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Commit 8b5536bb authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman
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[PATCH] kref: avoid an atomic operation in kref_put() 



Avoid an atomic operation in kref_put() when the last reference is
dropped. On most platforms, atomic_read() is a plan read of the counter
and involves no atomic at all.

Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 48944738

lib/kref.c

+6 −1
Original line number Diff line number Diff line
@@ -52,7 +52,12 @@ int kref_put(struct kref *kref, void (*release)(struct kref *kref)) 
	WARN_ON(release == NULL);

	WARN_ON(release == (void (*)(struct kref *))kfree);



	if (atomic_dec_and_test(&kref->refcount)) {

	/*

	 * if current count is one, we are the last user and can release object

	 * right now, avoiding an atomic operation on 'refcount'

	 */

	if ((atomic_read(&kref->refcount) == 1) ||

	    (atomic_dec_and_test(&kref->refcount))) {

		release(kref);

		return 1;

	}