From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752184AbcEYT5u (ORCPT ); Wed, 25 May 2016 15:57:50 -0400 Received: from mail-yw0-f180.google.com ([209.85.161.180]:33837 "EHLO mail-yw0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750732AbcEYT5t (ORCPT ); Wed, 25 May 2016 15:57:49 -0400 Date: Wed, 25 May 2016 15:57:45 -0400 From: Tejun Heo To: Peter Zijlstra Cc: Alexey Dobriyan , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Paul McKenney Subject: Re: [PATCH] seqlock: fix raw_read_seqcount_latch() Message-ID: <20160525195745.GH3354@mtj.duckdns.org> References: <20160521201448.GA7429@p183.telecom.by> <20160522104827.GP3193@twins.programming.kicks-ass.net> <20160522185040.GA23664@p183.telecom.by> <20160523093618.GG15728@worktop.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160523093618.GG15728@worktop.ger.corp.intel.com> User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Mon, May 23, 2016 at 11:36:18AM +0200, Peter Zijlstra wrote: > > include/linux/percpu-refcount.h:146:36: warning: initialization makes pointer from integer without a cast [-Wint-conversion] > > percpu_ptr = lockless_dereference(ref->percpu_count_ptr); > > TJ; would you prefer casting or not using lockless_dereference() here? Casting is nasty - *(unsigned long __percpu **)& - because the macro expects an lvalue. I think it'd be better to revert to opencoding READ_ONCE() and barrier there. It's a pretty special case anyway. Thanks. -- tejun