| /* Malloc implementation for multiple threads without lock contention. |
| Copyright (C) 2001-2016 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| Contributed by Wolfram Gloger <wg@malloc.de>, 2001. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public License as |
| published by the Free Software Foundation; either version 2.1 of the |
| License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library; see the file COPYING.LIB. If |
| not, see <http://www.gnu.org/licenses/>. */ |
| |
| #include <stdbool.h> |
| |
| /* Compile-time constants. */ |
| |
| #define HEAP_MIN_SIZE (32 * 1024) |
| #ifndef HEAP_MAX_SIZE |
| # ifdef DEFAULT_MMAP_THRESHOLD_MAX |
| # define HEAP_MAX_SIZE (2 * DEFAULT_MMAP_THRESHOLD_MAX) |
| # else |
| # define HEAP_MAX_SIZE (1024 * 1024) /* must be a power of two */ |
| # endif |
| #endif |
| |
| /* HEAP_MIN_SIZE and HEAP_MAX_SIZE limit the size of mmap()ed heaps |
| that are dynamically created for multi-threaded programs. The |
| maximum size must be a power of two, for fast determination of |
| which heap belongs to a chunk. It should be much larger than the |
| mmap threshold, so that requests with a size just below that |
| threshold can be fulfilled without creating too many heaps. */ |
| |
| /***************************************************************************/ |
| |
| #define top(ar_ptr) ((ar_ptr)->top) |
| |
| /* A heap is a single contiguous memory region holding (coalesceable) |
| malloc_chunks. It is allocated with mmap() and always starts at an |
| address aligned to HEAP_MAX_SIZE. */ |
| |
| typedef struct _heap_info |
| { |
| mstate ar_ptr; /* Arena for this heap. */ |
| struct _heap_info *prev; /* Previous heap. */ |
| size_t size; /* Current size in bytes. */ |
| size_t mprotect_size; /* Size in bytes that has been mprotected |
| PROT_READ|PROT_WRITE. */ |
| /* Make sure the following data is properly aligned, particularly |
| that sizeof (heap_info) + 2 * SIZE_SZ is a multiple of |
| MALLOC_ALIGNMENT. */ |
| char pad[-6 * SIZE_SZ & MALLOC_ALIGN_MASK]; |
| } heap_info; |
| |
| /* Get a compile-time error if the heap_info padding is not correct |
| to make alignment work as expected in sYSMALLOc. */ |
| extern int sanity_check_heap_info_alignment[(sizeof (heap_info) |
| + 2 * SIZE_SZ) % MALLOC_ALIGNMENT |
| ? -1 : 1]; |
| |
| /* Thread specific data. */ |
| |
| static __thread mstate thread_arena attribute_tls_model_ie; |
| |
| /* Arena free list. free_list_lock synchronizes access to the |
| free_list variable below, and the next_free and attached_threads |
| members of struct malloc_state objects. No other locks must be |
| acquired after free_list_lock has been acquired. */ |
| |
| static mutex_t free_list_lock = _LIBC_LOCK_INITIALIZER; |
| static size_t narenas = 1; |
| static mstate free_list; |
| |
| /* list_lock prevents concurrent writes to the next member of struct |
| malloc_state objects. |
| |
| Read access to the next member is supposed to synchronize with the |
| atomic_write_barrier and the write to the next member in |
| _int_new_arena. This suffers from data races; see the FIXME |
| comments in _int_new_arena and reused_arena. |
| |
| list_lock also prevents concurrent forks. At the time list_lock is |
| acquired, no arena lock must have been acquired, but it is |
| permitted to acquire arena locks subsequently, while list_lock is |
| acquired. */ |
| static mutex_t list_lock = _LIBC_LOCK_INITIALIZER; |
| |
| /* Mapped memory in non-main arenas (reliable only for NO_THREADS). */ |
| static unsigned long arena_mem; |
| |
| /* Already initialized? */ |
| int __malloc_initialized = -1; |
| |
| /**************************************************************************/ |
| |
| |
| /* arena_get() acquires an arena and locks the corresponding mutex. |
| First, try the one last locked successfully by this thread. (This |
