malloc/arena.c

   1 /* Malloc implementation for multiple threads without lock contention.
   2    Copyright (C) 2001-2012 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
  18    not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include <stdbool.h>
  21
  22 /* Get the implementation for check_may_shrink_heap.  */
  23 #include <malloc-sysdep.h>
  24
  25 /* Compile-time constants.  */
  26
  27 #define HEAP_MIN_SIZE (32*1024)
  28 #ifndef HEAP_MAX_SIZE
  29 # ifdef DEFAULT_MMAP_THRESHOLD_MAX
  30 #  define HEAP_MAX_SIZE (2 * DEFAULT_MMAP_THRESHOLD_MAX)
  31 # else
  32 #  define HEAP_MAX_SIZE (1024*1024) /* must be a power of two */
  33 # endif
  34 #endif
  35
  36 /* HEAP_MIN_SIZE and HEAP_MAX_SIZE limit the size of mmap()ed heaps
  37    that are dynamically created for multi-threaded programs.  The
  38    maximum size must be a power of two, for fast determination of
  39    which heap belongs to a chunk.  It should be much larger than the
  40    mmap threshold, so that requests with a size just below that
  41    threshold can be fulfilled without creating too many heaps.  */
  42
  43
  44 #ifndef THREAD_STATS
  45 #define THREAD_STATS 0
  46 #endif
  47
  48 /* If THREAD_STATS is non-zero, some statistics on mutex locking are
  49    computed.  */
  50
  51 /***************************************************************************/
  52
  53 #define top(ar_ptr) ((ar_ptr)->top)
  54
  55 /* A heap is a single contiguous memory region holding (coalesceable)
  56    malloc_chunks.  It is allocated with mmap() and always starts at an
  57    address aligned to HEAP_MAX_SIZE.  */
  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 = MUTEX_INITIALIZER;
  81 #ifdef PER_THREAD
  82 static size_t narenas = 1;
  83 static mstate free_list;
  84 #endif
  85
  86 #if THREAD_STATS
  87 static int stat_n_heaps;
  88 #define THREAD_STAT(x) x
  89 #else
  90 #define THREAD_STAT(x) do ; while(0)
  91 #endif
  92
  93 /* Mapped memory in non-main arenas (reliable only for NO_THREADS). */
  94 static unsigned long arena_mem;
  95
  96 /* Already initialized? */
  97 int __malloc_initialized = -1;
  98
  99 /**************************************************************************/
 100
 101
 102 /* arena_get() acquires an arena and locks the corresponding mutex.
 103    First, try the one last locked successfully by this thread.  (This
 104    is the common case and handled with a macro for speed.)  Then, loop
 105    once over the circularly linked list of arenas.  If no arena is
 106    readily available, create a new one.  In this latter case, `size'
 107    is just a hint as to how much memory will be required immediately
 108    in the new arena. */
 109
 110 #define arena_get(ptr, size) do { \
 111   arena_lookup(ptr); \
 112   arena_lock(ptr, size); \
 113 } while(0)
 114
 115 #define arena_lookup(ptr) do { \
 116   void *vptr = NULL; \
 117   ptr = (mstate)tsd_getspecific(arena_key, vptr); \
 118 } while(0)
 119
 120 #ifdef PER_THREAD
 121 # define arena_lock(ptr, size) do { \
 122   if(ptr) \
 123     (void)mutex_lock(&ptr->mutex); \
 124   else \
 125     ptr = arena_get2(ptr, (size), NULL); \
 126 } while(0)
 127 #else
 128 # define arena_lock(ptr, size) do { \
 129   if(ptr && !mutex_trylock(&ptr->mutex)) { \
 130     THREAD_STAT(++(ptr->stat_lock_direct)); \
 131   } else \
 132     ptr = arena_get2(ptr, (size), NULL); \
 133 } while(0)
 134 #endif
 135
 136 /* find the heap and corresponding arena for a given ptr */
 137
 138 #define heap_for_ptr(ptr) \
 139  ((heap_info *)((unsigned long)(ptr) & ~(HEAP_MAX_SIZE-1)))
 140 #define arena_for_chunk(ptr) \
 141  (chunk_non_main_arena(ptr) ? heap_for_ptr(ptr)->ar_ptr : &main_arena)
 142
 143
 144 /**************************************************************************/
 145
 146 #ifndef NO_THREADS
 147
 148 /* atfork support.  */
 149
 150 static __malloc_ptr_t (*save_malloc_hook) (size_t __size,
 151                                            const __malloc_ptr_t);
 152 static void           (*save_free_hook) (__malloc_ptr_t __ptr,
 153                                          const __malloc_ptr_t);
 154 static void*        save_arena;
 155
 156 #ifdef ATFORK_MEM
 157 ATFORK_MEM;
 158 #endif
 159
 160 /* Magic value for the thread-specific arena pointer when
 161    malloc_atfork() is in use.  */
 162
 163 #define ATFORK_ARENA_PTR ((void*)-1)
 164
 165 /* The following hooks are used while the `atfork' handling mechanism
 166    is active. */
 167
 168 static void*
 169 malloc_atfork(size_t sz, const void *caller)
 170 {
 171   void *vptr = NULL;
 172   void *victim;
 173
 174   tsd_getspecific(arena_key, vptr);
 175   if(vptr == ATFORK_ARENA_PTR) {
 176     /* We are the only thread that may allocate at all.  */
 177     if(save_malloc_hook != malloc_check) {
 178       return _int_malloc(&main_arena, sz);
 179     } else {
 180       if(top_check()<0)
 181         return 0;
 182       victim = _int_malloc(&main_arena, sz+1);
 183       return mem2mem_check(victim, sz);
 184     }
 185   } else {
 186     /* Suspend the thread until the `atfork' handlers have completed.
