1 /* $OpenBSD: _atomic_lock.c,v 1.1 2021/04/29 18:33:36 drahn Exp $ */ 2 /* 3 * Copyright (c) 2020 Mars Li <mengshi.li.mars@gmail.com> 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18 /* 19 * Atomic lock for riscv64 20 */ 21 22 #include <sys/types.h> 23 #include <machine/spinlock.h> 24 25 /* 26 * Spinlock does not have Aquire/Release semantics, so amoswap.w.aq 27 * should not used here. 28 */ 29 int 30 _atomic_lock(volatile _atomic_lock_t *lock) 31 { 32 _atomic_lock_t old; 33 34 /* 35 * Use the amoswap instruction to swap the lock value with 36 * a local variable containing the locked state. 37 */ 38 __asm__("amoswap.w %0, %1, (%2)" 39 : "=r" (old) 40 : "r" (_ATOMIC_LOCK_LOCKED), "r" (lock) : "memory"); 41 42 return (old != _ATOMIC_LOCK_UNLOCKED); 43 } 44