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[PATCH] kref: avoid an atomic operation in kref_put()

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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: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Eric Dumazet 2006-01-30 06:19:35 +01:00 committed by Greg Kroah-Hartman
parent 489447380a
commit 8b5536bbee
1 changed files with 6 additions and 1 deletions
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7
lib/kref.c
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@ -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;
}