arena.c

一个很好的内存泄露的监测代码

  s = NULL;
  if (__builtin_expect (_environ != NULL, 1))
    {
      char **runp = _environ;
      char *envline;

      while (__builtin_expect ((envline = next_env_entry (&runp)) != NULL,
			       0))
	{
	  size_t len = strcspn (envline, "=");

	  if (envline[len] != '=')
	    /* This is a "MALLOC_" variable at the end of the string
	       without a '=' character.  Ignore it since otherwise we
	       will access invalid memory below.  */
	    continue;

	  switch (len)
	    {
	    case 6:
	      if (memcmp (envline, "CHECK_", 6) == 0)
		s = &envline[7];
	      break;
	    case 8:
	      if (! secure && memcmp (envline, "TOP_PAD_", 8) == 0)
		mALLOPt(M_TOP_PAD, atoi(&envline[9]));
	      break;
	    case 9:
	      if (! secure && memcmp (envline, "MMAP_MAX_", 9) == 0)
		mALLOPt(M_MMAP_MAX, atoi(&envline[10]));
	      break;
	    case 15:
	      if (! secure)
		{
		  if (memcmp (envline, "TRIM_THRESHOLD_", 15) == 0)
		    mALLOPt(M_TRIM_THRESHOLD, atoi(&envline[16]));
		  else if (memcmp (envline, "MMAP_THRESHOLD_", 15) == 0)
		    mALLOPt(M_MMAP_THRESHOLD, atoi(&envline[16]));
		}
	      break;
	    default:
	      break;
	    }
	}
    }
#else
  if (! secure)
    {
      if((s = getenv("MALLOC_TRIM_THRESHOLD_")))
	mALLOPt(M_TRIM_THRESHOLD, atoi(s));
      if((s = getenv("MALLOC_TOP_PAD_")))
	mALLOPt(M_TOP_PAD, atoi(s));
      if((s = getenv("MALLOC_MMAP_THRESHOLD_")))
	mALLOPt(M_MMAP_THRESHOLD, atoi(s));
      if((s = getenv("MALLOC_MMAP_MAX_")))
	mALLOPt(M_MMAP_MAX, atoi(s));
    }
  s = getenv("MALLOC_CHECK_");
#endif
  if(s) {
    if(s[0]) mALLOPt(M_CHECK_ACTION, (int)(s[0] - '0'));
    __malloc_check_init();
  }
  if(__malloc_initialize_hook != NULL)
    (*__malloc_initialize_hook)();
  __malloc_initialized = 1;
}

/* There are platforms (e.g. Hurd) with a link-time hook mechanism. */
#ifdef thread_atfork_static
thread_atfork_static(ptmalloc_lock_all, ptmalloc_unlock_all, \
                     ptmalloc_unlock_all2)
#endif



/* Managing heaps and arenas (for concurrent threads) */

#if USE_ARENAS

#if MALLOC_DEBUG > 1

/* Print the complete contents of a single heap to stderr. */

static void
#if __STD_C
dump_heap(heap_info *heap)
#else
dump_heap(heap) heap_info *heap;
#endif
{
  char *ptr;
  mchunkptr p;

  fprintf(stderr, "Heap %p, size %10lx:\n", heap, (long)heap->size);
  ptr = (heap->ar_ptr != (mstate)(heap+1)) ?
    (char*)(heap + 1) : (char*)(heap + 1) + sizeof(struct malloc_state);
  p = (mchunkptr)(((unsigned long)ptr + MALLOC_ALIGN_MASK) &
                  ~MALLOC_ALIGN_MASK);
  for(;;) {
    fprintf(stderr, "chunk %p size %10lx", p, (long)p->size);
    if(p == top(heap->ar_ptr)) {
      fprintf(stderr, " (top)\n");
      break;
    } else if(p->size == (0|PREV_INUSE)) {
      fprintf(stderr, " (fence)\n");
      break;
    }
    fprintf(stderr, "\n");
    p = next_chunk(p);
  }
}

#endif /* MALLOC_DEBUG > 1 */

/* Create a new heap.  size is automatically rounded up to a multiple
   of the page size. */

static heap_info *
internal_function
#if __STD_C
new_heap(size_t size, size_t top_pad)
#else
new_heap(size, top_pad) size_t size, top_pad;
#endif
{
  size_t page_mask = malloc_getpagesize - 1;
  char *p1, *p2;
  unsigned long ul;
  heap_info *h;

  if(size+top_pad < HEAP_MIN_SIZE)
    size = HEAP_MIN_SIZE;
  else if(size+top_pad <= HEAP_MAX_SIZE)
    size += top_pad;
  else if(size > HEAP_MAX_SIZE)
    return 0;
  else
    size = HEAP_MAX_SIZE;
  size = (size + page_mask) & ~page_mask;

