malloc/arena.c

   1 /* Malloc implementation for multiple threads without lock contention.
   2    Copyright (C) 2001,2002,2003,2004,2005,2006,2007
   3    Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5    Contributed by Wolfram Gloger <wg@malloc.de>, 2001.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public License as
   9    published by the Free Software Foundation; either version 2.1 of the
  10    License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  19    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 #include <stdbool.h>
  23
  24 /* Compile-time constants.  */
  25
  26 #define HEAP_MIN_SIZE (32*1024)
  27 #ifndef HEAP_MAX_SIZE
  28 # ifdef DEFAULT_MMAP_THRESHOLD_MAX
  29 #  define HEAP_MAX_SIZE (2 * DEFAULT_MMAP_THRESHOLD_MAX)
  30 # else
  31 #  define HEAP_MAX_SIZE (1024*1024) /* must be a power of two */
  32 # endif
  33 #endif
  34
  35 /* HEAP_MIN_SIZE and HEAP_MAX_SIZE limit the size of mmap()ed heaps
  36    that are dynamically created for multi-threaded programs.  The
  37    maximum size must be a power of two, for fast determination of
  38    which heap belongs to a chunk.  It should be much larger than the
  39    mmap threshold, so that requests with a size just below that
  40    threshold can be fulfilled without creating too many heaps.  */
  41
  42
  43 #ifndef THREAD_STATS
  44 #define THREAD_STATS 0
  45 #endif
  46
  47 /* If THREAD_STATS is non-zero, some statistics on mutex locking are
  48    computed.  */
  49
  50 /***************************************************************************/
  51
  52 #define top(ar_ptr) ((ar_ptr)->top)
  53
  54 /* A heap is a single contiguous memory region holding (coalesceable)
  55    malloc_chunks.  It is allocated with mmap() and always starts at an
  56    address aligned to HEAP_MAX_SIZE.  Not used unless compiling with
  57    USE_ARENAS. */
  58
  59 typedef struct _heap_info {
  60   mstate ar_ptr; /* Arena for this heap. */
  61   struct _heap_info *prev; /* Previous heap. */
  62   size_t size;   /* Current size in bytes. */
  63   size_t mprotect_size; /* Size in bytes that has been mprotected
  64                            PROT_READ|PROT_WRITE.  */
  65   /* Make sure the following data is properly aligned, particularly
  66      that sizeof (heap_info) + 2 * SIZE_SZ is a multiple of
  67      MALLOC_ALIGNMENT. */
  68   char pad[-6 * SIZE_SZ & MALLOC_ALIGN_MASK];
  69 } heap_info;
  70
  71 /* Get a compile-time error if the heap_info padding is not correct
  72    to make alignment work as expected in sYSMALLOc.  */
  73 extern int sanity_check_heap_info_alignment[(sizeof (heap_info)
  74                                              + 2 * SIZE_SZ) % MALLOC_ALIGNMENT
  75                                             ? -1 : 1];
  76
  77 /* Thread specific data */
  78
  79 static tsd_key_t arena_key;
  80 static mutex_t list_lock;
  81
  82 #if THREAD_STATS
  83 static int stat_n_heaps;
  84 #define THREAD_STAT(x) x
  85 #else
  86 #define THREAD_STAT(x) do ; while(0)
  87 #endif
  88
  89 /* Mapped memory in non-main arenas (reliable only for NO_THREADS). */
  90 static unsigned long arena_mem;
  91
  92 /* Already initialized? */
  93 int __malloc_initialized = -1;
  94
  95 /**************************************************************************/
  96
  97 #if USE_ARENAS
  98
  99 /* arena_get() acquires an arena and locks the corresponding mutex.
