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Commit ecf7ace9 authored by Thomas Hellstrom's avatar Thomas Hellstrom Committed by Dave Airlie
Browse files

kref: Add a kref_sub function 



Makes it possible to optimize batched multiple unrefs.
Initial user will be drivers/gpu/ttm which accumulates unrefs to be
processed outside of atomic code.

Signed-off-by: default avatarThomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent d6ea8886

include/linux/kref.h

+2 −0
Original line number Diff line number Diff line
@@ -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_ */

lib/kref.c

+30 −0
Original line number Diff line number Diff line
@@ -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);