1//===-- tsan_dense_alloc.h --------------------------------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file is a part of ThreadSanitizer (TSan), a race detector. 11// 12// A DenseSlabAlloc is a freelist-based allocator of fixed-size objects. 13// DenseSlabAllocCache is a thread-local cache for DenseSlabAlloc. 14// The only difference with traditional slab allocators is that DenseSlabAlloc 15// allocates/free indices of objects and provide a functionality to map 16// the index onto the real pointer. The index is u32, that is, 2 times smaller 17// than uptr (hense the Dense prefix). 18//===----------------------------------------------------------------------===// 19#ifndef TSAN_DENSE_ALLOC_H 20#define TSAN_DENSE_ALLOC_H 21 22#include "sanitizer_common/sanitizer_common.h" 23#include "tsan_defs.h" 24#include "tsan_mutex.h" 25 26namespace __tsan { 27 28class DenseSlabAllocCache { 29 static const uptr kSize = 128; 30 typedef u32 IndexT; 31 uptr pos; 32 IndexT cache[kSize]; 33 template<typename T, uptr kL1Size, uptr kL2Size> friend class DenseSlabAlloc; 34}; 35 36template<typename T, uptr kL1Size, uptr kL2Size> 37class DenseSlabAlloc { 38 public: 39 typedef DenseSlabAllocCache Cache; 40 typedef typename Cache::IndexT IndexT; 41 42 DenseSlabAlloc() { 43 // Check that kL1Size and kL2Size are sane. 44 CHECK_EQ(kL1Size & (kL1Size - 1), 0); 45 CHECK_EQ(kL2Size & (kL2Size - 1), 0); 46 CHECK_GE(1ull << (sizeof(IndexT) * 8), kL1Size * kL2Size); 47 // Check that it makes sense to use the dense alloc. 48 CHECK_GE(sizeof(T), sizeof(IndexT)); 49 internal_memset(map_, 0, sizeof(map_)); 50 freelist_ = 0; 51 fillpos_ = 0; 52 } 53 54 ~DenseSlabAlloc() { 55 for (uptr i = 0; i < kL1Size; i++) { 56 if (map_[i] != 0) 57 UnmapOrDie(map_[i], kL2Size * sizeof(T)); 58 } 59 } 60 61 IndexT Alloc(Cache *c) { 62 if (c->pos == 0) 63 Refill(c); 64 return c->cache[--c->pos]; 65 } 66 67 void Free(Cache *c, IndexT idx) { 68 DCHECK_NE(idx, 0); 69 if (c->pos == Cache::kSize) 70 Drain(c); 71 c->cache[c->pos++] = idx; 72 } 73 74 T *Map(IndexT idx) { 75 DCHECK_NE(idx, 0); 76 DCHECK_LE(idx, kL1Size * kL2Size); 77 return &map_[idx / kL2Size][idx % kL2Size]; 78 } 79 80 void FlushCache(Cache *c) { 81 SpinMutexLock lock(&mtx_); 82 while (c->pos) { 83 IndexT idx = c->cache[--c->pos]; 84 *(IndexT*)Map(idx) = freelist_; 85 freelist_ = idx; 86 } 87 } 88 89 void InitCache(Cache *c) { 90 c->pos = 0; 91 internal_memset(c->cache, 0, sizeof(c->cache)); 92 } 93 94 private: 95 T *map_[kL1Size]; 96 SpinMutex mtx_; 97 IndexT freelist_; 98 uptr fillpos_; 99 100 void Refill(Cache *c) { 101 SpinMutexLock lock(&mtx_); 102 if (freelist_ == 0) { 103 if (fillpos_ == kL1Size) { 104 Printf("ThreadSanitizer: DenseSlabAllocator overflow. Dying.\n"); 105 Die(); 106 } 107 T *batch = (T*)MmapOrDie(kL2Size * sizeof(T), "DenseSlabAllocator"); 108 // Reserve 0 as invalid index. 109 IndexT start = fillpos_ == 0 ? 1 : 0; 110 for (IndexT i = start; i < kL2Size; i++) { 111 new(batch + i) T(); 112 *(IndexT*)(batch + i) = i + 1 + fillpos_ * kL2Size; 113 } 114 *(IndexT*)(batch + kL2Size - 1) = 0; 115 freelist_ = fillpos_ * kL2Size + start; 116 map_[fillpos_++] = batch; 117 } 118 for (uptr i = 0; i < Cache::kSize / 2 && freelist_ != 0; i++) { 119 IndexT idx = freelist_; 120 c->cache[c->pos++] = idx; 121 freelist_ = *(IndexT*)Map(idx); 122 } 123 } 124 125 void Drain(Cache *c) { 126 SpinMutexLock lock(&mtx_); 127 for (uptr i = 0; i < Cache::kSize / 2; i++) { 128 IndexT idx = c->cache[--c->pos]; 129 *(IndexT*)Map(idx) = freelist_; 130 freelist_ = idx; 131 } 132 } 133}; 134 135} // namespace __tsan 136 137#endif // TSAN_DENSE_ALLOC_H 138