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147 lines
5.2 KiB
C
147 lines
5.2 KiB
C
/* elision-conf.c: Lock elision tunable parameters.
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Copyright (C) 2015-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include "config.h"
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#include <pthreadP.h>
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#include <elision-conf.h>
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#include <unistd.h>
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#include <dl-procinfo.h>
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#if HAVE_TUNABLES
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# define TUNABLE_NAMESPACE elision
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#endif
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#include <elf/dl-tunables.h>
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/* Reasonable initial tuning values, may be revised in the future.
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This is a conservative initial value. */
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struct elision_config __elision_aconf =
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{
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/* How many times to use a non-transactional lock after a transactional
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failure has occurred because the lock is already acquired. Expressed
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in number of lock acquisition attempts. */
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.skip_lock_busy = 3,
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/* How often to not attempt to use elision if a transaction aborted due
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to reasons other than other threads' memory accesses. Expressed in
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number of lock acquisition attempts. */
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.skip_lock_internal_abort = 3,
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/* How often to not attempt to use elision if a lock used up all retries
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without success. Expressed in number of lock acquisition attempts. */
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.skip_lock_out_of_tbegin_retries = 3,
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/* How often we retry using elision if there is chance for the transaction
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to finish execution (e.g., it wasn't aborted due to the lock being
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already acquired. */
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.try_tbegin = 3,
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/* Same as SKIP_LOCK_INTERNAL_ABORT but for trylock. */
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.skip_trylock_internal_abort = 3,
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};
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/* Force elision for all new locks. This is used to decide whether existing
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DEFAULT locks should be automatically use elision in pthread_mutex_lock().
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Disabled for suid programs. Only used when elision is available. */
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int __pthread_force_elision attribute_hidden = 0;
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#if HAVE_TUNABLES
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static inline void
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__always_inline
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do_set_elision_enable (int32_t elision_enable)
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{
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/* Enable elision if it's avaliable in hardware. It's not necessary to check
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if __libc_enable_secure isn't enabled since elision_enable will be set
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according to the default, which is disabled. */
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if (elision_enable == 1)
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__pthread_force_elision = (GLRO (dl_hwcap2)
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& PPC_FEATURE2_HAS_HTM) ? 1 : 0;
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}
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/* The pthread->elision_enable tunable is 0 or 1 indicating that elision
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should be disabled or enabled respectively. The feature will only be used
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if it's supported by the hardware. */
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void
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TUNABLE_CALLBACK (set_elision_enable) (tunable_val_t *valp)
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{
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int32_t elision_enable = (int32_t) valp->numval;
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do_set_elision_enable (elision_enable);
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}
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#define TUNABLE_CALLBACK_FNDECL(__name, __type) \
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static inline void \
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__always_inline \
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do_set_elision_ ## __name (__type value) \
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{ \
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__elision_aconf.__name = value; \
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} \
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void \
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TUNABLE_CALLBACK (set_elision_ ## __name) (tunable_val_t *valp) \
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{ \
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__type value = (__type) (valp)->numval; \
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do_set_elision_ ## __name (value); \
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}
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TUNABLE_CALLBACK_FNDECL (skip_lock_busy, int32_t);
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TUNABLE_CALLBACK_FNDECL (skip_lock_internal_abort, int32_t);
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TUNABLE_CALLBACK_FNDECL (skip_lock_out_of_tbegin_retries, int32_t);
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TUNABLE_CALLBACK_FNDECL (try_tbegin, int32_t);
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TUNABLE_CALLBACK_FNDECL (skip_trylock_internal_abort, int32_t);
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#endif
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/* Initialize elision. */
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static void
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elision_init (int argc __attribute__ ((unused)),
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char **argv __attribute__ ((unused)),
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char **environ)
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{
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#if HAVE_TUNABLES
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/* Elision depends on tunables and must be explicitly turned on by setting
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the appropriate tunable on a supported platform. */
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TUNABLE_GET (enable, int32_t,
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TUNABLE_CALLBACK (set_elision_enable));
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TUNABLE_GET (skip_lock_busy, int32_t,
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TUNABLE_CALLBACK (set_elision_skip_lock_busy));
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TUNABLE_GET (skip_lock_internal_abort, int32_t,
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TUNABLE_CALLBACK (set_elision_skip_lock_internal_abort));
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TUNABLE_GET (skip_lock_after_retries, int32_t,
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TUNABLE_CALLBACK (set_elision_skip_lock_out_of_tbegin_retries));
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TUNABLE_GET (tries, int32_t,
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TUNABLE_CALLBACK (set_elision_try_tbegin));
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TUNABLE_GET (skip_trylock_internal_abort, int32_t,
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TUNABLE_CALLBACK (set_elision_skip_trylock_internal_abort));
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#endif
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if (!__pthread_force_elision)
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__elision_aconf.try_tbegin = 0; /* Disable elision on rwlocks. */
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}
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#ifdef SHARED
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# define INIT_SECTION ".init_array"
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# define MAYBE_CONST
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#else
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# define INIT_SECTION ".preinit_array"
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# define MAYBE_CONST const
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#endif
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void (*MAYBE_CONST __pthread_init_array []) (int, char **, char **)
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__attribute__ ((section (INIT_SECTION), aligned (sizeof (void *)))) =
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{
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&elision_init
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};
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