sanitizer_persistent_allocator.h revision 1.1.1.1 
1//===-- sanitizer_persistent_allocator.h ------------------------*- C++ -*-===//
2//
3// This file is distributed under the University of Illinois Open Source
4// License. See LICENSE.TXT for details.
5//
6//===----------------------------------------------------------------------===//
7//
8// A fast memory allocator that does not support free() nor realloc().
9// All allocations are forever.
10//===----------------------------------------------------------------------===//
11#ifndef SANITIZER_PERSISTENT_ALLOCATOR_H
12#define SANITIZER_PERSISTENT_ALLOCATOR_H
13
14#include "sanitizer_internal_defs.h"
15#include "sanitizer_mutex.h"
16#include "sanitizer_atomic.h"
17#include "sanitizer_common.h"
18
19namespace __sanitizer {
20
21class PersistentAllocator {
22 public:
23  void *alloc(uptr size);
24
25 private:
26  void *tryAlloc(uptr size);
27  StaticSpinMutex mtx;  // Protects alloc of new blocks for region allocator.
28  atomic_uintptr_t region_pos;  // Region allocator for Node's.
29  atomic_uintptr_t region_end;
30};
31
32inline void *PersistentAllocator::tryAlloc(uptr size) {
33  // Optimisic lock-free allocation, essentially try to bump the region ptr.
34  for (;;) {
35    uptr cmp = atomic_load(&region_pos, memory_order_acquire);
36    uptr end = atomic_load(&region_end, memory_order_acquire);
37    if (cmp == 0 || cmp + size > end) return 0;
38    if (atomic_compare_exchange_weak(&region_pos, &cmp, cmp + size,
39                                     memory_order_acquire))
40      return (void *)cmp;
41  }
42}
43
44inline void *PersistentAllocator::alloc(uptr size) {
45  // First, try to allocate optimisitically.
46  void *s = tryAlloc(size);
47  if (s) return s;
48  // If failed, lock, retry and alloc new superblock.
49  SpinMutexLock l(&mtx);
50  for (;;) {
51    s = tryAlloc(size);
52    if (s) return s;
53    atomic_store(&region_pos, 0, memory_order_relaxed);
54    uptr allocsz = 64 * 1024;
55    if (allocsz < size) allocsz = size;
56    uptr mem = (uptr)MmapOrDie(allocsz, "stack depot");
57    atomic_store(&region_end, mem + allocsz, memory_order_release);
58    atomic_store(&region_pos, mem, memory_order_release);
59  }
60}
61
62extern PersistentAllocator thePersistentAllocator;
63inline void *PersistentAlloc(uptr sz) {
64  return thePersistentAllocator.alloc(sz);
65}
66
67} // namespace __sanitizer
68
69#endif  // SANITIZER_PERSISTENT_ALLOCATOR_H
70