| is the common case and handled with a macro for speed.) Then, loop |
| once over the circularly linked list of arenas. If no arena is |
| readily available, create a new one. In this latter case, `size' |
| is just a hint as to how much memory will be required immediately |
| in the new arena. */ |
| |
| #define arena_get(ptr, size) do { \ |
| ptr = thread_arena; \ |
| arena_lock (ptr, size); \ |
| } while (0) |
| |
| #define arena_lock(ptr, size) do { \ |
| if (ptr && !arena_is_corrupt (ptr)) \ |
| (void) mutex_lock (&ptr->mutex); \ |
| else \ |
| ptr = arena_get2 ((size), NULL); \ |
| } while (0) |
| |
| /* find the heap and corresponding arena for a given ptr */ |
| |
| #define heap_for_ptr(ptr) \ |
| ((heap_info *) ((unsigned long) (ptr) & ~(HEAP_MAX_SIZE - 1))) |
| #define arena_for_chunk(ptr) \ |
| (chunk_non_main_arena (ptr) ? heap_for_ptr (ptr)->ar_ptr : &main_arena) |
| |
| |
| /**************************************************************************/ |
| |
| #ifndef NO_THREADS |
| |
| /* atfork support. */ |
| |
| static void *(*save_malloc_hook)(size_t __size, const void *); |
| static void (*save_free_hook) (void *__ptr, const void *); |
| static void *save_arena; |
| |
| # ifdef ATFORK_MEM |
| ATFORK_MEM; |
| # endif |
| |
| /* Magic value for the thread-specific arena pointer when |
| malloc_atfork() is in use. */ |
| |
| # define ATFORK_ARENA_PTR ((void *) -1) |
| |
| /* The following hooks are used while the `atfork' handling mechanism |
| is active. */ |
| |
| static void * |
| malloc_atfork (size_t sz, const void *caller) |
| { |
| void *victim; |
| |
| if (thread_arena == ATFORK_ARENA_PTR) |
| { |
| /* We are the only thread that may allocate at all. */ |
| if (save_malloc_hook != malloc_check) |
| { |
| return _int_malloc (&main_arena, sz); |
| } |
| else |
| { |
| if (top_check () < 0) |
| return 0; |
| |
| victim = _int_malloc (&main_arena, sz + 1); |
| return mem2mem_check (victim, sz); |
| } |
| } |
| else |
| { |
| /* Suspend the thread until the `atfork' handlers have completed. |
| By that time, the hooks will have been reset as well, so that |
| mALLOc() can be used again. */ |
| (void) mutex_lock (&list_lock); |
| (void) mutex_unlock (&list_lock); |
| return __libc_malloc (sz); |
| } |
| } |
| |
| static void |
| free_atfork (void *mem, const void *caller) |
| { |
| mstate ar_ptr; |
| mchunkptr p; /* chunk corresponding to mem */ |
| |
| if (mem == 0) /* free(0) has no effect */ |
| return; |
| |
| p = mem2chunk (mem); /* do not bother to replicate free_check here */ |
| |
| if (chunk_is_mmapped (p)) /* release mmapped memory. */ |
| { |
| munmap_chunk (p); |
| return; |
| } |
| |
| ar_ptr = arena_for_chunk (p); |
| _int_free (ar_ptr, p, thread_arena == ATFORK_ARENA_PTR); |
| } |
| |
| |
| /* Counter for number of times the list is locked by the same thread. */ |
| static unsigned int atfork_recursive_cntr; |
| |
| /* The following two functions are registered via thread_atfork() to |
| make sure that the mutexes remain in a consistent state in the |
| fork()ed version of a thread. Also adapt the malloc and free hooks |
| temporarily, because the `atfork' handler mechanism may use |
| malloc/free internally (e.g. in LinuxThreads). */ |
| |
| static void |
| ptmalloc_lock_all (void) |
| { |
| mstate ar_ptr; |
| |
| if (__malloc_initialized < 1) |
| return; |
| |
| /* We do not acquire free_list_lock here because we completely |
| reconstruct free_list in ptmalloc_unlock_all2. */ |
| |
| if (mutex_trylock (&list_lock)) |
| { |
| if (thread_arena == ATFORK_ARENA_PTR) |
| /* This is the same thread which already locks the global list. |
| Just bump the counter. */ |
| goto out; |
| |
| /* This thread has to wait its turn. */ |
| (void) mutex_lock (&list_lock); |
| } |
| for (ar_ptr = &main_arena;; ) |
| { |
