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/* $OpenBSD: _atomic_lock.c,v 1.1 2021/04/29 18:33:36 drahn Exp $ */
/*
* Copyright (c) 2020 Mars Li <mengshi.li.mars@gmail.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* Atomic lock for riscv64
*/
#include <sys/types.h>
#include <machine/spinlock.h>
/*
* Spinlock does not have Aquire/Release semantics, so amoswap.w.aq
* should not used here.
*/
int
_atomic_lock(volatile _atomic_lock_t *lock)
{
_atomic_lock_t old;
/*
* Use the amoswap instruction to swap the lock value with
* a local variable containing the locked state.
*/
__asm__("amoswap.w %0, %1, (%2)"
: "=r" (old)
: "r" (_ATOMIC_LOCK_LOCKED), "r" (lock) : "memory");
return (old != _ATOMIC_LOCK_UNLOCKED);
}
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