mirror of
https://github.com/llvm/llvm-project.git
synced 2025-04-26 16:26:05 +00:00
2946cd7010
to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
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
|