| (void) mutex_lock (&ar_ptr->mutex); |
| ar_ptr = ar_ptr->next; |
| if (ar_ptr == &main_arena) |
| break; |
| } |
| save_malloc_hook = __malloc_hook; |
| save_free_hook = __free_hook; |
| __malloc_hook = malloc_atfork; |
| __free_hook = free_atfork; |
| /* Only the current thread may perform malloc/free calls now. |
| save_arena will be reattached to the current thread, in |
| ptmalloc_lock_all, so save_arena->attached_threads is not |
| updated. */ |
| save_arena = thread_arena; |
| thread_arena = ATFORK_ARENA_PTR; |
| out: |
| ++atfork_recursive_cntr; |
| } |
| |
| static void |
| ptmalloc_unlock_all (void) |
| { |
| mstate ar_ptr; |
| |
| if (__malloc_initialized < 1) |
| return; |
| |
| if (--atfork_recursive_cntr != 0) |
| return; |
| |
| /* Replace ATFORK_ARENA_PTR with save_arena. |
| save_arena->attached_threads was not changed in ptmalloc_lock_all |
| and is still correct. */ |
| thread_arena = save_arena; |
| __malloc_hook = save_malloc_hook; |
| __free_hook = save_free_hook; |
| for (ar_ptr = &main_arena;; ) |
| { |
| (void) mutex_unlock (&ar_ptr->mutex); |
| ar_ptr = ar_ptr->next; |
| if (ar_ptr == &main_arena) |
| break; |
| } |
| (void) mutex_unlock (&list_lock); |
| } |
| |
| # ifdef __linux__ |
| |
| /* In NPTL, unlocking a mutex in the child process after a |
| fork() is currently unsafe, whereas re-initializing it is safe and |
| does not leak resources. Therefore, a special atfork handler is |
| installed for the child. */ |
| |
| static void |
| ptmalloc_unlock_all2 (void) |
| { |
| mstate ar_ptr; |
| |
| if (__malloc_initialized < 1) |
| return; |
| |
| thread_arena = save_arena; |
| __malloc_hook = save_malloc_hook; |
| __free_hook = save_free_hook; |
| |
| /* Push all arenas to the free list, except save_arena, which is |
| attached to the current thread. */ |
| mutex_init (&free_list_lock); |
| if (save_arena != NULL) |
| ((mstate) save_arena)->attached_threads = 1; |
| free_list = NULL; |
| for (ar_ptr = &main_arena;; ) |
| { |
| mutex_init (&ar_ptr->mutex); |
| if (ar_ptr != save_arena) |
| { |
| /* This arena is no longer attached to any thread. */ |
| ar_ptr->attached_threads = 0; |
| ar_ptr->next_free = free_list; |
| free_list = ar_ptr; |
| } |
| ar_ptr = ar_ptr->next; |
| if (ar_ptr == &main_arena) |
| break; |
| } |
| |
| mutex_init (&list_lock); |
| atfork_recursive_cntr = 0; |
| } |
| |
| # else |
| |
| # define ptmalloc_unlock_all2 ptmalloc_unlock_all |
| # endif |
| #endif /* !NO_THREADS */ |
| |
| /* Initialization routine. */ |
| #include <string.h> |
| extern char **_environ; |
| |
| static char * |
| internal_function |
| next_env_entry (char ***position) |
| { |
| char **current = *position; |
| char *result = NULL; |
| |
| while (*current != NULL) |
| { |
| if (__builtin_expect ((*current)[0] == 'M', 0) |
| && (*current)[1] == 'A' |
| && (*current)[2] == 'L' |
| && (*current)[3] == 'L' |
| && (*current)[4] == 'O' |
| && (*current)[5] == 'C' |
| && (*current)[6] == '_') |
| { |
| result = &(*current)[7]; |
| |
| /* Save current position for next visit. */ |
| *position = ++current; |
| |
| break; |
| } |
| |
| ++current; |
| } |
| |
| return result; |
| } |
| |
| |
| #ifdef SHARED |
| static void * |
| __failing_morecore (ptrdiff_t d) |
| { |
| return (void *) MORECORE_FAILURE; |
| } |
| |
| extern struct dl_open_hook *_dl_open_hook; |
| libc_hidden_proto (_dl_open_hook); |
| #endif |
| |
| static void |
| ptmalloc_init (void) |
| { |
| if (__malloc_initialized >= 0) |
| return; |
| |
| __malloc_initialized = 0; |
| |
| #ifdef SHARED |
| /* In case this libc copy is in a non-default namespace, never use brk. |
| Likewise if dlopened from statically linked program. */ |
| Dl_info di; |
| struct link_map *l; |
| |
| if (_dl_open_hook != NULL |
| || (_dl_addr (ptmalloc_init, &di, &l, NULL) != 0 |
| && l->l_ns != LM_ID_BASE)) |