  /* A memory region aligned to a multiple of HEAP_MAX_SIZE is needed.
     No swap space needs to be reserved for the following large
     mapping (on Linux, this is the case for all non-writable mappings
     anyway). */
  p1 = (char *)MMAP(0, HEAP_MAX_SIZE<<1, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE);
  if(p1 != MAP_FAILED) {
    p2 = (char *)(((unsigned long)p1 + (HEAP_MAX_SIZE-1)) & ~(HEAP_MAX_SIZE-1));
    ul = p2 - p1;
    munmap(p1, ul);
    munmap(p2 + HEAP_MAX_SIZE, HEAP_MAX_SIZE - ul);
  } else {
    /* Try to take the chance that an allocation of only HEAP_MAX_SIZE
       is already aligned. */
    p2 = (char *)MMAP(0, HEAP_MAX_SIZE, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE);
    if(p2 == MAP_FAILED)
      return 0;
    if((unsigned long)p2 & (HEAP_MAX_SIZE-1)) {
      munmap(p2, HEAP_MAX_SIZE);
      return 0;
    }
  }
  if(mprotect(p2, size, PROT_READ|PROT_WRITE) != 0) {
    munmap(p2, HEAP_MAX_SIZE);
    return 0;
  }
  h = (heap_info *)p2;
  h->size = size;
  THREAD_STAT(stat_n_heaps++);
  return h;
}

/* Grow or shrink a heap.  size is automatically rounded up to a
   multiple of the page size if it is positive. */

static int
#if __STD_C
grow_heap(heap_info *h, long diff)
#else
grow_heap(h, diff) heap_info *h; long diff;
#endif
{
  size_t page_mask = malloc_getpagesize - 1;
  long new_size;

  if(diff >= 0) {
    diff = (diff + page_mask) & ~page_mask;
    new_size = (long)h->size + diff;
    if(new_size > HEAP_MAX_SIZE)
      return -1;
    if(mprotect((char *)h + h->size, diff, PROT_READ|PROT_WRITE) != 0)
      return -2;
  } else {
    new_size = (long)h->size + diff;
    if(new_size < (long)sizeof(*h))
      return -1;
    /* Try to re-map the extra heap space freshly to save memory, and
       make it inaccessible. */
    if((char *)MMAP((char *)h + new_size, -diff, PROT_NONE,
                    MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
      return -2;
    /*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
  }
  h->size = new_size;
  return 0;
}

/* Delete a heap. */

#define delete_heap(heap) munmap((char*)(heap), HEAP_MAX_SIZE)

static int
internal_function
#if __STD_C
heap_trim(heap_info *heap, size_t pad)
#else
heap_trim(heap, pad) heap_info *heap; size_t pad;
#endif
{
  mstate ar_ptr = heap->ar_ptr;
  unsigned long pagesz = mp_.pagesize;
  mchunkptr top_chunk = top(ar_ptr), p, bck, fwd;
  heap_info *prev_heap;
  long new_size, top_size, extra;

  /* Can this heap go away completely? */
  while(top_chunk == chunk_at_offset(heap, sizeof(*heap))) {
    prev_heap = heap->prev;
    p = chunk_at_offset(prev_heap, prev_heap->size - (MINSIZE-2*SIZE_SZ));
    assert(p->size == (0|PREV_INUSE)); /* must be fencepost */
    p = prev_chunk(p);
    new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ);
    assert(new_size>0 && new_size<(long)(2*MINSIZE));
    if(!prev_inuse(p))
      new_size += p->prev_size;
    assert(new_size>0 && new_size<HEAP_MAX_SIZE);
    if(new_size + (HEAP_MAX_SIZE - prev_heap->size) < pad + MINSIZE + pagesz)
      break;
    ar_ptr->system_mem -= heap->size;
    arena_mem -= heap->size;
    delete_heap(heap);
    heap = prev_heap;
    if(!prev_inuse(p)) { /* consolidate backward */
      p = prev_chunk(p);
      unlink(p, bck, fwd);
    }
    assert(((unsigned long)((char*)p + new_size) & (pagesz-1)) == 0);
    assert( ((char*)p + new_size) == ((char*)heap + heap->size) );
    top(ar_ptr) = top_chunk = p;
    set_head(top_chunk, new_size | PREV_INUSE);
    /*check_chunk(ar_ptr, top_chunk);*/
  }
  top_size = chunksize(top_chunk);
  extra = ((top_size - pad - MINSIZE + (pagesz-1))/pagesz - 1) * pagesz;
  if(extra < (long)pagesz)
    return 0;
  /* Try to shrink. */
  if(grow_heap(heap, -extra) != 0)
    return 0;
  ar_ptr->system_mem -= extra;
  arena_mem -= extra;

