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/* Copyright (C) 2008-2022 Free Software Foundation, Inc.
Contributed by Jakub Jelinek <jakub@redhat.com>.
This file is part of the GNU Offloading and Multi Processing Library
(libgomp).
Libgomp is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
Libgomp 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 General Public License for
more details.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/* This is a Linux specific implementation of a mutex synchronization
mechanism for libgomp. This type is private to the library. This
implementation uses atomic instructions and the futex syscall. */
#include <endian.h>
#include <limits.h>
#include "wait.h"
void *
gomp_ptrlock_get_slow (gomp_ptrlock_t *ptrlock)
{
int *intptr;
uintptr_t oldval = 1;
__atomic_compare_exchange_n (ptrlock, &oldval, 2, false,
MEMMODEL_RELAXED, MEMMODEL_RELAXED);
/* futex works on ints, not pointers.
But a valid work share pointer will be at least
8 byte aligned, so it is safe to assume the low
32-bits of the pointer won't contain values 1 or 2. */
__asm volatile ("" : "=r" (intptr) : "0" (ptrlock));
#if __BYTE_ORDER == __BIG_ENDIAN
if (sizeof (*ptrlock) > sizeof (int))
intptr += (sizeof (*ptrlock) / sizeof (int)) - 1;
#endif
do
do_wait (intptr, 2);
while (__atomic_load_n (intptr, MEMMODEL_RELAXED) == 2);
__asm volatile ("" : : : "memory");
return (void *) __atomic_load_n (ptrlock, MEMMODEL_ACQUIRE);
}
void
gomp_ptrlock_set_slow (gomp_ptrlock_t *ptrlock)
{
int *intptr;
__asm volatile ("" : "=r" (intptr) : "0" (ptrlock));
#if __BYTE_ORDER == __BIG_ENDIAN
if (sizeof (*ptrlock) > sizeof (int))
intptr += (sizeof (*ptrlock) / sizeof (int)) - 1;
#endif
futex_wake (intptr, INT_MAX);
}
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