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 # endif
 351
 352 # if defined SHARED && defined USE_TLS && !USE___THREAD
 353 # include <stdbool.h>
 354
 355 /* This is called by __pthread_initialize_minimal when it needs to use
 356    malloc to set up the TLS state.  We cannot do the full work of
 357    ptmalloc_init (below) until __pthread_initialize_minimal has finished,
 358    so it has to switch to using the special startup-time hooks while doing
 359    those allocations.  */
 360 void
 361 __libc_malloc_pthread_startup (bool first_time)
 362 {
 363   if (first_time)
 364     {
 365       ptmalloc_init_minimal ();
 366       save_malloc_hook = __malloc_hook;
 367       save_memalign_hook = __memalign_hook;
 368       save_free_hook = __free_hook;
 369       __malloc_hook = malloc_starter;
 370       __memalign_hook = memalign_starter;
 371       __free_hook = free_starter;
 372     }
 373   else
 374     {
 375       __malloc_hook = save_malloc_hook;
 376       __memalign_hook = save_memalign_hook;
 377       __free_hook = save_free_hook;
 378     }
 379 }
 380 # endif
 381 #endif
 382
 383 static void
 384 ptmalloc_init (void)
 385 {
 386 #if __STD_C
 387   const char* s;
 388 #else
 389   char* s;
 390 #endif
 391   int secure = 0;
 392
 393   if(__malloc_initialized >= 0) return;
 394   __malloc_initialized = 0;
 395
 396 #ifdef _LIBC
 397 # if defined SHARED && defined USE_TLS && !USE___THREAD
 398   /* ptmalloc_init_minimal may already have been called via
 399      __libc_malloc_pthread_startup, above.  */
 400   if (mp_.pagesize == 0)
 401 # endif
 402 #endif
 403     ptmalloc_init_minimal();
 404
 405 #ifndef NO_THREADS
 406 # if defined _LIBC && defined USE_TLS
 407   /* We know __pthread_initialize_minimal has already been called,
 408      and that is enough.  */
 409 #   define NO_STARTER
 410 # endif
 411 # ifndef NO_STARTER
 412   /* With some threads implementations, creating thread-specific data
 413      or initializing a mutex may call malloc() itself.  Provide a
 414      simple starter version (realloc() won't work). */
 415   save_malloc_hook = __malloc_hook;
 416   save_memalign_hook = __memalign_hook;
 417   save_free_hook = __free_hook;
 418   __malloc_hook = malloc_starter;
 419   __memalign_hook = memalign_starter;
 420   __free_hook = free_starter;
 421 #  ifdef _LIBC
 422   /* Initialize the pthreads interface. */
 423   if (__pthread_initialize != NULL)
 424     __pthread_initialize();
 425 #  endif /* !defined _LIBC */
 426 # endif /* !defined NO_STARTER */
 427 #endif /* !defined NO_THREADS */
 428   mutex_init(&main_arena.mutex);
 429   main_arena.next = &main_arena;
 430
 431 #if defined _LIBC && defined SHARED
 432   /* In case this libc copy is in a non-default namespace, never use brk.  */
 433   Dl_info di;
 434   struct link_map *l;
 435   if (_dl_addr (ptmalloc_init, &di, &l, NULL) != 0 && l->l_ns != LM_ID_BASE)
 436     __morecore = __failing_morecore;
 437 #endif
 438
 439   mutex_init(&list_lock);
 440   tsd_key_create(&arena_key, NULL);
 441   tsd_setspecific(arena_key, (Void_t *)&main_arena);
 442   thread_atfork(ptmalloc_lock_all, ptmalloc_unlock_all, ptmalloc_unlock_all2);
 443 #ifndef NO_THREADS
 444 # ifndef NO_STARTER
 445   __malloc_hook = save_malloc_hook;
 446   __memalign_hook = save_memalign_hook;
 447   __free_hook = save_free_hook;