 100    First, try the one last locked successfully by this thread.  (This
 101    is the common case and handled with a macro for speed.)  Then, loop
 102    once over the circularly linked list of arenas.  If no arena is
 103    readily available, create a new one.  In this latter case, `size'
 104    is just a hint as to how much memory will be required immediately
 105    in the new arena. */
 106
 107 #define arena_get(ptr, size) do { \
 108   Void_t *vptr = NULL; \
 109   ptr = (mstate)tsd_getspecific(arena_key, vptr); \
 110   if(ptr && !mutex_trylock(&ptr->mutex)) { \
 111     THREAD_STAT(++(ptr->stat_lock_direct)); \
 112   } else \
 113     ptr = arena_get2(ptr, (size)); \
 114 } while(0)
 115
 116 /* find the heap and corresponding arena for a given ptr */
 117
 118 #define heap_for_ptr(ptr) \
 119  ((heap_info *)((unsigned long)(ptr) & ~(HEAP_MAX_SIZE-1)))
 120 #define arena_for_chunk(ptr) \
 121  (chunk_non_main_arena(ptr) ? heap_for_ptr(ptr)->ar_ptr : &main_arena)
 122
 123 #else /* !USE_ARENAS */
 124
 125 /* There is only one arena, main_arena. */
 126
 127 #if THREAD_STATS
 128 #define arena_get(ar_ptr, sz) do { \
 129   ar_ptr = &main_arena; \
 130   if(!mutex_trylock(&ar_ptr->mutex)) \
 131     ++(ar_ptr->stat_lock_direct); \
 132   else { \
 133     (void)mutex_lock(&ar_ptr->mutex); \
 134     ++(ar_ptr->stat_lock_wait); \
 135   } \
 136 } while(0)
 137 #else
 138 #define arena_get(ar_ptr, sz) do { \
 139   ar_ptr = &main_arena; \
 140   (void)mutex_lock(&ar_ptr->mutex); \
 141 } while(0)
 142 #endif
 143 #define arena_for_chunk(ptr) (&main_arena)
 144
 145 #endif /* USE_ARENAS */
 146
 147 /**************************************************************************/
 148
 149 #ifndef NO_THREADS
 150
 151 /* atfork support.  */
 152
 153 static __malloc_ptr_t (*save_malloc_hook) (size_t __size,
 154                                            __const __malloc_ptr_t);
 155 # if !defined _LIBC || (defined SHARED && !USE___THREAD)
 156 static __malloc_ptr_t (*save_memalign_hook) (size_t __align, size_t __size,
 157                                              __const __malloc_ptr_t);
 158 # endif
 159 static void           (*save_free_hook) (__malloc_ptr_t __ptr,
 160                                          __const __malloc_ptr_t);
 161 static Void_t*        save_arena;
 162
 163 /* Magic value for the thread-specific arena pointer when
 164    malloc_atfork() is in use.  */
 165
 166 #define ATFORK_ARENA_PTR ((Void_t*)-1)
 167
 168 /* The following hooks are used while the `atfork' handling mechanism
 169    is active. */
 170
 171 static Void_t*
 172 malloc_atfork(size_t sz, const Void_t *caller)
 173 {
 174   Void_t *vptr = NULL;
 175   Void_t *victim;
 176
 177   tsd_getspecific(arena_key, vptr);
 178   if(vptr == ATFORK_ARENA_PTR) {
 179     /* We are the only thread that may allocate at all.  */
 180     if(save_malloc_hook != malloc_check) {
 181       return _int_malloc(&main_arena, sz);
 182     } else {
 183       if(top_check()<0)
 184         return 0;
 185       victim = _int_malloc(&main_arena, sz+1);
 186       return mem2mem_check(victim, sz);
 187     }
 188   } else {
 189     /* Suspend the thread until the `atfork' handlers have completed.
 190        By that time, the hooks will have been reset as well, so that
 191        mALLOc() can be used again. */
 192     (void)mutex_lock(&list_lock);
 193     (void)mutex_unlock(&list_lock);
 194     return public_mALLOc(sz);
 195   }
 196 }
 197
 198 static void
 199 free_atfork(Void_t* mem, const Void_t *caller)
 200 {
 201   Void_t *vptr = NULL;
 202   mstate ar_ptr;
 203   mchunkptr p;                          /* chunk corresponding to mem */
 204
 205   if (mem == 0)                              /* free(0) has no effect */
 206     return;
 207
 208   p = mem2chunk(mem);         /* do not bother to replicate free_check here */
 209
 210 #if HAVE_MMAP
 211   if (chunk_is_mmapped(p))                       /* release mmapped memory. */
 212   {
 213     munmap_chunk(p);
 214     return;
 215   }
 216 #endif
 217
 218   ar_ptr = arena_for_chunk(p);
 219   tsd_getspecific(arena_key, vptr);
 220   if(vptr != ATFORK_ARENA_PTR)
 221     (void)mutex_lock(&ar_ptr->mutex);
 222   _int_free(ar_ptr, mem);
 223   if(vptr != ATFORK_ARENA_PTR)
 224     (void)mutex_unlock(&ar_ptr->mutex);
 225 }
 226
 227
 228 /* Counter for number of times the list is locked by the same thread.  */
 229 static unsigned int atfork_recursive_cntr;
 230
 231 /* The following two functions are registered via thread_atfork() to
 232    make sure that the mutexes remain in a consistent state in the
 233    fork()ed version of a thread.  Also adapt the malloc and free hooks
 234    temporarily, because the `atfork' handler mechanism may use
 235    malloc/free internally (e.g. in LinuxThreads). */
 236
 237 static void
 238 ptmalloc_lock_all (void)
 239 {
 240   mstate ar_ptr;
 241
 242   if(__malloc_initialized < 1)
 243     return;
 244   if (mutex_trylock(&list_lock))
 245     {
 246       Void_t *my_arena;
 247       tsd_getspecific(arena_key, my_arena);
 248       if (my_arena == ATFORK_ARENA_PTR)
 249         /* This is the same thread which already locks the global list.
