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114 lines
3.1 KiB
C
114 lines
3.1 KiB
C
/*-
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* Copyright (c) 2005 John Baldwin <jhb@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD: releng/11.4/sys/sys/refcount.h 339862 2018-10-29 14:37:27Z hselasky $
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*/
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#ifndef __SYS_REFCOUNT_H__
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#define __SYS_REFCOUNT_H__
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#include <sys/limits.h>
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#include <machine/atomic.h>
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#ifdef _KERNEL
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#include <sys/systm.h>
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#else
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#define KASSERT(exp, msg) /* */
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#endif
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static __inline void
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refcount_init(volatile u_int *count, u_int value)
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{
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*count = value;
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}
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static __inline void
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refcount_acquire(volatile u_int *count)
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{
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KASSERT(*count < UINT_MAX, ("refcount %p overflowed", count));
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atomic_add_int(count, 1);
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}
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static __inline int
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refcount_release(volatile u_int *count)
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{
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u_int old;
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atomic_thread_fence_rel();
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old = atomic_fetchadd_int(count, -1);
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KASSERT(old > 0, ("refcount %p is zero", count));
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if (old > 1)
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return (0);
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/*
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* Last reference. Signal the user to call the destructor.
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*
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* Ensure that the destructor sees all updates. The fence_rel
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* at the start of the function synchronized with this fence.
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*/
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atomic_thread_fence_acq();
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return (1);
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}
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/*
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* This functions returns non-zero if the refcount was
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* incremented. Else zero is returned.
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*
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* A temporary hack until refcount_* APIs are sorted out.
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*/
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static __inline __result_use_check int
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refcount_acquire_if_not_zero(volatile u_int *count)
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{
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u_int old;
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old = *count;
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for (;;) {
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KASSERT(old < UINT_MAX, ("refcount %p overflowed", count));
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if (old == 0)
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return (0);
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if (atomic_fcmpset_int(count, &old, old + 1))
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return (1);
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}
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}
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static __inline __result_use_check int
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refcount_release_if_not_last(volatile u_int *count)
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{
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u_int old;
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old = *count;
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for (;;) {
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KASSERT(old > 0, ("refcount %p is zero", count));
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if (old == 1)
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return (0);
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if (atomic_fcmpset_int(count, &old, old - 1))
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return (1);
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}
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}
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#endif /* ! __SYS_REFCOUNT_H__ */
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