62 lines
1.8 KiB
C
62 lines
1.8 KiB
C
/* Copyright (C) 2005, 2008, 2009 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 semaphore 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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#include "wait.h"
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void
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gomp_sem_wait_slow (gomp_sem_t *sem)
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{
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while (1)
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{
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int val = __sync_val_compare_and_swap (sem, 0, -1);
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if (val > 0)
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{
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if (__sync_bool_compare_and_swap (sem, val, val - 1))
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return;
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}
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do_wait (sem, -1);
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}
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}
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void
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gomp_sem_post_slow (gomp_sem_t *sem)
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{
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int old, tmp = *sem, wake;
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do
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{
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old = tmp;
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wake = old > 0 ? old + 1 : 1;
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tmp = __sync_val_compare_and_swap (sem, old, wake);
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}
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while (old != tmp);
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futex_wake (sem, wake);
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}
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