From 8b5536bbee53620f8d5f367987e5727ba36d886d Mon Sep 17 00:00:00 2001
From: Eric Dumazet <dada1@cosmosbay.com>
Date: Mon, 30 Jan 2006 06:19:35 +0100
Subject: [PATCH] [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: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
lib/kref.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/lib/kref.c b/lib/kref.c
index 0d07cc31c8181..4a467faf1367b 100644
--- a/lib/kref.c
+++ b/lib/kref.c
@@ -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;
}
--
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