 187        By that time, the hooks will have been reset as well, so that
 188        mALLOc() can be used again. */
 189     (void)mutex_lock(&list_lock);
 190     (void)mutex_unlock(&list_lock);
 191     return __libc_malloc(sz);
 192   }
 193 }
 194
 195 static void
 196 free_atfork(void* mem, const void *caller)
 197 {
 198   void *vptr = NULL;
 199   mstate ar_ptr;
 200   mchunkptr p;                          /* chunk corresponding to mem */
 201
 202   if (mem == 0)                              /* free(0) has no effect */
 203     return;
 204
 205   p = mem2chunk(mem);         /* do not bother to replicate free_check here */
 206
 207   if (chunk_is_mmapped(p))                       /* release mmapped memory. */
 208   {
 209     munmap_chunk(p);
 210     return;
 211   }
 212
 213   ar_ptr = arena_for_chunk(p);
 214   tsd_getspecific(arena_key, vptr);
 215   _int_free(ar_ptr, p, vptr == ATFORK_ARENA_PTR);
 216 }
 217
 218
 219 /* Counter for number of times the list is locked by the same thread.  */
 220 static unsigned int atfork_recursive_cntr;
 221
 222 /* The following two functions are registered via thread_atfork() to
 223    make sure that the mutexes remain in a consistent state in the
 224    fork()ed version of a thread.  Also adapt the malloc and free hooks
 225    temporarily, because the `atfork' handler mechanism may use
 226    malloc/free internally (e.g. in LinuxThreads). */
 227
 228 static void
 229 ptmalloc_lock_all (void)
 230 {
 231   mstate ar_ptr;
 232
 233   if(__malloc_initialized < 1)
 234     return;
 235   if (mutex_trylock(&list_lock))
 236     {
 237       void *my_arena;
 238       tsd_getspecific(arena_key, my_arena);
 239       if (my_arena == ATFORK_ARENA_PTR)
 240         /* This is the same thread which already locks the global list.
