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 #if MALLOC_DEBUG
 374   mp_.n_mmaps_cmax   = DEFAULT_MMAP_MAX;
 375 #endif
 376   mp_.mmap_threshold = DEFAULT_MMAP_THRESHOLD;
 377   mp_.trim_threshold = DEFAULT_TRIM_THRESHOLD;
 378   mp_.pagesize       = malloc_getpagesize;
 379 }
 380
 381
 382 #ifdef _LIBC
 383 # ifdef SHARED
 384 static void *
 385 __failing_morecore (ptrdiff_t d)
 386 {
 387   return (void *) MORECORE_FAILURE;
 388 }
 389
 390 extern struct dl_open_hook *_dl_open_hook;
 391 libc_hidden_proto (_dl_open_hook);
 392 # endif
 393
 394 # if defined SHARED && !USE___THREAD
 395 /* This is called by __pthread_initialize_minimal when it needs to use
 396    malloc to set up the TLS state.  We cannot do the full work of
 397    ptmalloc_init (below) until __pthread_initialize_minimal has finished,
 398    so it has to switch to using the special startup-time hooks while doing
 399    those allocations.  */
 400 void
 401 __libc_malloc_pthread_startup (bool first_time)
 402 {
 403   if (first_time)
 404     {
 405       ptmalloc_init_minimal ();
 406       save_malloc_hook = __malloc_hook;
 407       save_memalign_hook = __memalign_hook;
 408       save_free_hook = __free_hook;
 409       __malloc_hook = malloc_starter;
 410       __memalign_hook = memalign_starter;
 411       __free_hook = free_starter;
 412     }
 413   else
 414     {
 415       __malloc_hook = save_malloc_hook;
 416       __memalign_hook = save_memalign_hook;
 417       __free_hook = save_free_hook;
 418     }
 419 }
 420 # endif
 421 #endif
 422
 423 static void
 424 ptmalloc_init (void)
 425 {
 426 #if __STD_C
 427   const char* s;
 428 #else
 429   char* s;
 430 #endif
 431   int secure = 0;
 432
 433   if(__malloc_initialized >= 0) return;
 434   __malloc_initialized = 0;
 435
 436 #ifdef _LIBC
 437 # if defined SHARED && !USE___THREAD
 438   /* ptmalloc_init_minimal may already have been called via
 439      __libc_malloc_pthread_startup, above.  */
 440   if (mp_.pagesize == 0)
 441 # endif
 442 #endif
 443     ptmalloc_init_minimal();
 444
 445 #ifndef NO_THREADS
 446 # if defined _LIBC
 447   /* We know __pthread_initialize_minimal has already been called,
 448      and that is enough.  */
 449 #   define NO_STARTER
 450 # endif
 451 # ifndef NO_STARTER
 452   /* With some threads implementations, creating thread-specific data
 453      or initializing a mutex may call malloc() itself.  Provide a
 454      simple starter version (realloc() won't work). */
 455   save_malloc_hook = __malloc_hook;
 456   save_memalign_hook = __memalign_hook;
 457   save_free_hook = __free_hook;
 458   __malloc_hook = malloc_starter;
 459   __memalign_hook = memalign_starter;
 460   __free_hook = free_starter;
 461 #  ifdef _LIBC
 462   /* Initialize the pthreads interface. */
 463   if (__pthread_initialize != NULL)
 464     __pthread_initialize();
 465 #  endif /* !defined _LIBC */
 466 # endif /* !defined NO_STARTER */
 467 #endif /* !defined NO_THREADS */
 468   mutex_init(&main_arena.mutex);
 469   main_arena.next = &main_arena;
 470
 471 #if defined _LIBC && defined SHARED
 472   /* In case this libc copy is in a non-default namespace, never use brk.