 250            Just bump the counter.  */
 251         goto out;
 252
 253       /* This thread has to wait its turn.  */
 254       (void)mutex_lock(&list_lock);
 255     }
 256   for(ar_ptr = &main_arena;;) {
 257     (void)mutex_lock(&ar_ptr->mutex);
 258     ar_ptr = ar_ptr->next;
 259     if(ar_ptr == &main_arena) break;
 260   }
 261   save_malloc_hook = __malloc_hook;
 262   save_free_hook = __free_hook;
 263   __malloc_hook = malloc_atfork;
 264   __free_hook = free_atfork;
 265   /* Only the current thread may perform malloc/free calls now. */
 266   tsd_getspecific(arena_key, save_arena);
 267   tsd_setspecific(arena_key, ATFORK_ARENA_PTR);
 268  out:
 269   ++atfork_recursive_cntr;
 270 }
 271
 272 static void
 273 ptmalloc_unlock_all (void)
 274 {
 275   mstate ar_ptr;
 276
 277   if(__malloc_initialized < 1)
 278     return;
 279   if (--atfork_recursive_cntr != 0)
 280     return;
 281   tsd_setspecific(arena_key, save_arena);
 282   __malloc_hook = save_malloc_hook;
 283   __free_hook = save_free_hook;
 284   for(ar_ptr = &main_arena;;) {
 285     (void)mutex_unlock(&ar_ptr->mutex);
 286     ar_ptr = ar_ptr->next;
 287     if(ar_ptr == &main_arena) break;
 288   }
 289   (void)mutex_unlock(&list_lock);
 290 }
 291
 292 #ifdef __linux__
 293
 294 /* In NPTL, unlocking a mutex in the child process after a
 295    fork() is currently unsafe, whereas re-initializing it is safe and
 296    does not leak resources.  Therefore, a special atfork handler is
 297    installed for the child. */
 298
 299 static void
 300 ptmalloc_unlock_all2 (void)
 301 {
 302   mstate ar_ptr;
 303
 304   if(__malloc_initialized < 1)
 305     return;
 306 #if defined _LIBC || defined MALLOC_HOOKS
 307   tsd_setspecific(arena_key, save_arena);
 308   __malloc_hook = save_malloc_hook;
 309   __free_hook = save_free_hook;
 310 #endif
 311   for(ar_ptr = &main_arena;;) {
 312     mutex_init(&ar_ptr->mutex);
 313     ar_ptr = ar_ptr->next;
 314     if(ar_ptr == &main_arena) break;
 315   }
 316   mutex_init(&list_lock);
 317   atfork_recursive_cntr = 0;
 318 }
 319
 320 #else
 321
 322 #define ptmalloc_unlock_all2 ptmalloc_unlock_all
 323
 324 #endif
 325
 326 #endif /* !defined NO_THREADS */
 327
 328 /* Initialization routine. */
 329 #ifdef _LIBC
 330 #include <string.h>
 331 extern char **_environ;
 332
 333 static char *
 334 internal_function
 335 next_env_entry (char ***position)
 336 {
 337   char **current = *position;
 338   char *result = NULL;
 339
 340   while (*current != NULL)
 341     {
 342       if (__builtin_expect ((*current)[0] == 'M', 0)
 343           && (*current)[1] == 'A'
 344           && (*current)[2] == 'L'
 345           && (*current)[3] == 'L'
 346           && (*current)[4] == 'O'
 347           && (*current)[5] == 'C'
 348           && (*current)[6] == '_')
 349         {
 350           result = &(*current)[7];
 351
 352           /* Save current position for next visit.  */
 353           *position = ++current;
 354
 355           break;
 356         }
 357
 358       ++current;
 359     }
 360
 361   return result;
 362 }
 363 #endif /* _LIBC */
 364
 365 /* Set up basic state so that _int_malloc et al can work.  */
 366 static void