 241            Just bump the counter.  */
 242         goto out;
 243
 244       /* This thread has to wait its turn.  */
 245       (void)mutex_lock(&list_lock);
 246     }
 247   for(ar_ptr = &main_arena;;) {
 248     (void)mutex_lock(&ar_ptr->mutex);
 249     ar_ptr = ar_ptr->next;
 250     if(ar_ptr == &main_arena) break;
 251   }
 252   save_malloc_hook = __malloc_hook;
 253   save_free_hook = __free_hook;
 254   __malloc_hook = malloc_atfork;
 255   __free_hook = free_atfork;
 256   /* Only the current thread may perform malloc/free calls now. */
 257   tsd_getspecific(arena_key, save_arena);
 258   tsd_setspecific(arena_key, ATFORK_ARENA_PTR);
 259  out:
 260   ++atfork_recursive_cntr;
 261 }
 262
 263 static void
 264 ptmalloc_unlock_all (void)
 265 {
 266   mstate ar_ptr;
 267
 268   if(__malloc_initialized < 1)
 269     return;
 270   if (--atfork_recursive_cntr != 0)
 271     return;
 272   tsd_setspecific(arena_key, save_arena);
 273   __malloc_hook = save_malloc_hook;
 274   __free_hook = save_free_hook;
 275   for(ar_ptr = &main_arena;;) {
 276     (void)mutex_unlock(&ar_ptr->mutex);
 277     ar_ptr = ar_ptr->next;
 278     if(ar_ptr == &main_arena) break;
 279   }
 280   (void)mutex_unlock(&list_lock);
 281 }
 282
 283 # ifdef __linux__
 284
 285 /* In NPTL, unlocking a mutex in the child process after a
 286    fork() is currently unsafe, whereas re-initializing it is safe and
 287    does not leak resources.  Therefore, a special atfork handler is
 288    installed for the child. */
 289
 290 static void
 291 ptmalloc_unlock_all2 (void)
 292 {
 293   mstate ar_ptr;
 294
 295   if(__malloc_initialized < 1)
 296     return;
 297   tsd_setspecific(arena_key, save_arena);
 298   __malloc_hook = save_malloc_hook;
 299   __free_hook = save_free_hook;
 300 #ifdef PER_THREAD
 301   free_list = NULL;
 302 #endif
 303   for(ar_ptr = &main_arena;;) {
 304     mutex_init(&ar_ptr->mutex);
 305 #ifdef PER_THREAD
 306     if (ar_ptr != save_arena) {
 307       ar_ptr->next_free = free_list;
 308       free_list = ar_ptr;
 309     }
 310 #endif
 311     ar_ptr = ar_ptr->next;
 312     if(ar_ptr == &main_arena) break;
 313   }
 314   mutex_init(&list_lock);
 315   atfork_recursive_cntr = 0;
 316 }
 317
 318 # else
 319
 320 #  define ptmalloc_unlock_all2 ptmalloc_unlock_all
 321
 322 # endif
 323
 324 #endif  /* !NO_THREADS */
 325
 326 /* Initialization routine. */
 327 #include <string.h>
 328 extern char **_environ;
 329
 330 static char *
 331 internal_function
 332 next_env_entry (char ***position)
 333 {
 334   char **current = *position;
 335   char *result = NULL;
 336
 337   while (*current != NULL)
 338     {
 339       if (__builtin_expect ((*current)[0] == 'M', 0)
 340           && (*current)[1] == 'A'
 341           && (*current)[2] == 'L'
 342           && (*current)[3] == 'L'
 343           && (*current)[4] == 'O'
 344           && (*current)[5] == 'C'
 345           && (*current)[6] == '_')
 346         {
 347           result = &(*current)[7];
 348
 349           /* Save current position for next visit.  */
 350           *position = ++current;
 351
 352           break;
 353         }
 354
 355       ++current;
 356     }
 357
 358   return result;
 359 }
 360
 361
 362 #ifdef SHARED
 363 static void *
 364 __failing_morecore (ptrdiff_t d)
 365 {
 366   return (void *) MORECORE_FAILURE;
 367 }
 368
 369 extern struct dl_open_hook *_dl_open_hook;
 370 libc_hidden_proto (_dl_open_hook);
 371 #endif
 372
 373 static void
 374 ptmalloc_init (void)
 375 {
 376   if(__malloc_initialized >= 0) return;
 377   __malloc_initialized = 0;
 378
 379 #ifdef SHARED
 380   /* In case this libc copy is in a non-default namespace, never use brk.
