Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932131Ab3FLUkw (ORCPT ); Wed, 12 Jun 2013 16:40:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60255 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756176Ab3FLUkj (ORCPT ); Wed, 12 Jun 2013 16:40:39 -0400 Date: Wed, 12 Jun 2013 13:40:32 -0700 From: Tejun Heo To: Kent Overstreet Cc: linux-kernel@vger.kernel.org, Rusty Russell , Oleg Nesterov , Christoph Lameter Subject: [PATCH percpu/for-3.11] percpu-refcount: consistently use plain (non-sched) RCU Message-ID: <20130612204031.GA15092@htj.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: 2042 Lines: 68 >From e96262150a513ce3d54ff221d4ace8aeec96e0bf Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 12 Jun 2013 13:37:42 -0700 percpu_ref_get/put() are using preempt_disable/enable() while percpu_ref_kill() is using plain call_rcu() instead of call_rcu_sched(). This is buggy as grace periods of the two may not match. Fix it by using plain RCU in percpu_ref_get/put(). (I suggested using sched RCU in the first place but there's no actual benefit in doing so unless we're gonna introduce different variants of get/put to be called while preemption is alredy disabled, which we definitely shouldn't.) Signed-off-by: Tejun Heo Reported-by: Rusty Russell --- include/linux/percpu-refcount.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index 24b31ef..abe1411 100644 --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -85,7 +85,7 @@ static inline void percpu_ref_get(struct percpu_ref *ref) { unsigned __percpu *pcpu_count; - preempt_disable(); + rcu_read_lock(); pcpu_count = ACCESS_ONCE(ref->pcpu_count); @@ -94,7 +94,7 @@ static inline void percpu_ref_get(struct percpu_ref *ref) else atomic_inc(&ref->count); - preempt_enable(); + rcu_read_unlock(); } /** @@ -107,7 +107,7 @@ static inline void percpu_ref_put(struct percpu_ref *ref) { unsigned __percpu *pcpu_count; - preempt_disable(); + rcu_read_lock(); pcpu_count = ACCESS_ONCE(ref->pcpu_count); @@ -116,7 +116,7 @@ static inline void percpu_ref_put(struct percpu_ref *ref) else if (unlikely(atomic_dec_and_test(&ref->count))) ref->release(ref); - preempt_enable(); + rcu_read_unlock(); } #endif -- 1.8.2.1 -- 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/