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