arean.c
glibc-2.14中的arean.c源代码，供研究malloc和free实现使用：
/* Malloc implementation for multiple threads without lock contention.
Copyright (C) 2001,2002,2003,2004,2005,2006,2007,2009,2010
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,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#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. */
#ifndef THREAD_STATS
#define THREAD_STATS 0
#endif
/* If THREAD_STATS is non-zero, some statistics on mutex locking are
computed. */
/***************************************************************************/
#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. Not used unless compiling with
USE_ARENAS. */
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 tsd_key_t arena_key;
static mutex_t list_lock;
#ifdef PER_THREAD
static size_t narenas;
static mstate free_list;
#endif
#if THREAD_STATS
static int stat_n_heaps;
#define THREAD_STAT(x) x
#else
#define THREAD_STAT(x) do ; while(0)
#endif
/* Mapped memory in non-main arenas (reliable only for NO_THREADS). */
static unsigned long arena_mem;
/* Already initialized? */
int __malloc_initialized = -1;
/**************************************************************************/
#if USE_ARENAS
/* 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 { \
arena_lookup(ptr); \
arena_lock(ptr, size); \
} while(0)
#define arena_lookup(ptr) do { \
Void_t *vptr = NULL; \
ptr = (mstate)tsd_getspecific(arena_key, vptr); \
} while(0)
#ifdef PER_THREAD
#define arena_lock(ptr, size) do { \
if(ptr) \
(void)mutex_lock(&ptr->mutex); \
else \
ptr = arena_get2(ptr, (size)); \
} while(0)
#else
#define arena_lock(ptr, size) do { \
if(ptr && !mutex_trylock(&ptr->mutex)) { \
THREAD_STAT(++(ptr->stat_lock_direct)); \
} else \
ptr = arena_get2(ptr, (size)); \
} while(0)
#endif
/* 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)
#else /* !USE_ARENAS */
/* There is only one arena, main_arena. */
#if THREAD_STATS
#define arena_get(ar_ptr, sz) do { \
ar_ptr = &main_arena; \
if(!mutex_trylock(&ar_ptr->mutex)) \
++(ar_ptr->stat_lock_direct); \
else { \
(void)mutex_lock(&ar_ptr->mutex); \
++(ar_ptr->stat_lock_wait); \
} \
} while(0)
#else
#define arena_get(ar_ptr, sz) do { \
ar_ptr = &main_arena; \
(void)mutex_lock(&ar_ptr->mutex); \
} while(0)
#endif
#define arena_for_chunk(ptr) (&main_arena)
#endif /* USE_ARENAS */
/**************************************************************************/
#ifndef NO_THREADS
/* atfork support. */
static __malloc_ptr_t (*save_malloc_hook) (size_t __size,
__const __malloc_ptr_t);
# if !defined _LIBC || (defined SHARED && !USE___THREAD)
static __malloc_ptr_t (*save_memalign_hook) (size_t __align, size_t __size,
__const __malloc_ptr_t);
# endif
static void (*save_free_hook) (__malloc_ptr_t __ptr,
__const __malloc_ptr_t);
static Void_t* 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_t*)-1)
/* The following hooks are used while the `atfork' handling mechanism
is active. */
static Void_t*
malloc_atfork(size_t sz, const Void_t *caller)
{
Void_t *vptr = NULL;
Void_t *victim;
tsd_getspecific(arena_key, vptr);
if(vptr == 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 public_mALLOc(sz);
}
}
static void
free_atfork(Void_t* mem, const Void_t *caller)
{
Void_t *vptr = NULL;
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 HAVE_MMAP
if (chunk_is_mmapped(p)) /* release mmapped memory. */
{
munmap_chunk(p);
return;
}
#endif
#ifdef ATOMIC_FASTBINS
ar_ptr = arena_for_chunk(p);
tsd_getspecific(arena_key, vptr);
_int_free(ar_ptr, p, vptr == ATFORK_ARENA_PTR);
#else
ar_ptr = arena_for_chunk(p);
tsd_getspecific(arena_key, vptr);
if(vptr != ATFORK_ARENA_PTR)
(void)mutex_lock(&ar_ptr->mutex);
_int_free(ar_ptr, p);
if(vptr != ATFORK_ARENA_PTR)
(void)mutex_unlock(&ar_ptr->mutex);
#endif
}
/* 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;
if (mutex_trylock(&list_lock))
{
Void_t *my_arena;
tsd_getspecific(arena_key, my_arena);
if (my_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. */
tsd_getspecific(arena_key, save_arena);