| __morecore = __failing_morecore; |
| #endif |
| |
| thread_arena = &main_arena; |
| thread_atfork (ptmalloc_lock_all, ptmalloc_unlock_all, ptmalloc_unlock_all2); |
| const char *s = NULL; |
| if (__glibc_likely (_environ != NULL)) |
| { |
| char **runp = _environ; |
| char *envline; |
| |
| while (__builtin_expect ((envline = next_env_entry (&runp)) != NULL, |
| 0)) |
| { |
| size_t len = strcspn (envline, "="); |
| |
| if (envline[len] != '=') |
| /* This is a "MALLOC_" variable at the end of the string |
| without a '=' character. Ignore it since otherwise we |
| will access invalid memory below. */ |
| continue; |
| |
| switch (len) |
| { |
| case 6: |
| if (memcmp (envline, "CHECK_", 6) == 0) |
| s = &envline[7]; |
| break; |
| case 8: |
| if (!__builtin_expect (__libc_enable_secure, 0)) |
| { |
| if (memcmp (envline, "TOP_PAD_", 8) == 0) |
| __libc_mallopt (M_TOP_PAD, atoi (&envline[9])); |
| else if (memcmp (envline, "PERTURB_", 8) == 0) |
| __libc_mallopt (M_PERTURB, atoi (&envline[9])); |
| } |
| break; |
| case 9: |
| if (!__builtin_expect (__libc_enable_secure, 0)) |
| { |
| if (memcmp (envline, "MMAP_MAX_", 9) == 0) |
| __libc_mallopt (M_MMAP_MAX, atoi (&envline[10])); |
| else if (memcmp (envline, "ARENA_MAX", 9) == 0) |
| __libc_mallopt (M_ARENA_MAX, atoi (&envline[10])); |
| } |
| break; |
| case 10: |
| if (!__builtin_expect (__libc_enable_secure, 0)) |
| { |
| if (memcmp (envline, "ARENA_TEST", 10) == 0) |
| __libc_mallopt (M_ARENA_TEST, atoi (&envline[11])); |
| } |
| break; |
| case 15: |
| if (!__builtin_expect (__libc_enable_secure, 0)) |
| { |
| if (memcmp (envline, "TRIM_THRESHOLD_", 15) == 0) |
| __libc_mallopt (M_TRIM_THRESHOLD, atoi (&envline[16])); |
| else if (memcmp (envline, "MMAP_THRESHOLD_", 15) == 0) |
| __libc_mallopt (M_MMAP_THRESHOLD, atoi (&envline[16])); |
| } |
| break; |
| default: |
| break; |
| } |
| } |
| } |
| if (s && s[0]) |
| { |
| __libc_mallopt (M_CHECK_ACTION, (int) (s[0] - '0')); |
| if (check_action != 0) |
| __malloc_check_init (); |
| } |
| void (*hook) (void) = atomic_forced_read (__malloc_initialize_hook); |
| if (hook != NULL) |
| (*hook)(); |
| __malloc_initialized = 1; |
| } |
| |
| /* There are platforms (e.g. Hurd) with a link-time hook mechanism. */ |
| #ifdef thread_atfork_static |
| thread_atfork_static (ptmalloc_lock_all, ptmalloc_unlock_all, \ |
| ptmalloc_unlock_all2) |
| #endif |
| |
| |
| |
| /* Managing heaps and arenas (for concurrent threads) */ |
| |
| #if MALLOC_DEBUG > 1 |
| |
| /* Print the complete contents of a single heap to stderr. */ |
| |
| static void |
| dump_heap (heap_info *heap) |
| { |
| char *ptr; |
| mchunkptr p; |
| |
| fprintf (stderr, "Heap %p, size %10lx:\n", heap, (long) heap->size); |
| ptr = (heap->ar_ptr != (mstate) (heap + 1)) ? |
| (char *) (heap + 1) : (char *) (heap + 1) + sizeof (struct malloc_state); |
| p = (mchunkptr) (((unsigned long) ptr + MALLOC_ALIGN_MASK) & |
| ~MALLOC_ALIGN_MASK); |
| for (;; ) |
| { |
| fprintf (stderr, "chunk %p size %10lx", p, (long) p->size); |
| if (p == top (heap->ar_ptr)) |
| { |
| fprintf (stderr, " (top)\n"); |
| break; |
| } |
| else if (p->size == (0 | PREV_INUSE)) |
| { |
| fprintf (stderr, " (fence)\n"); |
| break; |
| } |
| fprintf (stderr, "\n"); |
| p = next_chunk (p); |
| } |
| } |
| #endif /* MALLOC_DEBUG > 1 */ |
| |
| /* If consecutive mmap (0, HEAP_MAX_SIZE << 1, ...) calls return decreasing |
| addresses as opposed to increasing, new_heap would badly fragment the |
| address space. In that case remember the second HEAP_MAX_SIZE part |
| aligned to HEAP_MAX_SIZE from last mmap (0, HEAP_MAX_SIZE << 1, ...) |
| call (if it is already aligned) and try to reuse it next time. We need |
| no locking for it, as kernel ensures the atomicity for us - worst case |
| we'll call mmap (addr, HEAP_MAX_SIZE, ...) for some value of addr in |