 367 ptmalloc_init_minimal (void)
 368 {
 369 #if DEFAULT_TOP_PAD != 0
 370   mp_.top_pad        = DEFAULT_TOP_PAD;
 371 #endif
 372   mp_.n_mmaps_max    = DEFAULT_MMAP_MAX;
 373   mp_.mmap_threshold = DEFAULT_MMAP_THRESHOLD;
 374   mp_.trim_threshold = DEFAULT_TRIM_THRESHOLD;
 375   mp_.pagesize       = malloc_getpagesize;
 376 }
 377
 378
 379 #ifdef _LIBC
 380 # ifdef SHARED
 381 static void *
 382 __failing_morecore (ptrdiff_t d)
 383 {
 384   return (void *) MORECORE_FAILURE;
 385 }
 386
 387 extern struct dl_open_hook *_dl_open_hook;
 388 libc_hidden_proto (_dl_open_hook);
 389 # endif
 390
 391 # if defined SHARED && !USE___THREAD
 392 /* This is called by __pthread_initialize_minimal when it needs to use
 393    malloc to set up the TLS state.  We cannot do the full work of
 394    ptmalloc_init (below) until __pthread_initialize_minimal has finished,
 395    so it has to switch to using the special startup-time hooks while doing
 396    those allocations.  */
 397 void
 398 __libc_malloc_pthread_startup (bool first_time)
 399 {
 400   if (first_time)
 401     {
 402       ptmalloc_init_minimal ();
 403       save_malloc_hook = __malloc_hook;
 404       save_memalign_hook = __memalign_hook;
 405       save_free_hook = __free_hook;
 406       __malloc_hook = malloc_starter;
 407       __memalign_hook = memalign_starter;
 408       __free_hook = free_starter;
 409     }
 410   else
 411     {
 412       __malloc_hook = save_malloc_hook;
 413       __memalign_hook = save_memalign_hook;
 414       __free_hook = save_free_hook;
 415     }
 416 }
 417 # endif
 418 #endif
 419
 420 static void
 421 ptmalloc_init (void)
 422 {
 423 #if __STD_C
 424   const char* s;
 425 #else
 426   char* s;
 427 #endif
 428   int secure = 0;
 429
 430   if(__malloc_initialized >= 0) return;
 431   __malloc_initialized = 0;
 432
 433 #ifdef _LIBC
 434 # if defined SHARED && !USE___THREAD
 435   /* ptmalloc_init_minimal may already have been called via
 436      __libc_malloc_pthread_startup, above.  */
 437   if (mp_.pagesize == 0)
 438 # endif
 439 #endif
 440     ptmalloc_init_minimal();
 441
 442 #ifndef NO_THREADS
 443 # if defined _LIBC
 444   /* We know __pthread_initialize_minimal has already been called,
 445      and that is enough.  */
 446 #   define NO_STARTER
 447 # endif
 448 # ifndef NO_STARTER
 449   /* With some threads implementations, creating thread-specific data
 450      or initializing a mutex may call malloc() itself.  Provide a
 451      simple starter version (realloc() won't work). */
 452   save_malloc_hook = __malloc_hook;
 453   save_memalign_hook = __memalign_hook;
 454   save_free_hook = __free_hook;
 455   __malloc_hook = malloc_starter;
 456   __memalign_hook = memalign_starter;
 457   __free_hook = free_starter;
 458 #  ifdef _LIBC
 459   /* Initialize the pthreads interface. */
 460   if (__pthread_initialize != NULL)
 461     __pthread_initialize();
 462 #  endif /* !defined _LIBC */
 463 # endif /* !defined NO_STARTER */
 464 #endif /* !defined NO_THREADS */
 465   mutex_init(&main_arena.mutex);
 466   main_arena.next = &main_arena;
 467
 468 #if defined _LIBC && defined SHARED
 469   /* In case this libc copy is in a non-default namespace, never use brk.
