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