 448 # else
 449 #  undef NO_STARTER
 450 # endif
 451 #endif
 452 #ifdef _LIBC
 453   secure = __libc_enable_secure;
 454   s = NULL;
 455   if (__builtin_expect (_environ != NULL, 1))
 456     {
 457       char **runp = _environ;
 458       char *envline;
 459
 460       while (__builtin_expect ((envline = next_env_entry (&runp)) != NULL,
 461                                0))
 462         {
 463           size_t len = strcspn (envline, "=");
 464
 465           if (envline[len] != '=')
 466             /* This is a "MALLOC_" variable at the end of the string
 467                without a '=' character.  Ignore it since otherwise we
 468                will access invalid memory below.  */
 469             continue;
 470
 471           switch (len)
 472             {
 473             case 6:
 474               if (memcmp (envline, "CHECK_", 6) == 0)
 475                 s = &envline[7];
 476               break;
 477             case 8:
 478               if (! secure && memcmp (envline, "TOP_PAD_", 8) == 0)
 479                 mALLOPt(M_TOP_PAD, atoi(&envline[9]));
 480               break;
 481             case 9:
 482               if (! secure && memcmp (envline, "MMAP_MAX_", 9) == 0)
 483                 mALLOPt(M_MMAP_MAX, atoi(&envline[10]));
 484               break;
 485             case 15:
 486               if (! secure)
 487                 {
 488                   if (memcmp (envline, "TRIM_THRESHOLD_", 15) == 0)
 489                     mALLOPt(M_TRIM_THRESHOLD, atoi(&envline[16]));
 490                   else if (memcmp (envline, "MMAP_THRESHOLD_", 15) == 0)
 491                     mALLOPt(M_MMAP_THRESHOLD, atoi(&envline[16]));
 492                 }
 493               break;
 494             default:
 495               break;
 496             }
 497         }
 498     }
 499 #else
 500   if (! secure)
 501     {
 502       if((s = getenv("MALLOC_TRIM_THRESHOLD_")))
 503         mALLOPt(M_TRIM_THRESHOLD, atoi(s));
 504       if((s = getenv("MALLOC_TOP_PAD_")))
 505         mALLOPt(M_TOP_PAD, atoi(s));
 506       if((s = getenv("MALLOC_MMAP_THRESHOLD_")))
 507         mALLOPt(M_MMAP_THRESHOLD, atoi(s));
 508       if((s = getenv("MALLOC_MMAP_MAX_")))
 509         mALLOPt(M_MMAP_MAX, atoi(s));
 510     }
 511   s = getenv("MALLOC_CHECK_");
 512 #endif
 513   if(s) {
 514     if(s[0]) mALLOPt(M_CHECK_ACTION, (int)(s[0] - '0'));
 515     if (check_action != 0)
 516       __malloc_check_init();
 517   }
 518   if(__malloc_initialize_hook != NULL)
 519     (*__malloc_initialize_hook)();
 520   __malloc_initialized = 1;
 521 }
 522
 523 /* There are platforms (e.g. Hurd) with a link-time hook mechanism. */
 524 #ifdef thread_atfork_static
 525 thread_atfork_static(ptmalloc_lock_all, ptmalloc_unlock_all, \
 526                      ptmalloc_unlock_all2)
 527 #endif
 528
 529 \f
 530
 531 /* Managing heaps and arenas (for concurrent threads) */
 532
 533 #if USE_ARENAS
 534
 535 #if MALLOC_DEBUG > 1
 536
 537 /* Print the complete contents of a single heap to stderr. */
 538
 539 static void
 540 #if __STD_C
 541 dump_heap(heap_info *heap)
 542 #else
 543 dump_heap(heap) heap_info *heap;
 544 #endif
 545 {
 546   char *ptr;
 547   mchunkptr p;
 548
 549   fprintf(stderr, "Heap %p, size %10lx:\n", heap, (long)heap->size);
 550   ptr = (heap->ar_ptr != (mstate)(heap+1)) ?
