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glibc/sysdeps/unix/sysv/linux/x86/force-elision.h

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Add elision to pthread_mutex_{try,timed,un}lock Add elision paths to the basic mutex locks. The normal path has a check for RTM and upgrades the lock to RTM when available. Trylocks cannot automatically upgrade, so they check for elision every time. We use a 4 byte value in the mutex to store the lock elision adaptation state. This is separate from the adaptive spin state and uses a separate field. Condition variables currently do not support elision. Recursive mutexes and condition variables may be supported at some point, but are not in the current implementation. Also "trylock" will not automatically enable elision unless some other lock call has been already called on the lock. This version does not use IFUNC, so it means every lock has one additional check for elision. Benchmarking showed the overhead to be negligible.
2012-12-22 09:03:04 +00:00
/* force-elision.h: Automatic enabling of elision for mutexes
Update copyright dates with scripts/update-copyrights.
2015-01-02 16:28:19 +00:00
Copyright (C) 2013-2015 Free Software Foundation, Inc.
Add elision to pthread_mutex_{try,timed,un}lock Add elision paths to the basic mutex locks. The normal path has a check for RTM and upgrades the lock to RTM when available. Trylocks cannot automatically upgrade, so they check for elision every time. We use a 4 byte value in the mutex to store the lock elision adaptation state. This is separate from the adaptive spin state and uses a separate field. Condition variables currently do not support elision. Recursive mutexes and condition variables may be supported at some point, but are not in the current implementation. Also "trylock" will not automatically enable elision unless some other lock call has been already called on the lock. This version does not use IFUNC, so it means every lock has one additional check for elision. Benchmarking showed the overhead to be negligible.
2012-12-22 09:03:04 +00:00
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
Clean up whitespace in lock elision patches. Signed-off-by: Carlos O'Donell <carlos@redhat.com>
2013-07-19 05:16:28 +00:00
<http://www.gnu.org/licenses/>. */
Add elision to pthread_mutex_{try,timed,un}lock Add elision paths to the basic mutex locks. The normal path has a check for RTM and upgrades the lock to RTM when available. Trylocks cannot automatically upgrade, so they check for elision every time. We use a 4 byte value in the mutex to store the lock elision adaptation state. This is separate from the adaptive spin state and uses a separate field. Condition variables currently do not support elision. Recursive mutexes and condition variables may be supported at some point, but are not in the current implementation. Also "trylock" will not automatically enable elision unless some other lock call has been already called on the lock. This version does not use IFUNC, so it means every lock has one additional check for elision. Benchmarking showed the overhead to be negligible.
2012-12-22 09:03:04 +00:00
/* Automatically enable elision for existing user lock kinds. */
#define FORCE_ELISION(m, s) \
if (__pthread_force_elision \
&& (m->__data.__kind & PTHREAD_MUTEX_ELISION_FLAGS_NP) == 0) \
{ \
mutex->__data.__kind |= PTHREAD_MUTEX_ELISION_NP; \
s; \
}
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