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/* Defintions for lowlevel handling in ld.so.
Copyright (C) 2006, 2007 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#ifndef _RTLD_LOWLEVEL_H
#define _RTLD_LOWLEVEL_H 1
#include <atomic.h>
#include <lowlevellock.h>
/* Special multi-reader lock used in ld.so. */
#define __RTLD_MRLOCK_WRITER 1
#define __RTLD_MRLOCK_RWAIT 2
#define __RTLD_MRLOCK_WWAIT 4
#define __RTLD_MRLOCK_RBITS \
~(__RTLD_MRLOCK_WRITER | __RTLD_MRLOCK_RWAIT | __RTLD_MRLOCK_WWAIT)
#define __RTLD_MRLOCK_INC 8
#define __RTLD_MRLOCK_TRIES 5
typedef int __rtld_mrlock_t;
#define __rtld_mrlock_define(CLASS,NAME) \
CLASS __rtld_mrlock_t NAME;
#define _RTLD_MRLOCK_INITIALIZER 0
#define __rtld_mrlock_initialize(NAME) \
(void) ((NAME) = 0)
#define __rtld_mrlock_lock(lock) \
do { \
__label__ out; \
while (1) \
{ \
int oldval; \
for (int tries = 0; tries < __RTLD_MRLOCK_TRIES; ++tries) \
{ \
oldval = lock; \
while (__builtin_expect ((oldval \
& (__RTLD_MRLOCK_WRITER \
| __RTLD_MRLOCK_WWAIT)) \
== 0, 1)) \
{ \
int newval = ((oldval & __RTLD_MRLOCK_RBITS) \
+ __RTLD_MRLOCK_INC); \
int ret = atomic_compare_and_exchange_val_acq (&(lock), \
newval, \
oldval); \
if (__builtin_expect (ret == oldval, 1)) \
goto out; \
oldval = ret; \
} \
atomic_delay (); \
} \
if ((oldval & __RTLD_MRLOCK_RWAIT) == 0) \
{ \
atomic_or (&(lock), __RTLD_MRLOCK_RWAIT); \
oldval |= __RTLD_MRLOCK_RWAIT; \
} \
lll_private_futex_wait (lock, oldval); \
} \
out:; \
} while (0)
#define __rtld_mrlock_unlock(lock) \
do { \
int oldval = atomic_exchange_and_add (&(lock), -__RTLD_MRLOCK_INC); \
if (__builtin_expect ((oldval \
& (__RTLD_MRLOCK_RBITS | __RTLD_MRLOCK_WWAIT)) \
== (__RTLD_MRLOCK_INC | __RTLD_MRLOCK_WWAIT), 0)) \
/* We have to wake all threads since there might be some queued \
readers already. */ \
lll_private_futex_wake (&(lock), 0x7fffffff); \
} while (0)
/* There can only ever be one thread trying to get the exclusive lock. */
#define __rtld_mrlock_change(lock) \
do { \
__label__ out; \
while (1) \
{ \
int oldval; \
for (int tries = 0; tries < __RTLD_MRLOCK_TRIES; ++tries) \
{ \
oldval = lock; \
while (__builtin_expect ((oldval & __RTLD_MRLOCK_RBITS) == 0, 1)) \
{ \
int newval = ((oldval & __RTLD_MRLOCK_RWAIT) \
+ __RTLD_MRLOCK_WRITER); \
int ret = atomic_compare_and_exchange_val_acq (&(lock), \
newval, \
oldval); \
if (__builtin_expect (ret == oldval, 1)) \
goto out; \
oldval = ret; \
} \
atomic_delay (); \
} \
atomic_or (&(lock), __RTLD_MRLOCK_WWAIT); \
oldval |= __RTLD_MRLOCK_WWAIT; \
lll_private_futex_wait (lock, oldval); \
} \
out:; \
} while (0)
#define __rtld_mrlock_done(lock) \
do { \
int oldval = atomic_exchange_and_add (&(lock), -__RTLD_MRLOCK_WRITER); \
if (__builtin_expect ((oldval & __RTLD_MRLOCK_RWAIT) != 0, 0)) \
lll_private_futex_wake (&(lock), 0x7fffffff); \
} while (0)
/* Function to wait for variable become zero. Used in ld.so for
reference counters. */
#define __rtld_waitzero(word) \
do { \
while (1) \
{ \
int val = word; \
if (val == 0) \
break; \
lll_private_futex_wait (&(word), val); \
} \
} while (0)
#define __rtld_notify(word) \
lll_private_futex_wake (&(word), 1)
#endif
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