tsd_setspecific(arena_key, 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;
tsd_setspecific(arena_key, 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;
#if defined _LIBC || defined MALLOC_HOOKS
tsd_setspecific(arena_key, save_arena);
__malloc_hook = save_malloc_hook;
__free_hook = save_free_hook;
#endif
#ifdef PER_THREAD
free_list = NULL;
#endif
for(ar_ptr = &main_arena;;) {
mutex_init(&ar_ptr->mutex);
#ifdef PER_THREAD
if (ar_ptr != save_arena) {
ar_ptr->next_free = free_list;
free_list = ar_ptr;
}
#endif
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 /* !defined NO_THREADS */
/* Initialization routine. */
#ifdef _LIBC
#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;
}
#endif /* _LIBC */
/* Set up basic state so that _int_malloc et al can work. */
static void
ptmalloc_init_minimal (void)
{
#if DEFAULT_TOP_PAD != 0
mp_.top_pad = DEFAULT_TOP_PAD;
#endif
mp_.n_mmaps_max = DEFAULT_MMAP_MAX;
mp_.mmap_threshold = DEFAULT_MMAP_THRESHOLD;
mp_.trim_threshold = DEFAULT_TRIM_THRESHOLD;
mp_.pagesize = malloc_getpagesize;
#ifdef PER_THREAD
# define NARENAS_FROM_NCORES(n) ((n) * (sizeof(long) == 4 ? 2 : 8))
mp_.arena_test = NARENAS_FROM_NCORES (1);
narenas = 1;
#endif
}
#ifdef _LIBC
# 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
# if defined SHARED && !USE___THREAD
/* This is called by __pthread_initialize_minimal when it needs to use
malloc to set up the TLS state. We cannot do the full work of
ptmalloc_init (below) until __pthread_initialize_minimal has finished,
so it has to switch to using the special startup-time hooks while doing
those allocations. */
void
__libc_malloc_pthread_startup (bool first_time)
{
if (first_time)
{
ptmalloc_init_minimal ();
save_malloc_hook = __malloc_hook;
save_memalign_hook = __memalign_hook;
save_free_hook = __free_hook;
__malloc_hook = malloc_starter;
__memalign_hook = memalign_starter;
__free_hook = free_starter;
}
else
{
__malloc_hook = save_malloc_hook;
__memalign_hook = save_memalign_hook;
__free_hook = save_free_hook;
}
}
# endif
#endif
static void
ptmalloc_init (void)
{
#if __STD_C
const char* s;
#else
char* s;
#endif
int secure = 0;
if(__malloc_initialized >= 0) return;
__malloc_initialized = 0;
#ifdef _LIBC
# if defined SHARED && !USE___THREAD
/* ptmalloc_init_minimal may already have been called via
__libc_malloc_pthread_startup, above. */
if (mp_.pagesize == 0)
# endif
#endif
ptmalloc_init_minimal();
#ifndef NO_THREADS
# if defined _LIBC
/* We know __pthread_initialize_minimal has already been called,
and that is enough. */
# define NO_STARTER
# endif
# ifndef NO_STARTER
/* With some threads implementations, creating thread-specific data
or initializing a mutex may call malloc() itself. Provide a
simple starter version (realloc() won't work). */
save_malloc_hook = __malloc_hook;
save_memalign_hook = __memalign_hook;
save_free_hook = __free_hook;
__malloc_hook = malloc_starter;
__memalign_hook = memalign_starter;
__free_hook = free_starter;
# ifdef _LIBC
/* Initialize the pthreads interface. */
if (__pthread_initialize != NULL)
__pthread_initialize();
# endif /* !defined _LIBC */
# endif /* !defined NO_STARTER */
#endif /* !defined NO_THREADS */
mutex_init(&main_arena.mutex);
main_arena.next = &main_arena;
#if defined _LIBC && defined 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
mutex_init(&list_lock);
tsd_key_create(&arena_key, NULL);
tsd_setspecific(arena_key, (Void_t *)&main_arena);
thread_atfork(ptmalloc_lock_all, ptmalloc_unlock_all, ptmalloc_unlock_all2);
#ifndef NO_THREADS
# ifndef NO_STARTER
__malloc_hook = save_malloc_hook;
__memalign_hook = save_memalign_hook;
__free_hook = save_free_hook;
# else
# undef NO_STARTER
# endif
#endif
#ifdef _LIBC
secure = __libc_enable_secure;
s = NULL;
if (__builtin_expect (_environ != NULL, 1))
{
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 (! secure)
{
if (memcmp (envline, "TOP_PAD_", 8) == 0)
mALLOPt(M_TOP_PAD, atoi(&envline[9]));
else if (memcmp (envline, "PERTURB_", 8) == 0)
mALLOPt(M_PERTURB, atoi(&envline[9]));
}
break;
case 9:
