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/*
* Copyright (C) 2018, Emilio G. Cota <cota@braap.org>
*
* License: GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qemu/atomic.h"
#include "qemu/thread.h"
#include "qemu/cacheinfo.h"
#include "qemu/memalign.h"
#ifdef CONFIG_ATOMIC64
#error This file must only be compiled if !CONFIG_ATOMIC64
#endif
/*
* When !CONFIG_ATOMIC64, we serialize both reads and writes with spinlocks.
* We use an array of spinlocks, with padding computed at run-time based on
* the host's dcache line size.
* We point to the array with a void * to simplify the padding's computation.
* Each spinlock is located every lock_size bytes.
*/
static void *lock_array;
static size_t lock_size;
/*
* Systems without CONFIG_ATOMIC64 are unlikely to have many cores, so we use a
* small array of locks.
*/
#define NR_LOCKS 16
static QemuSpin *addr_to_lock(const void *addr)
{
uintptr_t a = (uintptr_t)addr;
uintptr_t idx;
idx = a >> qemu_dcache_linesize_log;
idx ^= (idx >> 8) ^ (idx >> 16);
idx &= NR_LOCKS - 1;
return lock_array + idx * lock_size;
}
#define GEN_READ(name, type) \
type name(const type *ptr) \
{ \
QemuSpin *lock = addr_to_lock(ptr); \
type ret; \
\
qemu_spin_lock(lock); \
ret = *ptr; \
qemu_spin_unlock(lock); \
return ret; \
}
GEN_READ(qatomic_read_i64, int64_t)
GEN_READ(qatomic_read_u64, uint64_t)
#undef GEN_READ
#define GEN_SET(name, type) \
void name(type *ptr, type val) \
{ \
QemuSpin *lock = addr_to_lock(ptr); \
\
qemu_spin_lock(lock); \
*ptr = val; \
qemu_spin_unlock(lock); \
}
GEN_SET(qatomic_set_i64, int64_t)
GEN_SET(qatomic_set_u64, uint64_t)
#undef GEN_SET
void qatomic64_init(void)
{
int i;
lock_size = ROUND_UP(sizeof(QemuSpin), qemu_dcache_linesize);
lock_array = qemu_memalign(qemu_dcache_linesize, lock_size * NR_LOCKS);
for (i = 0; i < NR_LOCKS; i++) {
QemuSpin *lock = lock_array + i * lock_size;
qemu_spin_init(lock);
}
}
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