 551     (char*)(heap + 1) : (char*)(heap + 1) + sizeof(struct malloc_state);
 552   p = (mchunkptr)(((unsigned long)ptr + MALLOC_ALIGN_MASK) &
 553                   ~MALLOC_ALIGN_MASK);
 554   for(;;) {
 555     fprintf(stderr, "chunk %p size %10lx", p, (long)p->size);
 556     if(p == top(heap->ar_ptr)) {
 557       fprintf(stderr, " (top)\n");
 558       break;
 559     } else if(p->size == (0|PREV_INUSE)) {
 560       fprintf(stderr, " (fence)\n");
 561       break;
 562     }
 563     fprintf(stderr, "\n");
 564     p = next_chunk(p);
 565   }
 566 }
 567
 568 #endif /* MALLOC_DEBUG > 1 */
 569
 570 /* If consecutive mmap (0, HEAP_MAX_SIZE << 1, ...) calls return decreasing
 571    addresses as opposed to increasing, new_heap would badly fragment the
 572    address space.  In that case remember the second HEAP_MAX_SIZE part
 573    aligned to HEAP_MAX_SIZE from last mmap (0, HEAP_MAX_SIZE << 1, ...)
 574    call (if it is already aligned) and try to reuse it next time.  We need
 575    no locking for it, as kernel ensures the atomicity for us - worst case
 576    we'll call mmap (addr, HEAP_MAX_SIZE, ...) for some value of addr in
 577    multiple threads, but only one will succeed.  */
 578 static char *aligned_heap_area;
 579
 580 /* Create a new heap.  size is automatically rounded up to a multiple
 581    of the page size. */
 582
 583 static heap_info *
 584 internal_function
 585 #if __STD_C
 586 new_heap(size_t size, size_t top_pad)
 587 #else
 588 new_heap(size, top_pad) size_t size, top_pad;
 589 #endif
 590 {
 591   size_t page_mask = malloc_getpagesize - 1;
 592   char *p1, *p2;
 593   unsigned long ul;
 594   heap_info *h;
 595
 596   if(size+top_pad < HEAP_MIN_SIZE)
 597     size = HEAP_MIN_SIZE;
 598   else if(size+top_pad <= HEAP_MAX_SIZE)
 599     size += top_pad;
 600   else if(size > HEAP_MAX_SIZE)
 601     return 0;
 602   else
 603     size = HEAP_MAX_SIZE;
 604   size = (size + page_mask) & ~page_mask;
 605
 606   /* A memory region aligned to a multiple of HEAP_MAX_SIZE is needed.
 607      No swap space needs to be reserved for the following large
 608      mapping (on Linux, this is the case for all non-writable mappings
 609      anyway). */
 610   p2 = MAP_FAILED;
 611   if(aligned_heap_area) {
 612     p2 = (char *)MMAP(aligned_heap_area, HEAP_MAX_SIZE, PROT_NONE,
 613                       MAP_PRIVATE|MAP_NORESERVE);
 614     aligned_heap_area = NULL;
 615     if (p2 != MAP_FAILED && ((unsigned long)p2 & (HEAP_MAX_SIZE-1))) {
 616       munmap(p2, HEAP_MAX_SIZE);
 617       p2 = MAP_FAILED;
 618     }
 619   }
 620   if(p2 == MAP_FAILED) {
 621     p1 = (char *)MMAP(0, HEAP_MAX_SIZE<<1, PROT_NONE,
 622                       MAP_PRIVATE|MAP_NORESERVE);
 623     if(p1 != MAP_FAILED) {
 624       p2 = (char *)(((unsigned long)p1 + (HEAP_MAX_SIZE-1))
 625                     & ~(HEAP_MAX_SIZE-1));
 626       ul = p2 - p1;
 627       if (ul)
 628         munmap(p1, ul);
 629       else
 630         aligned_heap_area = p2 + HEAP_MAX_SIZE;
 631       munmap(p2 + HEAP_MAX_SIZE, HEAP_MAX_SIZE - ul);
 632     } else {
 633       /* Try to take the chance that an allocation of only HEAP_MAX_SIZE
 634          is already aligned. */
 635       p2 = (char *)MMAP(0, HEAP_MAX_SIZE, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE);
 636       if(p2 == MAP_FAILED)
 637         return 0;
 638       if((unsigned long)p2 & (HEAP_MAX_SIZE-1)) {
 639         munmap(p2, HEAP_MAX_SIZE);
 640         return 0;
 641       }
 642     }
 643   }
 644   if(mprotect(p2, size, PROT_READ|PROT_WRITE) != 0) {
 645     munmap(p2, HEAP_MAX_SIZE);
