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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.
A ptrlock has four states:
0/NULL Initial
1 Owned by me, I get to write a pointer to ptrlock.
2 Some thread is waiting on the ptrlock.
>2 Ptrlock contains a valid pointer.
It is not valid to gain the ptrlock and then write a NULL to it. */
#ifndef GOMP_PTRLOCK_H
#define GOMP_PTRLOCK_H 1
typedef void *gomp_ptrlock_t;
static inline void gomp_ptrlock_init (gomp_ptrlock_t *ptrlock, void *ptr)
{
*ptrlock = ptr;
}
extern void *gomp_ptrlock_get_slow (gomp_ptrlock_t *ptrlock);
static inline void *gomp_ptrlock_get (gomp_ptrlock_t *ptrlock)
{
uintptr_t oldval;
uintptr_t v = (uintptr_t) __atomic_load_n (ptrlock, MEMMODEL_ACQUIRE);
if (v > 2)
return (void *) v;
oldval = 0;
if (__atomic_compare_exchange_n (ptrlock, &oldval, 1, false,
MEMMODEL_ACQUIRE, MEMMODEL_ACQUIRE))
return NULL;
return gomp_ptrlock_get_slow (ptrlock);
}
extern void gomp_ptrlock_set_slow (gomp_ptrlock_t *ptrlock);
static inline void gomp_ptrlock_set (gomp_ptrlock_t *ptrlock, void *ptr)
{
void *wait = __atomic_exchange_n (ptrlock, ptr, MEMMODEL_RELEASE);
if ((uintptr_t) wait != 1)
gomp_ptrlock_set_slow (ptrlock);
}
static inline void gomp_ptrlock_destroy (gomp_ptrlock_t *ptrlock)
{
}
#endif /* GOMP_PTRLOCK_H */
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