 381      Likewise if dlopened from statically linked program.  */
 382   Dl_info di;
 383   struct link_map *l;
 384
 385   if (_dl_open_hook != NULL
 386       || (_dl_addr (ptmalloc_init, &di, &l, NULL) != 0
 387           && l->l_ns != LM_ID_BASE))
 388     __morecore = __failing_morecore;
 389 #endif
 390
 391   tsd_key_create(&arena_key, NULL);
 392   tsd_setspecific(arena_key, (void *)&main_arena);
 393   thread_atfork(ptmalloc_lock_all, ptmalloc_unlock_all, ptmalloc_unlock_all2);
 394   const char *s = NULL;
 395   if (__builtin_expect (_environ != NULL, 1))
 396     {
 397       char **runp = _environ;
 398       char *envline;
 399
 400       while (__builtin_expect ((envline = next_env_entry (&runp)) != NULL,
 401                                0))
 402         {
 403           size_t len = strcspn (envline, "=");
 404
 405           if (envline[len] != '=')
 406             /* This is a "MALLOC_" variable at the end of the string
 407                without a '=' character.  Ignore it since otherwise we
 408                will access invalid memory below.  */
 409             continue;
 410
 411           switch (len)
 412             {
 413             case 6:
 414               if (memcmp (envline, "CHECK_", 6) == 0)
 415                 s = &envline[7];
 416               break;
 417             case 8:
 418               if (! __builtin_expect (__libc_enable_secure, 0))
 419                 {
 420                   if (memcmp (envline, "TOP_PAD_", 8) == 0)
 421                     __libc_mallopt(M_TOP_PAD, atoi(&envline[9]));
 422                   else if (memcmp (envline, "PERTURB_", 8) == 0)
 423                     __libc_mallopt(M_PERTURB, atoi(&envline[9]));
 424                 }
 425               break;
 426             case 9:
 427               if (! __builtin_expect (__libc_enable_secure, 0))
 428                 {
 429                   if (memcmp (envline, "MMAP_MAX_", 9) == 0)
 430                     __libc_mallopt(M_MMAP_MAX, atoi(&envline[10]));
 431 #ifdef PER_THREAD
 432                   else if (memcmp (envline, "ARENA_MAX", 9) == 0)
 433                     __libc_mallopt(M_ARENA_MAX, atoi(&envline[10]));
 434 #endif
 435                 }
 436               break;
 437 #ifdef PER_THREAD
 438             case 10:
 439               if (! __builtin_expect (__libc_enable_secure, 0))
 440                 {
 441                   if (memcmp (envline, "ARENA_TEST", 10) == 0)
 442                     __libc_mallopt(M_ARENA_TEST, atoi(&envline[11]));
 443                 }
 444               break;
 445 #endif
 446             case 15:
 447               if (! __builtin_expect (__libc_enable_secure, 0))
 448                 {
 449                   if (memcmp (envline, "TRIM_THRESHOLD_", 15) == 0)
 450                     __libc_mallopt(M_TRIM_THRESHOLD, atoi(&envline[16]));
 451                   else if (memcmp (envline, "MMAP_THRESHOLD_", 15) == 0)
 452                     __libc_mallopt(M_MMAP_THRESHOLD, atoi(&envline[16]));
 453                 }
 454               break;
 455             default:
 456               break;
 457             }
 458         }
 459     }
 460   if(s && s[0]) {
 461     __libc_mallopt(M_CHECK_ACTION, (int)(s[0] - '0'));
 462     if (check_action != 0)
 463       __malloc_check_init();
 464   }
 465   void (*hook) (void) = force_reg (__malloc_initialize_hook);
 466   if (hook != NULL)
 467     (*hook)();
 468   __malloc_initialized = 1;
 469 }
 470
 471 /* There are platforms (e.g. Hurd) with a link-time hook mechanism. */
 472 #ifdef thread_atfork_static
 473 thread_atfork_static(ptmalloc_lock_all, ptmalloc_unlock_all, \
 474                      ptmalloc_unlock_all2)
 475 #endif
 476
 477 \f
 478
 479 /* Managing heaps and arenas (for concurrent threads) */
 480
 481 #if MALLOC_DEBUG > 1
 482
 483 /* Print the complete contents of a single heap to stderr. */
 484
 485 static void
 486 dump_heap(heap_info *heap)
 487 {
 488   char *ptr;
 489   mchunkptr p;
 490
 491   fprintf(stderr, "Heap %p, size %10lx:\n", heap, (long)heap->size);
 492   ptr = (heap->ar_ptr != (mstate)(heap+1)) ?
 493     (char*)(heap + 1) : (char*)(heap + 1) + sizeof(struct malloc_state);
 494   p = (mchunkptr)(((unsigned long)ptr + MALLOC_ALIGN_MASK) &
 495                   ~MALLOC_ALIGN_MASK);
 496   for(;;) {
 497     fprintf(stderr, "chunk %p size %10lx", p, (long)p->size);
 498     if(p == top(heap->ar_ptr)) {
 499       fprintf(stderr, " (top)\n");
 500       break;
 501     } else if(p->size == (0|PREV_INUSE)) {
 502       fprintf(stderr, " (fence)\n");
 503       break;
 504     }
 505     fprintf(stderr, "\n");
 506     p = next_chunk(p);
 507   }
 508 }
 509
 510 #endif /* MALLOC_DEBUG > 1 */
 511
 512 /* If consecutive mmap (0, HEAP_MAX_SIZE << 1, ...) calls return decreasing
 513    addresses as opposed to increasing, new_heap would badly fragment the
 514    address space.  In that case remember the second HEAP_MAX_SIZE part
 515    aligned to HEAP_MAX_SIZE from last mmap (0, HEAP_MAX_SIZE << 1, ...)
