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 #ifdef _LIBC
 343 # if defined SHARED && defined USE_TLS && !USE___THREAD
 344 # include <stdbool.h>
 345
 346 /* This is called by __pthread_initialize_minimal when it needs to use
 347    malloc to set up the TLS state.  We cannot do the full work of
 348    ptmalloc_init (below) until __pthread_initialize_minimal has finished,
 349    so it has to switch to using the special startup-time hooks while doing
 350    those allocations.  */
 351 void
 352 __libc_malloc_pthread_startup (bool first_time)
 353 {
 354   if (first_time)
 355     {
 356       ptmalloc_init_minimal ();
 357       save_malloc_hook = __malloc_hook;
 358       save_memalign_hook = __memalign_hook;
 359       save_free_hook = __free_hook;
 360       __malloc_hook = malloc_starter;
 361       __memalign_hook = memalign_starter;
 362       __free_hook = free_starter;
 363     }
 364   else
 365     {
 366       __malloc_hook = save_malloc_hook;
 367       __memalign_hook = save_memalign_hook;
 368       __free_hook = save_free_hook;
 369     }
 370 }
 371 # endif
 372 #endif
 373
 374 static void
 375 ptmalloc_init (void)
 376 {
 377 #if __STD_C
 378   const char* s;
 379 #else
 380   char* s;
 381 #endif
 382   int secure = 0;
 383
 384   if(__malloc_initialized >= 0) return;
 385   __malloc_initialized = 0;
 386
 387 #ifdef _LIBC
 388 # if defined SHARED && defined USE_TLS && !USE___THREAD
 389   /* ptmalloc_init_minimal may already have been called via
 390      __libc_malloc_pthread_startup, above.  */
 391   if (mp_.pagesize == 0)
 392 # endif
 393 #endif
 394     ptmalloc_init_minimal();
 395
 396 #ifndef NO_THREADS
 397 # if defined _LIBC && defined USE_TLS
 398   /* We know __pthread_initialize_minimal has already been called,
 399      and that is enough.  */
 400 #   define NO_STARTER
 401 # endif
 402 # ifndef NO_STARTER
 403   /* With some threads implementations, creating thread-specific data
 404      or initializing a mutex may call malloc() itself.  Provide a
 405      simple starter version (realloc() won't work). */
 406   save_malloc_hook = __malloc_hook;
 407   save_memalign_hook = __memalign_hook;
 408   save_free_hook = __free_hook;
 409   __malloc_hook = malloc_starter;
 410   __memalign_hook = memalign_starter;
 411   __free_hook = free_starter;
 412 #  ifdef _LIBC
 413   /* Initialize the pthreads interface. */
 414   if (__pthread_initialize != NULL)
 415     __pthread_initialize();
 416 #  endif /* !defined _LIBC */
 417 # endif /* !defined NO_STARTER */
 418 #endif /* !defined NO_THREADS */
 419   mutex_init(&main_arena.mutex);
 420   main_arena.next = &main_arena;
 421
 422   mutex_init(&list_lock);
 423   tsd_key_create(&arena_key, NULL);
 424   tsd_setspecific(arena_key, (Void_t *)&main_arena);
 425   thread_atfork(ptmalloc_lock_all, ptmalloc_unlock_all, ptmalloc_unlock_all2);
 426 #ifndef NO_THREADS
 427 # ifndef NO_STARTER
 428   __malloc_hook = save_malloc_hook;
 429   __memalign_hook = save_memalign_hook;
 430   __free_hook = save_free_hook;
 431 # else
 432 #  undef NO_STARTER
 433 # endif
 434 #endif
 435 #ifdef _LIBC
 436   secure = __libc_enable_secure;
 437   s = NULL;
 438   if (__builtin_expect (_environ != NULL, 1))
 439     {
 440       char **runp = _environ;
 441       char *envline;
 442
 443       while (__builtin_expect ((envline = next_env_entry (&runp)) != NULL,
 444                                0))
 445         {
 446           size_t len = strcspn (envline, "=");
 447
 448           if (envline[len] != '=')
 449             /* This is a "MALLOC_" variable at the end of the string
 450                without a '=' character.  Ignore it since otherwise we
 451                will access invalid memory below.  */
 452             continue;
 453
 454           switch (len)
 455             {
 456             case 6:
 457               if (memcmp (envline, "CHECK_", 6) == 0)
