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84 lines
2.9 KiB
C
84 lines
2.9 KiB
C
/* elision-conf.c: Lock elision tunable parameters.
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Copyright (C) 2013-2016 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 <init-arch.h>
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#include <elision-conf.h>
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#include <unistd.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 often to not attempt to use elision if a transaction aborted
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because the lock is already acquired. Expressed in number of lock
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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 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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.retry_try_xbegin = 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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/* Set when the CPU supports elision. When false elision is never attempted.
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*/
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int __elision_available attribute_hidden;
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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 upgraded to elision in
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pthread_mutex_lock(). Disabled for suid programs. Only used when elision
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is available. */
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int __pthread_force_elision attribute_hidden;
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/* Initialize elison. */
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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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__elision_available = HAS_CPU_FEATURE (RTM);
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#ifdef ENABLE_LOCK_ELISION
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__pthread_force_elision = __libc_enable_secure ? 0 : __elision_available;
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#endif
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if (!HAS_CPU_FEATURE (RTM))
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__elision_aconf.retry_try_xbegin = 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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#else
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# define INIT_SECTION ".preinit_array"
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#endif
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void (*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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