 516    call (if it is already aligned) and try to reuse it next time.  We need
 517    no locking for it, as kernel ensures the atomicity for us - worst case
 518    we'll call mmap (addr, HEAP_MAX_SIZE, ...) for some value of addr in
 519    multiple threads, but only one will succeed.  */
 520 static char *aligned_heap_area;
 521
 522 /* Create a new heap.  size is automatically rounded up to a multiple
 523    of the page size. */
 524
 525 static heap_info *
 526 internal_function
 527 new_heap(size_t size, size_t top_pad)
 528 {
 529   size_t page_mask = GLRO(dl_pagesize) - 1;
 530   char *p1, *p2;
 531   unsigned long ul;
 532   heap_info *h;
 533
 534   if(size+top_pad < HEAP_MIN_SIZE)
 535     size = HEAP_MIN_SIZE;
 536   else if(size+top_pad <= HEAP_MAX_SIZE)
 537     size += top_pad;
 538   else if(size > HEAP_MAX_SIZE)
 539     return 0;
 540   else
 541     size = HEAP_MAX_SIZE;
 542   size = (size + page_mask) & ~page_mask;
 543
 544   /* A memory region aligned to a multiple of HEAP_MAX_SIZE is needed.
 545      No swap space needs to be reserved for the following large
 546      mapping (on Linux, this is the case for all non-writable mappings
 547      anyway). */
 548   p2 = MAP_FAILED;
 549   if(aligned_heap_area) {
 550     p2 = (char *)MMAP(aligned_heap_area, HEAP_MAX_SIZE, PROT_NONE,
 551                       MAP_NORESERVE);
 552     aligned_heap_area = NULL;
 553     if (p2 != MAP_FAILED && ((unsigned long)p2 & (HEAP_MAX_SIZE-1))) {
 554       __munmap(p2, HEAP_MAX_SIZE);
 555       p2 = MAP_FAILED;
 556     }
 557   }
 558   if(p2 == MAP_FAILED) {
 559     p1 = (char *)MMAP(0, HEAP_MAX_SIZE<<1, PROT_NONE, MAP_NORESERVE);
 560     if(p1 != MAP_FAILED) {
 561       p2 = (char *)(((unsigned long)p1 + (HEAP_MAX_SIZE-1))
 562                     & ~(HEAP_MAX_SIZE-1));
 563       ul = p2 - p1;
 564       if (ul)
 565         __munmap(p1, ul);
 566       else
 567         aligned_heap_area = p2 + HEAP_MAX_SIZE;
 568       __munmap(p2 + HEAP_MAX_SIZE, HEAP_MAX_SIZE - ul);
 569     } else {
 570       /* Try to take the chance that an allocation of only HEAP_MAX_SIZE
 571          is already aligned. */
 572       p2 = (char *)MMAP(0, HEAP_MAX_SIZE, PROT_NONE, MAP_NORESERVE);
 573       if(p2 == MAP_FAILED)
 574         return 0;
 575       if((unsigned long)p2 & (HEAP_MAX_SIZE-1)) {
 576         __munmap(p2, HEAP_MAX_SIZE);
 577         return 0;
 578       }
 579     }
 580   }
 581   if(__mprotect(p2, size, PROT_READ|PROT_WRITE) != 0) {
 582     __munmap(p2, HEAP_MAX_SIZE);
 583     return 0;
 584   }
 585   h = (heap_info *)p2;
 586   h->size = size;
 587   h->mprotect_size = size;
 588   THREAD_STAT(stat_n_heaps++);
 589   return h;
 590 }
 591
 592 /* Grow a heap.  size is automatically rounded up to a
 593    multiple of the page size. */
 594
 595 static int
 596 grow_heap(heap_info *h, long diff)
 597 {
 598   size_t page_mask = GLRO(dl_pagesize) - 1;
 599   long new_size;
 600
 601   diff = (diff + page_mask) & ~page_mask;
 602   new_size = (long)h->size + diff;
 603   if((unsigned long) new_size > (unsigned long) HEAP_MAX_SIZE)
 604     return -1;
 605   if((unsigned long) new_size > h->mprotect_size) {
 606     if (__mprotect((char *)h + h->mprotect_size,
 607                    (unsigned long) new_size - h->mprotect_size,
 608                    PROT_READ|PROT_WRITE) != 0)
 609       return -2;
 610     h->mprotect_size = new_size;
 611   }
 612
 613   h->size = new_size;
 614   return 0;
 615 }
 616
 617 /* Shrink a heap.  */
 618
 619 static int
 620 shrink_heap(heap_info *h, long diff)
 621 {
 622   long new_size;
 623
 624   new_size = (long)h->size - diff;
 625   if(new_size < (long)sizeof(*h))
 626     return -1;
 627   /* Try to re-map the extra heap space freshly to save memory, and make it
