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kref: add kref_test_and_get

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Add kref_test_and_get() function, which atomically add a reference only if
refcount is not zero. This prevent to add a reference to an object that is
already being removed.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Jerome Marchand 2011-01-05 16:57:37 +01:00 committed by Jens Axboe
parent a6e8dc46ff
commit e4a683c899
2 changed files with 13 additions and 0 deletions
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1
include/linux/kref.h
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@ -23,6 +23,7 @@ struct kref {
void kref_init(struct kref *kref);
void kref_get(struct kref *kref);
int kref_test_and_get(struct kref *kref);
int kref_put(struct kref *kref, void (*release) (struct kref *kref));
#endif /* _KREF_H_ */

12
lib/kref.c
View file

@ -36,6 +36,18 @@ void kref_get(struct kref *kref)
smp_mb__after_atomic_inc();
}
/**
* kref_test_and_get - increment refcount for object only if refcount is not
* zero.
* @kref: object.
*
* Return non-zero if the refcount was incremented, 0 otherwise
*/
int kref_test_and_get(struct kref *kref)
{
return atomic_inc_not_zero(&kref->refcount);
}
/**
* kref_put - decrement refcount for object.
* @kref: object.