From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932070Ab1I3Iy0 (ORCPT ); Fri, 30 Sep 2011 04:54:26 -0400 Received: from mta0.cl.cam.ac.uk ([128.232.25.20]:35827 "EHLO mta0.cl.cam.ac.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753964Ab1I3IyZ (ORCPT ); Fri, 30 Sep 2011 04:54:25 -0400 Date: Fri, 30 Sep 2011 09:54:21 +0100 From: Ripduman Sohan To: Tejun Heo Cc: Gilad Ben-Yossef , linux-kernel@vger.kernel.org, peterz@infradead.org Subject: Re: [PATCH] workqueue: Restore cpus_allowed mask for sleeping workqueue rescue threads Message-ID: <20110930085421.GA11756@tusker> References: <1314884193-20454-1-git-send-email-ripduman.sohan@cl.cam.ac.uk> <20110902002917.GD2752@htj.dyndns.org> <20110915161430.GE1548@tusker> <20110924030718.GA29319@htj.dyndns.org> <20110930080914.GM10425@mtj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110930080914.GM10425@mtj.dyndns.org> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Tejun Heo wrote: > Hmmm... indeed. This can cause an unnecessary wakeup / migration on > an isolated CPU when another CPU asks for the rescuer, so yeah it > makes sense to change the behavior. BTW, why didn't the original > patch simply use set_cpus_allowed_ptr(cpu_all_mask)? > Because while at present all (bound) rescuer threads have an associated workqueue on each CPU, I didn't want to assume this arrangement would _always_ be the case. It was my thinking that for bound threads, iterating over the CPUs to only set those that have an associated workqueue for the rescuer would insulate agsinst any future case where rescuer threads may be bound to a subset of CPUs. Kind regards, --rip