 458                 s = &envline[7];
 459               break;
 460             case 8:
 461               if (! secure && memcmp (envline, "TOP_PAD_", 8) == 0)
 462                 mALLOPt(M_TOP_PAD, atoi(&envline[9]));
 463               break;
 464             case 9:
 465               if (! secure && memcmp (envline, "MMAP_MAX_", 9) == 0)
 466                 mALLOPt(M_MMAP_MAX, atoi(&envline[10]));
 467               break;
 468             case 15:
 469               if (! secure)
 470                 {
 471                   if (memcmp (envline, "TRIM_THRESHOLD_", 15) == 0)
 472                     mALLOPt(M_TRIM_THRESHOLD, atoi(&envline[16]));
 473                   else if (memcmp (envline, "MMAP_THRESHOLD_", 15) == 0)
 474                     mALLOPt(M_MMAP_THRESHOLD, atoi(&envline[16]));
 475                 }
 476               break;
 477             default:
 478               break;
 479             }
 480         }
 481     }
 482 #else
 483   if (! secure)
 484     {
 485       if((s = getenv("MALLOC_TRIM_THRESHOLD_")))
 486         mALLOPt(M_TRIM_THRESHOLD, atoi(s));
 487       if((s = getenv("MALLOC_TOP_PAD_")))
 488         mALLOPt(M_TOP_PAD, atoi(s));
 489       if((s = getenv("MALLOC_MMAP_THRESHOLD_")))
 490         mALLOPt(M_MMAP_THRESHOLD, atoi(s));
 491       if((s = getenv("MALLOC_MMAP_MAX_")))
 492         mALLOPt(M_MMAP_MAX, atoi(s));
 493     }
 494   s = getenv("MALLOC_CHECK_");
 495 #endif
 496   if(s) {
 497     if(s[0]) mALLOPt(M_CHECK_ACTION, (int)(s[0] - '0'));
 498     if (check_action != 0)
 499       __malloc_check_init();
 500   }
 501   if(__malloc_initialize_hook != NULL)
 502     (*__malloc_initialize_hook)();
 503   __malloc_initialized = 1;
 504 }
 505
 506 /* There are platforms (e.g. Hurd) with a link-time hook mechanism. */
 507 #ifdef thread_atfork_static
 508 thread_atfork_static(ptmalloc_lock_all, ptmalloc_unlock_all, \
 509                      ptmalloc_unlock_all2)
 510 #endif
 511
 512 \f
 513
 514 /* Managing heaps and arenas (for concurrent threads) */
 515
 516 #if USE_ARENAS
 517
 518 #if MALLOC_DEBUG > 1
 519
 520 /* Print the complete contents of a single heap to stderr. */
 521
 522 static void
 523 #if __STD_C
 524 dump_heap(heap_info *heap)
 525 #else
 526 dump_heap(heap) heap_info *heap;
 527 #endif
 528 {
 529   char *ptr;
 530   mchunkptr p;
 531
 532   fprintf(stderr, "Heap %p, size %10lx:\n", heap, (long)heap->size);
 533   ptr = (heap->ar_ptr != (mstate)(heap+1)) ?
 534     (char*)(heap + 1) : (char*)(heap + 1) + sizeof(struct malloc_state);
 535   p = (mchunkptr)(((unsigned long)ptr + MALLOC_ALIGN_MASK) &
 536                   ~MALLOC_ALIGN_MASK);
 537   for(;;) {
 538     fprintf(stderr, "chunk %p size %10lx", p, (long)p->size);
 539     if(p == top(heap->ar_ptr)) {
 540       fprintf(stderr, " (top)\n");
 541       break;
 542     } else if(p->size == (0|PREV_INUSE)) {
 543       fprintf(stderr, " (fence)\n");
 544       break;
 545     }
 546     fprintf(stderr, "\n");
 547     p = next_chunk(p);
 548   }
 549 }
 550
 551 #endif /* MALLOC_DEBUG > 1 */
 552
 553 /* Create a new heap.  size is automatically rounded up to a multiple
 554    of the page size. */
 555
 556 static heap_info *
 557 internal_function
 558 #if __STD_C
 559 new_heap(size_t size, size_t top_pad)
 560 #else
 561 new_heap(size, top_pad) size_t size, top_pad;
 562 #endif
 563 {
 564   size_t page_mask = malloc_getpagesize - 1;
 565   char *p1, *p2;
 566   unsigned long ul;
 567   heap_info *h;
 568
 569   if(size+top_pad < HEAP_MIN_SIZE)
 570     size = HEAP_MIN_SIZE;
 571   else if(size+top_pad <= HEAP_MAX_SIZE)
 572     size += top_pad;
 573   else if(size > HEAP_MAX_SIZE)
 574     return 0;
 575   else
 576     size = HEAP_MAX_SIZE;
 577   size = (size + page_mask) & ~page_mask;
 578
 579   /* A memory region aligned to a multiple of HEAP_MAX_SIZE is needed.