| multiple threads, but only one will succeed. */ |
| static char *aligned_heap_area; |
| |
| /* Create a new heap. size is automatically rounded up to a multiple |
| of the page size. */ |
| |
| static heap_info * |
| internal_function |
| new_heap (size_t size, size_t top_pad) |
| { |
| size_t pagesize = GLRO (dl_pagesize); |
| char *p1, *p2; |
| unsigned long ul; |
| heap_info *h; |
| |
| if (size + top_pad < HEAP_MIN_SIZE) |
| size = HEAP_MIN_SIZE; |
| else if (size + top_pad <= HEAP_MAX_SIZE) |
| size += top_pad; |
| else if (size > HEAP_MAX_SIZE) |
| return 0; |
| else |
| size = HEAP_MAX_SIZE; |
| size = ALIGN_UP (size, pagesize); |
| |
| /* A memory region aligned to a multiple of HEAP_MAX_SIZE is needed. |
| No swap space needs to be reserved for the following large |
| mapping (on Linux, this is the case for all non-writable mappings |
| anyway). */ |
| p2 = MAP_FAILED; |
| if (aligned_heap_area) |
| { |
| p2 = (char *) MMAP (aligned_heap_area, HEAP_MAX_SIZE, PROT_NONE, |
| MAP_NORESERVE); |
| aligned_heap_area = NULL; |
| if (p2 != MAP_FAILED && ((unsigned long) p2 & (HEAP_MAX_SIZE - 1))) |
| { |
| __munmap (p2, HEAP_MAX_SIZE); |
| p2 = MAP_FAILED; |
| } |
| } |
| if (p2 == MAP_FAILED) |
| { |
| p1 = (char *) MMAP (0, HEAP_MAX_SIZE << 1, PROT_NONE, MAP_NORESERVE); |
| if (p1 != MAP_FAILED) |
| { |
| p2 = (char *) (((unsigned long) p1 + (HEAP_MAX_SIZE - 1)) |
| & ~(HEAP_MAX_SIZE - 1)); |
| ul = p2 - p1; |
| if (ul) |
| __munmap (p1, ul); |
| else |
| aligned_heap_area = p2 + HEAP_MAX_SIZE; |
| __munmap (p2 + HEAP_MAX_SIZE, HEAP_MAX_SIZE - ul); |
| } |
| else |
| { |
| /* Try to take the chance that an allocation of only HEAP_MAX_SIZE |
| is already aligned. */ |
| p2 = (char *) MMAP (0, HEAP_MAX_SIZE, PROT_NONE, MAP_NORESERVE); |
| if (p2 == MAP_FAILED) |
| return 0; |
| |
| if ((unsigned long) p2 & (HEAP_MAX_SIZE - 1)) |
| { |
| __munmap (p2, HEAP_MAX_SIZE); |
| return 0; |
| } |
| } |
| } |
| if (__mprotect (p2, size, PROT_READ | PROT_WRITE) != 0) |
| { |
| __munmap (p2, HEAP_MAX_SIZE); |
| return 0; |
| } |
| h = (heap_info *) p2; |
| h->size = size; |
| h->mprotect_size = size; |
| LIBC_PROBE (memory_heap_new, 2, h, h->size); |
| return h; |
| } |
| |
| /* Grow a heap. size is automatically rounded up to a |
| multiple of the page size. */ |
| |
| static int |
| grow_heap (heap_info *h, long diff) |
| { |
| size_t pagesize = GLRO (dl_pagesize); |
| long new_size; |
| |
| diff = ALIGN_UP (diff, pagesize); |
| new_size = (long) h->size + diff; |
| if ((unsigned long) new_size > (unsigned long) HEAP_MAX_SIZE) |
| return -1; |
| |
| if ((unsigned long) new_size > h->mprotect_size) |
| { |
| if (__mprotect ((char *) h + h->mprotect_size, |
| (unsigned long) new_size - h->mprotect_size, |
| PROT_READ | PROT_WRITE) != 0) |
| return -2; |
| |
| h->mprotect_size = new_size; |
| } |
| |
| h->size = new_size; |
| LIBC_PROBE (memory_heap_more, 2, h, h->size); |
| return 0; |
| } |
| |
| /* Shrink a heap. */ |
| |
| static int |
| shrink_heap (heap_info *h, long diff) |
| { |
| long new_size; |
| |
| new_size = (long) h->size - diff; |
| if (new_size < (long) sizeof (*h)) |
| return -1; |
| |
| /* Try to re-map the extra heap space freshly to save memory, and make it |
| inaccessible. See malloc-sysdep.h to know when this is true. */ |
| if (__glibc_unlikely (check_may_shrink_heap ())) |
| { |
| if ((char *) MMAP ((char *) h + new_size, diff, PROT_NONE, |
| MAP_FIXED) == (char *) MAP_FAILED) |
| return -2; |
| |
| h->mprotect_size = new_size; |
| } |
| else |
| __madvise ((char *) h + new_size, diff, MADV_DONTNEED); |
| /*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/ |
| |
| h->size = new_size; |
| LIBC_PROBE (memory_heap_less, 2, h, h->size); |
| return 0; |
| } |
| |
| /* Delete a heap. */ |
| |
| #define delete_heap(heap) \ |
| do { \ |
