Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758245AbaDXPdb (ORCPT ); Thu, 24 Apr 2014 11:33:31 -0400 Received: from mail-qa0-f48.google.com ([209.85.216.48]:37679 "EHLO mail-qa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757767AbaDXPdZ (ORCPT ); Thu, 24 Apr 2014 11:33:25 -0400 Date: Thu, 24 Apr 2014 11:33:20 -0400 From: Tejun Heo To: Frederic Weisbecker Cc: LKML , Christoph Lameter , Kevin Hilman , Lai Jiangshan , Mike Galbraith , "Paul E. McKenney" , Viresh Kumar Subject: Re: [PATCH 4/4] workqueue: Handle ordered workqueues on cpumask_unbounds change Message-ID: <20140424153320.GF14460@htj.dyndns.org> References: <1398350256-7834-1-git-send-email-fweisbec@gmail.com> <1398350256-7834-5-git-send-email-fweisbec@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1398350256-7834-5-git-send-email-fweisbec@gmail.com> 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 On Thu, Apr 24, 2014 at 04:37:36PM +0200, Frederic Weisbecker wrote: > Ordered unbound workqueues need some special care if we want to > modify their CPU affinity. These can't be simply handled through > apply_workqueue_attrs() since it works by hot plugging worker pools > which has parallelism side effects and this would break ordering. > > The way we solve this is to change the affinity of the (presumaly > unique) worker backing the ordered workqueues. > > NOTE: Now like Lai said, there may be bad side effects on this because > ordered wq may share their worker pool with non-ordered workqueues. > So changing the affinity of the worker itself is not a nice solution. > This patch is very likely to be replaced by Lai's patch > "workqueue: allow changing attributions of ordered workqueue" > https://lkml.org/lkml/2014/4/15/181 Yeah, it bothers me that we're taking two completely different approaches for ordered and !ordered workqueues. The only difference between them is concurrency and it probably would be a better idea to address that directly. 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/