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/* $NetBSD: refcount.h,v 1.3 2021/12/19 11:52:08 riastradh Exp $ */
/*-
* Copyright (c) 2020 The NetBSD Foundation, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef _LINUX_REFCOUNT_H_
#define _LINUX_REFCOUNT_H_
#include <linux/atomic.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
typedef struct refcount refcount_t;
struct refcount {
atomic_t rc_count;
};
static inline void
refcount_set(struct refcount *rc, int n)
{
atomic_set(&rc->rc_count, n);
}
static inline void
refcount_inc(struct refcount *rc)
{
atomic_inc(&rc->rc_count);
}
static inline int __must_check
refcount_inc_not_zero(struct refcount *rc)
{
unsigned old, new;
do {
old = atomic_read(&rc->rc_count);
if (old == 0)
break;
new = old + 1;
} while (atomic_cmpxchg(&rc->rc_count, old, new) != old);
return old;
}
static inline bool __must_check
refcount_dec_and_test(struct refcount *rc)
{
unsigned old, new;
do {
old = atomic_read(&rc->rc_count);
KASSERT(old);
new = old - 1;
} while (atomic_cmpxchg(&rc->rc_count, old, new) != old);
return old == 1;
}
static inline bool __must_check
refcount_dec_and_lock_irqsave(struct refcount *rc, struct spinlock *lock,
unsigned long *flagsp)
{
return atomic_dec_and_lock_irqsave(&rc->rc_count, lock, *flagsp);
}
static inline bool __must_check
refcount_dec_and_mutex_lock(struct refcount *rc, struct mutex *lock)
{
unsigned old, new;
do {
old = atomic_read(&rc->rc_count);
KASSERT(old);
if (old == 1) {
mutex_lock(lock);
if (atomic_dec_return(&rc->rc_count) == 0)
return true;
mutex_unlock(lock);
return false;
}
new = old - 1;
} while (atomic_cmpxchg(&rc->rc_count, old, new) != old);
KASSERT(old != 1);
KASSERT(new != 0);
return false;
}
#endif /* _LINUX_REFCOUNT_H_ */
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