libsanitizer/sanitizer_common/sanitizer_stackdepotbase.h

   1 //===-- sanitizer_stackdepotbase.h ------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Implementation of a mapping from arbitrary values to unique 32-bit
  10 // identifiers.
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef SANITIZER_STACKDEPOTBASE_H
  14 #define SANITIZER_STACKDEPOTBASE_H
  15
  16 #include <stdio.h>
  17
  18 #include "sanitizer_atomic.h"
  19 #include "sanitizer_internal_defs.h"
  20 #include "sanitizer_mutex.h"
  21 #include "sanitizer_persistent_allocator.h"
  22
  23 namespace __sanitizer {
  24
  25 template <class Node, int kReservedBits, int kTabSizeLog>
  26 class StackDepotBase {
  27  public:
  28   typedef typename Node::args_type args_type;
  29   typedef typename Node::handle_type handle_type;
  30   // Maps stack trace to an unique id.
  31   handle_type Put(args_type args, bool *inserted = nullptr);
  32   // Retrieves a stored stack trace by the id.
  33   args_type Get(u32 id);
  34
  35   StackDepotStats *GetStats() { return &stats; }
  36
  37   void LockAll();
  38   void UnlockAll();
  39   void PrintAll();
  40
  41  private:
  42   static Node *find(Node *s, args_type args, u32 hash);
  43   static Node *lock(atomic_uintptr_t *p);
  44   static void unlock(atomic_uintptr_t *p, Node *s);
  45
  46   static const int kTabSize = 1 << kTabSizeLog;  // Hash table size.
  47   static const int kPartBits = 8;
  48   static const int kPartShift = sizeof(u32) * 8 - kPartBits - kReservedBits;
  49   static const int kPartCount =
  50       1 << kPartBits;  // Number of subparts in the table.
  51   static const int kPartSize = kTabSize / kPartCount;
  52   static const int kMaxId = 1 << kPartShift;
  53
  54   atomic_uintptr_t tab[kTabSize];   // Hash table of Node's.
  55   atomic_uint32_t seq[kPartCount];  // Unique id generators.
  56
  57   StackDepotStats stats;
  58
  59   friend class StackDepotReverseMap;
  60 };
  61
  62 template <class Node, int kReservedBits, int kTabSizeLog>
  63 Node *StackDepotBase<Node, kReservedBits, kTabSizeLog>::find(Node *s,
  64                                                              args_type args,
  65                                                              u32 hash) {
  66   // Searches linked list s for the stack, returns its id.
  67   for (; s; s = s->link) {
  68     if (s->eq(hash, args)) {
  69       return s;
  70     }
  71   }
  72   return nullptr;
  73 }
  74
  75 template <class Node, int kReservedBits, int kTabSizeLog>
  76 Node *StackDepotBase<Node, kReservedBits, kTabSizeLog>::lock(
  77     atomic_uintptr_t *p) {
  78   // Uses the pointer lsb as mutex.
  79   for (int i = 0;; i++) {
  80     uptr cmp = atomic_load(p, memory_order_relaxed);
  81     if ((cmp & 1) == 0 &&
  82         atomic_compare_exchange_weak(p, &cmp, cmp | 1, memory_order_acquire))
  83       return (Node *)cmp;
  84     if (i < 10)
  85       proc_yield(10);
  86     else
  87       internal_sched_yield();
  88   }
  89 }
  90
  91 template <class Node, int kReservedBits, int kTabSizeLog>
  92 void StackDepotBase<Node, kReservedBits, kTabSizeLog>::unlock(
  93     atomic_uintptr_t *p, Node *s) {
  94   DCHECK_EQ((uptr)s & 1, 0);
  95   atomic_store(p, (uptr)s, memory_order_release);
  96 }
  97
  98 template <class Node, int kReservedBits, int kTabSizeLog>
  99 typename StackDepotBase<Node, kReservedBits, kTabSizeLog>::handle_type
 100 StackDepotBase<Node, kReservedBits, kTabSizeLog>::Put(args_type args,
 101                                                       bool *inserted) {
 102   if (inserted) *inserted = false;
 103   if (!Node::is_valid(args)) return handle_type();
 104   uptr h = Node::hash(args);
 105   atomic_uintptr_t *p = &tab[h % kTabSize];
 106   uptr v = atomic_load(p, memory_order_consume);
 107   Node *s = (Node *)(v & ~1);
 108   // First, try to find the existing stack.