 646     return 0;
 647   }
 648   h = (heap_info *)p2;
 649   h->size = size;
 650   THREAD_STAT(stat_n_heaps++);
 651   return h;
 652 }
 653
 654 /* Grow or shrink a heap.  size is automatically rounded up to a
 655    multiple of the page size if it is positive. */
 656
 657 static int
 658 #if __STD_C
 659 grow_heap(heap_info *h, long diff)
 660 #else
 661 grow_heap(h, diff) heap_info *h; long diff;
 662 #endif
 663 {
 664   size_t page_mask = malloc_getpagesize - 1;
 665   long new_size;
 666
 667   if(diff >= 0) {
 668     diff = (diff + page_mask) & ~page_mask;
 669     new_size = (long)h->size + diff;
 670     if(new_size > HEAP_MAX_SIZE)
 671       return -1;
 672     if(mprotect((char *)h + h->size, diff, PROT_READ|PROT_WRITE) != 0)
 673       return -2;
 674   } else {
 675     new_size = (long)h->size + diff;
 676     if(new_size < (long)sizeof(*h))
 677       return -1;
 678     /* Try to re-map the extra heap space freshly to save memory, and
 679        make it inaccessible. */
 680     if((char *)MMAP((char *)h + new_size, -diff, PROT_NONE,
 681                     MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
 682       return -2;
 683     /*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
 684   }
 685   h->size = new_size;
 686   return 0;
 687 }
 688
 689 /* Delete a heap. */
 690
 691 #define delete_heap(heap) \
 692   do {                                                          \
 693     if ((char *)(heap) + HEAP_MAX_SIZE == aligned_heap_area)    \
 694       aligned_heap_area = NULL;                                 \
 695     munmap((char*)(heap), HEAP_MAX_SIZE);                       \
 696   } while (0)
 697
 698 static int
 699 internal_function
 700 #if __STD_C
 701 heap_trim(heap_info *heap, size_t pad)
 702 #else
 703 heap_trim(heap, pad) heap_info *heap; size_t pad;
 704 #endif
 705 {
 706   mstate ar_ptr = heap->ar_ptr;
 707   unsigned long pagesz = mp_.pagesize;
 708   mchunkptr top_chunk = top(ar_ptr), p, bck, fwd;
 709   heap_info *prev_heap;
 710   long new_size, top_size, extra;
 711
 712   /* Can this heap go away completely? */
 713   while(top_chunk == chunk_at_offset(heap, sizeof(*heap))) {
 714     prev_heap = heap->prev;
 715     p = chunk_at_offset(prev_heap, prev_heap->size - (MINSIZE-2*SIZE_SZ));
 716     assert(p->size == (0|PREV_INUSE)); /* must be fencepost */
 717     p = prev_chunk(p);
 718     new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ);
 719     assert(new_size>0 && new_size<(long)(2*MINSIZE));
 720     if(!prev_inuse(p))
 721       new_size += p->prev_size;
 722     assert(new_size>0 && new_size<HEAP_MAX_SIZE);
 723     if(new_size + (HEAP_MAX_SIZE - prev_heap->size) < pad + MINSIZE + pagesz)
 724       break;
 725     ar_ptr->system_mem -= heap->size;
 726     arena_mem -= heap->size;
 727     delete_heap(heap);
 728     heap = prev_heap;
 729     if(!prev_inuse(p)) { /* consolidate backward */
 730       p = prev_chunk(p);
 731       unlink(p, bck, fwd);
 732     }
 733     assert(((unsigned long)((char*)p + new_size) & (pagesz-1)) == 0);
 734     assert( ((char*)p + new_size) == ((char*)heap + heap->size) );
 735     top(ar_ptr) = top_chunk = p;
 736     set_head(top_chunk, new_size | PREV_INUSE);
 737     /*check_chunk(ar_ptr, top_chunk);*/
 738   }
 739   top_size = chunksize(top_chunk);
 740   extra = ((top_size - pad - MINSIZE + (pagesz-1))/pagesz - 1) * pagesz;
 741   if(extra < (long)pagesz)
 742     return 0;
 743   /* Try to shrink. */
 744   if(grow_heap(heap, -extra) != 0)
 745     return 0;
 746   ar_ptr->system_mem -= extra;
