bfee0724e0
* config/linux/wait.h (do_spin): New inline, largely copied from do_wait, just don't do futex_wait here, instead return true if it should be done. (do_wait): Implement using do_spin. * config/linux/mutex.h (gomp_mutex_lock_slow): Add an int argument to prototype. (gomp_mutex_lock): Use __sync_val_compare_and_swap instead of __sync_bool_compare_and_swap, pass the oldval to gomp_mutex_lock_slow. * config/linux/mutex.c (gomp_mutex_lock_slow): Add oldval argument. If all mutex contenders are just spinning and not sleeping, don't change state to 2 unnecessarily. Optimize the loop when state has already become 2 to use just one atomic operation per loop instead of two. * config/linux/ia64/mutex.h (gomp_mutex_lock_slow): Add an int argument to prototype. (gomp_mutex_lock): Use __sync_val_compare_and_swap instead of __sync_bool_compare_and_swap, pass the oldval to gomp_mutex_lock_slow. From-SVN: r176326
72 lines
2.5 KiB
C
72 lines
2.5 KiB
C
/* Copyright (C) 2005, 2009, 2011 Free Software Foundation, Inc.
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Contributed by Richard Henderson <rth@redhat.com>.
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This file is part of the GNU OpenMP Library (libgomp).
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Libgomp is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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/* This is a Linux specific implementation of a mutex synchronization
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mechanism for libgomp. This type is private to the library. This
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implementation uses atomic instructions and the futex syscall. */
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#ifndef GOMP_MUTEX_H
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#define GOMP_MUTEX_H 1
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typedef int gomp_mutex_t;
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#define GOMP_MUTEX_INIT_0 1
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static inline void gomp_mutex_init (gomp_mutex_t *mutex)
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{
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*mutex = 0;
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}
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extern void gomp_mutex_lock_slow (gomp_mutex_t *mutex, int);
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static inline void gomp_mutex_lock (gomp_mutex_t *mutex)
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{
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int oldval = __sync_val_compare_and_swap (mutex, 0, 1);
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if (__builtin_expect (oldval, 0))
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gomp_mutex_lock_slow (mutex, oldval);
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}
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extern void gomp_mutex_unlock_slow (gomp_mutex_t *mutex);
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static inline void gomp_mutex_unlock (gomp_mutex_t *mutex)
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{
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/* Warning: By definition __sync_lock_test_and_set() does not have
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proper memory barrier semantics for a mutex unlock operation.
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However, this default implementation is written assuming that it
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does, which is true for some targets.
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Targets that require additional memory barriers before
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__sync_lock_test_and_set to achieve the release semantics of
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mutex unlock, are encouraged to include
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"config/linux/ia64/mutex.h" in a target specific mutex.h instead
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of using this file. */
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int val = __sync_lock_test_and_set (mutex, 0);
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if (__builtin_expect (val > 1, 0))
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gomp_mutex_unlock_slow (mutex);
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}
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static inline void gomp_mutex_destroy (gomp_mutex_t *mutex)
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{
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}
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#endif /* GOMP_MUTEX_H */
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