 473      Likewise if dlopened from statically linked program.  */
 474   Dl_info di;
 475   struct link_map *l;
 476
 477   if (_dl_open_hook != NULL
 478       || (_dl_addr (ptmalloc_init, &di, &l, NULL) != 0
 479           && l->l_ns != LM_ID_BASE))
 480     __morecore = __failing_morecore;
 481 #endif
 482
 483   mutex_init(&list_lock);
 484   tsd_key_create(&arena_key, NULL);
 485   tsd_setspecific(arena_key, (Void_t *)&main_arena);
 486   thread_atfork(ptmalloc_lock_all, ptmalloc_unlock_all, ptmalloc_unlock_all2);
 487 #ifndef NO_THREADS
 488 # ifndef NO_STARTER
 489   __malloc_hook = save_malloc_hook;
 490   __memalign_hook = save_memalign_hook;
 491   __free_hook = save_free_hook;
 492 # else
 493 #  undef NO_STARTER
 494 # endif
 495 #endif
 496 #ifdef _LIBC
 497   secure = __libc_enable_secure;
 498   s = NULL;
 499   if (__builtin_expect (_environ != NULL, 1))
 500     {
 501       char **runp = _environ;
 502       char *envline;
 503
 504       while (__builtin_expect ((envline = next_env_entry (&runp)) != NULL,
 505                                0))
 506         {
 507           size_t len = strcspn (envline, "=");
 508
 509           if (envline[len] != '=')
 510             /* This is a "MALLOC_" variable at the end of the string
 511                without a '=' character.  Ignore it since otherwise we
 512                will access invalid memory below.  */
 513             continue;
 514
 515           switch (len)
 516             {
 517             case 6:
 518               if (memcmp (envline, "CHECK_", 6) == 0)
 519                 s = &envline[7];
 520               break;
 521             case 8:
 522               if (! secure)
 523                 {
 524                   if (memcmp (envline, "TOP_PAD_", 8) == 0)
 525                     mALLOPt(M_TOP_PAD, atoi(&envline[9]));
 526                   else if (memcmp (envline, "PERTURB_", 8) == 0)
 527                     mALLOPt(M_PERTURB, atoi(&envline[9]));
 528                 }
 529               break;
 530             case 9:
 531               if (! secure && memcmp (envline, "MMAP_MAX_", 9) == 0)
 532                 mALLOPt(M_MMAP_MAX, atoi(&envline[10]));
 533               break;
 534             case 15:
 535               if (! secure)
 536                 {
 537                   if (memcmp (envline, "TRIM_THRESHOLD_", 15) == 0)
 538                     mALLOPt(M_TRIM_THRESHOLD, atoi(&envline[16]));
 539                   else if (memcmp (envline, "MMAP_THRESHOLD_", 15) == 0)
 540                     mALLOPt(M_MMAP_THRESHOLD, atoi(&envline[16]));
 541                 }
 542               break;
 543             default:
 544               break;
 545             }
 546         }
 547     }
 548 #else
 549   if (! secure)
 550     {
 551       if((s = getenv("MALLOC_TRIM_THRESHOLD_")))
 552         mALLOPt(M_TRIM_THRESHOLD, atoi(s));
 553       if((s = getenv("MALLOC_TOP_PAD_")))
 554         mALLOPt(M_TOP_PAD, atoi(s));
 555       if((s = getenv("MALLOC_PERTURB_")))
 556         mALLOPt(M_PERTURB, atoi(s));
 557       if((s = getenv("MALLOC_MMAP_THRESHOLD_")))
 558         mALLOPt(M_MMAP_THRESHOLD, atoi(s));
 559       if((s = getenv("MALLOC_MMAP_MAX_")))
 560         mALLOPt(M_MMAP_MAX, atoi(s));
 561     }
 562   s = getenv("MALLOC_CHECK_");
 563 #endif
 564   if(s && s[0]) {
 565     mALLOPt(M_CHECK_ACTION, (int)(s[0] - '0'));
 566     if (check_action != 0)
 567       __malloc_check_init();
 568   }
 569   if(__malloc_initialize_hook != NULL)
 570     (*__malloc_initialize_hook)();
 571   __malloc_initialized = 1;
 572 }
 573
 574 /* There are platforms (e.g. Hurd) with a link-time hook mechanism. */
 575 #ifdef thread_atfork_static
 576 thread_atfork_static(ptmalloc_lock_all, ptmalloc_unlock_all, \
 577                      ptmalloc_unlock_all2)
 578 #endif
 579
 580 \f
 581
 582 /* Managing heaps and arenas (for concurrent threads) */
 583
 584 #if USE_ARENAS
 585
 586 #if MALLOC_DEBUG > 1
 587
 588 /* Print the complete contents of a single heap to stderr. */
 589
 590 static void
 591 #if __STD_C
 592 dump_heap(heap_info *heap)
 593 #else
 594 dump_heap(heap) heap_info *heap;
 595 #endif
 596 {
 597   char *ptr;
 598   mchunkptr p;
 599
 600   fprintf(stderr, "Heap %p, size %10lx:\n", heap, (long)heap->size);
 601   ptr = (heap->ar_ptr != (mstate)(heap+1)) ?
