arean.c

glibc-2.14中的arean.c源代码，供研究malloc和free实现使用：

/* Malloc implementation for multiple threads without lock contention.   Copyright (C) 2001,2002,2003,2004,2005,2006,2007,2009,2010   Free Software Foundation, Inc.   This file is part of the GNU C Library.   Contributed by Wolfram Gloger <[e-mail]>, 2001.   The GNU C Library is free software; you can redistribute it and/or   modify it under the terms of the GNU Lesser General Public License as   published by the Free Software Foundation; either version 2.1 of the   License, or (at your option) any later version.   The GNU C Library is distributed in the hope that it will be useful,   but WITHOUT ANY WARRANTY; without even the implied warranty of   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU   Lesser General Public License for more details.   You should have received a copy of the GNU Lesser General Public   License along with the GNU C Library; see the file COPYING.LIB.  If not,   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,   Boston, MA 02111-1307, USA.  */#include <stdbool.h>/* Compile-time constants.  */#define HEAP_MIN_SIZE (32*1024)#ifndef HEAP_MAX_SIZE# ifdef DEFAULT_MMAP_THRESHOLD_MAX#  define HEAP_MAX_SIZE (2 * DEFAULT_MMAP_THRESHOLD_MAX)# else#  define HEAP_MAX_SIZE (1024*1024) /* must be a power of two */# endif#endif/* HEAP_MIN_SIZE and HEAP_MAX_SIZE limit the size of mmap()ed heaps   that are dynamically created for multi-threaded programs.  The   maximum size must be a power of two, for fast determination of   which heap belongs to a chunk.  It should be much larger than the   mmap threshold, so that requests with a size just below that   threshold can be fulfilled without creating too many heaps.  */#ifndef THREAD_STATS#define THREAD_STATS 0#endif/* If THREAD_STATS is non-zero, some statistics on mutex locking are   computed.  *//***************************************************************************/#define top(ar_ptr) ((ar_ptr)->top)/* A heap is a single contiguous memory region holding (coalesceable)   malloc_chunks.  It is allocated with mmap() and always starts at an   address aligned to HEAP_MAX_SIZE.  Not used unless compiling with   USE_ARENAS. */typedef struct _heap_info {  mstate ar_ptr; /* Arena for this heap. */  struct _heap_info *prev; /* Previous heap. */  size_t size;   /* Current size in bytes. */  size_t mprotect_size;/* Size in bytes that has been mprotected   PROT_READ|PROT_WRITE.  */  /* Make sure the following data is properly aligned, particularly     that sizeof (heap_info) + 2 * SIZE_SZ is a multiple of     MALLOC_ALIGNMENT. */  char pad[-6 * SIZE_SZ & MALLOC_ALIGN_MASK];} heap_info;/* Get a compile-time error if the heap_info padding is not correct   to make alignment work as expected in sYSMALLOc.  */extern int sanity_check_heap_info_alignment[(sizeof (heap_info)     + 2 * SIZE_SZ) % MALLOC_ALIGNMENT    ? -1 : 1];/* Thread specific data */static tsd_key_t arena_key;static mutex_t list_lock;#ifdef PER_THREADstatic size_t narenas;static mstate free_list;#endif#if THREAD_STATSstatic int stat_n_heaps;#define THREAD_STAT(x) x#else#define THREAD_STAT(x) do ; while(0)#endif/* Mapped memory in non-main arenas (reliable only for NO_THREADS). */static unsigned long arena_mem;/* Already initialized? */int __malloc_initialized = -1;/**************************************************************************/#if USE_ARENAS/* arena_get() acquires an arena and locks the corresponding mutex.   First, try the one last locked successfully by this thread.  (This   is the common case and handled with a macro for speed.)  Then, loop   once over the circularly linked list of arenas.  