1 //===-- sanitizer_stackdepotbase.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 // Implementation of a mapping from arbitrary values to unique 32-bit
11 // identifiers.
12 //===----------------------------------------------------------------------===//
13
14 #ifndef SANITIZER_STACKDEPOTBASE_H
15 #define SANITIZER_STACKDEPOTBASE_H
16
17 #include "sanitizer_internal_defs.h"
18 #include "sanitizer_mutex.h"
19 #include "sanitizer_atomic.h"
20 #include "sanitizer_persistent_allocator.h"
21
22 namespace __sanitizer {
23
24 template <class Node, int kReservedBits, int kTabSizeLog>
25 class StackDepotBase {
26 public:
27 typedef typename Node::args_type args_type;
28 typedef typename Node::handle_type handle_type;
29 // Maps stack trace to an unique id.
30 handle_type Put(args_type args, bool *inserted = nullptr);
31 // Retrieves a stored stack trace by the id.
32 args_type Get(u32 id);
33
GetStats()34 StackDepotStats *GetStats() { return &stats; }
35
36 void LockAll();
37 void UnlockAll();
38
39 private:
40 static Node *find(Node *s, args_type args, u32 hash);
41 static Node *lock(atomic_uintptr_t *p);
42 static void unlock(atomic_uintptr_t *p, Node *s);
43
44 static const int kTabSize = 1 << kTabSizeLog; // Hash table size.
45 static const int kPartBits = 8;
46 static const int kPartShift = sizeof(u32) * 8 - kPartBits - kReservedBits;
47 static const int kPartCount =
48 1 << kPartBits; // Number of subparts in the table.
49 static const int kPartSize = kTabSize / kPartCount;
50 static const int kMaxId = 1 << kPartShift;
51
52 atomic_uintptr_t tab[kTabSize]; // Hash table of Node's.
53 atomic_uint32_t seq[kPartCount]; // Unique id generators.
54
55 StackDepotStats stats;
56
57 friend class StackDepotReverseMap;
58 };
59
60 template <class Node, int kReservedBits, int kTabSizeLog>
find(Node * s,args_type args,u32 hash)61 Node *StackDepotBase<Node, kReservedBits, kTabSizeLog>::find(Node *s,
62 args_type args,
63 u32 hash) {
64 // Searches linked list s for the stack, returns its id.
65 for (; s; s = s->link) {
66 if (s->eq(hash, args)) {
67 return s;
68 }
69 }
70 return nullptr;
71 }
72
73 template <class Node, int kReservedBits, int kTabSizeLog>
lock(atomic_uintptr_t * p)74 Node *StackDepotBase<Node, kReservedBits, kTabSizeLog>::lock(
75 atomic_uintptr_t *p) {
76 // Uses the pointer lsb as mutex.
77 for (int i = 0;; i++) {
78 uptr cmp = atomic_load(p, memory_order_relaxed);
79 if ((cmp & 1) == 0 &&
80 atomic_compare_exchange_weak(p, &cmp, cmp | 1, memory_order_acquire))
81 return (Node *)cmp;
82 if (i < 10)
83 proc_yield(10);
84 else
85 internal_sched_yield();
86 }
87 }
88
89 template <class Node, int kReservedBits, int kTabSizeLog>
unlock(atomic_uintptr_t * p,Node * s)90 void StackDepotBase<Node, kReservedBits, kTabSizeLog>::unlock(
91 atomic_uintptr_t *p, Node *s) {
92 DCHECK_EQ((uptr)s & 1, 0);
93 atomic_store(p, (uptr)s, memory_order_release);
94 }
95
96 template <class Node, int kReservedBits, int kTabSizeLog>
97 typename StackDepotBase<Node, kReservedBits, kTabSizeLog>::handle_type
Put(args_type args,bool * inserted)98 StackDepotBase<Node, kReservedBits, kTabSizeLog>::Put(args_type args,
99 bool *inserted) {
100 if (inserted) *inserted = false;
101 if (!Node::is_valid(args)) return handle_type();
102 uptr h = Node::hash(args);
103 atomic_uintptr_t *p = &tab[h % kTabSize];
104 uptr v = atomic_load(p, memory_order_consume);
105 Node *s = (Node *)(v & ~1);
106 // First, try to find the existing stack.
107 Node *node = find(s, args, h);
108 if (node) return node->get_handle();
109 // If failed, lock, retry and insert new.
110 Node *s2 = lock(p);
111 if (s2 != s) {
112 node = find(s2, args, h);
113 if (node) {
114 unlock(p, s2);
115 return node->get_handle();
116 }
117 }
118 uptr part = (h % kTabSize) / kPartSize;
119 u32 id = atomic_fetch_add(&seq[part], 1, memory_order_relaxed) + 1;
120 stats.n_uniq_ids++;
121 CHECK_LT(id, kMaxId);
122 id |= part << kPartShift;
123 CHECK_NE(id, 0);
124 CHECK_EQ(id & (((u32)-1) >> kReservedBits), id);
125 uptr memsz = Node::storage_size(args);
126 s = (Node *)PersistentAlloc(memsz);
127 stats.allocated += memsz;
128 s->id = id;
129 s->store(args, h);
130 s->link = s2;
131 unlock(p, s);
132 if (inserted) *inserted = true;
133 return s->get_handle();
134 }
135
136 template <class Node, int kReservedBits, int kTabSizeLog>
137 typename StackDepotBase<Node, kReservedBits, kTabSizeLog>::args_type
Get(u32 id)138 StackDepotBase<Node, kReservedBits, kTabSizeLog>::Get(u32 id) {
139 if (id == 0) {
140 return args_type();
141 }
142 CHECK_EQ(id & (((u32)-1) >> kReservedBits), id);
143 // High kPartBits contain part id, so we need to scan at most kPartSize lists.
144 uptr part = id >> kPartShift;
145 for (int i = 0; i != kPartSize; i++) {
146 uptr idx = part * kPartSize + i;
147 CHECK_LT(idx, kTabSize);
148 atomic_uintptr_t *p = &tab[idx];
149 uptr v = atomic_load(p, memory_order_consume);
150 Node *s = (Node *)(v & ~1);
151 for (; s; s = s->link) {
152 if (s->id == id) {
153 return s->load();
154 }
155 }
156 }
157 return args_type();
158 }
159
160 template <class Node, int kReservedBits, int kTabSizeLog>
LockAll()161 void StackDepotBase<Node, kReservedBits, kTabSizeLog>::LockAll() {
162 for (int i = 0; i < kTabSize; ++i) {
163 lock(&tab[i]);
164 }
165 }
166
167 template <class Node, int kReservedBits, int kTabSizeLog>
UnlockAll()168 void StackDepotBase<Node, kReservedBits, kTabSizeLog>::UnlockAll() {
169 for (int i = 0; i < kTabSize; ++i) {
170 atomic_uintptr_t *p = &tab[i];
171 uptr s = atomic_load(p, memory_order_relaxed);
172 unlock(p, (Node *)(s & ~1UL));
173 }
174 }
175
176 } // namespace __sanitizer
177
178 #endif // SANITIZER_STACKDEPOTBASE_H
179