| if ((char *) (heap) + HEAP_MAX_SIZE == aligned_heap_area) \ |
| aligned_heap_area = NULL; \ |
| __munmap ((char *) (heap), HEAP_MAX_SIZE); \ |
| } while (0) |
| |
| static int |
| internal_function |
| heap_trim (heap_info *heap, size_t pad) |
| { |
| mstate ar_ptr = heap->ar_ptr; |
| unsigned long pagesz = GLRO (dl_pagesize); |
| mchunkptr top_chunk = top (ar_ptr), p, bck, fwd; |
| heap_info *prev_heap; |
| long new_size, top_size, top_area, extra, prev_size, misalign; |
| |
| /* Can this heap go away completely? */ |
| while (top_chunk == chunk_at_offset (heap, sizeof (*heap))) |
| { |
| prev_heap = heap->prev; |
| prev_size = prev_heap->size - (MINSIZE - 2 * SIZE_SZ); |
| p = chunk_at_offset (prev_heap, prev_size); |
| /* fencepost must be properly aligned. */ |
| misalign = ((long) p) & MALLOC_ALIGN_MASK; |
| p = chunk_at_offset (prev_heap, prev_size - misalign); |
| assert (p->size == (0 | PREV_INUSE)); /* must be fencepost */ |
| p = prev_chunk (p); |
| new_size = chunksize (p) + (MINSIZE - 2 * SIZE_SZ) + misalign; |
| assert (new_size > 0 && new_size < (long) (2 * MINSIZE)); |
| if (!prev_inuse (p)) |
| new_size += p->prev_size; |
| assert (new_size > 0 && new_size < HEAP_MAX_SIZE); |
| if (new_size + (HEAP_MAX_SIZE - prev_heap->size) < pad + MINSIZE + pagesz) |
| break; |
| ar_ptr->system_mem -= heap->size; |
| arena_mem -= heap->size; |
| LIBC_PROBE (memory_heap_free, 2, heap, heap->size); |
| delete_heap (heap); |
| heap = prev_heap; |
| if (!prev_inuse (p)) /* consolidate backward */ |
| { |
| p = prev_chunk (p); |
| unlink (ar_ptr, p, bck, fwd); |
| } |
| assert (((unsigned long) ((char *) p + new_size) & (pagesz - 1)) == 0); |
| assert (((char *) p + new_size) == ((char *) heap + heap->size)); |
| top (ar_ptr) = top_chunk = p; |
| set_head (top_chunk, new_size | PREV_INUSE); |
| /*check_chunk(ar_ptr, top_chunk);*/ |
| } |
| |
| /* Uses similar logic for per-thread arenas as the main arena with systrim |
| and _int_free by preserving the top pad and rounding down to the nearest |
| page. */ |
| top_size = chunksize (top_chunk); |
| if ((unsigned long)(top_size) < |
| (unsigned long)(mp_.trim_threshold)) |
| return 0; |
| |
| top_area = top_size - MINSIZE - 1; |
| if (top_area < 0 || (size_t) top_area <= pad) |
| return 0; |
| |
| /* Release in pagesize units and round down to the nearest page. */ |
| extra = ALIGN_DOWN(top_area - pad, pagesz); |
| if (extra == 0) |
| return 0; |
| |
| /* Try to shrink. */ |
| if (shrink_heap (heap, extra) != 0) |
| return 0; |
| |
| ar_ptr->system_mem -= extra; |
| arena_mem -= extra; |
| |
| /* Success. Adjust top accordingly. */ |
| set_head (top_chunk, (top_size - extra) | PREV_INUSE); |
| /*check_chunk(ar_ptr, top_chunk);*/ |
| return 1; |
| } |
| |
| /* Create a new arena with initial size "size". */ |
| |
| /* If REPLACED_ARENA is not NULL, detach it from this thread. Must be |
| called while free_list_lock is held. */ |
| static void |
| detach_arena (mstate replaced_arena) |
| { |
| if (replaced_arena != NULL) |
| { |
| assert (replaced_arena->attached_threads > 0); |
| /* The current implementation only detaches from main_arena in |
| case of allocation failure. This means that it is likely not |
| beneficial to put the arena on free_list even if the |
| reference count reaches zero. */ |
| --replaced_arena->attached_threads; |
| } |
| } |
| |
| static mstate |
| _int_new_arena (size_t size) |
| { |
| mstate a; |
| heap_info *h; |
| char *ptr; |
| unsigned long misalign; |
| |
| h = new_heap (size + (sizeof (*h) + sizeof (*a) + MALLOC_ALIGNMENT), |
| mp_.top_pad); |
| if (!h) |
| { |
| /* Maybe size is too large to fit in a single heap. So, just try |
| to create a minimally-sized arena and let _int_malloc() attempt |
| to deal with the large request via mmap_chunk(). */ |