 602     (char*)(heap + 1) : (char*)(heap + 1) + sizeof(struct malloc_state);
 603   p = (mchunkptr)(((unsigned long)ptr + MALLOC_ALIGN_MASK) &
 604                   ~MALLOC_ALIGN_MASK);
 605   for(;;) {
 606     fprintf(stderr, "chunk %p size %10lx", p, (long)p->size);
 607     if(p == top(heap->ar_ptr)) {
 608       fprintf(stderr, " (top)\n");
 609       break;
 610     } else if(p->size == (0|PREV_INUSE)) {
 611       fprintf(stderr, " (fence)\n");
 612       break;
 613     }
 614     fprintf(stderr, "\n");
 615     p = next_chunk(p);
 616   }
 617 }
 618
 619 #endif /* MALLOC_DEBUG > 1 */
 620
 621 /* If consecutive mmap (0, HEAP_MAX_SIZE << 1, ...) calls return decreasing
 622    addresses as opposed to increasing, new_heap would badly fragment the
 623    address space.  In that case remember the second HEAP_MAX_SIZE part
 624    aligned to HEAP_MAX_SIZE from last mmap (0, HEAP_MAX_SIZE << 1, ...)
 625    call (if it is already aligned) and try to reuse it next time.  We need
 626    no locking for it, as kernel ensures the atomicity for us - worst case
 627    we'll call mmap (addr, HEAP_MAX_SIZE, ...) for some value of addr in
 628    multiple threads, but only one will succeed.  */
 629 static char *aligned_heap_area;
 630
 631 /* Create a new heap.  size is automatically rounded up to a multiple
 632    of the page size. */
 633
 634 static heap_info *
 635 internal_function
 636 #if __STD_C
 637 new_heap(size_t size, size_t top_pad)
 638 #else
 639 new_heap(size, top_pad) size_t size, top_pad;
 640 #endif
 641 {
 642   size_t page_mask = malloc_getpagesize - 1;
 643   char *p1, *p2;
 644   unsigned long ul;
 645   heap_info *h;
 646
 647   if(size+top_pad < HEAP_MIN_SIZE)
 648     size = HEAP_MIN_SIZE;
 649   else if(size+top_pad <= HEAP_MAX_SIZE)
 650     size += top_pad;
 651   else if(size > HEAP_MAX_SIZE)
 652     return 0;
 653   else
 654     size = HEAP_MAX_SIZE;
 655   size = (size + page_mask) & ~page_mask;
 656
 657   /* A memory region aligned to a multiple of HEAP_MAX_SIZE is needed.
 658      No swap space needs to be reserved for the following large
 659      mapping (on Linux, this is the case for all non-writable mappings
 660      anyway). */
 661   p2 = MAP_FAILED;
 662   if(aligned_heap_area) {
 663     p2 = (char *)MMAP(aligned_heap_area, HEAP_MAX_SIZE, PROT_NONE,
 664                       MAP_PRIVATE|MAP_NORESERVE);
 665     aligned_heap_area = NULL;
 666     if (p2 != MAP_FAILED && ((unsigned long)p2 & (HEAP_MAX_SIZE-1))) {
 667       munmap(p2, HEAP_MAX_SIZE);
 668       p2 = MAP_FAILED;
 669     }
 670   }
 671   if(p2 == MAP_FAILED) {
 672     p1 = (char *)MMAP(0, HEAP_MAX_SIZE<<1, PROT_NONE,
 673                       MAP_PRIVATE|MAP_NORESERVE);
 674     if(p1 != MAP_FAILED) {
 675       p2 = (char *)(((unsigned long)p1 + (HEAP_MAX_SIZE-1))
 676                     & ~(HEAP_MAX_SIZE-1));
 677       ul = p2 - p1;
 678       if (ul)
 679         munmap(p1, ul);
 680       else
 681         aligned_heap_area = p2 + HEAP_MAX_SIZE;
 682       munmap(p2 + HEAP_MAX_SIZE, HEAP_MAX_SIZE - ul);
 683     } else {
 684       /* Try to take the chance that an allocation of only HEAP_MAX_SIZE
 685          is already aligned. */
 686       p2 = (char *)MMAP(0, HEAP_MAX_SIZE, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE);
 687       if(p2 == MAP_FAILED)
 688         return 0;
 689       if((unsigned long)p2 & (HEAP_MAX_SIZE-1)) {
 690         munmap(p2, HEAP_MAX_SIZE);
 691         return 0;
 692       }
 693     }
 694   }
 695   if(mprotect(p2, size, PROT_READ|PROT_WRITE) != 0) {
 696     munmap(p2, HEAP_MAX_SIZE);
 697     return 0;
 698   }
 699   h = (heap_info *)p2;
 700   h->size = size;
 701   h->mprotect_size = size;
 702   THREAD_STAT(stat_n_heaps++);
 703   return h;
 704 }
 705
 706 /* Grow or shrink a heap.  size is automatically rounded up to a