  /* Success. Adjust top accordingly. */
  set_head(top_chunk, (top_size - extra) | PREV_INUSE);
  /*check_chunk(ar_ptr, top_chunk);*/
  return 1;
}

static mstate
internal_function
#if __STD_C
arena_get2(mstate a_tsd, size_t size)
#else
arena_get2(a_tsd, size) mstate a_tsd; size_t size;
#endif
{
  mstate a;
  int err;

  if(!a_tsd)
    a = a_tsd = &main_arena;
  else {
    a = a_tsd->next;
    if(!a) {
      /* This can only happen while initializing the new arena. */
      (void)mutex_lock(&main_arena.mutex);
      THREAD_STAT(++(main_arena.stat_lock_wait));
      return &main_arena;
    }
  }

  /* Check the global, circularly linked list for available arenas. */
 repeat:
  do {
    if(!mutex_trylock(&a->mutex)) {
      THREAD_STAT(++(a->stat_lock_loop));
      tsd_setspecific(arena_key, (Void_t *)a);
      return a;
    }
    a = a->next;
  } while(a != a_tsd);

  /* If not even the list_lock can be obtained, try again.  This can
     happen during `atfork', or for example on systems where thread
     creation makes it temporarily impossible to obtain _any_
     locks. */
  if(mutex_trylock(&list_lock)) {
    a = a_tsd;
    goto repeat;
  }
  (void)mutex_unlock(&list_lock);

  /* Nothing immediately available, so generate a new arena.  */
  a = _int_new_arena(size);
  if(!a)
    return 0;

  tsd_setspecific(arena_key, (Void_t *)a);
  mutex_init(&a->mutex);
  err = mutex_lock(&a->mutex); /* remember result */

  /* Add the new arena to the global list.  */
  (void)mutex_lock(&list_lock);
  a->next = main_arena.next;
  atomic_write_barrier ();
  main_arena.next = a;
  (void)mutex_unlock(&list_lock);

  if(err) /* locking failed; keep arena for further attempts later */
    return 0;

  THREAD_STAT(++(a->stat_lock_loop));
  return a;
}

/* Create a new arena with initial size "size".  */

mstate
_int_new_arena(size_t size)
{
  mstate a;
  heap_info *h;
  char *ptr;
  unsigned long misalign;

  h = new_heap(size + (sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT),
	       mp_.top_pad);
  if(!h) {
    /* Maybe size is too large to fit in a single heap.  So, just try
       to create a minimally-sized arena and let _int_malloc() attempt
       to deal with the large request via mmap_chunk().  */
    h = new_heap(sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT, mp_.top_pad);
    if(!h)
      return 0;
  }
  a = h->ar_ptr = (mstate)(h+1);
  malloc_init_state(a);
  /*a->next = NULL;*/
  a->system_mem = a->max_system_mem = h->size;
  arena_mem += h->size;
#ifdef NO_THREADS
  if((unsigned long)(mp_.mmapped_mem + arena_mem + main_arena.system_mem) >
     mp_.max_total_mem)
    mp_.max_total_mem = mp_.mmapped_mem + arena_mem + main_arena.system_mem;
#endif

  /* Set up the top chunk, with proper alignment. */
  ptr = (char *)(a + 1);
  misalign = (unsigned long)chunk2mem(ptr) & MALLOC_ALIGN_MASK;
  if (misalign > 0)
    ptr += MALLOC_ALIGNMENT - misalign;
  top(a) = (mchunkptr)ptr;
  set_head(top(a), (((char*)h + h->size) - ptr) | PREV_INUSE);

  return a;
}

/* Obtain the arena number n.  Needed in malloc_stats.  */

mstate
_int_get_arena (int n)
{
  mstate a = &main_arena;

  while (n-- != 0) {
    a = a->next;
    if (a == &main_arena)
      return 0;
  }
  return a;
}

#endif /* USE_ARENAS */

/*
 * Local variables:
 * c-basic-offset: 2
 * End:
 */