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/*
* Copyright (c) 2012-2017 Richard Braun.
* Copyright (c) 2017 Agustina Arzille.
*
* This program 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 of the License, or
* (at your option) any later version.
*
* This program 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.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*
* Architecture-specific definitions for atomic operations.
*/
#ifndef _X86_ATOMIC_H
#define _X86_ATOMIC_H
#ifndef KERN_ATOMIC_H
#error "don't include <machine/atomic.h> directly, use <kern/atomic.h> instead"
#endif
#include <stdbool.h>
#include <stdint.h>
#include <kern/macros.h>
#ifndef __LP64__
/*
* On i386, the compiler generates either an FP-stack read/write, or an SSE2
* store/load to implement these 64-bit atomic operations. Since that's not
* feasible in the kernel, fall back to cmpxchg8b. Note that, in this case,
* loading becomes a potentially mutating operation, but it's not expected
* to be a problem since atomic operations are normally not used on read-only
* memory. Also note that this assumes the processor is at least an i586.
*/
/*
* Temporarily discard qualifiers when loading 64-bits values with a
* compare-and-swap operation.
*/
#define atomic_load_64(ptr, mo) \
MACRO_BEGIN \
uint64_t ret___ = 0; \
\
__atomic_compare_exchange_n((uint64_t *)(ptr), &ret___, 0, \
false, mo, __ATOMIC_RELAXED); \
ret___; \
MACRO_END
#define atomic_load(ptr, mo) \
(typeof(*(ptr)))__builtin_choose_expr(sizeof(*(ptr)) == 8, \
atomic_load_64(ptr, mo), \
__atomic_load_n(ptr, mo))
#define atomic_store(ptr, val, mo) \
MACRO_BEGIN \
if (sizeof(*(ptr)) != 8) { \
__atomic_store_n(ptr, val, mo); \
} else { \
typeof(*(ptr)) oval___, nval___; \
bool done___; \
\
oval___ = *(ptr); \
nval___ = (val); \
\
do { \
done___ = __atomic_compare_exchange_n(ptr, &oval___, nval___, \
false, mo, \
__ATOMIC_RELAXED); \
} while (!done___); \
\
} \
MACRO_END
/*
* Report that load and store are architecture-specific.
*/
#define ATOMIC_ARCH_SPECIFIC_LOAD
#define ATOMIC_ARCH_SPECIFIC_STORE
#endif /* __LP64__ */
/*
* XXX Clang seems to have trouble with 64-bits operations on 32-bits
* processors.
*/
#if defined(__LP64__) || !defined(__clang__)
/*
* Report that 64-bits operations are supported.
*/
#define ATOMIC_HAVE_64B_OPS
#endif /* __clang__ */
#endif /* _X86_ATOMIC_H */
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