if (! secure)
{
if (memcmp (envline, "MMAP_MAX_", 9) == 0)
mALLOPt(M_MMAP_MAX, atoi(&envline[10]));
#ifdef PER_THREAD
else if (memcmp (envline, "ARENA_MAX", 9) == 0)
mALLOPt(M_ARENA_MAX, atoi(&envline[10]));
#endif
}
break;
#ifdef PER_THREAD
case 10:
if (! secure)
{
if (memcmp (envline, "ARENA_TEST", 10) == 0)
mALLOPt(M_ARENA_TEST, atoi(&envline[11]));
}
break;
#endif
case 15:
if (! secure)
{
if (memcmp (envline, "TRIM_THRESHOLD_", 15) == 0)
mALLOPt(M_TRIM_THRESHOLD, atoi(&envline[16]));
else if (memcmp (envline, "MMAP_THRESHOLD_", 15) == 0)
mALLOPt(M_MMAP_THRESHOLD, atoi(&envline[16]));
}
break;
default:
break;
}
}
}
#else
if (! secure)
{
if((s = getenv("MALLOC_TRIM_THRESHOLD_")))
mALLOPt(M_TRIM_THRESHOLD, atoi(s));
if((s = getenv("MALLOC_TOP_PAD_")))
mALLOPt(M_TOP_PAD, atoi(s));
if((s = getenv("MALLOC_PERTURB_")))
mALLOPt(M_PERTURB, atoi(s));
if((s = getenv("MALLOC_MMAP_THRESHOLD_")))
mALLOPt(M_MMAP_THRESHOLD, atoi(s));
if((s = getenv("MALLOC_MMAP_MAX_")))
mALLOPt(M_MMAP_MAX, atoi(s));
}
s = getenv("MALLOC_CHECK_");
#endif
if(s && s[0]) {
mALLOPt(M_CHECK_ACTION, (int)(s[0] - '0'));
if (check_action != 0)
__malloc_check_init();
}
void (*hook) (void) = force_reg (__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 USE_ARENAS
#if MALLOC_DEBUG > 1
/* Print the complete contents of a single heap to stderr. */
static void
#if __STD_C
dump_heap(heap_info *heap)
#else
dump_heap(heap) heap_info *heap;
#endif
{
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
#if __STD_C
new_heap(size_t size, size_t top_pad)
#else
new_heap(size, top_pad) size_t size, top_pad;
#endif
{
size_t page_mask = malloc_getpagesize - 1;
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 = (size + page_mask) & ~page_mask;
/* 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_PRIVATE|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_PRIVATE|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_PRIVATE|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;
THREAD_STAT(stat_n_heaps++);
return h;
}
/* Grow a heap. size is automatically rounded up to a
multiple of the page size. */
static int
#if __STD_C
grow_heap(heap_info *h, long diff)
#else
grow_heap(h, diff) heap_info *h; long diff;
#endif
{
size_t page_mask = malloc_getpagesize - 1;
long new_size;
diff = (diff + page_mask) & ~page_mask;
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;
return 0;
}
/* Shrink a heap. */
static int
#if __STD_C
shrink_heap(heap_info *h, long diff)
#else
shrink_heap(h, diff) heap_info *h; long diff;
#endif
{
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. */
#ifdef _LIBC
if (__builtin_expect (__libc_enable_secure, 0))
#else
if (1)
#endif
{
if((char *)MMAP((char *)h + new_size, diff, PROT_NONE,
MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
return -2;
h->mprotect_size = new_size;
}
#ifdef _LIBC
else
madvise ((char *)h + new_size, diff, MADV_DONTNEED);
#endif
/*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
h->size = new_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
#if __STD_C
heap_trim(heap_info *heap, size_t pad)
#else
heap_trim(heap, pad) heap_info *heap; size_t pad;
#endif
{
mstate ar_ptr = heap->ar_ptr;
unsigned long pagesz = mp_.pagesize;
mchunkptr top_chunk = top(ar_ptr), p, bck, fwd;
heap_info *prev_heap;
long new_size, top_size, extra;
/* Can this heap go away completely? */
while(top_chunk == chunk_at_offset(heap, sizeof(*heap))) {
prev_heap = heap->prev;
p = chunk_at_offset(prev_heap, prev_heap->size - (MINSIZE-2*SIZE_SZ));
assert(p->size == (0|PREV_INUSE)); /* must be fencepost */
p = prev_chunk(p);
new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ);
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;
delete_heap(heap);
heap = prev_heap;
if(!prev_inuse(p)) { /* consolidate backward */
p = prev_chunk(p);
unlink(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);*/
}
top_size = chunksize(top_chunk);
extra = (top_size - pad - MINSIZE - 1) & ~(pagesz - 1);
if(extra < (long)pagesz)
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". */