If no arena is   readily available, create a new one.  In this latter case, `size'   is just a hint as to how much memory will be required immediately   in the new arena. */#define arena_get(ptr, size) do { \  arena_lookup(ptr); \  arena_lock(ptr, size); \} while(0)#define arena_lookup(ptr) do { \  Void_t *vptr = NULL; \  ptr = (mstate)tsd_getspecific(arena_key, vptr); \} while(0)#ifdef PER_THREAD#define arena_lock(ptr, size) do { \  if(ptr) \    (void)mutex_lock(&ptr->mutex); \  else \    ptr = arena_get2(ptr, (size)); \} while(0)#else#define arena_lock(ptr, size) do { \  if(ptr && !mutex_trylock(&ptr->mutex)) { \    THREAD_STAT(++(ptr->stat_lock_direct)); \  } else \    ptr = arena_get2(ptr, (size)); \} while(0)#endif/* find the heap and corresponding arena for a given ptr */#define heap_for_ptr(ptr) \ ((heap_info *)((unsigned long)(ptr) & ~(HEAP_MAX_SIZE-1)))#define arena_for_chunk(ptr) \ (chunk_non_main_arena(ptr) ? heap_for_ptr(ptr)->ar_ptr : &main_arena)#else /* !USE_ARENAS *//* There is only one arena, main_arena. */#if THREAD_STATS#define arena_get(ar_ptr, sz) do { \  ar_ptr = &main_arena; \  if(!mutex_trylock(&ar_ptr->mutex)) \    ++(ar_ptr->stat_lock_direct); \  else { \    (void)mutex_lock(&ar_ptr->mutex); \    ++(ar_ptr->stat_lock_wait); \  } \} while(0)#else#define arena_get(ar_ptr, sz) do { \  ar_ptr = &main_arena; \  (void)mutex_lock(&ar_ptr->mutex); \} while(0)#endif#define arena_for_chunk(ptr) (&main_arena)#endif /* USE_ARENAS *//**************************************************************************/#ifndef NO_THREADS/* atfork support.  */static __malloc_ptr_t (*save_malloc_hook) (size_t __size,   __const __malloc_ptr_t);# if !defined _LIBC || (defined SHARED && !USE___THREAD)static __malloc_ptr_t (*save_memalign_hook) (size_t __align, size_t __size,     __const __malloc_ptr_t);# endifstatic void           (*save_free_hook) (__malloc_ptr_t __ptr, __const __malloc_ptr_t);static Void_t*        save_arena;#ifdef ATFORK_MEMATFORK_MEM;#endif/* Magic value for the thread-specific arena pointer when   malloc_atfork() is in use.  */#define ATFORK_ARENA_PTR ((Void_t*)-1)/* The following hooks are used while the `atfork' handling mechanism   is active. */static Void_t*malloc_atfork(size_t sz, const Void_t *caller){  Void_t *vptr = NULL;  Void_t *victim;  tsd_getspecific(arena_key, vptr);  if(vptr == ATFORK_ARENA_PTR) {    /* We are the only thread that may allocate at all.  */    if(save_malloc_hook != malloc_check) {      return _int_malloc(&main_arena, sz);    } else {      if(top_check()<0)return 0;      victim = _int_malloc(&main_arena, sz+1);      return mem2mem_check(victim, sz);    }  } else {    /* Suspend the thread until the `atfork' handlers have completed.       By that time, the hooks will have been reset as well, so that       mALLOc() can be used again. */    (void)mutex_lock(&list_lock);    (void)mutex_unlock(&list_lock);    return public_mALLOc(sz);  }}static voidfree_atfork(Void_t* mem, const Void_t *caller){  Void_t *vptr = NULL;  mstate ar_ptr;  mchunkptr p;                          /* chunk corresponding to mem */  if (mem == 0)                              /* free(0) has no effect */    return;  p = mem2chunk(mem);         /* do not bother to replicate free_check here */#if HAVE_MMAP  if (chunk_is_mmapped(p))                       /* release mmapped memory. */  {    munmap_chunk(p);    return;  }#endif#ifdef ATOMIC_FASTBINS  ar_ptr = arena_for_chunk(p);  tsd_getspecific(arena_key, vptr);  _int_free(ar_ptr, p, vptr == ATFORK_ARENA_PTR);#else  ar_ptr = arena_for_chunk(p);  tsd_getspecific(arena_key, vptr);  if(vptr != ATFORK_ARENA_PTR)    (void)mutex_lock(&ar_ptr->mutex);  _int_free(ar_ptr, p);  if(vptr != ATFORK_ARENA_PTR)    (void)mutex_unlock(&ar_ptr->mutex);#endif}/* Counter for number of times the list is locked by the same thread.  */static unsigned int atfork_recursive_cntr;/* The following two functions are registered via thread_atfork() to   make sure that the mutexes remain in a consistent state in the   fork()ed version of a thread.  Also adapt the malloc and free hooks   temporarily, because the `atfork' handler mechanism may use   malloc/free internally (e.g. in LinuxThreads). */static voidptmalloc_lock_all (void){  mstate ar_ptr;  if(__malloc_initialized < 1)    return;  if (mutex_trylock(&list_lock))    {      Void_t *my_arena;      tsd_getspecific(arena_key, my_arena);      if (my_arena == ATFORK_ARENA_PTR)/* This is the same thread which already locks the global list.   Just bump the counter.  */goto out;      /* This thread has to wait its turn.  */      (void)mutex_lock(&list_lock);    }  for(ar_ptr = &main_arena;;) {    (void)mutex_lock(&ar_ptr->mutex);    ar_ptr = ar_ptr->next;    if(ar_ptr == &main_arena) break;  }  save_malloc_hook = __malloc_hook;  save_free_hook = __free_hook;  __malloc_hook = malloc_atfork;  __free_hook = free_atfork;  /* Only the current thread may perform malloc/free calls now. */  tsd_getspecific(arena_key, save_arena);  tsd_setspecific(arena_key, ATFORK_ARENA_PTR); out:  ++atfork_recursive_cntr;}static voidptmalloc_unlock_all (void){  mstate ar_ptr;  if(__malloc_initialized < 1)    return;  if (--atfork_recursive_cntr != 0)    return;  tsd_setspecific(arena_key, save_arena);  __malloc_hook = save_malloc_hook;  __free_hook = save_free_hook;  for(ar_ptr = &main_arena;;) {    (void)mutex_unlock(&ar_ptr->mutex);    ar_ptr = ar_ptr->next;    if(ar_ptr == &main_arena) break;  }  (void)mutex_unlock(&list_lock);}#ifdef __linux__/* In NPTL, unlocking a mutex in the child process after a   fork() is currently unsafe, whereas re-initializing it is safe and   does not leak resources.  Therefore, a special atfork handler is   installed for the child. */static voidptmalloc_unlock_all2 (void){  mstate ar_ptr;  if(__malloc_initialized < 1)    return;#if defined _LIBC || defined MALLOC_HOOKS  tsd_setspecific(arena_key, save_arena);  __malloc_hook = save_malloc_hook;  __free_hook = save_free_hook;#endif#ifdef PER_THREAD  free_list = NULL;#endif  for(ar_ptr = &main_arena;;) {    mutex_init(&ar_ptr->mutex);#ifdef PER_THREAD    if (ar_ptr != save_arena) {      ar_ptr->next_free = free_list;      free_list = ar_ptr;    }#endif    ar_ptr = ar_ptr->next;    if(ar_ptr == &main_arena) break;  }  mutex_init(&list_lock);  atfork_recursive_cntr = 0;}#else#define ptmalloc_unlock_all2 ptmalloc_unlock_all#endif#endif /* !defined NO_THREADS *//* Initialization routine. */#ifdef _LIBC#include <string.h>extern char **_environ;static char *internal_functionnext_env_entry (char ***position){  char **current = *position;  char *result = NULL;  while (*current != NULL)    {      if (__builtin_expect ((*current)[0] == 'M', 0)  && (*current)[1] == 'A'  && (*current)[2] == 'L'  && (*current)[3] == 'L'  && (*current)[4] == 'O'  && (*current)[5] == 'C'  && (*current)[6] == '_'){  result = &(*current)[7];  /* Save current position for next visit.  */  *position = ++current;  break;}      ++current;    }  return result;}#endif /* _LIBC *//* Set up basic state so that _int_malloc et al can work.  */static voidptmalloc_init_minimal (void){#if DEFAULT_TOP_PAD != 0  mp_.top_pad        = DEFAULT_TOP_PAD;#endif  mp_.n_mmaps_max    = DEFAULT_MMAP_MAX;  mp_.mmap_threshold = DEFAULT_MMAP_THRESHOLD;  mp_.trim_threshold = DEFAULT_TRIM_THRESHOLD;  mp_.pagesize       = malloc_getpagesize;#ifdef PER_THREAD# define NARENAS_FROM_NCORES(n) ((n) * (sizeof(long) == 4 ? 