 707    multiple of the page size if it is positive. */
 708
 709 static int
 710 #if __STD_C
 711 grow_heap(heap_info *h, long diff)
 712 #else
 713 grow_heap(h, diff) heap_info *h; long diff;
 714 #endif
 715 {
 716   size_t page_mask = malloc_getpagesize - 1;
 717   long new_size;
 718
 719   if(diff >= 0) {
 720     diff = (diff + page_mask) & ~page_mask;
 721     new_size = (long)h->size + diff;
 722     if((unsigned long) new_size > (unsigned long) HEAP_MAX_SIZE)
 723       return -1;
 724     if((unsigned long) new_size > h->mprotect_size) {
 725       if (mprotect((char *)h + h->mprotect_size,
 726                    (unsigned long) new_size - h->mprotect_size,
 727                    PROT_READ|PROT_WRITE) != 0)
 728         return -2;
 729       h->mprotect_size = new_size;
 730     }
 731   } else {
 732     new_size = (long)h->size + diff;
 733     if(new_size < (long)sizeof(*h))
 734       return -1;
 735     /* Try to re-map the extra heap space freshly to save memory, and
 736        make it inaccessible. */
 737 #ifdef _LIBC
 738     if (__builtin_expect (__libc_enable_secure, 0))
 739 #else
 740     if (1)
 741 #endif
 742       {
 743         if((char *)MMAP((char *)h + new_size, -diff, PROT_NONE,
 744                         MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
 745           return -2;
 746         h->mprotect_size = new_size;
 747       }
 748 #ifdef _LIBC
 749     else
 750       madvise ((char *)h + new_size, -diff, MADV_DONTNEED);
 751 #endif
 752     /*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
 753   }
 754   h->size = new_size;
 755   return 0;
 756 }
 757
 758 /* Delete a heap. */
 759
 760 #define delete_heap(heap) \
 761   do {                                                          \
 762     if ((char *)(heap) + HEAP_MAX_SIZE == aligned_heap_area)    \
 763       aligned_heap_area = NULL;                                 \
 764     munmap((char*)(heap), HEAP_MAX_SIZE);                       \
 765   } while (0)
 766
 767 static int
 768 internal_function
 769 #if __STD_C
 770 heap_trim(heap_info *heap, size_t pad)
 771 #else
 772 heap_trim(heap, pad) heap_info *heap; size_t pad;
 773 #endif
 774 {
 775   mstate ar_ptr = heap->ar_ptr;
 776   unsigned long pagesz = mp_.pagesize;
 777   mchunkptr top_chunk = top(ar_ptr), p, bck, fwd;
 778   heap_info *prev_heap;
 779   long new_size, top_size, extra;
 780
 781   /* Can this heap go away completely? */
 782   while(top_chunk == chunk_at_offset(heap, sizeof(*heap))) {
 783     prev_heap = heap->prev;
 784     p = chunk_at_offset(prev_heap, prev_heap->size - (MINSIZE-2*SIZE_SZ));
 785     assert(p->size == (0|PREV_INUSE)); /* must be fencepost */
 786     p = prev_chunk(p);
 787     new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ);
 788     assert(new_size>0 && new_size<(long)(2*MINSIZE));
 789     if(!prev_inuse(p))
 790       new_size += p->prev_size;
 791     assert(new_size>0 && new_size<HEAP_MAX_SIZE);
 792     if(new_size + (HEAP_MAX_SIZE - prev_heap->size) < pad + MINSIZE + pagesz)
 793       break;
 794     ar_ptr->system_mem -= heap->size;
 795     arena_mem -= heap->size;
 796     delete_heap(heap);
 797     heap = prev_heap;
 798     if(!prev_inuse(p)) { /* consolidate backward */
 799       p = prev_chunk(p);
 800       unlink(p, bck, fwd);
 801     }
 802     assert(((unsigned long)((char*)p + new_size) & (pagesz-1)) == 0);
 803     assert( ((char*)p + new_size) == ((char*)heap + heap->size) );
 804     top(ar_ptr) = top_chunk = p;
 805     set_head(top_chunk, new_size | PREV_INUSE);
 806     /*check_chunk(ar_ptr, top_chunk);*/
 807   }
 808   top_size = chunksize(top_chunk);
 809   extra = ((top_size - pad - MINSIZE + (pagesz-1))/pagesz - 1) * pagesz;
 810   if(extra < (long)pagesz)
 811     return 0;
 812   /* Try to shrink. */
 813   if(grow_heap(heap, -extra) != 0)
 814     return 0;
 815   ar_ptr->system_mem -= extra;