 470      Likewise if dlopened from statically linked program.  */
 471   Dl_info di;
 472   struct link_map *l;
 473
 474   if (_dl_open_hook != NULL
 475       || (_dl_addr (ptmalloc_init, &di, &l, NULL) != 0
 476           && l->l_ns != LM_ID_BASE))
 477     __morecore = __failing_morecore;
 478 #endif
 479
 480   mutex_init(&list_lock);
 481   tsd_key_create(&arena_key, NULL);
 482   tsd_setspecific(arena_key, (Void_t *)&main_arena);
 483   thread_atfork(ptmalloc_lock_all, ptmalloc_unlock_all, ptmalloc_unlock_all2);
 484 #ifndef NO_THREADS
 485 # ifndef NO_STARTER
 486   __malloc_hook = save_malloc_hook;
 487   __memalign_hook = save_memalign_hook;
 488   __free_hook = save_free_hook;
 489 # else
 490 #  undef NO_STARTER
 491 # endif
 492 #endif
 493 #ifdef _LIBC
 494   secure = __libc_enable_secure;
 495   s = NULL;
 496   if (__builtin_expect (_environ != NULL, 1))
 497     {
 498       char **runp = _environ;
 499       char *envline;
 500
 501       while (__builtin_expect ((envline = next_env_entry (&runp)) != NULL,
 502                                0))
 503         {
 504           size_t len = strcspn (envline, "=");
 505
 506           if (envline[len] != '=')
 507             /* This is a "MALLOC_" variable at the end of the string
 508                without a '=' character.  Ignore it since otherwise we
 509                will access invalid memory below.  */
 510             continue;
 511
 512           switch (len)
 513             {
 514             case 6:
 515               if (memcmp (envline, "CHECK_", 6) == 0)
 516                 s = &envline[7];
 517               break;
 518             case 8:
 519               if (! secure)
 520                 {
 521                   if (memcmp (envline, "TOP_PAD_", 8) == 0)
 522                     mALLOPt(M_TOP_PAD, atoi(&envline[9]));
 523                   else if (memcmp (envline, "PERTURB_", 8) == 0)
 524                     mALLOPt(M_PERTURB, atoi(&envline[9]));
 525                 }
 526               break;
 527             case 9:
 528               if (! secure && memcmp (envline, "MMAP_MAX_", 9) == 0)
 529                 mALLOPt(M_MMAP_MAX, atoi(&envline[10]));
 530               break;
 531             case 15:
 532               if (! secure)
 533                 {
 534                   if (memcmp (envline, "TRIM_THRESHOLD_", 15) == 0)
 535                     mALLOPt(M_TRIM_THRESHOLD, atoi(&envline[16]));
 536                   else if (memcmp (envline, "MMAP_THRESHOLD_", 15) == 0)
 537                     mALLOPt(M_MMAP_THRESHOLD, atoi(&envline[16]));
 538                 }
 539               break;
 540             default:
 541               break;
 542             }
 543         }
 544     }
 545 #else
 546   if (! secure)
 547     {
 548       if((s = getenv("MALLOC_TRIM_THRESHOLD_")))
 549         mALLOPt(M_TRIM_THRESHOLD, atoi(s));
 550       if((s = getenv("MALLOC_TOP_PAD_")))
 551         mALLOPt(M_TOP_PAD, atoi(s));
 552       if((s = getenv("MALLOC_PERTURB_")))
 553         mALLOPt(M_PERTURB, atoi(s));
 554       if((s = getenv("MALLOC_MMAP_THRESHOLD_")))
 555         mALLOPt(M_MMAP_THRESHOLD, atoi(s));
 556       if((s = getenv("MALLOC_MMAP_MAX_")))
 557         mALLOPt(M_MMAP_MAX, atoi(s));
 558     }
 559   s = getenv("MALLOC_CHECK_");
 560 #endif
 561   if(s && s[0]) {
 562     mALLOPt(M_CHECK_ACTION, (int)(s[0] - '0'));
 563     if (check_action != 0)
 564       __malloc_check_init();
 565   }
 566   if(__malloc_initialize_hook != NULL)
 567     (*__malloc_initialize_hook)();
 568   __malloc_initialized = 1;
 569 }
 570
 571 /* There are platforms (e.g. Hurd) with a link-time hook mechanism. */
 572 #ifdef thread_atfork_static
 573 thread_atfork_static(ptmalloc_lock_all, ptmalloc_unlock_all, \
 574                      ptmalloc_unlock_all2)
 575 #endif
 576
 577 \f
 578
 579 /* Managing heaps and arenas (for concurrent threads) */
 580
 581 #if USE_ARENAS
 582
 583 #if MALLOC_DEBUG > 1
 584
 585 /* Print the complete contents of a single heap to stderr. */
 586
 587 static void
 588 #if __STD_C
 589 dump_heap(heap_info *heap)
 590 #else
 591 dump_heap(heap) heap_info *heap;
 592 #endif
 593 {
 594   char *ptr;
 595   mchunkptr p;
 596
 597   fprintf(stderr, "Heap %p, size %10lx:\n", heap, (long)heap->size);
 598   ptr = (heap->ar_ptr != (mstate)(heap+1)) ?
