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//===-- tsan_dense_alloc.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
//
//===----------------------------------------------------------------------===//
//
// This file is a part of ThreadSanitizer (TSan), a race detector.
//
// A DenseSlabAlloc is a freelist-based allocator of fixed-size objects.
// DenseSlabAllocCache is a thread-local cache for DenseSlabAlloc.
// The only difference with traditional slab allocators is that DenseSlabAlloc
// allocates/free indices of objects and provide a functionality to map
// the index onto the real pointer. The index is u32, that is, 2 times smaller
// than uptr (hense the Dense prefix).
//===----------------------------------------------------------------------===//
#ifndef TSAN_DENSE_ALLOC_H
#define TSAN_DENSE_ALLOC_H
#include "sanitizer_common/sanitizer_common.h"
#include "tsan_defs.h"
#include "tsan_mutex.h"
namespace __tsan {
class DenseSlabAllocCache {
static const uptr kSize = 128;
typedef u32 IndexT;
uptr pos;
IndexT cache[kSize];
template<typename T, uptr kL1Size, uptr kL2Size> friend class DenseSlabAlloc;
};
template<typename T, uptr kL1Size, uptr kL2Size>
class DenseSlabAlloc {
public:
typedef DenseSlabAllocCache Cache;
typedef typename Cache::IndexT IndexT;
explicit DenseSlabAlloc(const char *name) {
// Check that kL1Size and kL2Size are sane.
CHECK_EQ(kL1Size & (kL1Size - 1), 0);
CHECK_EQ(kL2Size & (kL2Size - 1), 0);
CHECK_GE(1ull << (sizeof(IndexT) * 8), kL1Size * kL2Size);
// Check that it makes sense to use the dense alloc.
CHECK_GE(sizeof(T), sizeof(IndexT));
internal_memset(map_, 0, sizeof(map_));
freelist_ = 0;
fillpos_ = 0;
name_ = name;
}
~DenseSlabAlloc() {
for (uptr i = 0; i < kL1Size; i++) {
if (map_[i] != 0)
UnmapOrDie(map_[i], kL2Size * sizeof(T));
}
}
IndexT Alloc(Cache *c) {
if (c->pos == 0)
Refill(c);
return c->cache[--c->pos];
}
void Free(Cache *c, IndexT idx) {
DCHECK_NE(idx, 0);
if (c->pos == Cache::kSize)
Drain(c);
c->cache[c->pos++] = idx;
}
T *Map(IndexT idx) {
DCHECK_NE(idx, 0);
DCHECK_LE(idx, kL1Size * kL2Size);
return &map_[idx / kL2Size][idx % kL2Size];
}
void FlushCache(Cache *c) {
SpinMutexLock lock(&mtx_);
while (c->pos) {
IndexT idx = c->cache[--c->pos];
*(IndexT*)Map(idx) = freelist_;
freelist_ = idx;
}
}
void InitCache(Cache *c) {
c->pos = 0;
internal_memset(c->cache, 0, sizeof(c->cache));
}
private:
T *map_[kL1Size];
SpinMutex mtx_;
IndexT freelist_;
uptr fillpos_;
const char *name_;
void Refill(Cache *c) {
SpinMutexLock lock(&mtx_);
if (freelist_ == 0) {
if (fillpos_ == kL1Size) {
Printf("ThreadSanitizer: %s overflow (%zu*%zu). Dying.\n",
name_, kL1Size, kL2Size);
Die();
}
VPrintf(2, "ThreadSanitizer: growing %s: %zu out of %zu*%zu\n",
name_, fillpos_, kL1Size, kL2Size);
T *batch = (T*)MmapOrDie(kL2Size * sizeof(T), name_);
// Reserve 0 as invalid index.
IndexT start = fillpos_ == 0 ? 1 : 0;
for (IndexT i = start; i < kL2Size; i++) {
new(batch + i) T;
*(IndexT*)(batch + i) = i + 1 + fillpos_ * kL2Size;
}
*(IndexT*)(batch + kL2Size - 1) = 0;
freelist_ = fillpos_ * kL2Size + start;
map_[fillpos_++] = batch;
}
for (uptr i = 0; i < Cache::kSize / 2 && freelist_ != 0; i++) {
IndexT idx = freelist_;
c->cache[c->pos++] = idx;
freelist_ = *(IndexT*)Map(idx);
}
}
void Drain(Cache *c) {
SpinMutexLock lock(&mtx_);
for (uptr i = 0; i < Cache::kSize / 2; i++) {
IndexT idx = c->cache[--c->pos];
*(IndexT*)Map(idx) = freelist_;
freelist_ = idx;
}
}
};
} // namespace __tsan
#endif // TSAN_DENSE_ALLOC_H
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