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/* elision-conf.c: Lock elision tunable parameters.
Copyright (C) 2013-2015 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, see
<http://www.gnu.org/licenses/>. */
#include "config.h"
#include <pthreadP.h>
#include <init-arch.h>
#include <elision-conf.h>
#include <unistd.h>
/* Reasonable initial tuning values, may be revised in the future.
This is a conservative initial value. */
struct elision_config __elision_aconf =
{
/* How often to not attempt to use elision if a transaction aborted
because the lock is already acquired. Expressed in number of lock
acquisition attempts. */
.skip_lock_busy = 3,
/* How often to not attempt to use elision if a transaction aborted due
to reasons other than other threads' memory accesses. Expressed in
number of lock acquisition attempts. */
.skip_lock_internal_abort = 3,
/* How often we retry using elision if there is chance for the transaction
to finish execution (e.g., it wasn't aborted due to the lock being
already acquired. */
.retry_try_xbegin = 3,
/* Same as SKIP_LOCK_INTERNAL_ABORT but for trylock. */
.skip_trylock_internal_abort = 3,
};
/* Set when the CPU supports elision. When false elision is never attempted.
*/
int __elision_available attribute_hidden;
/* Force elision for all new locks. This is used to decide whether existing
DEFAULT locks should be automatically upgraded to elision in
pthread_mutex_lock(). Disabled for suid programs. Only used when elision
is available. */
int __pthread_force_elision attribute_hidden;
/* Initialize elison. */
static void
elision_init (int argc __attribute__ ((unused)),
char **argv __attribute__ ((unused)),
char **environ)
{
__elision_available = HAS_CPU_FEATURE (RTM);
#ifdef ENABLE_LOCK_ELISION
__pthread_force_elision = __libc_enable_secure ? 0 : __elision_available;
#endif
if (!HAS_CPU_FEATURE (RTM))
__elision_aconf.retry_try_xbegin = 0; /* Disable elision on rwlocks */
}
#ifdef SHARED
# define INIT_SECTION ".init_array"
#else
# define INIT_SECTION ".preinit_array"
#endif
void (*const __pthread_init_array []) (int, char **, char **)
__attribute__ ((section (INIT_SECTION), aligned (sizeof (void *)))) =
{
&elision_init
};
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