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->next = NULL;*/
a->system_mem = a->max_system_mem = h->size;
arena_mem += h->size;
#ifdef NO_THREADS
if((unsigned long)(mp_.mmapped_mem + arena_mem + main_arena.system_mem) >
mp_.max_total_mem)
mp_.max_total_mem = mp_.mmapped_mem + arena_mem + main_arena.system_mem;
#endif
/* 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);
tsd_setspecific(arena_key, (Void_t *)a);
mutex_init(&a->mutex);
(void)mutex_lock(&a->mutex);
#ifdef PER_THREAD
(void)mutex_lock(&list_lock);
#endif
/* Add the new arena to the global list. */
a->next = main_arena.next;
atomic_write_barrier ();
main_arena.next = a;
#ifdef PER_THREAD
++narenas;
(void)mutex_unlock(&list_lock);
#endif
THREAD_STAT(++(a->stat_lock_loop));
return a;
}
#ifdef PER_THREAD
static mstate
get_free_list (void)
{
mstate result = free_list;
if (result != NULL)
{
(void)mutex_lock(&list_lock);
result = free_list;
if (result != NULL)
free_list = result->next_free;
(void)mutex_unlock(&list_lock);
if (result != NULL)
{
(void)mutex_lock(&result->mutex);
tsd_setspecific(arena_key, (Void_t *)result);
THREAD_STAT(++(result->stat_lock_loop));
}
}
return result;
}
static mstate
reused_arena (void)
{
if (narenas <= mp_.arena_test)
return NULL;
static int narenas_limit;
if (narenas_limit == 0)
{
if (mp_.arena_max != 0)
narenas_limit = mp_.arena_max;
else
{
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);
}
}
if (narenas < narenas_limit)
return NULL;
mstate result;
static mstate next_to_use;
if (next_to_use == NULL)
next_to_use = &main_arena;
result = next_to_use;
do
{
if (!mutex_trylock(&result->mutex))
goto out;
result = result->next;
}
while (result != next_to_use);
/* No arena available. Wait for the next in line. */
(void)mutex_lock(&result->mutex);
out:
tsd_setspecific(arena_key, (Void_t *)result);
THREAD_STAT(++(result->stat_lock_loop));
next_to_use = result->next;
return result;
}
#endif
static mstate
internal_function
#if __STD_C
arena_get2(mstate a_tsd, size_t size)
#else
arena_get2(a_tsd, size) mstate a_tsd; size_t size;
#endif
{
mstate a;
#ifdef PER_THREAD
if ((a = get_free_list ()) == NULL
&& (a = reused_arena ()) == NULL)
/* Nothing immediately available, so generate a new arena. */
a = _int_new_arena(size);
#else
if(!a_tsd)
a = a_tsd = &main_arena;
else {
a = a_tsd->next;
if(!a) {
/* This can only happen while initializing the new arena. */
(void)mutex_lock(&main_arena.mutex);
THREAD_STAT(++(main_arena.stat_lock_wait));
return &main_arena;
}
}
/* Check the global, circularly linked list for available arenas. */
bool retried = false;
repeat:
do {
if(!mutex_trylock(&a->mutex)) {
if (retried)
(void)mutex_unlock(&list_lock);
THREAD_STAT(++(a->stat_lock_loop));
tsd_setspecific(arena_key, (Void_t *)a);
return a;
}
a = a->next;
} while(a != a_tsd);
/* If not even the list_lock can be obtained, try again. This can
happen during `atfork', or for example on systems where thread
creation makes it temporarily impossible to obtain _any_
locks. */
if(!retried && mutex_trylock(&list_lock)) {
/* We will block to not run in a busy loop. */
(void)mutex_lock(&list_lock);
/* Since we blocked there might be an arena available now. */
retried = true;
a = a_tsd;
goto repeat;
}
/* Nothing immediately available, so generate a new arena. */
a = _int_new_arena(size);
(void)mutex_unlock(&list_lock);
#endif
return a;
}
#ifdef PER_THREAD
static void __attribute__ ((section ("__libc_thread_freeres_fn")))
arena_thread_freeres (void)
{
Void_t *vptr = NULL;
mstate a = tsd_getspecific(arena_key, vptr);
tsd_setspecific(arena_key, NULL);
if (a != NULL)
{
(void)mutex_lock(&list_lock);
a->next_free = free_list;
free_list = a;
(void)mutex_unlock(&list_lock);
}
}
text_set_element (__libc_thread_subfreeres, arena_thread_freeres);
#endif
#endif /* USE_ARENAS */
/*
* Local variables:
* c-basic-offset: 2
* End:
*/
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原始发表：2015-10-09 ，如有侵权请联系 cloudcommunity@tencent.com 删除
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