 599     (char*)(heap + 1) : (char*)(heap + 1) + sizeof(struct malloc_state);
 600   p = (mchunkptr)(((unsigned long)ptr + MALLOC_ALIGN_MASK) &
 601                   ~MALLOC_ALIGN_MASK);
 602   for(;;) {
 603     fprintf(stderr, "chunk %p size %10lx", p, (long)p->size);
 604     if(p == top(heap->ar_ptr)) {
 605       fprintf(stderr, " (top)\n");
 606       break;
 607     } else if(p->size == (0|PREV_INUSE)) {
 608       fprintf(stderr, " (fence)\n");
 609       break;
 610     }
 611     fprintf(stderr, "\n");
 612     p = next_chunk(p);
 613   }
 614 }
 615
 616 #endif /* MALLOC_DEBUG > 1 */
 617
 618 /* If consecutive mmap (0, HEAP_MAX_SIZE << 1, ...) calls return decreasing
 619    addresses as opposed to increasing, new_heap would badly fragment the
 620    address space.  In that case remember the second HEAP_MAX_SIZE part
 621    aligned to HEAP_MAX_SIZE from last mmap (0, HEAP_MAX_SIZE << 1, ...)
 622    call (if it is already aligned) and try to reuse it next time.  We need
 623    no locking for it, as kernel ensures the atomicity for us - worst case
 624    we'll call mmap (addr, HEAP_MAX_SIZE, ...) for some value of addr in
 625    multiple threads, but only one will succeed.  */
 626 static char *aligned_heap_area;
 627
 628 /* Create a new heap.  size is automatically rounded up to a multiple
 629    of the page size. */
 630
 631 static heap_info *
 632 internal_function
 633 #if __STD_C
 634 new_heap(size_t size, size_t top_pad)
 635 #else
 636 new_heap(size, top_pad) size_t size, top_pad;
 637 #endif
 638 {
 639   size_t page_mask = malloc_getpagesize - 1;
 640   char *p1, *p2;
 641   unsigned long ul;
 642   heap_info *h;
 643
 644   if(size+top_pad < HEAP_MIN_SIZE)
 645     size = HEAP_MIN_SIZE;
 646   else if(size+top_pad <= HEAP_MAX_SIZE)
 647     size += top_pad;
 648   else if(size > HEAP_MAX_SIZE)
 649     return 0;
 650   else
 651     size = HEAP_MAX_SIZE;
 652   size = (size + page_mask) & ~page_mask;
 653
 654   /* A memory region aligned to a multiple of HEAP_MAX_SIZE is needed.
 655      No swap space needs to be reserved for the following large
 656      mapping (on Linux, this is the case for all non-writable mappings
 657      anyway). */
 658   p2 = MAP_FAILED;
 659   if(aligned_heap_area) {
 660     p2 = (char *)MMAP(aligned_heap_area, HEAP_MAX_SIZE, PROT_NONE,
 661                       MAP_PRIVATE|MAP_NORESERVE);
 662     aligned_heap_area = NULL;
 663     if (p2 != MAP_FAILED && ((unsigned long)p2 & (HEAP_MAX_SIZE-1))) {
 664       munmap(p2, HEAP_MAX_SIZE);
 665       p2 = MAP_FAILED;
 666     }
 667   }
 668   if(p2 == MAP_FAILED) {
 669     p1 = (char *)MMAP(0, HEAP_MAX_SIZE<<1, PROT_NONE,
 670                       MAP_PRIVATE|MAP_NORESERVE);
 671     if(p1 != MAP_FAILED) {
 672       p2 = (char *)(((unsigned long)p1 + (HEAP_MAX_SIZE-1))
 673                     & ~(HEAP_MAX_SIZE-1));
 674       ul = p2 - p1;
 675       if (ul)
 676         munmap(p1, ul);
 677       else
 678         aligned_heap_area = p2 + HEAP_MAX_SIZE;
 679       munmap(p2 + HEAP_MAX_SIZE, HEAP_MAX_SIZE - ul);
 680     } else {
 681       /* Try to take the chance that an allocation of only HEAP_MAX_SIZE
 682          is already aligned. */
 683       p2 = (char *)MMAP(0, HEAP_MAX_SIZE, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE);
 684       if(p2 == MAP_FAILED)
 685         return 0;
 686       if((unsigned long)p2 & (HEAP_MAX_SIZE-1)) {
 687         munmap(p2, HEAP_MAX_SIZE);
 688         return 0;
 689       }
 690     }
 691   }
 692   if(mprotect(p2, size, PROT_READ|PROT_WRITE) != 0) {
 693     munmap(p2, HEAP_MAX_SIZE);
 694     return 0;
 695   }
 696   h = (heap_info *)p2;
 697   h->size = size;
 698   h->mprotect_size = size;
 699   THREAD_STAT(stat_n_heaps++);
 700   return h;
 701 }
 702
 703 /* Grow or shrink a heap.  size is automatically rounded up to a
