84 lines
2.4 KiB
C
84 lines
2.4 KiB
C
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/*
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* Copyright (C) 2018, Emilio G. Cota <cota@braap.org>
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*
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* License: GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#include "qemu/osdep.h"
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#include "qemu/atomic.h"
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#include "qemu/thread.h"
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#ifdef CONFIG_ATOMIC64
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#error This file must only be compiled if !CONFIG_ATOMIC64
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#endif
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/*
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* When !CONFIG_ATOMIC64, we serialize both reads and writes with spinlocks.
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* We use an array of spinlocks, with padding computed at run-time based on
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* the host's dcache line size.
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* We point to the array with a void * to simplify the padding's computation.
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* Each spinlock is located every lock_size bytes.
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*/
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static void *lock_array;
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static size_t lock_size;
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/*
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* Systems without CONFIG_ATOMIC64 are unlikely to have many cores, so we use a
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* small array of locks.
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*/
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#define NR_LOCKS 16
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static QemuSpin *addr_to_lock(const void *addr)
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{
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uintptr_t a = (uintptr_t)addr;
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uintptr_t idx;
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idx = a >> qemu_dcache_linesize_log;
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idx ^= (idx >> 8) ^ (idx >> 16);
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idx &= NR_LOCKS - 1;
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return lock_array + idx * lock_size;
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}
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#define GEN_READ(name, type) \
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type name(const type *ptr) \
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{ \
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QemuSpin *lock = addr_to_lock(ptr); \
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type ret; \
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\
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qemu_spin_lock(lock); \
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ret = *ptr; \
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qemu_spin_unlock(lock); \
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return ret; \
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}
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GEN_READ(atomic_read_i64, int64_t)
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GEN_READ(atomic_read_u64, uint64_t)
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#undef GEN_READ
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#define GEN_SET(name, type) \
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void name(type *ptr, type val) \
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{ \
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QemuSpin *lock = addr_to_lock(ptr); \
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\
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qemu_spin_lock(lock); \
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*ptr = val; \
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qemu_spin_unlock(lock); \
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}
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GEN_SET(atomic_set_i64, int64_t)
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GEN_SET(atomic_set_u64, uint64_t)
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#undef GEN_SET
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void atomic64_init(void)
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{
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int i;
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lock_size = ROUND_UP(sizeof(QemuSpin), qemu_dcache_linesize);
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lock_array = qemu_memalign(qemu_dcache_linesize, lock_size * NR_LOCKS);
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for (i = 0; i < NR_LOCKS; i++) {
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QemuSpin *lock = lock_array + i * lock_size;
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qemu_spin_init(lock);
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}
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}
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