 816   arena_mem -= extra;
 817
 818   /* Success. Adjust top accordingly. */
 819   set_head(top_chunk, (top_size - extra) | PREV_INUSE);
 820   /*check_chunk(ar_ptr, top_chunk);*/
 821   return 1;
 822 }
 823
 824 /* Create a new arena with initial size "size".  */
 825
 826 static mstate
 827 _int_new_arena(size_t size)
 828 {
 829   mstate a;
 830   heap_info *h;
 831   char *ptr;
 832   unsigned long misalign;
 833
 834   h = new_heap(size + (sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT),
 835                mp_.top_pad);
 836   if(!h) {
 837     /* Maybe size is too large to fit in a single heap.  So, just try
 838        to create a minimally-sized arena and let _int_malloc() attempt
 839        to deal with the large request via mmap_chunk().  */
 840     h = new_heap(sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT, mp_.top_pad);
 841     if(!h)
 842       return 0;
 843   }
 844   a = h->ar_ptr = (mstate)(h+1);
 845   malloc_init_state(a);
 846   /*a->next = NULL;*/
 847   a->system_mem = a->max_system_mem = h->size;
 848   arena_mem += h->size;
 849 #ifdef NO_THREADS
 850   if((unsigned long)(mp_.mmapped_mem + arena_mem + main_arena.system_mem) >
 851      mp_.max_total_mem)
 852     mp_.max_total_mem = mp_.mmapped_mem + arena_mem + main_arena.system_mem;
 853 #endif
 854
 855   /* Set up the top chunk, with proper alignment. */
 856   ptr = (char *)(a + 1);
 857   misalign = (unsigned long)chunk2mem(ptr) & MALLOC_ALIGN_MASK;
 858   if (misalign > 0)
 859     ptr += MALLOC_ALIGNMENT - misalign;
 860   top(a) = (mchunkptr)ptr;
 861   set_head(top(a), (((char*)h + h->size) - ptr) | PREV_INUSE);
 862
 863   return a;
 864 }
 865
 866 static mstate
 867 internal_function
 868 #if __STD_C
 869 arena_get2(mstate a_tsd, size_t size)
 870 #else
 871 arena_get2(a_tsd, size) mstate a_tsd; size_t size;
 872 #endif
 873 {
 874   mstate a;
 875
 876   if(!a_tsd)
 877     a = a_tsd = &main_arena;
 878   else {
 879     a = a_tsd->next;
 880     if(!a) {
 881       /* This can only happen while initializing the new arena. */
 882       (void)mutex_lock(&main_arena.mutex);
 883       THREAD_STAT(++(main_arena.stat_lock_wait));
 884       return &main_arena;
 885     }
 886   }
 887
 888   /* Check the global, circularly linked list for available arenas. */
 889   bool retried = false;
 890  repeat:
 891   do {
 892     if(!mutex_trylock(&a->mutex)) {
 893       if (retried)
 894         (void)mutex_unlock(&list_lock);
 895       THREAD_STAT(++(a->stat_lock_loop));
 896       tsd_setspecific(arena_key, (Void_t *)a);
 897       return a;
 898     }
 899     a = a->next;
 900   } while(a != a_tsd);
 901
 902   /* If not even the list_lock can be obtained, try again.  This can
 903      happen during `atfork', or for example on systems where thread
 904      creation makes it temporarily impossible to obtain _any_
 905      locks. */
 906   if(!retried && mutex_trylock(&list_lock)) {
 907     /* We will block to not run in a busy loop.  */
 908     (void)mutex_lock(&list_lock);
 909
 910     /* Since we blocked there might be an arena available now.  */
 911     retried = true;
 912     a = a_tsd;
 913     goto repeat;
 914   }
 915
 916   /* Nothing immediately available, so generate a new arena.  */
 917   a = _int_new_arena(size);
 918   if(a)
 919     {
 920       tsd_setspecific(arena_key, (Void_t *)a);
 921       mutex_init(&a->mutex);
 922       mutex_lock(&a->mutex); /* remember result */
 923
 924       /* Add the new arena to the global list.  */
 925       a->next = main_arena.next;
 926       atomic_write_barrier ();
 927       main_arena.next = a;
 928
 929       THREAD_STAT(++(a->stat_lock_loop));
 930     }
 931   (void)mutex_unlock(&list_lock);
 932
 933   return a;
 934 }
 935
 936 #endif /* USE_ARENAS */
 937
 938 /*
 939  * Local variables:
 940  * c-basic-offset: 2
 941  * End:
 942  */