 704    multiple of the page size if it is positive. */
 705
 706 static int
 707 #if __STD_C
 708 grow_heap(heap_info *h, long diff)
 709 #else
 710 grow_heap(h, diff) heap_info *h; long diff;
 711 #endif
 712 {
 713   size_t page_mask = malloc_getpagesize - 1;
 714   long new_size;
 715
 716   if(diff >= 0) {
 717     diff = (diff + page_mask) & ~page_mask;
 718     new_size = (long)h->size + diff;
 719     if((unsigned long) new_size > (unsigned long) HEAP_MAX_SIZE)
 720       return -1;
 721     if((unsigned long) new_size > h->mprotect_size) {
 722       if (mprotect((char *)h + h->mprotect_size,
 723                    (unsigned long) new_size - h->mprotect_size,
 724                    PROT_READ|PROT_WRITE) != 0)
 725         return -2;
 726       h->mprotect_size = new_size;
 727     }
 728   } else {
 729     new_size = (long)h->size + diff;
 730     if(new_size < (long)sizeof(*h))
 731       return -1;
 732     /* Try to re-map the extra heap space freshly to save memory, and
 733        make it inaccessible. */
 734 #ifdef _LIBC
 735     if (__builtin_expect (__libc_enable_secure, 0))
 736 #else
 737     if (1)
 738 #endif
 739       {
 740         if((char *)MMAP((char *)h + new_size, -diff, PROT_NONE,
 741                         MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
 742           return -2;
 743         h->mprotect_size = new_size;
 744       }
 745 #ifdef _LIBC
 746     else
 747       madvise ((char *)h + new_size, -diff, MADV_DONTNEED);
 748 #endif
 749     /*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
 750   }
 751   h->size = new_size;
 752   return 0;
 753 }
 754
 755 /* Delete a heap. */
 756
 757 #define delete_heap(heap) \
 758   do {                                                          \
 759     if ((char *)(heap) + HEAP_MAX_SIZE == aligned_heap_area)    \
 760       aligned_heap_area = NULL;                                 \
 761     munmap((char*)(heap), HEAP_MAX_SIZE);                       \
 762   } while (0)
 763
 764 static int
 765 internal_function
 766 #if __STD_C
 767 heap_trim(heap_info *heap, size_t pad)
 768 #else
 769 heap_trim(heap, pad) heap_info *heap; size_t pad;
 770 #endif
 771 {
 772   mstate ar_ptr = heap->ar_ptr;
 773   unsigned long pagesz = mp_.pagesize;
 774   mchunkptr top_chunk = top(ar_ptr), p, bck, fwd;
 775   heap_info *prev_heap;
 776   long new_size, top_size, extra;
 777
 778   /* Can this heap go away completely? */
 779   while(top_chunk == chunk_at_offset(heap, sizeof(*heap))) {
 780     prev_heap = heap->prev;
 781     p = chunk_at_offset(prev_heap, prev_heap->size - (MINSIZE-2*SIZE_SZ));
 782     assert(p->size == (0|PREV_INUSE)); /* must be fencepost */
 783     p = prev_chunk(p);
 784     new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ);
 785     assert(new_size>0 && new_size<(long)(2*MINSIZE));
 786     if(!prev_inuse(p))
 787       new_size += p->prev_size;
 788     assert(new_size>0 && new_size<HEAP_MAX_SIZE);
 789     if(new_size + (HEAP_MAX_SIZE - prev_heap->size) < pad + MINSIZE + pagesz)
 790       break;
 791     ar_ptr->system_mem -= heap->size;
 792     arena_mem -= heap->size;
 793     delete_heap(heap);
 794     heap = prev_heap;
 795     if(!prev_inuse(p)) { /* consolidate backward */
 796       p = prev_chunk(p);
 797       unlink(p, bck, fwd);
 798     }
 799     assert(((unsigned long)((char*)p + new_size) & (pagesz-1)) == 0);
 800     assert( ((char*)p + new_size) == ((char*)heap + heap->size) );
 801     top(ar_ptr) = top_chunk = p;
 802     set_head(top_chunk, new_size | PREV_INUSE);
 803     /*check_chunk(ar_ptr, top_chunk);*/
 804   }
 805   top_size = chunksize(top_chunk);
 806   extra = ((top_size - pad - MINSIZE + (pagesz-1))/pagesz - 1) * pagesz;
 807   if(extra < (long)pagesz)
 808     return 0;
 809   /* Try to shrink. */
 810   if(grow_heap(heap, -extra) != 0)
 811     return 0;
 812   ar_ptr->system_mem -= extra;
