pci patches

1 files changed, 36 insertions, 0 deletions

diff --git a/driver/kref-avoid-an-atomic-operation-in-kref_put.patch b/driver/kref-avoid-an-atomic-operation-in-kref_put.patch
new file mode 100644
index 0000000000000..919101fe879a9
--- /dev/null
+++ b/driver/kref-avoid-an-atomic-operation-in-kref_put.patch
@@ -0,0 +1,36 @@
+From linux-kernel-owner+greg=40kroah.com-S1751243AbWA3FTq@vger.kernel.org Sun Jan 29 21:20:33 2006
+Message-ID: <43DDA1E7.5010109@cosmosbay.com>
+Date: Mon, 30 Jan 2006 06:19:35 +0100
+From: Eric Dumazet <dada1@cosmosbay.com>
+To: Greg KH <greg@kroah.com>
+Cc: "Eric W. Biederman" <ebiederm@xmission.com>, Herbert Poetzl <herbert@13thfloor.at>, "Serge E. Hallyn" <serue@us.ibm.com>, Alan Cox <alan@lxorguk.ukuu.org.uk>, Dave Hansen <haveblue@us.ibm.com>, Arjan van de Ven <arjan@infradead.org>, Suleiman Souhlal <ssouhlal@FreeBSD.org>, Hubertus Franke <frankeh@watson.ibm.com>, Cedric Le Goater <clg@fr.ibm.com>, Kyle Moffett <mrmacman_g4@mac.com>
+Subject: 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(-)
+
+--- gregkh-2.6.orig/lib/kref.c
++++ gregkh-2.6/lib/kref.c
+@@ -52,7 +52,12 @@ int kref_put(struct kref *kref, void (*r
+ 	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;
+ 	}