 628      inaccessible.  See malloc-sysdep.h to know when this is true.  */
 629   if (__builtin_expect (check_may_shrink_heap (), 0))
 630     {
 631       if((char *)MMAP((char *)h + new_size, diff, PROT_NONE,
 632                       MAP_FIXED) == (char *) MAP_FAILED)
 633         return -2;
 634       h->mprotect_size = new_size;
 635     }
 636   else
 637     __madvise ((char *)h + new_size, diff, MADV_DONTNEED);
 638   /*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
 639
 640   h->size = new_size;
 641   return 0;
 642 }
 643
 644 /* Delete a heap. */
 645
 646 #define delete_heap(heap) \
 647   do {                                                          \
 648     if ((char *)(heap) + HEAP_MAX_SIZE == aligned_heap_area)    \
 649       aligned_heap_area = NULL;                                 \
 650     __munmap((char*)(heap), HEAP_MAX_SIZE);                     \
 651   } while (0)
 652
 653 static int
 654 internal_function
 655 heap_trim(heap_info *heap, size_t pad)
 656 {
 657   mstate ar_ptr = heap->ar_ptr;
 658   unsigned long pagesz = GLRO(dl_pagesize);
 659   mchunkptr top_chunk = top(ar_ptr), p, bck, fwd;
 660   heap_info *prev_heap;
 661   long new_size, top_size, extra, prev_size, misalign;
 662
 663   /* Can this heap go away completely? */
 664   while(top_chunk == chunk_at_offset(heap, sizeof(*heap))) {
 665     prev_heap = heap->prev;
 666     prev_size = prev_heap->size - (MINSIZE-2*SIZE_SZ);
 667     p = chunk_at_offset(prev_heap, prev_size);
 668     /* fencepost must be properly aligned.  */
 669     misalign = ((long) p) & MALLOC_ALIGN_MASK;
 670     p = chunk_at_offset(prev_heap, prev_size - misalign);
 671     assert(p->size == (0|PREV_INUSE)); /* must be fencepost */
 672     p = prev_chunk(p);
 673     new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ) + misalign;
 674     assert(new_size>0 && new_size<(long)(2*MINSIZE));
 675     if(!prev_inuse(p))
 676       new_size += p->prev_size;
 677     assert(new_size>0 && new_size<HEAP_MAX_SIZE);
 678     if(new_size + (HEAP_MAX_SIZE - prev_heap->size) < pad + MINSIZE + pagesz)
 679       break;
 680     ar_ptr->system_mem -= heap->size;
 681     arena_mem -= heap->size;
 682     delete_heap(heap);
 683     heap = prev_heap;
 684     if(!prev_inuse(p)) { /* consolidate backward */
 685       p = prev_chunk(p);
 686       unlink(p, bck, fwd);
 687     }
 688     assert(((unsigned long)((char*)p + new_size) & (pagesz-1)) == 0);
 689     assert( ((char*)p + new_size) == ((char*)heap + heap->size) );
 690     top(ar_ptr) = top_chunk = p;
 691     set_head(top_chunk, new_size | PREV_INUSE);
 692     /*check_chunk(ar_ptr, top_chunk);*/
 693   }
 694   top_size = chunksize(top_chunk);
 695   extra = (top_size - pad - MINSIZE - 1) & ~(pagesz - 1);
 696   if(extra < (long)pagesz)
 697     return 0;
 698   /* Try to shrink. */
 699   if(shrink_heap(heap, extra) != 0)
 700     return 0;
 701   ar_ptr->system_mem -= extra;
 702   arena_mem -= extra;
 703
 704   /* Success. Adjust top accordingly. */
 705   set_head(top_chunk, (top_size - extra) | PREV_INUSE);
 706   /*check_chunk(ar_ptr, top_chunk);*/
 707   return 1;
 708 }
 709
 710 /* Create a new arena with initial size "size".  */
 711
 712 static mstate
 713 _int_new_arena(size_t size)
 714 {
 715   mstate a;
 716   heap_info *h;
 717   char *ptr;
 718   unsigned long misalign;
 719
 720   h = new_heap(size + (sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT),
 721                mp_.top_pad);
 722   if(!h) {
 723     /* Maybe size is too large to fit in a single heap.  So, just try
 724        to create a minimally-sized arena and let _int_malloc() attempt
 725        to deal with the large request via mmap_chunk().  */
 726     h = new_heap(sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT, mp_.top_pad);
