linux-stable/include/linux/lockref.h
Andreas Gruenbacher 450b1f6f56 lockref: Add lockref_put_not_zero
Put a lockref unless the lockref is dead or its count would become zero.
This is the same as lockref_put_or_lock except that the lock is never
left held.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
2018-04-12 09:41:19 -07:00

53 lines
1.5 KiB
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;
};
};
};
extern void lockref_get(struct lockref *);
extern int lockref_put_return(struct lockref *);
extern int lockref_get_not_zero(struct lockref *);
extern int lockref_put_not_zero(struct lockref *);
extern int lockref_get_or_lock(struct lockref *);
extern int lockref_put_or_lock(struct lockref *);
extern void lockref_mark_dead(struct lockref *);
extern int lockref_get_not_dead(struct 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 */