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/*
* Copyright (c) 2012-2018 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 <kern/atomic_types.h>
#include <kern/macros.h>
#ifdef __LP64__
/* Report that 64-bits operations are supported */
#define ATOMIC_HAVE_64B_OPS
#else /* __LP64__ */
/*
* XXX Clang doesn't provide any __atomic_xxx_8 functions on i386.
*/
#ifndef __clang__
/* Report that 64-bits operations are supported */
#define ATOMIC_HAVE_64B_OPS
/*
* On i386, GCC 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.
*
* XXX 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.
*/
static inline unsigned long long
atomic_i386_load_64(union atomic_constptr_64 ptr, int memorder)
{
unsigned long long prev;
prev = 0;
__atomic_compare_exchange_n((unsigned long long *)(ptr.ull_ptr),
&prev, 0, false, memorder, __ATOMIC_RELAXED);
return prev;
}
#define atomic_load_64 atomic_i386_load_64
static inline void
atomic_i386_store_64(union atomic_ptr_64 ptr, union atomic_val_64 val,
int memorder)
{
unsigned long long prev;
bool done;
prev = *ptr.ull_ptr;
do {
done = __atomic_compare_exchange_n(ptr.ull_ptr, &prev, val.ull,
false, memorder, __ATOMIC_RELAXED);
} while (!done);
}
#define atomic_store_64 atomic_i386_store_64
#endif /* __clang__ */
#endif /* __LP64__ */
#endif /* X86_ATOMIC_H */
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