 727     if(!h)
 728       return 0;
 729   }
 730   a = h->ar_ptr = (mstate)(h+1);
 731   malloc_init_state(a);
 732   /*a->next = NULL;*/
 733   a->system_mem = a->max_system_mem = h->size;
 734   arena_mem += h->size;
 735
 736   /* Set up the top chunk, with proper alignment. */
 737   ptr = (char *)(a + 1);
 738   misalign = (unsigned long)chunk2mem(ptr) & MALLOC_ALIGN_MASK;
 739   if (misalign > 0)
 740     ptr += MALLOC_ALIGNMENT - misalign;
 741   top(a) = (mchunkptr)ptr;
 742   set_head(top(a), (((char*)h + h->size) - ptr) | PREV_INUSE);
 743
 744   tsd_setspecific(arena_key, (void *)a);
 745   mutex_init(&a->mutex);
 746   (void)mutex_lock(&a->mutex);
 747
 748 #ifdef PER_THREAD
 749   (void)mutex_lock(&list_lock);
 750 #endif
 751
 752   /* Add the new arena to the global list.  */
 753   a->next = main_arena.next;
 754   atomic_write_barrier ();
 755   main_arena.next = a;
 756
 757 #ifdef PER_THREAD
 758   (void)mutex_unlock(&list_lock);
 759 #endif
 760
 761   THREAD_STAT(++(a->stat_lock_loop));
 762
 763   return a;
 764 }
 765
 766
 767 #ifdef PER_THREAD
 768 static mstate
 769 get_free_list (void)
 770 {
 771   mstate result = free_list;
 772   if (result != NULL)
 773     {
 774       (void)mutex_lock(&list_lock);
 775       result = free_list;
 776       if (result != NULL)
 777         free_list = result->next_free;
 778       (void)mutex_unlock(&list_lock);
 779
 780       if (result != NULL)
 781         {
 782           (void)mutex_lock(&result->mutex);
 783           tsd_setspecific(arena_key, (void *)result);
 784           THREAD_STAT(++(result->stat_lock_loop));
 785         }
 786     }
 787
 788   return result;
 789 }
 790
 791 /* Lock and return an arena that can be reused for memory allocation.
 792    Avoid AVOID_ARENA as we have already failed to allocate memory in
 793    it and it is currently locked.  */
 794 static mstate
 795 reused_arena (mstate avoid_arena)
 796 {
 797   mstate result;
 798   static mstate next_to_use;
 799   if (next_to_use == NULL)
 800     next_to_use = &main_arena;
 801
 802   result = next_to_use;
 803   do
 804     {
 805       if (!mutex_trylock(&result->mutex))
 806         goto out;
 807
 808       result = result->next;
 809     }
 810   while (result != next_to_use);
 811
 812   /* Avoid AVOID_ARENA as we have already failed to allocate memory
 813      in that arena and it is currently locked.   */
 814   if (result == avoid_arena)
 815     result = result->next;
 816
 817   /* No arena available.  Wait for the next in line.  */
 818   (void)mutex_lock(&result->mutex);
 819
 820  out:
 821   tsd_setspecific(arena_key, (void *)result);
 822   THREAD_STAT(++(result->stat_lock_loop));
 823   next_to_use = result->next;
 824
 825   return result;
 826 }
 827 #endif
 828
 829 static mstate
 830 internal_function
 831 arena_get2(mstate a_tsd, size_t size, mstate avoid_arena)
 832 {
 833   mstate a;
 834
 835 #ifdef PER_THREAD
 836   static size_t narenas_limit;
 837
 838   a = get_free_list ();
 839   if (a == NULL)
 840     {
 841       /* Nothing immediately available, so generate a new arena.  */
 842       if (narenas_limit == 0)
 843         {
 844           if (mp_.arena_max != 0)
 845             narenas_limit = mp_.arena_max;
 846           else if (narenas > mp_.arena_test)
 847             {
 848               int n  = __get_nprocs ();
 849
 850               if (n >= 1)
 851                 narenas_limit = NARENAS_FROM_NCORES (n);
 852               else
 853                 /* We have no information about the system.  Assume two
 854                    cores.  */
 855                 narenas_limit = NARENAS_FROM_NCORES (2);
 856             }
 857         }
 858     repeat:;
 859       size_t n = narenas;
 860       /* NB: the following depends on the fact that (size_t)0 - 1 is a
