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//===-- sanitizer_stackdepotbase.h ------------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Implementation of a mapping from arbitrary values to unique 32-bit
// identifiers.
//===----------------------------------------------------------------------===//
#ifndef SANITIZER_STACKDEPOTBASE_H
#define SANITIZER_STACKDEPOTBASE_H
#include "sanitizer_internal_defs.h"
#include "sanitizer_mutex.h"
#include "sanitizer_atomic.h"
#include "sanitizer_persistent_allocator.h"
namespace __sanitizer {
template <class Node, int kReservedBits, int kTabSizeLog>
class StackDepotBase {
public:
typedef typename Node::args_type args_type;
typedef typename Node::handle_type handle_type;
// Maps stack trace to an unique id.
handle_type Put(args_type args, bool *inserted = nullptr);
// Retrieves a stored stack trace by the id.
args_type Get(u32 id);
StackDepotStats *GetStats() { return &stats; }
void LockAll();
void UnlockAll();
private:
static Node *find(Node *s, args_type args, u32 hash);
static Node *lock(atomic_uintptr_t *p);
static void unlock(atomic_uintptr_t *p, Node *s);
static const int kTabSize = 1 << kTabSizeLog; // Hash table size.
static const int kPartBits = 8;
static const int kPartShift = sizeof(u32) * 8 - kPartBits - kReservedBits;
static const int kPartCount =
1 << kPartBits; // Number of subparts in the table.
static const int kPartSize = kTabSize / kPartCount;
static const int kMaxId = 1 << kPartShift;
atomic_uintptr_t tab[kTabSize]; // Hash table of Node's.
atomic_uint32_t seq[kPartCount]; // Unique id generators.
StackDepotStats stats;
friend class StackDepotReverseMap;
};
template <class Node, int kReservedBits, int kTabSizeLog>
Node *StackDepotBase<Node, kReservedBits, kTabSizeLog>::find(Node *s,
args_type args,
u32 hash) {
// Searches linked list s for the stack, returns its id.
for (; s; s = s->link) {
if (s->eq(hash, args)) {
return s;
}
}
return nullptr;
}
template <class Node, int kReservedBits, int kTabSizeLog>
Node *StackDepotBase<Node, kReservedBits, kTabSizeLog>::lock(
atomic_uintptr_t *p) {
// Uses the pointer lsb as mutex.
for (int i = 0;; i++) {
uptr cmp = atomic_load(p, memory_order_relaxed);
if ((cmp & 1) == 0 &&
atomic_compare_exchange_weak(p, &cmp, cmp | 1, memory_order_acquire))
return (Node *)cmp;
if (i < 10)
proc_yield(10);
else
internal_sched_yield();
}
}
template <class Node, int kReservedBits, int kTabSizeLog>
void StackDepotBase<Node, kReservedBits, kTabSizeLog>::unlock(
atomic_uintptr_t *p, Node *s) {
DCHECK_EQ((uptr)s & 1, 0);
atomic_store(p, (uptr)s, memory_order_release);
}
template <class Node, int kReservedBits, int kTabSizeLog>
typename StackDepotBase<Node, kReservedBits, kTabSizeLog>::handle_type
StackDepotBase<Node, kReservedBits, kTabSizeLog>::Put(args_type args,
bool *inserted) {
if (inserted) *inserted = false;
if (!Node::is_valid(args)) return handle_type();
uptr h = Node::hash(args);
atomic_uintptr_t *p = &tab[h % kTabSize];
uptr v = atomic_load(p, memory_order_consume);
Node *s = (Node *)(v & ~1);
// First, try to find the existing stack.
Node *node = find(s, args, h);
if (node) return node->get_handle();
// If failed, lock, retry and insert new.
Node *s2 = lock(p);
if (s2 != s) {
node = find(s2, args, h);
if (node) {
unlock(p, s2);
return node->get_handle();
}
}
uptr part = (h % kTabSize) / kPartSize;
u32 id = atomic_fetch_add(&seq[part], 1, memory_order_relaxed) + 1;
stats.n_uniq_ids++;
CHECK_LT(id, kMaxId);
id |= part << kPartShift;
CHECK_NE(id, 0);
CHECK_EQ(id & (((u32)-1) >> kReservedBits), id);
uptr memsz = Node::storage_size(args);
s = (Node *)PersistentAlloc(memsz);
stats.allocated += memsz;
s->id = id;
s->store(args, h);
s->link = s2;
unlock(p, s);
if (inserted) *inserted = true;
return s->get_handle();
}
template <class Node, int kReservedBits, int kTabSizeLog>
typename StackDepotBase<Node, kReservedBits, kTabSizeLog>::args_type
StackDepotBase<Node, kReservedBits, kTabSizeLog>::Get(u32 id) {
if (id == 0) {
return args_type();
}
CHECK_EQ(id & (((u32)-1) >> kReservedBits), id);
// High kPartBits contain part id, so we need to scan at most kPartSize lists.
uptr part = id >> kPartShift;
for (int i = 0; i != kPartSize; i++) {
uptr idx = part * kPartSize + i;
CHECK_LT(idx, kTabSize);
atomic_uintptr_t *p = &tab[idx];
uptr v = atomic_load(p, memory_order_consume);
Node *s = (Node *)(v & ~1);
for (; s; s = s->link) {
if (s->id == id) {
return s->load();
}
}
}
return args_type();
}
template <class Node, int kReservedBits, int kTabSizeLog>
void StackDepotBase<Node, kReservedBits, kTabSizeLog>::LockAll() {
for (int i = 0; i < kTabSize; ++i) {
lock(&tab[i]);
}
}
template <class Node, int kReservedBits, int kTabSizeLog>
void StackDepotBase<Node, kReservedBits, kTabSizeLog>::UnlockAll() {
for (int i = 0; i < kTabSize; ++i) {
atomic_uintptr_t *p = &tab[i];
uptr s = atomic_load(p, memory_order_relaxed);
unlock(p, (Node *)(s & ~1UL));
}
}
} // namespace __sanitizer
#endif // SANITIZER_STACKDEPOTBASE_H
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