 2014 Google Inc. 2 * Copyright 2014 Google Inc.
3 * 3 *
4 * Use of this source code is governed by a BSD-style license that can be 4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file. 5 * found in the LICENSE file.
6 */ 6 */
7 7
8 #ifndef SkDynamicAnnotations_DEFINED 8 #ifndef SkDynamicAnnotations_DEFINED
9 #define SkDynamicAnnotations_DEFINED 9 #define SkDynamicAnnotations_DEFINED
10 10
11 // This file contains macros used to send out-of-band signals to dynamic instrum entation systems, 11 // This file contains macros used to send out-of-band signals to dynamic instrum entation systems,
12 // namely thread sanitizer. This is a cut-down version of the full dynamic_anno tations library with 12 // namely thread sanitizer. This is a cut-down version of the full dynamic_anno tations library with
13 // only the features used by Skia. 13 // only the features used by Skia.
14 14
15 // We check the same define to know to enable the annotations, but prefix all ou r macros with SK_. 15 // We check the same define to know to enable the annotations, but prefix all ou r macros with SK_.
16 #if DYNAMIC_ANNOTATIONS_ENABLED 16 #if DYNAMIC_ANNOTATIONS_ENABLED
17 17
18 extern "C" { 18 extern "C" {
19 // TSAN provides these hooks. 19 // TSAN provides these hooks.
20 void AnnotateIgnoreReadsBegin(const char* file, int line); 20 void AnnotateIgnoreReadsBegin(const char* file, int line);
21 void AnnotateIgnoreReadsEnd(const char* file, int line); 21 void AnnotateIgnoreReadsEnd(const char* file, int line);
22 void AnnotateBenignRaceSized(const char* file, int line,
23 const void* addr, long size, const char* desc);
24 } // extern "C" 22 } // extern "C"
25 23
26 // SK_ANNOTATE_UNPROTECTED_READ can wrap any variable read to tell TSAN to ignor e that it appears to 24 // SK_ANNOTATE_UNPROTECTED_READ can wrap any variable read to tell TSAN to ignor e that it appears to
27 // be a racy read. This should be used only when we can make an external guaran tee that though this 25 // be a racy read. This should be used only when we can make an external guaran tee that though this
28 // particular read is racy, it is being used as part of a mechanism which is thr ead safe. Examples: 26 // particular read is racy, it is being used as part of a mechanism which is thr ead safe. Examples:
29 // - the first check in double-checked locking; 27 // - the first check in double-checked locking;
30 // - checking if a ref count is equal to 1. 28 // - checking if a ref count is equal to 1.
31 // Note that in both these cases, we must still add terrifyingly subtle memory b arriers to provide 29 // Note that in both these cases, we must still add terrifyingly subtle memory b arriers to provide
32 // that overall thread safety guarantee. Using this macro to shut TSAN up witho ut providing such an 30 // that overall thread safety guarantee. Using this macro to shut TSAN up witho ut providing such an
33 // external guarantee is pretty much never correct. 31 // external guarantee is pretty much never correct.
34 template <typename T> 32 template <typename T>
35 inline T SK_ANNOTATE_UNPROTECTED_READ(const volatile T& x) { 33 inline T SK_ANNOTATE_UNPROTECTED_READ(const volatile T& x) {
36 AnnotateIgnoreReadsBegin(__FILE__, __LINE__); 34 AnnotateIgnoreReadsBegin(__FILE__, __LINE__);
37 T read = x; 35 T read = x;
38 AnnotateIgnoreReadsEnd(__FILE__, __LINE__); 36 AnnotateIgnoreReadsEnd(__FILE__, __LINE__);
39 return read; 37 return read;
40 } 38 }
41 39
42 // Ignore racy reads and racy writes to this pointer, indefinitely.
43 // If at all possible, use the more precise SK_ANNOTATE_UNPROTECTED_READ.
44 template <typename T>
45 void SK_ANNOTATE_BENIGN_RACE(T* ptr) {
46 AnnotateBenignRaceSized(__FILE__, __LINE__, ptr, sizeof(*ptr), "SK_ANNOTATE_ BENIGN_RACE");
47 }
48
49 #else // !DYNAMIC_ANNOTATIONS_ENABLED 40 #else // !DYNAMIC_ANNOTATIONS_ENABLED
50 41
51 #define SK_ANNOTATE_UNPROTECTED_READ(x) (x) 42 #define SK_ANNOTATE_UNPROTECTED_READ(x) (x)
52 #define SK_ANNOTATE_BENIGN_RACE(ptr)
53 43
54 #endif 44 #endif
55 45
56 // Can be used to wrap values that are intentionally racy, usually small mutable cached values, e.g.
57 // - SkMatrix type mask
58 // - SkPathRef bounds
59 // - SkPixelRef genIDs
60 template <typename T>
61 class SkTRacy {
62 public:
63 SkTRacy() { SK_ANNOTATE_BENIGN_RACE(&fVal); }
64
65 operator const T&() const {
66 return fVal;
67 }
68
69 SkTRacy& operator=(const T& val) {
70 fVal = val;
71 return *this;
72 }
73
74 const T* get() const { return &fVal; }
75 T* get() { return &fVal; }
76
77 const T* operator->() const { return &fVal; }
78 T* operator->() { return &fVal; }
79
80 private:
81 T fVal;
82 };
83
84 #endif//SkDynamicAnnotations_DEFINED 46 #endif//SkDynamicAnnotations_DEFINED
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