| h = new_heap (sizeof (*h) + sizeof (*a) + MALLOC_ALIGNMENT, mp_.top_pad); |
| if (!h) |
| return 0; |
| } |
| a = h->ar_ptr = (mstate) (h + 1); |
| malloc_init_state (a); |
| a->attached_threads = 1; |
| /*a->next = NULL;*/ |
| a->system_mem = a->max_system_mem = h->size; |
| arena_mem += h->size; |
| |
| /* Set up the top chunk, with proper alignment. */ |
| ptr = (char *) (a + 1); |
| misalign = (unsigned long) chunk2mem (ptr) & MALLOC_ALIGN_MASK; |
| if (misalign > 0) |
| ptr += MALLOC_ALIGNMENT - misalign; |
| top (a) = (mchunkptr) ptr; |
| set_head (top (a), (((char *) h + h->size) - ptr) | PREV_INUSE); |
| |
| LIBC_PROBE (memory_arena_new, 2, a, size); |
| mstate replaced_arena = thread_arena; |
| thread_arena = a; |
| mutex_init (&a->mutex); |
| |
| (void) mutex_lock (&list_lock); |
| |
| /* Add the new arena to the global list. */ |
| a->next = main_arena.next; |
| /* FIXME: The barrier is an attempt to synchronize with read access |
| in reused_arena, which does not acquire list_lock while |
| traversing the list. */ |
| atomic_write_barrier (); |
| main_arena.next = a; |
| |
| (void) mutex_unlock (&list_lock); |
| |
| (void) mutex_lock (&free_list_lock); |
| detach_arena (replaced_arena); |
| (void) mutex_unlock (&free_list_lock); |
| |
| /* Lock this arena. NB: Another thread may have been attached to |
| this arena because the arena is now accessible from the |
| main_arena.next list and could have been picked by reused_arena. |
| This can only happen for the last arena created (before the arena |
| limit is reached). At this point, some arena has to be attached |
| to two threads. We could acquire the arena lock before list_lock |
| to make it less likely that reused_arena picks this new arena, |
| but this could result in a deadlock with ptmalloc_lock_all. */ |
| |
| (void) mutex_lock (&a->mutex); |
| |
| return a; |
| } |
| |
| |
| /* Remove an arena from free_list. The arena may be in use because it |
| was attached concurrently to a thread by reused_arena below. */ |
| static mstate |
| get_free_list (void) |
| { |
| mstate replaced_arena = thread_arena; |
| mstate result = free_list; |
| if (result != NULL) |
| { |
| (void) mutex_lock (&free_list_lock); |
| result = free_list; |
| if (result != NULL) |
| { |
| free_list = result->next_free; |
| |
| /* The arena will be attached to this thread. */ |
| ++result->attached_threads; |
| |
| detach_arena (replaced_arena); |
| } |
| (void) mutex_unlock (&free_list_lock); |
| |
| if (result != NULL) |
| { |
| LIBC_PROBE (memory_arena_reuse_free_list, 1, result); |
| (void) mutex_lock (&result->mutex); |
| thread_arena = result; |
| } |
| } |
| |
| return result; |
| } |
| |
| /* Lock and return an arena that can be reused for memory allocation. |
| Avoid AVOID_ARENA as we have already failed to allocate memory in |
| it and it is currently locked. */ |
| static mstate |
| reused_arena (mstate avoid_arena) |
| { |
| mstate result; |
| /* FIXME: Access to next_to_use suffers from data races. */ |
| static mstate next_to_use; |
| if (next_to_use == NULL) |
| next_to_use = &main_arena; |
| |
| /* Iterate over all arenas (including those linked from |
| free_list). */ |
| result = next_to_use; |
| do |
| { |
| if (!arena_is_corrupt (result) && !mutex_trylock (&result->mutex)) |
| goto out; |
| |
| /* FIXME: This is a data race, see _int_new_arena. */ |
| result = result->next; |
| } |
| while (result != next_to_use); |
| |
| /* Avoid AVOID_ARENA as we have already failed to allocate memory |
| in that arena and it is currently locked. */ |
| if (result == avoid_arena) |
| result = result->next; |
| |
| /* Make sure that the arena we get is not corrupted. */ |
| mstate begin = result; |
| while (arena_is_corrupt (result) || result == avoid_arena) |
| { |
| result = result->next; |
| if (result == begin) |
| break; |
| } |
| |