 813   arena_mem -= extra;
 814
 815   /* Success. Adjust top accordingly. */
 816   set_head(top_chunk, (top_size - extra) | PREV_INUSE);
 817   /*check_chunk(ar_ptr, top_chunk);*/
 818   return 1;
 819 }
 820
 821 /* Create a new arena with initial size "size".  */
 822
 823 static mstate
 824 _int_new_arena(size_t size)
 825 {
 826   mstate a;
 827   heap_info *h;
 828   char *ptr;
 829   unsigned long misalign;
 830
 831   h = new_heap(size + (sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT),
 832                mp_.top_pad);
 833   if(!h) {
 834     /* Maybe size is too large to fit in a single heap.  So, just try
 835        to create a minimally-sized arena and let _int_malloc() attempt
 836        to deal with the large request via mmap_chunk().  */
 837     h = new_heap(sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT, mp_.top_pad);
 838     if(!h)
 839       return 0;
 840   }
 841   a = h->ar_ptr = (mstate)(h+1);
 842   malloc_init_state(a);
 843   /*a->next = NULL;*/
 844   a->system_mem = a->max_system_mem = h->size;
 845   arena_mem += h->size;
 846 #ifdef NO_THREADS
 847   if((unsigned long)(mp_.mmapped_mem + arena_mem + main_arena.system_mem) >
 848      mp_.max_total_mem)
 849     mp_.max_total_mem = mp_.mmapped_mem + arena_mem + main_arena.system_mem;
 850 #endif
 851
 852   /* Set up the top chunk, with proper alignment. */
 853   ptr = (char *)(a + 1);
 854   misalign = (unsigned long)chunk2mem(ptr) & MALLOC_ALIGN_MASK;
 855   if (misalign > 0)
 856     ptr += MALLOC_ALIGNMENT - misalign;
 857   top(a) = (mchunkptr)ptr;
 858   set_head(top(a), (((char*)h + h->size) - ptr) | PREV_INUSE);
 859
 860   return a;
 861 }
 862
 863 static mstate
 864 internal_function
 865 #if __STD_C
 866 arena_get2(mstate a_tsd, size_t size)
 867 #else
 868 arena_get2(a_tsd, size) mstate a_tsd; size_t size;
 869 #endif
 870 {
 871   mstate a;
 872
 873   if(!a_tsd)
 874     a = a_tsd = &main_arena;
 875   else {
 876     a = a_tsd->next;
 877     if(!a) {
 878       /* This can only happen while initializing the new arena. */
 879       (void)mutex_lock(&main_arena.mutex);
 880       THREAD_STAT(++(main_arena.stat_lock_wait));
 881       return &main_arena;
 882     }
 883   }
 884
 885   /* Check the global, circularly linked list for available arenas. */
 886   bool retried = false;
 887  repeat:
 888   do {
 889     if(!mutex_trylock(&a->mutex)) {
 890       if (retried)
 891         (void)mutex_unlock(&list_lock);
 892       THREAD_STAT(++(a->stat_lock_loop));
 893       tsd_setspecific(arena_key, (Void_t *)a);
 894       return a;
 895     }
 896     a = a->next;
 897   } while(a != a_tsd);
 898
 899   /* If not even the list_lock can be obtained, try again.  This can
 900      happen during `atfork', or for example on systems where thread
 901      creation makes it temporarily impossible to obtain _any_
 902      locks. */
 903   if(!retried && mutex_trylock(&list_lock)) {
 904     /* We will block to not run in a busy loop.  */
 905     (void)mutex_lock(&list_lock);
 906
 907     /* Since we blocked there might be an arena available now.  */
 908     retried = true;
 909     a = a_tsd;
 910     goto repeat;
 911   }
 912
 913   /* Nothing immediately available, so generate a new arena.  */
 914   a = _int_new_arena(size);
 915   if(a)
 916     {
 917       tsd_setspecific(arena_key, (Void_t *)a);
 918       mutex_init(&a->mutex);
 919       mutex_lock(&a->mutex); /* remember result */
 920
 921       /* Add the new arena to the global list.  */
 922       a->next = main_arena.next;
 923       atomic_write_barrier ();
 924       main_arena.next = a;
 925
 926       THREAD_STAT(++(a->stat_lock_loop));
 927     }
 928   (void)mutex_unlock(&list_lock);
 929
 930   return a;
 931 }
 932
 933 #endif /* USE_ARENAS */
 934
 935 /*
 936  * Local variables:
 937  * c-basic-offset: 2
 938  * End:
 939  */