diff options
| -rw-r--r-- | include/linux/kref.h | 2 | ||||
| -rw-r--r-- | lib/kref.c | 30 |
2 files changed, 32 insertions, 0 deletions
diff --git a/include/linux/kref.h b/include/linux/kref.h index 6cc38fc07ab7..d4a62ab2ee5e 100644 --- a/include/linux/kref.h +++ b/include/linux/kref.h @@ -24,5 +24,7 @@ struct kref { void kref_init(struct kref *kref); void kref_get(struct kref *kref); int kref_put(struct kref *kref, void (*release) (struct kref *kref)); +int kref_sub(struct kref *kref, unsigned int count, + void (*release) (struct kref *kref)); #endif /* _KREF_H_ */ diff --git a/lib/kref.c b/lib/kref.c index d3d227a08a4b..3efb882b11db 100644 --- a/lib/kref.c +++ b/lib/kref.c @@ -62,6 +62,36 @@ int kref_put(struct kref *kref, void (*release)(struct kref *kref)) return 0; } + +/** + * kref_sub - subtract a number of refcounts for object. + * @kref: object. + * @count: Number of recounts to subtract. + * @release: pointer to the function that will clean up the object when the + * last reference to the object is released. + * This pointer is required, and it is not acceptable to pass kfree + * in as this function. + * + * Subtract @count from the refcount, and if 0, call release(). + * Return 1 if the object was removed, otherwise return 0. Beware, if this + * function returns 0, you still can not count on the kref from remaining in + * memory. Only use the return value if you want to see if the kref is now + * gone, not present. + */ +int kref_sub(struct kref *kref, unsigned int count, + void (*release)(struct kref *kref)) +{ + WARN_ON(release == NULL); + WARN_ON(release == (void (*)(struct kref *))kfree); + + if (atomic_sub_and_test((int) count, &kref->refcount)) { + release(kref); + return 1; + } + return 0; +} + EXPORT_SYMBOL(kref_init); EXPORT_SYMBOL(kref_get); EXPORT_SYMBOL(kref_put); +EXPORT_SYMBOL(kref_sub); |