Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752313AbaFRPc1 (ORCPT ); Wed, 18 Jun 2014 11:32:27 -0400 Received: from mail-qc0-f175.google.com ([209.85.216.175]:58157 "EHLO mail-qc0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751101AbaFRPc0 (ORCPT ); Wed, 18 Jun 2014 11:32:26 -0400 Date: Wed, 18 Jun 2014 11:32:22 -0400 From: Tejun Heo To: Lai Jiangshan Cc: cl@linux-foundation.org, kmo@daterainc.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 6/6] percpu-refcount: implement percpu_ref_reinit() and percpu_ref_is_zero() Message-ID: <20140618153222.GA11042@htj.dyndns.org> References: <1403053685-28240-1-git-send-email-tj@kernel.org> <1403053685-28240-7-git-send-email-tj@kernel.org> <53A1097F.3060400@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53A1097F.3060400@cn.fujitsu.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 18, 2014 at 11:37:35AM +0800, Lai Jiangshan wrote: > > @@ -97,7 +98,10 @@ static inline void percpu_ref_kill(struct percpu_ref *ref) > > static inline bool __pcpu_ref_alive(struct percpu_ref *ref, > > unsigned __percpu **pcpu_countp) > > { > > - unsigned long pcpu_ptr = ACCESS_ONCE(ref->pcpu_count_ptr); > > + unsigned long pcpu_ptr; > > + > > + /* paired with smp_store_release() in percpu_ref_reinit() */ > > + pcpu_ptr = smp_load_acquire(&ref->pcpu_count_ptr); > > > Does "smp_load_acquire()" hurts the performance of percpu_ref_get/put() > in non-x86 system? It's equivalent to data dependency barrier. The only arch which needs something more than barrier() is alpha. It isn't an issue. Thanks. -- tejun -- 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/