Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932588Ab3FMDwI (ORCPT ); Wed, 12 Jun 2013 23:52:08 -0400 Received: from mail-gh0-f169.google.com ([209.85.160.169]:38330 "EHLO mail-gh0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756659Ab3FMDwG (ORCPT ); Wed, 12 Jun 2013 23:52:06 -0400 Date: Wed, 12 Jun 2013 20:52:01 -0700 From: Tejun Heo To: Kent Overstreet , linux-kernel@vger.kernel.org, Rusty Russell , Oleg Nesterov , Christoph Lameter Subject: [PATCH percpu/for-3.11 1/2] percpu-refcount: add __must_check to percpu_ref_init() and don't use ACCESS_ONCE() in percpu_ref_kill_rcu() Message-ID: <20130613035201.GD9451@mtj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1780 Lines: 50 Two small changes. * Unlike most init functions, percpu_ref_init() allocates memory and may fail. Let's mark it with __must_check in case the caller forgets. * percpu_ref_kill_rcu() is unnecessarily using ACCESS_ONCE() to dereference @ref->pcpu_count, which can be misleading. The pointer is guaranteed to be valid and visible and can't change underneath the function. Drop ACCESS_ONCE(). Signed-off-by: Tejun Heo --- include/linux/percpu-refcount.h | 3 ++- lib/percpu-refcount.c | 4 +--- 2 files changed, 3 insertions(+), 4 deletions(-) --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -67,7 +67,8 @@ struct percpu_ref { struct rcu_head rcu; }; -int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release); +int __must_check percpu_ref_init(struct percpu_ref *ref, + percpu_ref_func_t *release); void percpu_ref_kill_and_confirm(struct percpu_ref *ref, percpu_ref_func_t *confirm_kill); --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -57,12 +57,10 @@ int percpu_ref_init(struct percpu_ref *r static void percpu_ref_kill_rcu(struct rcu_head *rcu) { struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu); - unsigned __percpu *pcpu_count; + unsigned __percpu *pcpu_count = ref->pcpu_count; unsigned count = 0; int cpu; - pcpu_count = ACCESS_ONCE(ref->pcpu_count); - /* Mask out PCPU_REF_DEAD */ pcpu_count = (unsigned __percpu *) (((unsigned long) pcpu_count) & ~PCPU_STATUS_MASK); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/