 109   Node *node = find(s, args, h);
 110   if (node) return node->get_handle();
 111   // If failed, lock, retry and insert new.
 112   Node *s2 = lock(p);
 113   if (s2 != s) {
 114     node = find(s2, args, h);
 115     if (node) {
 116       unlock(p, s2);
 117       return node->get_handle();
 118     }
 119   }
 120   uptr part = (h % kTabSize) / kPartSize;
 121   u32 id = atomic_fetch_add(&seq[part], 1, memory_order_relaxed) + 1;
 122   stats.n_uniq_ids++;
 123   CHECK_LT(id, kMaxId);
 124   id |= part << kPartShift;
 125   CHECK_NE(id, 0);
 126   CHECK_EQ(id & (((u32)-1) >> kReservedBits), id);
 127   uptr memsz = Node::storage_size(args);
 128   s = (Node *)PersistentAlloc(memsz);
 129   stats.allocated += memsz;
 130   s->id = id;
 131   s->store(args, h);
 132   s->link = s2;
 133   unlock(p, s);
 134   if (inserted) *inserted = true;
 135   return s->get_handle();
 136 }
 137
 138 template <class Node, int kReservedBits, int kTabSizeLog>
 139 typename StackDepotBase<Node, kReservedBits, kTabSizeLog>::args_type
 140 StackDepotBase<Node, kReservedBits, kTabSizeLog>::Get(u32 id) {
 141   if (id == 0) {
 142     return args_type();
 143   }
 144   CHECK_EQ(id & (((u32)-1) >> kReservedBits), id);
 145   // High kPartBits contain part id, so we need to scan at most kPartSize lists.
 146   uptr part = id >> kPartShift;
 147   for (int i = 0; i != kPartSize; i++) {
 148     uptr idx = part * kPartSize + i;
 149     CHECK_LT(idx, kTabSize);
 150     atomic_uintptr_t *p = &tab[idx];
 151     uptr v = atomic_load(p, memory_order_consume);
 152     Node *s = (Node *)(v & ~1);
 153     for (; s; s = s->link) {
 154       if (s->id == id) {
 155         return s->load();
 156       }
 157     }
 158   }
 159   return args_type();
 160 }
 161
 162 template <class Node, int kReservedBits, int kTabSizeLog>
 163 void StackDepotBase<Node, kReservedBits, kTabSizeLog>::LockAll() {
 164   for (int i = 0; i < kTabSize; ++i) {
 165     lock(&tab[i]);
 166   }
 167 }
 168
 169 template <class Node, int kReservedBits, int kTabSizeLog>
 170 void StackDepotBase<Node, kReservedBits, kTabSizeLog>::UnlockAll() {
 171   for (int i = 0; i < kTabSize; ++i) {
 172     atomic_uintptr_t *p = &tab[i];
 173     uptr s = atomic_load(p, memory_order_relaxed);
 174     unlock(p, (Node *)(s & ~1UL));
 175   }
 176 }
 177
 178 template <class Node, int kReservedBits, int kTabSizeLog>
 179 void StackDepotBase<Node, kReservedBits, kTabSizeLog>::PrintAll() {
 180   for (int i = 0; i < kTabSize; ++i) {
 181     atomic_uintptr_t *p = &tab[i];
 182     lock(p);
 183     uptr v = atomic_load(p, memory_order_relaxed);
 184     Node *s = (Node *)(v & ~1UL);
 185     for (; s; s = s->link) {
 186       Printf("Stack for id %u:\n", s->id);
 187       s->load().Print();
 188     }
 189     unlock(p, s);
 190   }
 191 }
 192
 193 } // namespace __sanitizer
 194
 195 #endif // SANITIZER_STACKDEPOTBASE_H