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/* Copyright (C) 2008-2021 Free Software Foundation, Inc.
Contributed by Jakub Jelinek <>.
This file is part of the GNU Offloading and Multi Processing Library
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
<>. */
/* 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. */
#ifndef GOMP_WAIT_H
#define GOMP_WAIT_H 1
#include "libgomp.h"
#include <errno.h>
#define FUTEX_WAIT 0
#define FUTEX_WAKE 1
# pragma GCC visibility push(hidden)
extern int gomp_futex_wait, gomp_futex_wake;
#include <futex.h>
static inline int do_spin (int *addr, int val)
unsigned long long i, count = gomp_spin_count_var;
if (__builtin_expect (__atomic_load_n (&gomp_managed_threads,
> gomp_available_cpus, 0))
count = gomp_throttled_spin_count_var;
for (i = 0; i < count; i++)
if (__builtin_expect (__atomic_load_n (addr, MEMMODEL_RELAXED) != val, 0))
return 0;
cpu_relax ();
return 1;
static inline void do_wait (int *addr, int val)
if (do_spin (addr, val))
futex_wait (addr, val);
# pragma GCC visibility pop
#endif /* GOMP_WAIT_H */