2 : 8))  mp_.arena_test     = NARENAS_FROM_NCORES (1);  narenas = 1;#endif}#ifdef _LIBC# ifdef SHAREDstatic void *__failing_morecore (ptrdiff_t d){  return (void *) MORECORE_FAILURE;}extern struct dl_open_hook *_dl_open_hook;libc_hidden_proto (_dl_open_hook);# endif# if defined SHARED && !USE___THREAD/* This is called by __pthread_initialize_minimal when it needs to use   malloc to set up the TLS state.  We cannot do the full work of   ptmalloc_init (below) until __pthread_initialize_minimal has finished,   so it has to switch to using the special startup-time hooks while doing   those allocations.  */void__libc_malloc_pthread_startup (bool first_time){  if (first_time)    {      ptmalloc_init_minimal ();      save_malloc_hook = __malloc_hook;      save_memalign_hook = __memalign_hook;      save_free_hook = __free_hook;      __malloc_hook = malloc_starter;      __memalign_hook = memalign_starter;      __free_hook = free_starter;    }  else    {      __malloc_hook = save_malloc_hook;      __memalign_hook = save_memalign_hook;      __free_hook = save_free_hook;    }}# endif#endifstatic voidptmalloc_init (void){#if __STD_C  const char* s;#else  char* s;#endif  int secure = 0;  if(__malloc_initialized >= 0) return;  __malloc_initialized = 0;#ifdef _LIBC# if defined SHARED && !USE___THREAD  /* ptmalloc_init_minimal may already have been called via     __libc_malloc_pthread_startup, above.  */  if (mp_.pagesize == 0)# endif#endif    ptmalloc_init_minimal();#ifndef NO_THREADS# if defined _LIBC  /* We know __pthread_initialize_minimal has already been called,     and that is enough.  */#   define NO_STARTER# endif# ifndef NO_STARTER  /* With some threads implementations, creating thread-specific data     or initializing a mutex may call malloc() itself.  Provide a     simple starter version (realloc() won't work). */  save_malloc_hook = __malloc_hook;  save_memalign_hook = __memalign_hook;  save_free_hook = __free_hook;  __malloc_hook = malloc_starter;  __memalign_hook = memalign_starter;  __free_hook = free_starter;#  ifdef _LIBC  /* Initialize the pthreads interface. */  if (__pthread_initialize != NULL)    __pthread_initialize();#  endif /* !defined _LIBC */# endif/* !defined NO_STARTER */#endif /* !defined NO_THREADS */  mutex_init(&main_arena.mutex);  main_arena.next = &main_arena;#if defined _LIBC && defined SHARED  /* In case this libc copy is in a non-default namespace, never use brk.     Likewise if dlopened from statically linked program.  */  Dl_info di;  struct link_map *l;  if (_dl_open_hook != NULL      || (_dl_addr (ptmalloc_init, &di, &l, NULL) != 0  && l->l_ns != LM_ID_BASE))    __morecore = __failing_morecore;#endif  mutex_init(&list_lock);  tsd_key_create(&arena_key, NULL);  tsd_setspecific(arena_key, (Void_t *)&main_arena);  thread_atfork(ptmalloc_lock_all, ptmalloc_unlock_all, ptmalloc_unlock_all2);#ifndef NO_THREADS# ifndef NO_STARTER  __malloc_hook = save_malloc_hook;  __memalign_hook = save_memalign_hook;  __free_hook = save_free_hook;# else#  undef NO_STARTER# endif#endif#ifdef _LIBC  secure = __libc_enable_secure;  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){  if (memcmp (envline, "TOP_PAD_", 8) == 0)    mALLOPt(M_TOP_PAD, atoi(&envline[9]));  else if (memcmp (envline, "PERTURB_", 8) == 0)    mALLOPt(M_PERTURB, atoi(&envline[9]));}      break;    case 9:      if (! secure){  if (memcmp (envline, "MMAP_MAX_", 9) == 0)    mALLOPt(M_MMAP_MAX, atoi(&envline[10]));#ifdef PER_THREAD  else if (memcmp (envline, "ARENA_MAX", 9) == 0)    mALLOPt(M_ARENA_MAX, atoi(&envline[10]));#endif}      break;#ifdef PER_THREAD    case 