 747   arena_mem -= extra;
 748
 749   /* Success. Adjust top accordingly. */
 750   set_head(top_chunk, (top_size - extra) | PREV_INUSE);
 751   /*check_chunk(ar_ptr, top_chunk);*/
 752   return 1;
 753 }
 754
 755 static mstate
 756 internal_function
 757 #if __STD_C
 758 arena_get2(mstate a_tsd, size_t size)
 759 #else
 760 arena_get2(a_tsd, size) mstate a_tsd; size_t size;
 761 #endif
 762 {
 763   mstate a;
 764
 765   if(!a_tsd)
 766     a = a_tsd = &main_arena;
 767   else {
 768     a = a_tsd->next;
 769     if(!a) {
 770       /* This can only happen while initializing the new arena. */
 771       (void)mutex_lock(&main_arena.mutex);
 772       THREAD_STAT(++(main_arena.stat_lock_wait));
 773       return &main_arena;
 774     }
 775   }
 776
 777   /* Check the global, circularly linked list for available arenas. */
 778  repeat:
 779   do {
 780     if(!mutex_trylock(&a->mutex)) {
 781       THREAD_STAT(++(a->stat_lock_loop));
 782       tsd_setspecific(arena_key, (Void_t *)a);
 783       return a;
 784     }
 785     a = a->next;
 786   } while(a != a_tsd);
 787
 788   /* If not even the list_lock can be obtained, try again.  This can
 789      happen during `atfork', or for example on systems where thread
 790      creation makes it temporarily impossible to obtain _any_
 791      locks. */
 792   if(mutex_trylock(&list_lock)) {
 793     a = a_tsd;
 794     goto repeat;
 795   }
 796   (void)mutex_unlock(&list_lock);
 797
 798   /* Nothing immediately available, so generate a new arena.  */
 799   a = _int_new_arena(size);
 800   if(!a)
 801     return 0;
 802
 803   tsd_setspecific(arena_key, (Void_t *)a);
 804   mutex_init(&a->mutex);
 805   mutex_lock(&a->mutex); /* remember result */
 806
 807   /* Add the new arena to the global list.  */
 808   (void)mutex_lock(&list_lock);
 809   a->next = main_arena.next;
 810   atomic_write_barrier ();
 811   main_arena.next = a;
 812   (void)mutex_unlock(&list_lock);
 813
 814   THREAD_STAT(++(a->stat_lock_loop));
 815   return a;
 816 }
 817
 818 /* Create a new arena with initial size "size".  */
 819
 820 mstate
 821 _int_new_arena(size_t size)
 822 {
 823   mstate a;
 824   heap_info *h;
 825   char *ptr;
 826   unsigned long misalign;
 827
 828   h = new_heap(size + (sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT),
 829                mp_.top_pad);
 830   if(!h) {
 831     /* Maybe size is too large to fit in a single heap.  So, just try
 832        to create a minimally-sized arena and let _int_malloc() attempt
 833        to deal with the large request via mmap_chunk().  */
 834     h = new_heap(sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT, mp_.top_pad);
 835     if(!h)
 836       return 0;
 837   }
 838   a = h->ar_ptr = (mstate)(h+1);
 839   malloc_init_state(a);
 840   /*a->next = NULL;*/
 841   a->system_mem = a->max_system_mem = h->size;
 842   arena_mem += h->size;
 843 #ifdef NO_THREADS
 844   if((unsigned long)(mp_.mmapped_mem + arena_mem + main_arena.system_mem) >
 845      mp_.max_total_mem)
 846     mp_.max_total_mem = mp_.mmapped_mem + arena_mem + main_arena.system_mem;
 847 #endif
 848
 849   /* Set up the top chunk, with proper alignment. */
 850   ptr = (char *)(a + 1);
 851   misalign = (unsigned long)chunk2mem(ptr) & MALLOC_ALIGN_MASK;
 852   if (misalign > 0)
 853     ptr += MALLOC_ALIGNMENT - misalign;
 854   top(a) = (mchunkptr)ptr;
 855   set_head(top(a), (((char*)h + h->size) - ptr) | PREV_INUSE);
 856
 857   return a;
 858 }
 859
 860 #endif /* USE_ARENAS */
 861
 862 /*
 863  * Local variables:
 864  * c-basic-offset: 2
 865  * End:
 866  */