 580      No swap space needs to be reserved for the following large
 581      mapping (on Linux, this is the case for all non-writable mappings
 582      anyway). */
 583   p1 = (char *)MMAP(0, HEAP_MAX_SIZE<<1, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE);
 584   if(p1 != MAP_FAILED) {
 585     p2 = (char *)(((unsigned long)p1 + (HEAP_MAX_SIZE-1)) & ~(HEAP_MAX_SIZE-1));
 586     ul = p2 - p1;
 587     munmap(p1, ul);
 588     munmap(p2 + HEAP_MAX_SIZE, HEAP_MAX_SIZE - ul);
 589   } else {
 590     /* Try to take the chance that an allocation of only HEAP_MAX_SIZE
 591        is already aligned. */
 592     p2 = (char *)MMAP(0, HEAP_MAX_SIZE, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE);
 593     if(p2 == MAP_FAILED)
 594       return 0;
 595     if((unsigned long)p2 & (HEAP_MAX_SIZE-1)) {
 596       munmap(p2, HEAP_MAX_SIZE);
 597       return 0;
 598     }
 599   }
 600   if(mprotect(p2, size, PROT_READ|PROT_WRITE) != 0) {
 601     munmap(p2, HEAP_MAX_SIZE);
 602     return 0;
 603   }
 604   h = (heap_info *)p2;
 605   h->size = size;
 606   THREAD_STAT(stat_n_heaps++);
 607   return h;
 608 }
 609
 610 /* Grow or shrink a heap.  size is automatically rounded up to a
 611    multiple of the page size if it is positive. */
 612
 613 static int
 614 #if __STD_C
 615 grow_heap(heap_info *h, long diff)
 616 #else
 617 grow_heap(h, diff) heap_info *h; long diff;
 618 #endif
 619 {
 620   size_t page_mask = malloc_getpagesize - 1;
 621   long new_size;
 622
 623   if(diff >= 0) {
 624     diff = (diff + page_mask) & ~page_mask;
 625     new_size = (long)h->size + diff;
 626     if(new_size > HEAP_MAX_SIZE)
 627       return -1;
 628     if(mprotect((char *)h + h->size, diff, PROT_READ|PROT_WRITE) != 0)
 629       return -2;
 630   } else {
 631     new_size = (long)h->size + diff;
 632     if(new_size < (long)sizeof(*h))
 633       return -1;
 634     /* Try to re-map the extra heap space freshly to save memory, and
 635        make it inaccessible. */
 636     if((char *)MMAP((char *)h + new_size, -diff, PROT_NONE,
 637                     MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
 638       return -2;
 639     /*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
 640   }
 641   h->size = new_size;
 642   return 0;
 643 }
 644
 645 /* Delete a heap. */
 646
 647 #define delete_heap(heap) munmap((char*)(heap), HEAP_MAX_SIZE)
 648
 649 static int
 650 internal_function
 651 #if __STD_C
 652 heap_trim(heap_info *heap, size_t pad)
 653 #else
 654 heap_trim(heap, pad) heap_info *heap; size_t pad;
 655 #endif
 656 {
 657   mstate ar_ptr = heap->ar_ptr;
 658   unsigned long pagesz = mp_.pagesize;
 659   mchunkptr top_chunk = top(ar_ptr), p, bck, fwd;
 660   heap_info *prev_heap;
 661   long new_size, top_size, extra;
 662
 663   /* Can this heap go away completely? */
 664   while(top_chunk == chunk_at_offset(heap, sizeof(*heap))) {
 665     prev_heap = heap->prev;
 666     p = chunk_at_offset(prev_heap, prev_heap->size - (MINSIZE-2*SIZE_SZ));
 667     assert(p->size == (0|PREV_INUSE)); /* must be fencepost */
 668     p = prev_chunk(p);
 669     new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ);
 670     assert(new_size>0 && new_size<(long)(2*MINSIZE));
 671     if(!prev_inuse(p))
 672       new_size += p->prev_size;
 673     assert(new_size>0 && new_size<HEAP_MAX_SIZE);
 674     if(new_size + (HEAP_MAX_SIZE - prev_heap->size) < pad + MINSIZE + pagesz)
 675       break;
 676     ar_ptr->system_mem -= heap->size;
 677     arena_mem -= heap->size;
 678     delete_heap(heap);
 679     heap = prev_heap;
 680     if(!prev_inuse(p)) { /* consolidate backward */
 681       p = prev_chunk(p);
 682       unlink(p, bck, fwd);
 683     }
 684     assert(((unsigned long)((char*)p + new_size) & (pagesz-1)) == 0);
 685     assert( ((char*)p + new_size) == ((char*)heap + heap->size) );
 686     top(ar_ptr) = top_chunk = p;
 687     set_head(top_chunk, new_size | PREV_INUSE);