| /* We could not find any arena that was either not corrupted or not the one |
| we wanted to avoid. */ |
| if (result == begin || result == avoid_arena) |
| return NULL; |
| |
| /* No arena available without contention. Wait for the next in line. */ |
| LIBC_PROBE (memory_arena_reuse_wait, 3, &result->mutex, result, avoid_arena); |
| (void) mutex_lock (&result->mutex); |
| |
| out: |
| /* Attach the arena to the current thread. Note that we may have |
| selected an arena which was on free_list. */ |
| { |
| /* Update the arena thread attachment counters. */ |
| mstate replaced_arena = thread_arena; |
| (void) mutex_lock (&free_list_lock); |
| detach_arena (replaced_arena); |
| ++result->attached_threads; |
| (void) mutex_unlock (&free_list_lock); |
| } |
| |
| LIBC_PROBE (memory_arena_reuse, 2, result, avoid_arena); |
| thread_arena = result; |
| next_to_use = result->next; |
| |
| return result; |
| } |
| |
| static mstate |
| internal_function |
| arena_get2 (size_t size, mstate avoid_arena) |
| { |
| mstate a; |
| |
| static size_t narenas_limit; |
| |
| a = get_free_list (); |
| if (a == NULL) |
| { |
| /* Nothing immediately available, so generate a new arena. */ |
| if (narenas_limit == 0) |
| { |
| if (mp_.arena_max != 0) |
| narenas_limit = mp_.arena_max; |
| else if (narenas > mp_.arena_test) |
| { |
| int n = __get_nprocs (); |
| |
| if (n >= 1) |
| narenas_limit = NARENAS_FROM_NCORES (n); |
| else |
| /* We have no information about the system. Assume two |
| cores. */ |
| narenas_limit = NARENAS_FROM_NCORES (2); |
| } |
| } |
| repeat:; |
| size_t n = narenas; |
| /* NB: the following depends on the fact that (size_t)0 - 1 is a |
| very large number and that the underflow is OK. If arena_max |
| is set the value of arena_test is irrelevant. If arena_test |
| is set but narenas is not yet larger or equal to arena_test |
| narenas_limit is 0. There is no possibility for narenas to |
| be too big for the test to always fail since there is not |
| enough address space to create that many arenas. */ |
| if (__glibc_unlikely (n <= narenas_limit - 1)) |
| { |
| if (catomic_compare_and_exchange_bool_acq (&narenas, n + 1, n)) |
| goto repeat; |
| a = _int_new_arena (size); |
| if (__glibc_unlikely (a == NULL)) |
| catomic_decrement (&narenas); |
| } |
| else |
| a = reused_arena (avoid_arena); |
| } |
| return a; |
| } |
| |
| /* If we don't have the main arena, then maybe the failure is due to running |
| out of mmapped areas, so we can try allocating on the main arena. |
| Otherwise, it is likely that sbrk() has failed and there is still a chance |
| to mmap(), so try one of the other arenas. */ |
| static mstate |
| arena_get_retry (mstate ar_ptr, size_t bytes) |
| { |
| LIBC_PROBE (memory_arena_retry, 2, bytes, ar_ptr); |
| if (ar_ptr != &main_arena) |
| { |
| (void) mutex_unlock (&ar_ptr->mutex); |
| /* Don't touch the main arena if it is corrupt. */ |
| if (arena_is_corrupt (&main_arena)) |
| return NULL; |
| |
| ar_ptr = &main_arena; |
| (void) mutex_lock (&ar_ptr->mutex); |
| } |
| else |
| { |
| (void) mutex_unlock (&ar_ptr->mutex); |
| ar_ptr = arena_get2 (bytes, ar_ptr); |
| } |
| |
| return ar_ptr; |
| } |
| |
| static void __attribute__ ((section ("__libc_thread_freeres_fn"))) |
| arena_thread_freeres (void) |
| { |
| mstate a = thread_arena; |
| thread_arena = NULL; |
| |
| if (a != NULL) |
| { |
| (void) mutex_lock (&free_list_lock); |
| /* If this was the last attached thread for this arena, put the |
| arena on the free list. */ |
| assert (a->attached_threads > 0); |
| if (--a->attached_threads == 0) |
| { |
| a->next_free = free_list; |
| free_list = a; |
| } |
| (void) mutex_unlock (&free_list_lock); |
| } |
| } |
| text_set_element (__libc_thread_subfreeres, arena_thread_freeres); |
| |
| /* |
| * Local variables: |
| * c-basic-offset: 2 |
| * End: |
| */ |