From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752815AbdCPPiw (ORCPT ); Thu, 16 Mar 2017 11:38:52 -0400 Received: from mail-yw0-f182.google.com ([209.85.161.182]:36558 "EHLO mail-yw0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752719AbdCPPiv (ORCPT ); Thu, 16 Mar 2017 11:38:51 -0400 Date: Thu, 16 Mar 2017 11:38:43 -0400 From: Tejun Heo To: Oleg Nesterov Cc: Linus Torvalds , Andrew Morton , Peter Zijlstra , Thomas Gleixner , Chris Mason , linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 1/2] kthread: add barriers to set_kthread_struct() and to_kthread() Message-ID: <20170316153843.GB15810@htj.duckdns.org> References: <20170315231827.GA13656@htj.duckdns.org> <20170316145436.GA24478@redhat.com> <20170316153301.GA15810@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170316153301.GA15810@htj.duckdns.org> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 16, 2017 at 11:33:01AM -0400, Tejun Heo wrote: > > And perhaps we should add another helper, say, > > > > #define lockless_assign_pointer(ptr, val) \ > > smp_store_release(&ptr, val) > > > > for set_kthread_struct() ? it can have more users. > > > > Not that I think you should change your patch, I am just asking. > > Ah yeah, that would look better. I vaguely remembered the new macro > but couldn't quite remember it fully. :) Will update the patch. Oops, as for adding lockless_assign_pointer(), wouldn't smp_wmb() be a better match for smp_read_barrier_depends()? ISTR acquire/release pairs being more expensive on some archs. Thanks. -- tejun