 688     /*check_chunk(ar_ptr, top_chunk);*/
 689   }
 690   top_size = chunksize(top_chunk);
 691   extra = ((top_size - pad - MINSIZE + (pagesz-1))/pagesz - 1) * pagesz;
 692   if(extra < (long)pagesz)
 693     return 0;
 694   /* Try to shrink. */
 695   if(grow_heap(heap, -extra) != 0)
 696     return 0;
 697   ar_ptr->system_mem -= extra;
 698   arena_mem -= extra;
 699
 700   /* Success. Adjust top accordingly. */
 701   set_head(top_chunk, (top_size - extra) | PREV_INUSE);
 702   /*check_chunk(ar_ptr, top_chunk);*/
 703   return 1;
 704 }
 705
 706 static mstate
 707 internal_function
 708 #if __STD_C
 709 arena_get2(mstate a_tsd, size_t size)
 710 #else
 711 arena_get2(a_tsd, size) mstate a_tsd; size_t size;
 712 #endif
 713 {
 714   mstate a;
 715
 716   if(!a_tsd)
 717     a = a_tsd = &main_arena;
 718   else {
 719     a = a_tsd->next;
 720     if(!a) {
 721       /* This can only happen while initializing the new arena. */
 722       (void)mutex_lock(&main_arena.mutex);
 723       THREAD_STAT(++(main_arena.stat_lock_wait));
 724       return &main_arena;
 725     }
 726   }
 727
 728   /* Check the global, circularly linked list for available arenas. */
 729  repeat:
 730   do {
 731     if(!mutex_trylock(&a->mutex)) {
 732       THREAD_STAT(++(a->stat_lock_loop));
 733       tsd_setspecific(arena_key, (Void_t *)a);
 734       return a;
 735     }
 736     a = a->next;
 737   } while(a != a_tsd);
 738
 739   /* If not even the list_lock can be obtained, try again.  This can
 740      happen during `atfork', or for example on systems where thread
 741      creation makes it temporarily impossible to obtain _any_
 742      locks. */
 743   if(mutex_trylock(&list_lock)) {
 744     a = a_tsd;
 745     goto repeat;
 746   }
 747   (void)mutex_unlock(&list_lock);
 748
 749   /* Nothing immediately available, so generate a new arena.  */
 750   a = _int_new_arena(size);
 751   if(!a)
 752     return 0;
 753
 754   tsd_setspecific(arena_key, (Void_t *)a);
 755   mutex_init(&a->mutex);
 756   mutex_lock(&a->mutex); /* remember result */
 757
 758   /* Add the new arena to the global list.  */
 759   (void)mutex_lock(&list_lock);
 760   a->next = main_arena.next;
 761   atomic_write_barrier ();
 762   main_arena.next = a;
 763   (void)mutex_unlock(&list_lock);
 764
 765   THREAD_STAT(++(a->stat_lock_loop));
 766   return a;
 767 }
 768
 769 /* Create a new arena with initial size "size".  */
 770
 771 mstate
 772 _int_new_arena(size_t size)
 773 {
 774   mstate a;
 775   heap_info *h;
 776   char *ptr;
 777   unsigned long misalign;
 778
 779   h = new_heap(size + (sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT),
 780                mp_.top_pad);
 781   if(!h) {
 782     /* Maybe size is too large to fit in a single heap.  So, just try
 783        to create a minimally-sized arena and let _int_malloc() attempt
 784        to deal with the large request via mmap_chunk().  */
 785     h = new_heap(sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT, mp_.top_pad);
 786     if(!h)
 787       return 0;
 788   }
 789   a = h->ar_ptr = (mstate)(h+1);
 790   malloc_init_state(a);
 791   /*a->next = NULL;*/
 792   a->system_mem = a->max_system_mem = h->size;
 793   arena_mem += h->size;
 794 #ifdef NO_THREADS
 795   if((unsigned long)(mp_.mmapped_mem + arena_mem + main_arena.system_mem) >
 796      mp_.max_total_mem)
 797     mp_.max_total_mem = mp_.mmapped_mem + arena_mem + main_arena.system_mem;
 798 #endif
 799
 800   /* Set up the top chunk, with proper alignment. */
 801   ptr = (char *)(a + 1);
 802   misalign = (unsigned long)chunk2mem(ptr) & MALLOC_ALIGN_MASK;
 803   if (misalign > 0)
 804     ptr += MALLOC_ALIGNMENT - misalign;
 805   top(a) = (mchunkptr)ptr;
 806   set_head(top(a), (((char*)h + h->size) - ptr) | PREV_INUSE);
 807
 808   return a;
 809 }
 810
 811 #endif /* USE_ARENAS */
 812
 813 /*
 814  * Local variables:
 815  * c-basic-offset: 2
 816  * End:
 817  */