71 lines
2.4 KiB
C
71 lines
2.4 KiB
C
/* Copyright (C) 2008-2019 Free Software Foundation, Inc.
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Contributed by Jakub Jelinek <jakub@redhat.com>.
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This file is part of the GNU Offloading and Multi Processing Library
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(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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#include <endian.h>
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#include <limits.h>
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#include "wait.h"
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void *
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gomp_ptrlock_get_slow (gomp_ptrlock_t *ptrlock)
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{
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int *intptr;
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uintptr_t oldval = 1;
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__atomic_compare_exchange_n (ptrlock, &oldval, 2, false,
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MEMMODEL_RELAXED, MEMMODEL_RELAXED);
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/* futex works on ints, not pointers.
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But a valid work share pointer will be at least
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8 byte aligned, so it is safe to assume the low
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32-bits of the pointer won't contain values 1 or 2. */
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__asm volatile ("" : "=r" (intptr) : "0" (ptrlock));
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#if __BYTE_ORDER == __BIG_ENDIAN
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if (sizeof (*ptrlock) > sizeof (int))
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intptr += (sizeof (*ptrlock) / sizeof (int)) - 1;
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#endif
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do
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do_wait (intptr, 2);
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while (__atomic_load_n (intptr, MEMMODEL_RELAXED) == 2);
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__asm volatile ("" : : : "memory");
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return (void *) __atomic_load_n (ptrlock, MEMMODEL_ACQUIRE);
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}
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void
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gomp_ptrlock_set_slow (gomp_ptrlock_t *ptrlock)
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{
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int *intptr;
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__asm volatile ("" : "=r" (intptr) : "0" (ptrlock));
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#if __BYTE_ORDER == __BIG_ENDIAN
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if (sizeof (*ptrlock) > sizeof (int))
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intptr += (sizeof (*ptrlock) / sizeof (int)) - 1;
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#endif
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futex_wake (intptr, INT_MAX);
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}
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