From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753837AbZLHKfL (ORCPT ); Tue, 8 Dec 2009 05:35:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753794AbZLHKfJ (ORCPT ); Tue, 8 Dec 2009 05:35:09 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:57480 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753807AbZLHKfI (ORCPT ); Tue, 8 Dec 2009 05:35:08 -0500 Subject: Re: [PATCH 4/7] sched: implement force_cpus_allowed() From: Peter Zijlstra To: Tejun Heo Cc: tglx@linutronix.de, mingo@elte.hu, avi@redhat.com, efault@gmx.de, rusty@rustcorp.com.au, linux-kernel@vger.kernel.org, Gautham R Shenoy , Linus Torvalds In-Reply-To: <4B1E189B.1070204@kernel.org> References: <1259726212-30259-1-git-send-email-tj@kernel.org> <1259726212-30259-5-git-send-email-tj@kernel.org> <1259923259.3977.1928.camel@laptop> <1259923381.3977.1934.camel@laptop> <4B1C85D3.3080401@kernel.org> <1260174900.8223.1159.camel@laptop> <4B1CDA1C.3000802@kernel.org> <1260183278.8223.1500.camel@laptop> <4B1CE1E8.2070803@kernel.org> <4B1E1130.9050108@kernel.org> <1260262963.3935.1002.camel@laptop> <4B1E189B.1070204@kernel.org> Content-Type: text/plain; charset="UTF-8" Date: Tue, 08 Dec 2009 11:34:13 +0100 Message-ID: <1260268453.3935.1106.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2009-12-08 at 18:12 +0900, Tejun Heo wrote: > > So its only needed in order to flush a workqueue from CPU_DOWN_PREPARE? > > And all you need it to place a new kthread on a !active cpu? > > Yes, that's all I need. Then you don't need most of that patch, you don't need to touch the migration stuff since a new kthread isn't running. All you need to do is make a kthread_bind/set_cpus_allowed variant that checks against cpu_online_mask instead of cpu_active_mask. It might even make sense to have kthread_bind() always check with cpu_online_mask as the kernel really ought to know what its doing anyway. You also don't need to play trickery with PF_THREAD_BOUND, since a new kthread will not have that set. In fact, your patch is against a tree that still has cpu_online_mask in all those places, so you wouldn't have needed any of that, confused.. ?!