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73 lines
2.1 KiB
C++
73 lines
2.1 KiB
C++
//===-- sanitizer_lfstack.h -=-----------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// Lock-free stack.
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// Uses 32/17 bits as ABA-counter on 32/64-bit platforms.
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// The memory passed to Push() must not be ever munmap'ed.
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// The type T must contain T *next field.
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//
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//===----------------------------------------------------------------------===//
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#ifndef SANITIZER_LFSTACK_H
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#define SANITIZER_LFSTACK_H
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#include "sanitizer_internal_defs.h"
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#include "sanitizer_common.h"
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#include "sanitizer_atomic.h"
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namespace __sanitizer {
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template<typename T>
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struct LFStack {
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void Clear() {
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atomic_store(&head_, 0, memory_order_relaxed);
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}
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bool Empty() const {
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return (atomic_load(&head_, memory_order_relaxed) & kPtrMask) == 0;
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}
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void Push(T *p) {
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u64 cmp = atomic_load(&head_, memory_order_relaxed);
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for (;;) {
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u64 cnt = (cmp & kCounterMask) + kCounterInc;
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u64 xch = (u64)(uptr)p | cnt;
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p->next = (T*)(uptr)(cmp & kPtrMask);
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if (atomic_compare_exchange_weak(&head_, &cmp, xch,
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memory_order_release))
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break;
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}
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}
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T *Pop() {
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u64 cmp = atomic_load(&head_, memory_order_acquire);
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for (;;) {
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T *cur = (T*)(uptr)(cmp & kPtrMask);
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if (!cur)
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return nullptr;
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T *nxt = cur->next;
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u64 cnt = (cmp & kCounterMask);
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u64 xch = (u64)(uptr)nxt | cnt;
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if (atomic_compare_exchange_weak(&head_, &cmp, xch,
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memory_order_acquire))
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return cur;
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}
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}
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// private:
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static const int kCounterBits = FIRST_32_SECOND_64(32, 17);
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static const u64 kPtrMask = ((u64)-1) >> kCounterBits;
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static const u64 kCounterMask = ~kPtrMask;
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static const u64 kCounterInc = kPtrMask + 1;
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atomic_uint64_t head_;
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};
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} // namespace __sanitizer
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#endif // SANITIZER_LFSTACK_H
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