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/*
* Copyright (c) 2014-2018 Richard Braun.
*
* 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/>.
*/
#ifndef KERN_SREF_I_H
#define KERN_SREF_I_H
#include <stdint.h>
#include <kern/slist.h>
#include <kern/spinlock.h>
#include <kern/work.h>
#define SREF_WEAKREF_DYING ((uintptr_t)1)
#define SREF_WEAKREF_MASK (~SREF_WEAKREF_DYING)
/*
* Weak reference.
*
* A weak reference is a pointer to a reference counter in which the
* least-significant bit is used to indicate whether the counter is
* "dying", i.e. about to be destroyed.
*
* It must be accessed with atomic instructions. There is no need to
* enforce memory order on access since the only data that depends on
* the weak reference are cpu-local deltas.
*/
struct sref_weakref {
uintptr_t addr;
};
#define SREF_QUEUED 0x1
#define SREF_DIRTY 0x2
/*
* Scalable reference counter.
*
* It's tempting to merge the flags into the node member, but since they're
* not protected by the same lock, store them separately.
*
* Locking keys :
* (c) sref_counter
* (g) sref_data
*
* Interrupts must be disabled when accessing a global counter.
*/
struct sref_counter {
sref_noref_fn_t noref_fn;
union {
struct {
struct slist_node node; /* (g) */
struct spinlock lock;
int flags; /* (c) */
unsigned long value; /* (c) */
struct sref_weakref *weakref;
};
struct work work;
};
};
#endif /* KERN_SREF_I_H */
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