10:      if (! secure){  if (memcmp (envline, "ARENA_TEST", 10) == 0)    mALLOPt(M_ARENA_TEST, atoi(&envline[11]));}      break;#endif    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_PERTURB_")))mALLOPt(M_PERTURB, 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 && s[0]) {    mALLOPt(M_CHECK_ACTION, (int)(s[0] - '0'));    if (check_action != 0)      __malloc_check_init();  }  void (*hook) (void) = force_reg (__malloc_initialize_hook);  if (hook != NULL)    (*hook)();  __malloc_initialized = 1;}/* There are platforms (e.g. Hurd) with a link-time hook mechanism. */#ifdef thread_atfork_staticthread_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_Cdump_heap(heap_info *heap)#elsedump_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 *//* If consecutive mmap (0, HEAP_MAX_SIZE << 1, ...) calls return decreasing   addresses as opposed to increasing, new_heap would badly fragment the   address space.  In that case remember the second HEAP_MAX_SIZE part   aligned to HEAP_MAX_SIZE from last mmap (0, HEAP_MAX_SIZE << 1, ...)   call (if it is already aligned) and try to reuse it next time.  We need   no locking for it, as kernel ensures the atomicity for us - worst case   we'll call mmap (addr, HEAP_MAX_SIZE, ...) for some value of addr in   multiple threads, but only one will succeed.  */static char *aligned_heap_area;/* Create a new heap.  size is automatically rounded up to a multiple   of the page size. */static heap_info *internal_function#if __STD_Cnew_heap(size_t size, size_t top_pad)#elsenew_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). */  p2 = MAP_FAILED;  if(aligned_heap_area) {    p2 = (char *)MMAP(aligned_heap_area, HEAP_MAX_SIZE, PROT_NONE,      MAP_PRIVATE|MAP_NORESERVE);    aligned_heap_area = NULL;    if (p2 != MAP_FAILED && ((unsigned long)p2 & (HEAP_MAX_SIZE-1))) {      munmap(p2, HEAP_MAX_SIZE);      p2 = MAP_FAILED;    }  }  if(p2 == MAP_FAILED) {    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;      if (ul)munmap(p1, ul);      elsealigned_heap_area = p2 + HEAP_MAX_SIZE;      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;  h->mprotect_size = size;  THREAD_STAT(stat_n_heaps++);  return h;}/* Grow a heap.  size is automatically rounded up to a   multiple of the page size. */static int#if __STD_Cgrow_heap(heap_info *h, long diff)#elsegrow_heap(h, diff) heap_info *h; long diff;#endif{  size_t page_mask = malloc_getpagesize - 1;  long new_size;  diff = (diff + page_mask) & ~page_mask;  new_size = (long)h->size + diff;  if((unsigned long) new_size > (unsigned long) HEAP_MAX_SIZE)    return -1;  if((unsigned long) new_size > h->mprotect_size) {    if (mprotect((char *)h + h->mprotect_size, (unsigned long) new_size - h->mprotect_size, PROT_READ|PROT_WRITE) != 0)      return -2;    h->mprotect_size = new_size;  }  h->size = new_size;  return 0;}/* Shrink a heap.  */static int#if __STD_Cshrink_heap(heap_info *h, long diff)#elseshrink_heap(h, diff) heap_info *h; long diff;#endif{  long new_size;  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. */#ifdef _LIBC  if (__builtin_expect (__libc_enable_secure, 0))#else  if (1)#endif    {      if((char *)MMAP((char *)h + new_size, diff, PROT_NONE,      MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)return -2;      h->mprotect_size = new_size;    }#ifdef _LIBC  else    madvise ((char *)h + new_size, diff, MADV_DONTNEED);#endif  /*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/  h->size = new_size;  return 0;}/* Delete a heap. */#define delete_heap(heap) \  do {\    if ((char *)(heap) + HEAP_MAX_SIZE == aligned_heap_area)\      aligned_heap_area = NULL;\    munmap((char*)(heap), HEAP_MAX_SIZE);\  } while (0)static intinternal_function#if __STD_Cheap_trim(heap_info *heap, size_t pad)#elseheap_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 - 1) & ~(pagesz - 1);  if(extra < (long)pagesz)    return 0;  /* Try to shrink. */  if(shrink_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;}/* Create a new arena with initial size "size".  */static 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);  tsd_setspecific(arena_key, (Void_t *)a);  mutex_init(&a->mutex);  (void)mutex_lock(&a->mutex);#ifdef PER_THREAD  (void)mutex_lock(&list_lock);#endif  /* Add the new arena to the global list.  */  a->next = main_arena.next;  atomic_write_barrier ();  main_arena.next = a;#ifdef PER_THREAD  ++narenas;  (void)mutex_unlock(&list_lock);#endif  THREAD_STAT(++(a->stat_lock_loop));  return a;}#ifdef PER_THREADstatic mstateget_free_list (void){  mstate result = free_list;  if (result != NULL)    {      (void)mutex_lock(&list_lock);      result = free_list;      if (result != NULL)free_list = result->next_free;      (void)mutex_unlock(&list_lock);      if (result != NULL){  (void)mutex_lock(&result->mutex);  tsd_setspecific(arena_key, (Void_t *)result);  THREAD_STAT(++(result->stat_lock_loop));}    }  return result;}static mstatereused_arena (void){  if (narenas <= mp_.arena_test)    return NULL;  static int narenas_limit;  if (narenas_limit == 0)    {      if (mp_.arena_max != 0)narenas_limit = mp_.arena_max;      else{  int n  = __get_nprocs ();  if (n >= 1)    narenas_limit = NARENAS_FROM_NCORES (n);  else    /* We have no information about the system.  Assume two       cores.  */    narenas_limit = NARENAS_FROM_NCORES (2);}    }  if (narenas < narenas_limit)    return NULL;  mstate result;  static mstate next_to_use;  if (next_to_use == NULL)    next_to_use = &main_arena;  result = next_to_use;  do    {      if (!mutex_trylock(&result->mutex))goto out;      result = result->next;    }  while (result != next_to_use);  /* No arena available.  Wait for the next in line.  */  (void)mutex_lock(&result->mutex); out:  tsd_setspecific(arena_key, (Void_t *)result);  THREAD_STAT(++(result->stat_lock_loop));  next_to_use = result->next;  return result;}#endifstatic mstateinternal_function#if __STD_Carena_get2(mstate a_tsd, size_t size)#elsearena_get2(a_tsd, size) mstate a_tsd; size_t size;#endif{  mstate a;#ifdef PER_THREAD  if ((a = get_free_list ()) == NULL      && (a = reused_arena ()) == NULL)    /* Nothing immediately available, so generate a new arena.  */    a = _int_new_arena(size);#else  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. */  bool retried = false; repeat:  do {    if(!mutex_trylock(&a->mutex)) {      if (retried)(void)mutex_unlock(&list_lock);      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(!retried && mutex_trylock(&list_lock)) {    /* We will block to not run in a busy loop.  */    (void)mutex_lock(&list_lock);    /* Since we blocked there might be an arena available now.  */    retried = true;    a = a_tsd;    goto repeat;  }  /* Nothing immediately available, so generate a new arena.  */  a = _int_new_arena(size);  (void)mutex_unlock(&list_lock);#endif  return a;}#ifdef PER_THREADstatic void __attribute__ ((section ("__libc_thread_freeres_fn")))arena_thread_freeres (void){  Void_t *vptr = NULL;  mstate a = tsd_getspecific(arena_key, vptr);  tsd_setspecific(arena_key, NULL);  if (a != NULL)    {      (void)mutex_lock(&list_lock);      a->next_free = free_list;      free_list = a;      (void)mutex_unlock(&list_lock);    }}text_set_element (__libc_thread_subfreeres, arena_thread_freeres);#endif#endif /* USE_ARENAS *//* * Local variables: * c-basic-offset: 2 * End: */