malloc/arena.c

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