blob: 422d98db43d2f92bcb049872cec24db33c012c51 [file] [log] [blame]
* 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.
extern "C" {
// TSAN provides these hooks.
void AnnotateIgnoreReadsBegin(const char* file, int line);
void AnnotateIgnoreReadsEnd(const char* file, int line);
void AnnotateIgnoreWritesBegin(const char* file, int line);
void AnnotateIgnoreWritesEnd(const char* file, int line);
void AnnotateBenignRaceSized(const char* file, int line,
const volatile void* addr, long size, const char* desc);
} // 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;
// Like SK_ANNOTATE_UNPROTECTED_READ, but for writes.
template <typename T>
inline void SK_ANNOTATE_UNPROTECTED_WRITE(T* ptr, const volatile T& val) {
AnnotateIgnoreWritesBegin(__FILE__, __LINE__);
*ptr = val;
AnnotateIgnoreWritesEnd(__FILE__, __LINE__);
// Ignore racy reads and racy writes to this pointer, indefinitely.
// If at all possible, use the more precise SK_ANNOTATE_UNPROTECTED_READ.
template <typename T>
AnnotateBenignRaceSized(__FILE__, __LINE__, ptr, sizeof(*ptr), "SK_ANNOTATE_BENIGN_RACE");
#define SK_ANNOTATE_UNPROTECTED_WRITE(ptr, val) *(ptr) = (val)
// Can be used to wrap values that are intentionally racy, usually small mutable cached values, e.g.
// - SkMatrix type mask
// - SkPixelRef genIDs
template <typename T>
class SkTRacy {
operator const T() const {
SkTRacy& operator=(const T& val) {
return *this;
T fVal;
// This is like SkTRacy, but allows you to return the value by reference.
// TSAN is better at suppressing SkTRacy than SkTRacyReffable, so use SkTRacy when possible.
// We use this for SkPathRef bounds, which is an SkRect we pass around by reference publically.
template <typename T>
class SkTRacyReffable {
SkTRacyReffable() { SK_ANNOTATE_BENIGN_RACE(&fVal); }
operator const T&() const {
return fVal;
SkTRacyReffable& operator=(const T& val) {
fVal = val;
return *this;
const T* get() const { return &fVal; }
T* get() { return &fVal; }
const T* operator->() const { return &fVal; }
T* operator->() { return &fVal; }
T fVal;