Quelle lockref.h Sprache: C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_LOCKREF_H
#define __LINUX_LOCKREF_H

/*
* Locked reference counts.
*
* These are different from just plain atomic refcounts in that they
* are atomic with respect to the spinlock that goes with them.  In
* particular, there can be implementations that don't actually get
* the spinlock for the common decrement/increment operations, but they
* still have to check that the operation is done semantically as if
* the spinlock had been taken (using a cmpxchg operation that covers
* both the lock and the count word, or using memory transactions, for
* example).
*/

#include <linux/spinlock.h>
#include <generated/bounds.h>

#define USE_CMPXCHG_LOCKREF \
(IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
  IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)

struct lockref {
union {
#if USE_CMPXCHG_LOCKREF
  aligned_u64 lock_count;
#endif
  struct {
   spinlock_t lock;
   int count;
  };
};
};

/**
* lockref_init - Initialize a lockref
* @lockref: pointer to lockref structure
*
* Initializes @lockref->count to 1.
*/
static inline void lockref_init(struct lockref *lockref)
{
spin_lock_init(&lockref->lock);
lockref->count = 1;
}

void lockref_get(struct lockref *lockref);
int lockref_put_return(struct lockref *lockref);
bool lockref_get_not_zero(struct lockref *lockref);
bool lockref_put_or_lock(struct lockref *lockref);

void lockref_mark_dead(struct lockref *lockref);
bool lockref_get_not_dead(struct lockref *lockref);

/* Must be called under spinlock for reliable results */
static inline bool __lockref_is_dead(const struct lockref *l)
{
return ((int)l->count < 0);
}

#endif /* __LINUX_LOCKREF_H */

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