 861          very large number and that the underflow is OK.  If arena_max
 862          is set the value of arena_test is irrelevant.  If arena_test
 863          is set but narenas is not yet larger or equal to arena_test
 864          narenas_limit is 0.  There is no possibility for narenas to
 865          be too big for the test to always fail since there is not
 866          enough address space to create that many arenas.  */
 867       if (__builtin_expect (n <= narenas_limit - 1, 0))
 868         {
 869           if (catomic_compare_and_exchange_bool_acq (&narenas, n + 1, n))
 870             goto repeat;
 871           a = _int_new_arena (size);
 872           if (__builtin_expect (a == NULL, 0))
 873             catomic_decrement (&narenas);
 874         }
 875       else
 876         a = reused_arena (avoid_arena);
 877     }
 878 #else
 879   if(!a_tsd)
 880     a = a_tsd = &main_arena;
 881   else {
 882     a = a_tsd->next;
 883     if(!a) {
 884       /* This can only happen while initializing the new arena. */
 885       (void)mutex_lock(&main_arena.mutex);
 886       THREAD_STAT(++(main_arena.stat_lock_wait));
 887       return &main_arena;
 888     }
 889   }
 890
 891   /* Check the global, circularly linked list for available arenas. */
 892   bool retried = false;
 893  repeat:
 894   do {
 895     if(!mutex_trylock(&a->mutex)) {
 896       if (retried)
 897         (void)mutex_unlock(&list_lock);
 898       THREAD_STAT(++(a->stat_lock_loop));
 899       tsd_setspecific(arena_key, (void *)a);
 900       return a;
 901     }
 902     a = a->next;
 903   } while(a != a_tsd);
 904
 905   /* If not even the list_lock can be obtained, try again.  This can
 906      happen during `atfork', or for example on systems where thread
 907      creation makes it temporarily impossible to obtain _any_
 908      locks. */
 909   if(!retried && mutex_trylock(&list_lock)) {
 910     /* We will block to not run in a busy loop.  */
 911     (void)mutex_lock(&list_lock);
 912
 913     /* Since we blocked there might be an arena available now.  */
 914     retried = true;
 915     a = a_tsd;
 916     goto repeat;
 917   }
 918
 919   /* Nothing immediately available, so generate a new arena.  */
 920   a = _int_new_arena(size);
 921   (void)mutex_unlock(&list_lock);
 922 #endif
 923
 924   return a;
 925 }
 926
 927 /* If we don't have the main arena, then maybe the failure is due to running
 928    out of mmapped areas, so we can try allocating on the main arena.
 929    Otherwise, it is likely that sbrk() has failed and there is still a chance
 930    to mmap(), so try one of the other arenas.  */
 931 static mstate
 932 arena_get_retry (mstate ar_ptr, size_t bytes)
 933 {
 934   if(ar_ptr != &main_arena) {
 935     (void)mutex_unlock(&ar_ptr->mutex);
 936     ar_ptr = &main_arena;
 937     (void)mutex_lock(&ar_ptr->mutex);
 938   } else {
 939     /* Grab ar_ptr->next prior to releasing its lock.  */
 940     mstate prev = ar_ptr->next ? ar_ptr : 0;
 941     (void)mutex_unlock(&ar_ptr->mutex);
 942     ar_ptr = arena_get2(prev, bytes, ar_ptr);
 943   }
 944
 945   return ar_ptr;
 946 }
 947
 948 #ifdef PER_THREAD
 949 static void __attribute__ ((section ("__libc_thread_freeres_fn")))
 950 arena_thread_freeres (void)
 951 {
 952   void *vptr = NULL;
 953   mstate a = tsd_getspecific(arena_key, vptr);
 954   tsd_setspecific(arena_key, NULL);
 955
 956   if (a != NULL)
 957     {
 958       (void)mutex_lock(&list_lock);
 959       a->next_free = free_list;
 960       free_list = a;
 961       (void)mutex_unlock(&list_lock);
 962     }
 963 }
 964 text_set_element (__libc_thread_subfreeres, arena_thread_freeres);
 965 #endif
 966
 967 /*
 968  * Local variables:
 969  * c-basic-offset: 2
 970  * End:
 971  */