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8491ed6d70
This patch relies on the C version of the rwlocks posted earlier. With C rwlocks it is very straight forward to do adaptive elision using TSX. It is based on the infrastructure added earlier for mutexes, but uses its own elision macros. The macros are fairly general purpose and could be used for other elision purposes too. This version is much cleaner than the earlier assembler based version, and in particular implements adaptation which makes it safer. I changed the behavior slightly to not require any changes in the test suite and fully conform to all expected behaviors (generally at the cost of not eliding in various situations). In particular this means the timedlock variants are not elided. Nested trylock aborts.
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) 2013-2014 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_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_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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