malloc/arena.c

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