942e99b9c4
- Use SkAtomic<int32_t> for pending work count so we're statically
forced to operate on it with atomic methods.
- Replacing old methods like sk_atomic_inc/dec gives us finer control
over which barriers we need for each operation.
No public API changes.
TBR=reed@google.com
BUG=skia:
Review URL: https://codereview.chromium.org/1193493003
117 lines
3.9 KiB
C++
117 lines
3.9 KiB
C++
/*
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* Copyright 2015 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 SkAtomics_DEFINED
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#define SkAtomics_DEFINED
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// This file is not part of the public Skia API.
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#include "SkTypes.h"
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enum sk_memory_order {
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sk_memory_order_relaxed,
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sk_memory_order_consume,
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sk_memory_order_acquire,
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sk_memory_order_release,
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sk_memory_order_acq_rel,
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sk_memory_order_seq_cst,
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};
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template <typename T>
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T sk_atomic_load(const T*, sk_memory_order = sk_memory_order_seq_cst);
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template <typename T>
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void sk_atomic_store(T*, T, sk_memory_order = sk_memory_order_seq_cst);
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template <typename T>
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T sk_atomic_fetch_add(T*, T, sk_memory_order = sk_memory_order_seq_cst);
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template <typename T>
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bool sk_atomic_compare_exchange(T*, T* expected, T desired,
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sk_memory_order success = sk_memory_order_seq_cst,
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sk_memory_order failure = sk_memory_order_seq_cst);
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template <typename T>
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T sk_atomic_exchange(T*, T, sk_memory_order = sk_memory_order_seq_cst);
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// A little wrapper class for small T (think, builtins: int, float, void*) to
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// ensure they're always used atomically. This is our stand-in for std::atomic<T>.
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template <typename T>
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class SkAtomic : SkNoncopyable {
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public:
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SkAtomic() {}
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explicit SkAtomic(const T& val) : fVal(val) {}
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// It is essential we return by value rather than by const&. fVal may change at any time.
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T load(sk_memory_order mo = sk_memory_order_seq_cst) const {
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return sk_atomic_load(&fVal, mo);
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}
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void store(const T& val, sk_memory_order mo = sk_memory_order_seq_cst) {
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sk_atomic_store(&fVal, val, mo);
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}
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T fetch_add(const T& val, sk_memory_order mo = sk_memory_order_seq_cst) {
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return sk_atomic_fetch_add(&fVal, val, mo);
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}
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bool compare_exchange(T* expected, const T& desired,
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sk_memory_order success = sk_memory_order_seq_cst,
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sk_memory_order failure = sk_memory_order_seq_cst) {
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return sk_atomic_compare_exchange(&fVal, expected, desired, success, failure);
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}
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private:
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T fVal;
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};
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#if defined(_MSC_VER)
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#include "../ports/SkAtomics_std.h"
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#elif !defined(SK_BUILD_FOR_IOS) && defined(__ATOMIC_RELAXED)
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#include "../ports/SkAtomics_atomic.h"
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#else
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#include "../ports/SkAtomics_sync.h"
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#endif
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// From here down we have shims for our old atomics API, to be weaned off of.
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// We use the default sequentially-consistent memory order to make things simple
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// and to match the practical reality of our old _sync and _win implementations.
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inline int32_t sk_atomic_inc(int32_t* ptr) { return sk_atomic_fetch_add(ptr, +1); }
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inline int32_t sk_atomic_dec(int32_t* ptr) { return sk_atomic_fetch_add(ptr, -1); }
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inline int32_t sk_atomic_add(int32_t* ptr, int32_t v) { return sk_atomic_fetch_add(ptr, v); }
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inline int64_t sk_atomic_inc(int64_t* ptr) { return sk_atomic_fetch_add<int64_t>(ptr, +1); }
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inline bool sk_atomic_cas(int32_t* ptr, int32_t expected, int32_t desired) {
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return sk_atomic_compare_exchange(ptr, &expected, desired);
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}
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inline void* sk_atomic_cas(void** ptr, void* expected, void* desired) {
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(void)sk_atomic_compare_exchange(ptr, &expected, desired);
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return expected;
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}
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inline int32_t sk_atomic_conditional_inc(int32_t* ptr) {
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int32_t prev = sk_atomic_load(ptr);
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do {
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if (0 == prev) {
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break;
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}
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} while(!sk_atomic_compare_exchange(ptr, &prev, prev+1));
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return prev;
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}
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template <typename T>
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T sk_acquire_load(T* ptr) { return sk_atomic_load(ptr, sk_memory_order_acquire); }
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template <typename T>
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void sk_release_store(T* ptr, T val) { sk_atomic_store(ptr, val, sk_memory_order_release); }
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inline void sk_membar_acquire__after_atomic_dec() {}
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inline void sk_membar_acquire__after_atomic_conditional_inc() {}
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#endif//SkAtomics_DEFINED
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