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47 lines
1.0 KiB
C
47 lines
1.0 KiB
C
/*
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* Copyright (C) 2014 Freie Universität Berlin
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*
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* This file is subject to the terms and conditions of the GNU Lesser General
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* Public License v2.1. See the file LICENSE in the top level directory for more
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* details.
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*/
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/**
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* @ingroup cpu_cortexm4_common
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* @{
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*
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* @file
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* @brief Implementation of the kernels atomic interface
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*
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* @author Stefan Pfeiffer <stefan.pfeiffer@fu-berlin.de>
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* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
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* @author Joakim Gebart <joakim.gebart@eistec.se>
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*
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* @}
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*/
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#include <stdint.h>
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#include "atomic.h"
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#include "irq.h"
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#include "cpu.h"
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int atomic_cas(atomic_int_t *var, int old, int now)
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{
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int tmp;
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int status;
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/* Load exclusive */
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tmp = __LDREXW((volatile uint32_t *)(&ATOMIC_VALUE(*var)));
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if (tmp != old) {
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/* Clear memory exclusivity */
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__CLREX();
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return 0;
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}
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/* Try to write the new value */
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status = __STREXW(now, (volatile uint32_t *)(&ATOMIC_VALUE(*var)));
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return (status == 0);
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}
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